[android] enable image shared element transition for API 21+22

There's an Android framework bug (#224270) on these APIs that causes a NPE
when the shared element is not visible anymore when returning.
Since we know restore the list position, the shared element should be
visible and thus not produce NPEs anymore.

bramble-api/src/main/java/org/briarproject/bramble/api/versioning/ClientVersioningManager.java

@@ -38,6 +38,13 @@ public interface ClientVersioningManager {
 	Visibility getClientVisibility(Transaction txn, ContactId contactId,
 			ClientId clientId, int majorVersion) throws DbException;
 
+	/**
+	 * Returns the minor version of the given client that is supported by the
+	 * given contact, or -1 if the contact does not support the client.
+	 */
+	int getClientMinorVersion(Transaction txn, ContactId contactId,
+			ClientId clientId, int majorVersion) throws DbException;
+
 	interface ClientVersioningHook {
 
 		void onClientVisibilityChanging(Transaction txn, Contact c,

bramble-core/src/main/java/org/briarproject/bramble/versioning/ClientVersioningManagerImpl.java

@@ -89,14 +89,9 @@ class ClientVersioningManagerImpl implements ClientVersioningManager, Client,
 	public Visibility getClientVisibility(Transaction txn, ContactId contactId,
 			ClientId clientId, int majorVersion) throws DbException {
 		try {
-			Contact contact = db.getContact(txn, contactId);
-			Group g = getContactGroup(contact);
-			// Contact may be in the process of being added or removed, so
-			// contact group may not exist
-			if (!db.containsGroup(txn, g.getId())) return INVISIBLE;
-			LatestUpdates latest = findLatestUpdates(txn, g.getId());
+			LatestUpdates latest = findLatestUpdates(txn, contactId);
+			if (latest == null || latest.remote == null) return INVISIBLE;
 			if (latest.local == null) throw new DbException();
-			if (latest.remote == null) return INVISIBLE;
 			Update localUpdate = loadUpdate(txn, latest.local.messageId);
 			Update remoteUpdate = loadUpdate(txn, latest.remote.messageId);
 			Map<ClientMajorVersion, Visibility> visibilities =
@@ -110,6 +105,24 @@ class ClientVersioningManagerImpl implements ClientVersioningManager, Client,
 		}
 	}
 
+	@Override
+	public int getClientMinorVersion(Transaction txn, ContactId contactId,
+			ClientId clientId, int majorVersion) throws DbException {
+		try {
+			LatestUpdates latest = findLatestUpdates(txn, contactId);
+			if (latest == null || latest.remote == null) return -1;
+			Update remoteUpdate = loadUpdate(txn, latest.remote.messageId);
+			ClientMajorVersion cv =
+					new ClientMajorVersion(clientId, majorVersion);
+			for (ClientState remote : remoteUpdate.states) {
+				if (remote.majorVersion.equals(cv)) return remote.minorVersion;
+			}
+			return -1;
+		} catch (FormatException e) {
+			throw new DbException(e);
+		}
+	}
+
 	@Override
 	public void createLocalState(Transaction txn) throws DbException {
 		if (db.containsGroup(txn, localGroup.getId())) return;
@@ -336,6 +349,17 @@ class ClientVersioningManagerImpl implements ClientVersioningManager, Client,
 				MAJOR_VERSION, c);
 	}
 
+	@Nullable
+	private LatestUpdates findLatestUpdates(Transaction txn, ContactId c)
+			throws DbException, FormatException {
+		Contact contact = db.getContact(txn, c);
+		Group g = getContactGroup(contact);
+		// Contact may be in the process of being added or removed, so
+		// contact group may not exist
+		if (!db.containsGroup(txn, g.getId())) return null;
+		return findLatestUpdates(txn, g.getId());
+	}
+
 	private LatestUpdates findLatestUpdates(Transaction txn, GroupId g)
 			throws DbException, FormatException {
 		Map<MessageId, BdfDictionary> metadata =

bramble-core/src/test/java/org/briarproject/bramble/versioning/ClientVersioningManagerImplTest.java

@@ -8,6 +8,7 @@ import org.briarproject.bramble.api.data.BdfDictionary;
 import org.briarproject.bramble.api.data.BdfEntry;
 import org.briarproject.bramble.api.data.BdfList;
 import org.briarproject.bramble.api.db.DatabaseComponent;
+import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.Metadata;
 import org.briarproject.bramble.api.db.Transaction;
 import org.briarproject.bramble.api.sync.ClientId;
@@ -43,6 +44,7 @@ import static org.briarproject.bramble.util.StringUtils.getRandomString;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.GROUP_KEY_CONTACT_ID;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_LOCAL;
 import static org.briarproject.bramble.versioning.ClientVersioningConstants.MSG_KEY_UPDATE_VERSION;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 
 public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
@@ -657,4 +659,327 @@ public class ClientVersioningManagerImplTest extends BrambleMockTestCase {
 		c.registerClient(clientId, 123, 234, hook);
 		assertFalse(c.incomingMessage(txn, newRemoteUpdate, new Metadata()));
 	}
+
+	@Test
+	public void testReturnsInvisibleIfContactGroupDoesNotExist()
+			throws Exception {
+		expectGetContactGroup(false);
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(INVISIBLE, c.getClientVisibility(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsInvisibleIfNoRemoteUpdateExists() throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(singletonMap(localUpdateId, localUpdateMeta)));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(INVISIBLE, c.getClientVisibility(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test(expected = DbException.class)
+	public void testThrowsExceptionIfNoLocalUpdateExists() throws Exception {
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(singletonMap(remoteUpdateId, remoteUpdateMeta)));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		c.getClientVisibility(txn, contact.getId(), clientId, 123);
+	}
+
+	@Test
+	public void testReturnsInvisibleIfClientNotSupportedLocally()
+			throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(localUpdateId, localUpdateMeta);
+		messageMetadata.put(remoteUpdateId, remoteUpdateMeta);
+		// The client is supported remotely but not locally
+		BdfList localUpdateBody = BdfList.of(new BdfList(), 1L);
+		BdfList remoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			will(returnValue(localUpdateBody));
+			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			will(returnValue(remoteUpdateBody));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(INVISIBLE, c.getClientVisibility(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsInvisibleIfClientNotSupportedRemotely()
+			throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(localUpdateId, localUpdateMeta);
+		messageMetadata.put(remoteUpdateId, remoteUpdateMeta);
+		// The client is supported locally but not remotely
+		BdfList localUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+		BdfList remoteUpdateBody = BdfList.of(new BdfList(), 1L);
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			will(returnValue(localUpdateBody));
+			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			will(returnValue(remoteUpdateBody));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(INVISIBLE, c.getClientVisibility(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsVisibleIfClientNotActiveRemotely() throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(localUpdateId, localUpdateMeta);
+		messageMetadata.put(remoteUpdateId, remoteUpdateMeta);
+		// The client is supported locally and remotely but not active
+		BdfList localUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+		BdfList remoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			will(returnValue(localUpdateBody));
+			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			will(returnValue(remoteUpdateBody));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(VISIBLE, c.getClientVisibility(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsSharedIfClientActiveRemotely() throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(localUpdateId, localUpdateMeta);
+		messageMetadata.put(remoteUpdateId, remoteUpdateMeta);
+		// The client is supported locally and remotely and active
+		BdfList localUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, true)), 1L);
+		BdfList remoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, true)), 1L);
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, localUpdateId);
+			will(returnValue(localUpdateBody));
+			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			will(returnValue(remoteUpdateBody));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(SHARED, c.getClientVisibility(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsNegativeIfContactGroupDoesNotExist()
+			throws Exception {
+		expectGetContactGroup(false);
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(-1, c.getClientMinorVersion(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsNegativeIfNoRemoteUpdateExists() throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(singletonMap(localUpdateId, localUpdateMeta)));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(-1, c.getClientMinorVersion(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsNegativeIfClientNotSupportedRemotely()
+			throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(localUpdateId, localUpdateMeta);
+		messageMetadata.put(remoteUpdateId, remoteUpdateMeta);
+		// The client is not supported remotely
+		BdfList remoteUpdateBody = BdfList.of(new BdfList(), 1L);
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			will(returnValue(remoteUpdateBody));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(-1, c.getClientMinorVersion(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsMinorVersionIfClientNotActiveRemotely()
+			throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(localUpdateId, localUpdateMeta);
+		messageMetadata.put(remoteUpdateId, remoteUpdateMeta);
+		// The client is supported remotely but not active
+		BdfList remoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, false)), 1L);
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			will(returnValue(remoteUpdateBody));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(234, c.getClientMinorVersion(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	@Test
+	public void testReturnsMinorVersionIfClientActiveRemotely()
+			throws Exception {
+		MessageId localUpdateId = new MessageId(getRandomId());
+		BdfDictionary localUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, true));
+		MessageId remoteUpdateId = new MessageId(getRandomId());
+		BdfDictionary remoteUpdateMeta = BdfDictionary.of(
+				new BdfEntry(MSG_KEY_UPDATE_VERSION, 1L),
+				new BdfEntry(MSG_KEY_LOCAL, false));
+		Map<MessageId, BdfDictionary> messageMetadata = new HashMap<>();
+		messageMetadata.put(localUpdateId, localUpdateMeta);
+		messageMetadata.put(remoteUpdateId, remoteUpdateMeta);
+		// The client is supported remotely and active
+		BdfList remoteUpdateBody = BdfList.of(BdfList.of(
+				BdfList.of(clientId.getString(), 123, 234, true)), 1L);
+
+		expectGetContactGroup(true);
+		context.checking(new Expectations() {{
+			oneOf(clientHelper).getMessageMetadataAsDictionary(txn,
+					contactGroup.getId());
+			will(returnValue(messageMetadata));
+			oneOf(clientHelper).getMessageAsList(txn, remoteUpdateId);
+			will(returnValue(remoteUpdateBody));
+		}});
+
+		ClientVersioningManagerImpl c = createInstance();
+		assertEquals(234, c.getClientMinorVersion(txn, contact.getId(),
+				clientId, 123));
+	}
+
+	private void expectGetContactGroup(boolean exists) throws Exception {
+		context.checking(new Expectations() {{
+			oneOf(db).getContact(txn, contact.getId());
+			will(returnValue(contact));
+			oneOf(contactGroupFactory).createContactGroup(CLIENT_ID,
+					MAJOR_VERSION, contact);
+			will(returnValue(contactGroup));
+			oneOf(db).containsGroup(txn, contactGroup.getId());
+			will(returnValue(exists));
+		}});
+	}
 }

briar-android/src/main/java/org/briarproject/briar/android/activity/ActivityComponent.java

@@ -20,6 +20,7 @@ import org.briarproject.briar.android.contact.ContactModule;
 import org.briarproject.briar.android.conversation.AliasDialogFragment;
 import org.briarproject.briar.android.conversation.ConversationActivity;
 import org.briarproject.briar.android.conversation.ImageActivity;
+import org.briarproject.briar.android.conversation.ImageFragment;
 import org.briarproject.briar.android.forum.CreateForumActivity;
 import org.briarproject.briar.android.forum.ForumActivity;
 import org.briarproject.briar.android.forum.ForumListFragment;
@@ -218,4 +219,6 @@ public interface ActivityComponent {
 
 	void inject(AliasDialogFragment aliasDialogFragment);
 
+	void inject(ImageFragment imageFragment);
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/AttachmentController.java

@@ -16,6 +16,7 @@ import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
 
+import java.io.BufferedInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.ArrayList;
@@ -90,22 +91,44 @@ class AttachmentController {
 		return attachments;
 	}
 
+	/**
+	 * Creates {@link AttachmentItem}s from the passed headers and Attachments.
+	 *
+	 * Note: This closes the {@link Attachment}'s {@link InputStream}.
+	 */
 	List<AttachmentItem> getAttachmentItems(
 			List<Pair<AttachmentHeader, Attachment>> attachments) {
+		boolean needsSize = attachments.size() == 1;
 		List<AttachmentItem> items = new ArrayList<>(attachments.size());
 		for (Pair<AttachmentHeader, Attachment> a : attachments) {
 			AttachmentItem item =
-					getAttachmentItem(a.getFirst(), a.getSecond());
+					getAttachmentItem(a.getFirst(), a.getSecond(), needsSize);
 			items.add(item);
 		}
 		return items;
 	}
 
-	private AttachmentItem getAttachmentItem(AttachmentHeader h, Attachment a) {
+	/**
+	 * Creates an {@link AttachmentItem} from the {@link Attachment}'s
+	 * {@link InputStream} which will be closed when this method returns.
+	 */
+	AttachmentItem getAttachmentItem(AttachmentHeader h, Attachment a,
+			boolean needsSize) {
 		MessageId messageId = h.getMessageId();
-		Size size = new Size();
+		if (!needsSize) {
+			String mimeType = h.getContentType();
+			String extension = getExtensionFromMimeType(mimeType);
+			boolean hasError = false;
+			if (extension == null) {
+				extension = "";
+				hasError = true;
+			}
+			return new AttachmentItem(messageId, 0, 0, mimeType, extension, 0,
+					0, hasError);
+		}
 
-		InputStream is = a.getStream();
+		Size size = new Size();
+		InputStream is = new BufferedInputStream(a.getStream());
 		is.mark(Integer.MAX_VALUE);
 		try {
 			// use exif to get size
@@ -134,14 +157,19 @@ class AttachmentController {
 					getThumbnailSize(size.width, size.height, size.mimeType);
 		}
 		// get file extension
-		MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
-		String extension = mimeTypeMap.getExtensionFromMimeType(size.mimeType);
+		String extension = getExtensionFromMimeType(size.mimeType);
 		if (extension == null) {
 			return new AttachmentItem(messageId, 0, 0, "", "", 0, 0, true);
 		}
 		return new AttachmentItem(messageId, size.width, size.height,
-				size.mimeType, extension, thumbnailSize.width, thumbnailSize.height,
-				size.error);
+				size.mimeType, extension, thumbnailSize.width,
+				thumbnailSize.height, size.error);
+	}
+
+	@Nullable
+	private String getExtensionFromMimeType(String mimeType) {
+		MimeTypeMap mimeTypeMap = MimeTypeMap.getSingleton();
+		return mimeTypeMap.getExtensionFromMimeType(mimeType);
 	}
 
 	/**

briar-android/src/main/java/org/briarproject/briar/android/conversation/AttachmentItem.java

@@ -2,6 +2,7 @@ package org.briarproject.briar.android.conversation;
 
 import android.os.Parcel;
 import android.os.Parcelable;
+import android.support.annotation.Nullable;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.bramble.api.sync.MessageId;
@@ -111,4 +112,10 @@ public class AttachmentItem implements Parcelable {
 		dest.writeByte((byte) (hasError ? 1 : 0));
 	}
 
+	@Override
+	public boolean equals(@Nullable Object o) {
+		return o instanceof AttachmentItem &&
+				messageId.equals(((AttachmentItem) o).messageId);
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationActivity.java

@@ -8,6 +8,7 @@ import android.content.DialogInterface;
 import android.content.Intent;
 import android.net.Uri;
 import android.os.Bundle;
+import android.os.Parcelable;
 import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
 import android.support.design.widget.Snackbar;
@@ -29,7 +30,6 @@ import android.widget.ImageView;
 import android.widget.TextView;
 import android.widget.Toast;
 
-import org.briarproject.bramble.api.FormatException;
 import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
@@ -49,7 +49,6 @@ import org.briarproject.bramble.api.plugin.event.ContactDisconnectedEvent;
 import org.briarproject.bramble.api.settings.Settings;
 import org.briarproject.bramble.api.settings.SettingsManager;
 import org.briarproject.bramble.api.sync.GroupId;
-import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.bramble.api.sync.event.MessagesAckedEvent;
 import org.briarproject.bramble.api.sync.event.MessagesSentEvent;
@@ -83,7 +82,6 @@ import org.briarproject.briar.api.introduction.IntroductionManager;
 import org.briarproject.briar.api.messaging.Attachment;
 import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
-import org.briarproject.briar.api.messaging.PrivateMessage;
 import org.briarproject.briar.api.messaging.PrivateMessageFactory;
 import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 import org.briarproject.briar.api.privategroup.invitation.GroupInvitationManager;
@@ -110,7 +108,6 @@ import static android.support.v4.app.ActivityOptionsCompat.makeSceneTransitionAn
 import static android.support.v4.view.ViewCompat.setTransitionName;
 import static android.support.v7.util.SortedList.INVALID_POSITION;
 import static android.view.Gravity.RIGHT;
-import static android.widget.Toast.LENGTH_LONG;
 import static android.widget.Toast.LENGTH_SHORT;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.sort;
@@ -124,7 +121,8 @@ import static org.briarproject.bramble.util.StringUtils.isNullOrEmpty;
 import static org.briarproject.briar.android.TestingConstants.FEATURE_FLAG_IMAGE_ATTACHMENTS;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_ATTACH_IMAGE;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_INTRODUCTION;
-import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENT;
+import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENTS;
+import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENT_POSITION;
 import static org.briarproject.briar.android.conversation.ImageActivity.DATE;
 import static org.briarproject.briar.android.conversation.ImageActivity.NAME;
 import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
@@ -197,7 +195,7 @@ public class ConversationActivity extends BriarActivity
 
 	private volatile ContactId contactId;
 	@Nullable
-	private volatile GroupId messagingGroupId;
+	private Parcelable layoutManagerState;
 
 	private final Observer<String> contactNameObserver = name -> {
 		requireNonNull(name);
@@ -245,6 +243,8 @@ public class ConversationActivity extends BriarActivity
 			requireNonNull(deleted);
 			if (deleted) finish();
 		});
+		viewModel.getAddedPrivateMessage()
+				.observe(this, this::onAddedPrivateMessage);
 
 		setTransitionName(toolbarAvatar, getAvatarTransitionName(contactId));
 		setTransitionName(toolbarStatus, getBulbTransitionName(contactId));
@@ -311,6 +311,21 @@ public class ConversationActivity extends BriarActivity
 		list.stopPeriodicUpdate();
 	}
 
+	@Override
+	protected void onSaveInstanceState(Bundle outState) {
+		super.onSaveInstanceState(outState);
+		if (layoutManager != null) {
+			layoutManagerState = layoutManager.onSaveInstanceState();
+			outState.putParcelable("layoutManager", layoutManagerState);
+		}
+	}
+
+	@Override
+	protected void onRestoreInstanceState(Bundle savedInstanceState) {
+		super.onRestoreInstanceState(savedInstanceState);
+		layoutManagerState = savedInstanceState.getParcelable("layoutManager");
+	}
+
 	@Override
 	public boolean onCreateOptionsMenu(Menu menu) {
 		// Inflate the menu items for use in the action bar
@@ -397,7 +412,7 @@ public class ConversationActivity extends BriarActivity
 								textCache.put(id, text);
 							}
 						}
-						if (!h.getAttachmentHeaders().isEmpty()) {
+						if (h.getAttachmentHeaders().size() == 1) {
 							List<AttachmentItem> items =
 									attachmentController.get(id);
 							if (items == null) {
@@ -430,8 +445,12 @@ public class ConversationActivity extends BriarActivity
 				List<ConversationItem> items = createItems(headers);
 				adapter.addAll(items);
 				list.showData();
-				// Scroll to the bottom
-				list.scrollToPosition(adapter.getItemCount() - 1);
+				if (layoutManagerState == null) {
+					// Scroll to the bottom
+					list.scrollToPosition(adapter.getItemCount() - 1);
+				} else {
+					layoutManager.onRestoreInstanceState(layoutManagerState);
+				}
 			} else {
 				LOG.info("Concurrent update, reloading");
 				loadMessages();
@@ -473,7 +492,8 @@ public class ConversationActivity extends BriarActivity
 					adapter.getMessageItem(m);
 			if (pair != null) {
 				pair.getSecond().setText(text);
-				boolean bottom = adapter.isScrolledToBottom(layoutManager);
+				boolean bottom = layoutManagerState == null &&
+						adapter.isScrolledToBottom(layoutManager);
 				adapter.notifyItemChanged(pair.getFirst());
 				if (bottom) list.scrollToPosition(adapter.getItemCount() - 1);
 			}
@@ -486,7 +506,7 @@ public class ConversationActivity extends BriarActivity
 			try {
 				List<Pair<AttachmentHeader, Attachment>> attachments =
 						attachmentController.getMessageAttachments(headers);
-				// TODO move getting the items off to the IoExecutor
+				// TODO move getting the items off to IoExecutor, if size == 1
 				List<AttachmentItem> items =
 						attachmentController.getAttachmentItems(attachments);
 				displayMessageAttachments(messageId, items);
@@ -504,7 +524,8 @@ public class ConversationActivity extends BriarActivity
 					adapter.getMessageItem(m);
 			if (pair != null) {
 				pair.getSecond().setAttachments(items);
-				boolean bottom = adapter.isScrolledToBottom(layoutManager);
+				boolean bottom = layoutManagerState == null &&
+						adapter.isScrolledToBottom(layoutManager);
 				adapter.notifyItemChanged(pair.getFirst());
 				if (bottom) list.scrollToPosition(adapter.getItemCount() - 1);
 			}
@@ -555,7 +576,8 @@ public class ConversationActivity extends BriarActivity
 
 	private void addConversationItem(ConversationItem item) {
 		runOnUiThreadUnlessDestroyed(() -> {
-			boolean bottom = adapter.isScrolledToBottom(layoutManager);
+			boolean bottom = layoutManagerState == null &&
+					adapter.isScrolledToBottom(layoutManager);
 			adapter.incrementRevision();
 			adapter.add(item);
 			if (bottom) list.scrollToPosition(adapter.getItemCount() - 1);
@@ -600,16 +622,11 @@ public class ConversationActivity extends BriarActivity
 
 	@Override
 	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
-		if (!imageUris.isEmpty()) {
-			Toast.makeText(this, "Not yet implemented.", LENGTH_LONG).show();
-			textInputView.clearText();
-			return;
-		}
-		if (isNullOrEmpty(text)) throw new AssertionError();
+		if (isNullOrEmpty(text) && imageUris.isEmpty())
+			throw new AssertionError();
 		long timestamp = System.currentTimeMillis();
 		timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
-		if (messagingGroupId == null) loadGroupId(text, timestamp);
-		else createMessage(text, timestamp);
+		viewModel.sendMessage(text, imageUris, timestamp);
 		textInputView.clearText();
 	}
 
@@ -619,48 +636,10 @@ public class ConversationActivity extends BriarActivity
 		return item == null ? 0 : item.getTime() + 1;
 	}
 
-	private void loadGroupId(String text, long timestamp) {
-		runOnDbThread(() -> {
-			try {
-				messagingGroupId =
-						messagingManager.getConversationId(contactId);
-				createMessage(text, timestamp);
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-
-		});
-	}
-
-	private void createMessage(String text, long timestamp) {
-		cryptoExecutor.execute(() -> {
-			try {
-				//noinspection ConstantConditions init in loadGroupId()
-				storeMessage(privateMessageFactory.createPrivateMessage(
-						messagingGroupId, timestamp, text, emptyList()), text);
-			} catch (FormatException e) {
-				throw new RuntimeException(e);
-			}
-		});
-	}
-
-	private void storeMessage(PrivateMessage m, String text) {
-		runOnDbThread(() -> {
-			try {
-				long start = now();
-				messagingManager.addLocalMessage(m);
-				logDuration(LOG, "Storing message", start);
-				Message message = m.getMessage();
-				PrivateMessageHeader h = new PrivateMessageHeader(
-						message.getId(), message.getGroupId(),
-						message.getTimestamp(), true, false, false, false,
-						true, emptyList());
-				textCache.put(message.getId(), text);
-				addConversationItem(h.accept(visitor));
-			} catch (DbException e) {
-				logException(LOG, WARNING, e);
-			}
-		});
+	private void onAddedPrivateMessage(@Nullable PrivateMessageHeader h) {
+		if (h == null) return;
+		addConversationItem(h.accept(visitor));
+		viewModel.onAddedPrivateMessageSeen();
 	}
 
 	private void askToRemoveContact() {
@@ -858,19 +837,18 @@ public class ConversationActivity extends BriarActivity
 		} else {
 			name = getString(R.string.you);
 		}
+		ArrayList<AttachmentItem> attachments =
+				new ArrayList<>(messageItem.getAttachments());
 		Intent i = new Intent(this, ImageActivity.class);
-		i.putExtra(ATTACHMENT, item);
+		i.putParcelableArrayListExtra(ATTACHMENTS, attachments);
+		i.putExtra(ATTACHMENT_POSITION, attachments.indexOf(item));
 		i.putExtra(NAME, name);
 		i.putExtra(DATE, messageItem.getTime());
-		if (SDK_INT >= 23) {
-			String transitionName = item.getTransitionName();
-			ActivityOptionsCompat options =
-					makeSceneTransitionAnimation(this, view, transitionName);
-			ActivityCompat.startActivity(this, i, options.toBundle());
-		} else {
-			// work-around for android bug #224270
-			startActivity(i);
-		}
+		// restoring list position should not trigger android bug #224270
+		String transitionName = item.getTransitionName();
+		ActivityOptionsCompat options =
+				makeSceneTransitionAnimation(this, view, transitionName);
+		ActivityCompat.startActivity(this, i, options.toBundle());
 	}
 
 	@DatabaseExecutor

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationAdapter.java

@@ -3,6 +3,7 @@ package org.briarproject.briar.android.conversation;
 import android.content.Context;
 import android.support.annotation.LayoutRes;
 import android.support.v7.widget.LinearLayoutManager;
+import android.support.v7.widget.RecyclerView.RecycledViewPool;
 import android.util.SparseArray;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -21,11 +22,17 @@ class ConversationAdapter
 		extends BriarAdapter<ConversationItem, ConversationItemViewHolder> {
 
 	private ConversationListener listener;
+	private final RecycledViewPool imageViewPool;
+	private final ImageItemDecoration imageItemDecoration;
 
 	ConversationAdapter(Context ctx,
 			ConversationListener conversationListener) {
 		super(ctx, ConversationItem.class);
 		listener = conversationListener;
+		// This shares the same pool for view recycling between all image lists
+		imageViewPool = new RecycledViewPool();
+		// Share the item decoration as well
+		imageItemDecoration = new ImageItemDecoration(ctx);
 	}
 
 	@LayoutRes
@@ -42,15 +49,17 @@ class ConversationAdapter
 				type, viewGroup, false);
 		switch (type) {
 			case R.layout.list_item_conversation_msg_in:
-				return new ConversationMessageViewHolder(v, true);
+				return new ConversationMessageViewHolder(v, listener, true,
+						imageViewPool, imageItemDecoration);
 			case R.layout.list_item_conversation_msg_out:
-				return new ConversationMessageViewHolder(v, false);
+				return new ConversationMessageViewHolder(v, listener, false,
+						imageViewPool, imageItemDecoration);
 			case R.layout.list_item_conversation_notice_in:
-				return new ConversationNoticeViewHolder(v, true);
+				return new ConversationNoticeViewHolder(v, listener, true);
 			case R.layout.list_item_conversation_notice_out:
-				return new ConversationNoticeViewHolder(v, false);
+				return new ConversationNoticeViewHolder(v, listener, false);
 			case R.layout.list_item_conversation_request:
-				return new ConversationRequestViewHolder(v, true);
+				return new ConversationRequestViewHolder(v, listener, true);
 			default:
 				throw new IllegalArgumentException("Unknown ConversationItem");
 		}
@@ -59,7 +68,7 @@ class ConversationAdapter
 	@Override
 	public void onBindViewHolder(ConversationItemViewHolder ui, int position) {
 		ConversationItem item = items.get(position);
-		ui.bind(item, listener);
+		ui.bind(item);
 		listener.onItemVisible(item);
 	}
 

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationItemViewHolder.java

@@ -18,14 +18,17 @@ import static org.briarproject.briar.android.util.UiUtils.formatDate;
 @NotNullByDefault
 abstract class ConversationItemViewHolder extends ViewHolder {
 
+	protected final ConversationListener listener;
 	protected final ConstraintLayout layout;
 	@Nullable
 	private final OutItemViewHolder outViewHolder;
 	private final TextView text;
 	protected final TextView time;
 
-	ConversationItemViewHolder(View v, boolean isIncoming) {
+	ConversationItemViewHolder(View v, ConversationListener listener,
+			boolean isIncoming) {
 		super(v);
+		this.listener = listener;
 		this.outViewHolder = isIncoming ? null : new OutItemViewHolder(v);
 		layout = v.findViewById(R.id.layout);
 		text = v.findViewById(R.id.text);
@@ -33,7 +36,7 @@ abstract class ConversationItemViewHolder extends ViewHolder {
 	}
 
 	@CallSuper
-	void bind(ConversationItem item, ConversationListener listener) {
+	void bind(ConversationItem item) {
 		if (item.getText() != null) {
 			text.setText(trim(item.getText()));
 		}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationMessageViewHolder.java

@@ -1,63 +1,45 @@
 package org.briarproject.briar.android.conversation;
 
-import android.content.res.Configuration;
-import android.graphics.Bitmap;
-import android.support.annotation.DrawableRes;
 import android.support.annotation.UiThread;
 import android.support.constraint.ConstraintSet;
-import android.support.v4.content.ContextCompat;
+import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.RecyclerView.RecycledViewPool;
 import android.view.View;
 import android.view.ViewGroup;
-import android.widget.ImageView;
-
-import com.bumptech.glide.load.Transformation;
 
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
-import org.briarproject.briar.android.conversation.glide.BriarImageTransformation;
-import org.briarproject.briar.android.conversation.glide.GlideApp;
 
-import static android.os.Build.VERSION.SDK_INT;
-import static android.support.v4.view.ViewCompat.LAYOUT_DIRECTION_RTL;
-import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
-import static com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions.withCrossFade;
+import static android.support.constraint.ConstraintSet.WRAP_CONTENT;
+import static android.support.v4.content.ContextCompat.getColor;
 
 @UiThread
 @NotNullByDefault
 class ConversationMessageViewHolder extends ConversationItemViewHolder {
 
-	@DrawableRes
-	private static final int ERROR_RES = R.drawable.ic_image_broken;
-
-	private final ImageView imageView;
+	private final ImageAdapter adapter;
 	private final ViewGroup statusLayout;
 	private final int timeColor, timeColorBubble;
-	private final int radiusBig, radiusSmall;
-	private final boolean isRtl;
 	private final ConstraintSet textConstraints = new ConstraintSet();
 	private final ConstraintSet imageConstraints = new ConstraintSet();
 	private final ConstraintSet imageTextConstraints = new ConstraintSet();
 
-	ConversationMessageViewHolder(View v, boolean isIncoming) {
-		super(v, isIncoming);
-		imageView = v.findViewById(R.id.imageView);
+	ConversationMessageViewHolder(View v, ConversationListener listener,
+			boolean isIncoming, RecycledViewPool imageViewPool,
+			ImageItemDecoration imageItemDecoration) {
+		super(v, listener, isIncoming);
 		statusLayout = v.findViewById(R.id.statusLayout);
-		radiusBig = v.getContext().getResources()
-				.getDimensionPixelSize(R.dimen.message_bubble_radius_big);
-		radiusSmall = v.getContext().getResources()
-				.getDimensionPixelSize(R.dimen.message_bubble_radius_small);
+
+		// image list
+		RecyclerView list = v.findViewById(R.id.imageList);
+		list.setRecycledViewPool(imageViewPool);
+		adapter = new ImageAdapter(v.getContext(), listener);
+		list.setAdapter(adapter);
+		list.addItemDecoration(imageItemDecoration);
 
 		// remember original status text color
 		timeColor = time.getCurrentTextColor();
-		timeColorBubble =
-				ContextCompat.getColor(v.getContext(), R.color.briar_white);
-
-		// find out if we are showing a RTL language, Use the configuration,
-		// because getting the layout direction of views is not reliable
-		Configuration config =
-				imageView.getContext().getResources().getConfiguration();
-		isRtl = SDK_INT >= 17 &&
-				config.getLayoutDirection() == LAYOUT_DIRECTION_RTL;
+		timeColorBubble = getColor(v.getContext(), R.color.briar_white);
 
 		// clone constraint sets from layout files
 		textConstraints
@@ -77,85 +59,55 @@ class ConversationMessageViewHolder extends ConversationItemViewHolder {
 	}
 
 	@Override
-	void bind(ConversationItem conversationItem,
-			ConversationListener listener) {
-		super.bind(conversationItem, listener);
+	void bind(ConversationItem conversationItem) {
+		super.bind(conversationItem);
 		ConversationMessageItem item =
 				(ConversationMessageItem) conversationItem;
 		if (item.getAttachments().isEmpty()) {
 			bindTextItem();
 		} else {
-			bindImageItem(item, listener);
+			bindImageItem(item);
 		}
 	}
 
 	private void bindTextItem() {
-		clearImage();
+		resetStatusLayoutForText();
+		textConstraints.applyTo(layout);
+		adapter.clear();
+	}
+
+	private void bindImageItem(ConversationMessageItem item) {
+		ConstraintSet constraintSet;
+		if (item.getText() == null) {
+			statusLayout.setBackgroundResource(R.drawable.msg_status_bubble);
+			time.setTextColor(timeColorBubble);
+			constraintSet = imageConstraints;
+		} else {
+			resetStatusLayoutForText();
+			constraintSet = imageTextConstraints;
+		}
+
+		if (item.getAttachments().size() == 1) {
+			// apply image size constraints for a single image
+			AttachmentItem attachment = item.getAttachments().get(0);
+			int width = attachment.getThumbnailWidth();
+			int height = attachment.getThumbnailHeight();
+			constraintSet.constrainWidth(R.id.imageList, width);
+			constraintSet.constrainHeight(R.id.imageList, height);
+		} else {
+			// bubble adapts to size of image list
+			constraintSet.constrainWidth(R.id.imageList, WRAP_CONTENT);
+			constraintSet.constrainHeight(R.id.imageList, WRAP_CONTENT);
+		}
+		constraintSet.applyTo(layout);
+		adapter.setConversationItem(item);
+	}
+
+	private void resetStatusLayoutForText() {
 		statusLayout.setBackgroundResource(0);
 		// also reset padding (the background drawable defines some)
 		statusLayout.setPadding(0, 0, 0, 0);
 		time.setTextColor(timeColor);
-		textConstraints.applyTo(layout);
-	}
-
-	private void bindImageItem(ConversationMessageItem item,
-			ConversationListener listener) {
-		// TODO show more than just the first image
-		AttachmentItem attachment = item.getAttachments().get(0);
-
-		ConstraintSet constraintSet;
-		if (item.getText() == null) {
-			statusLayout
-					.setBackgroundResource(R.drawable.msg_status_bubble);
-			time.setTextColor(timeColorBubble);
-			constraintSet = imageConstraints;
-		} else {
-			statusLayout.setBackgroundResource(0);
-			// also reset padding (the background drawable defines some)
-			statusLayout.setPadding(0, 0, 0, 0);
-			time.setTextColor(timeColor);
-			constraintSet = imageTextConstraints;
-		}
-
-		// apply image size constraints, so glides picks them up for scaling
-		int width = attachment.getThumbnailWidth();
-		int height = attachment.getThumbnailHeight();
-		constraintSet.constrainWidth(R.id.imageView, width);
-		constraintSet.constrainHeight(R.id.imageView, height);
-		constraintSet.applyTo(layout);
-
-		if (attachment.hasError()) {
-			clearImage();
-			imageView.setImageResource(ERROR_RES);
-		} else {
-			loadImage(item, attachment, listener);
-		}
-	}
-
-	private void clearImage() {
-		GlideApp.with(imageView)
-				.clear(imageView);
-		imageView.setOnClickListener(null);
-	}
-
-	private void loadImage(ConversationMessageItem item,
-			AttachmentItem attachment, ConversationListener listener) {
-		boolean leftCornerSmall =
-				(isIncoming() && !isRtl) || (!isIncoming() && isRtl);
-		boolean bottomRound = item.getText() == null;
-		Transformation<Bitmap> transformation = new BriarImageTransformation(
-				radiusSmall, radiusBig, leftCornerSmall, bottomRound);
-
-		GlideApp.with(imageView)
-				.load(attachment)
-				.diskCacheStrategy(NONE)
-				.error(ERROR_RES)
-				.transform(transformation)
-				.transition(withCrossFade())
-				.into(imageView)
-				.waitForLayout();
-		imageView.setOnClickListener(
-				view -> listener.onAttachmentClicked(view, item, attachment));
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationNoticeViewHolder.java

@@ -19,16 +19,17 @@ class ConversationNoticeViewHolder extends ConversationItemViewHolder {
 
 	private final TextView msgText;
 
-	ConversationNoticeViewHolder(View v, boolean isIncoming) {
-		super(v, isIncoming);
+	ConversationNoticeViewHolder(View v, ConversationListener listener,
+			boolean isIncoming) {
+		super(v, listener, isIncoming);
 		msgText = v.findViewById(R.id.msgText);
 	}
 
 	@Override
 	@CallSuper
-	void bind(ConversationItem item, ConversationListener listener) {
+	void bind(ConversationItem item) {
 		ConversationNoticeItem notice = (ConversationNoticeItem) item;
-		super.bind(notice, listener);
+		super.bind(notice);
 
 		String text = notice.getMsgText();
 		if (isNullOrEmpty(text)) {

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationRequestViewHolder.java

@@ -17,16 +17,17 @@ class ConversationRequestViewHolder extends ConversationNoticeViewHolder {
 	private final Button acceptButton;
 	private final Button declineButton;
 
-	ConversationRequestViewHolder(View v, boolean isIncoming) {
-		super(v, isIncoming);
+	ConversationRequestViewHolder(View v, ConversationListener listener,
+			boolean isIncoming) {
+		super(v, listener, isIncoming);
 		acceptButton = v.findViewById(R.id.acceptButton);
 		declineButton = v.findViewById(R.id.declineButton);
 	}
 
 	@Override
-	void bind(ConversationItem item, ConversationListener listener) {
+	void bind(ConversationItem item) {
 		ConversationRequestItem request = (ConversationRequestItem) item;
-		super.bind(request, listener);
+		super.bind(request);
 
 		if (request.wasAnswered() && request.canBeOpened()) {
 			acceptButton.setVisibility(VISIBLE);

briar-android/src/main/java/org/briarproject/briar/android/conversation/ConversationViewModel.java

@@ -5,19 +5,36 @@ import android.arch.lifecycle.AndroidViewModel;
 import android.arch.lifecycle.LiveData;
 import android.arch.lifecycle.MutableLiveData;
 import android.arch.lifecycle.Transformations;
+import android.content.ContentResolver;
+import android.net.Uri;
 import android.support.annotation.Nullable;
+import android.support.annotation.UiThread;
 
+import org.briarproject.bramble.api.FormatException;
+import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.contact.Contact;
 import org.briarproject.bramble.api.contact.ContactId;
 import org.briarproject.bramble.api.contact.ContactManager;
+import org.briarproject.bramble.api.crypto.CryptoExecutor;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.db.NoSuchContactException;
 import org.briarproject.bramble.api.identity.AuthorId;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
+import org.briarproject.bramble.api.sync.Message;
 import org.briarproject.briar.android.util.UiUtils;
+import org.briarproject.briar.api.messaging.Attachment;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 import org.briarproject.briar.api.messaging.MessagingManager;
+import org.briarproject.briar.api.messaging.PrivateMessage;
+import org.briarproject.briar.api.messaging.PrivateMessageFactory;
+import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -26,9 +43,11 @@ import javax.inject.Inject;
 import static java.util.Objects.requireNonNull;
 import static java.util.logging.Level.WARNING;
 import static java.util.logging.Logger.getLogger;
+import static org.briarproject.bramble.util.IoUtils.tryToClose;
 import static org.briarproject.bramble.util.LogUtils.logDuration;
 import static org.briarproject.bramble.util.LogUtils.logException;
 import static org.briarproject.bramble.util.LogUtils.now;
+import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
 
 @NotNullByDefault
 public class ConversationViewModel extends AndroidViewModel {
@@ -38,7 +57,11 @@ public class ConversationViewModel extends AndroidViewModel {
 
 	@DatabaseExecutor
 	private final Executor dbExecutor;
+	@CryptoExecutor
+	private final Executor cryptoExecutor;
+	private final MessagingManager messagingManager;
 	private final ContactManager contactManager;
+	private final PrivateMessageFactory privateMessageFactory;
 	private final AttachmentController attachmentController;
 
 	@Nullable
@@ -50,14 +73,24 @@ public class ConversationViewModel extends AndroidViewModel {
 			Transformations.map(contact, UiUtils::getContactDisplayName);
 	private final MutableLiveData<Boolean> contactDeleted =
 			new MutableLiveData<>();
+	private final MutableLiveData<GroupId> messagingGroupId =
+			new MutableLiveData<>();
+	private final MutableLiveData<PrivateMessageHeader> addedHeader =
+			new MutableLiveData<>();
 
 	@Inject
 	ConversationViewModel(Application application,
 			@DatabaseExecutor Executor dbExecutor,
-			ContactManager contactManager, MessagingManager messagingManager) {
+			@CryptoExecutor Executor cryptoExecutor,
+			MessagingManager messagingManager,
+			ContactManager contactManager,
+			PrivateMessageFactory privateMessageFactory) {
 		super(application);
 		this.dbExecutor = dbExecutor;
+		this.cryptoExecutor = cryptoExecutor;
+		this.messagingManager = messagingManager;
 		this.contactManager = contactManager;
+		this.privateMessageFactory = privateMessageFactory;
 		this.attachmentController = new AttachmentController(messagingManager,
 				application.getResources());
 		contactDeleted.setValue(false);
@@ -100,6 +133,119 @@ public class ConversationViewModel extends AndroidViewModel {
 		});
 	}
 
+	void sendMessage(@Nullable String text, List<Uri> uris, long timestamp) {
+		if (messagingGroupId.getValue() == null) loadGroupId();
+		observeForeverOnce(messagingGroupId, groupId -> {
+			if (groupId == null) return;
+			// calls through to creating and storing the message
+			storeAttachments(groupId, text, uris, timestamp);
+		});
+	}
+
+	private void loadGroupId() {
+		if (contactId == null) throw new IllegalStateException();
+		dbExecutor.execute(() -> {
+			try {
+				messagingGroupId.postValue(
+						messagingManager.getConversationId(contactId));
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	private void storeAttachments(GroupId groupId, @Nullable String text,
+			List<Uri> uris, long timestamp) {
+		dbExecutor.execute(() -> {
+			long start = now();
+			List<AttachmentHeader> attachments = new ArrayList<>();
+			List<AttachmentItem> items = new ArrayList<>();
+			boolean needsSize = uris.size() == 1;
+			for (Uri uri : uris) {
+				Pair<AttachmentHeader, AttachmentItem> pair =
+						createAttachmentHeader(groupId, uri, timestamp,
+								needsSize);
+				if (pair == null) continue;
+				attachments.add(pair.getFirst());
+				items.add(pair.getSecond());
+			}
+			logDuration(LOG, "Storing attachments", start);
+			createMessage(groupId, text, attachments, items, timestamp);
+		});
+	}
+
+	@Nullable
+	@DatabaseExecutor
+	private Pair<AttachmentHeader, AttachmentItem> createAttachmentHeader(
+			GroupId groupId, Uri uri, long timestamp, boolean needsSize) {
+		InputStream is = null;
+		try {
+			ContentResolver contentResolver =
+					getApplication().getContentResolver();
+			is = contentResolver.openInputStream(uri);
+			if (is == null) throw new IOException();
+			String contentType = contentResolver.getType(uri);
+			if (contentType == null) throw new IOException("null content type");
+			AttachmentHeader h = messagingManager
+					.addLocalAttachment(groupId, timestamp, contentType, is);
+			is.close();
+			// re-open stream to get AttachmentItem
+			is = contentResolver.openInputStream(uri);
+			if (is == null) throw new IOException();
+			AttachmentItem item = attachmentController
+					.getAttachmentItem(h, new Attachment(is), needsSize);
+			return new Pair<>(h, item);
+		} catch (DbException | IOException e) {
+			logException(LOG, WARNING, e);
+			return null;
+		} finally {
+			if (is != null) tryToClose(is, LOG, WARNING);
+		}
+	}
+
+	private void createMessage(GroupId groupId, @Nullable String text,
+			List<AttachmentHeader> attachments, List<AttachmentItem> aItems,
+			long timestamp) {
+		cryptoExecutor.execute(() -> {
+			try {
+				// TODO remove when text can be null in the backend
+				String msgText = text == null ? "null" : text;
+				PrivateMessage pm = privateMessageFactory
+						.createPrivateMessage(groupId, timestamp, msgText,
+								attachments);
+				attachmentController.put(pm.getMessage().getId(), aItems);
+				storeMessage(pm, msgText, attachments);
+			} catch (FormatException e) {
+				throw new RuntimeException(e);
+			}
+		});
+	}
+
+	private void storeMessage(PrivateMessage m, @Nullable String text,
+			List<AttachmentHeader> attachments) {
+		dbExecutor.execute(() -> {
+			try {
+				long start = now();
+				messagingManager.addLocalMessage(m);
+				logDuration(LOG, "Storing message", start);
+				Message message = m.getMessage();
+				PrivateMessageHeader h = new PrivateMessageHeader(
+						message.getId(), message.getGroupId(),
+						message.getTimestamp(), true, true, false, false,
+						text != null, attachments);
+				// TODO add text to cache when available here
+				addedHeader.postValue(h);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		});
+	}
+
+	@UiThread
+	void onAddedPrivateMessageSeen() {
+		addedHeader.setValue(null);
+	}
+
 	AttachmentController getAttachmentController() {
 		return attachmentController;
 	}
@@ -120,4 +266,8 @@ public class ConversationViewModel extends AndroidViewModel {
 		return contactDeleted;
 	}
 
+	LiveData<PrivateMessageHeader> getAddedPrivateMessage() {
+		return addedHeader;
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageActivity.java

@@ -4,15 +4,18 @@ import android.arch.lifecycle.ViewModelProvider;
 import android.arch.lifecycle.ViewModelProviders;
 import android.content.DialogInterface.OnClickListener;
 import android.content.Intent;
-import android.graphics.drawable.Animatable;
 import android.graphics.drawable.Drawable;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.annotation.RequiresApi;
 import android.support.design.widget.AppBarLayout;
 import android.support.design.widget.Snackbar;
+import android.support.v4.app.Fragment;
+import android.support.v4.app.FragmentManager;
+import android.support.v4.app.FragmentStatePagerAdapter;
 import android.support.v4.content.ContextCompat;
 import android.support.v4.graphics.drawable.DrawableCompat;
+import android.support.v4.view.ViewPager;
 import android.support.v7.app.AlertDialog.Builder;
 import android.support.v7.widget.Toolbar;
 import android.transition.Fade;
@@ -20,23 +23,18 @@ import android.transition.Transition;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
+import android.view.ViewTreeObserver.OnGlobalLayoutListener;
 import android.view.Window;
 import android.widget.TextView;
 
-import com.bumptech.glide.load.DataSource;
-import com.bumptech.glide.load.engine.GlideException;
-import com.bumptech.glide.request.RequestListener;
-import com.bumptech.glide.request.target.Target;
-import com.github.chrisbanes.photoview.PhotoView;
-
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.activity.ActivityComponent;
 import org.briarproject.briar.android.activity.BriarActivity;
-import org.briarproject.briar.android.conversation.glide.GlideApp;
 import org.briarproject.briar.android.view.PullDownLayout;
 
 import java.text.SimpleDateFormat;
 import java.util.Date;
+import java.util.List;
 import java.util.Locale;
 
 import javax.inject.Inject;
@@ -53,16 +51,15 @@ import static android.view.View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN;
 import static android.view.View.SYSTEM_UI_FLAG_LAYOUT_STABLE;
 import static android.view.View.VISIBLE;
 import static android.view.WindowManager.LayoutParams.FLAG_TRANSLUCENT_STATUS;
-import static android.widget.ImageView.ScaleType.FIT_START;
-import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
 import static java.util.Objects.requireNonNull;
 import static org.briarproject.briar.android.activity.RequestCodes.REQUEST_SAVE_ATTACHMENT;
 import static org.briarproject.briar.android.util.UiUtils.formatDateAbsolute;
 
 public class ImageActivity extends BriarActivity
-		implements PullDownLayout.Callback {
+		implements PullDownLayout.Callback, OnGlobalLayoutListener {
 
-	final static String ATTACHMENT = "attachment";
+	final static String ATTACHMENTS = "attachments";
+	final static String ATTACHMENT_POSITION = "position";
 	final static String NAME = "name";
 	final static String DATE = "date";
 
@@ -72,8 +69,8 @@ public class ImageActivity extends BriarActivity
 	private ImageViewModel viewModel;
 	private PullDownLayout layout;
 	private AppBarLayout appBarLayout;
-	private PhotoView photoView;
-	private AttachmentItem attachment;
+	private ViewPager viewPager;
+	private List<AttachmentItem> attachments;
 
 	@Override
 	public void injectActivity(ActivityComponent component) {
@@ -85,7 +82,7 @@ public class ImageActivity extends BriarActivity
 		super.onCreate(state);
 
 		// Transitions
-		supportPostponeEnterTransition();
+		if (state == null) supportPostponeEnterTransition();
 		Window window = getWindow();
 		if (SDK_INT >= 21) {
 			Transition transition = new Fade();
@@ -102,6 +99,7 @@ public class ImageActivity extends BriarActivity
 		layout = findViewById(R.id.layout);
 		layout.getBackground().setAlpha(255);
 		layout.setCallback(this);
+		layout.getViewTreeObserver().addOnGlobalLayoutListener(this);
 
 		// Status Bar
 		if (SDK_INT >= 21) {
@@ -118,59 +116,29 @@ public class ImageActivity extends BriarActivity
 		TextView dateView = toolbar.findViewById(R.id.dateView);
 
 		// Intent Extras
-		attachment = getIntent().getParcelableExtra(ATTACHMENT);
-		String name = getIntent().getStringExtra(NAME);
-		long time = getIntent().getLongExtra(DATE, 0);
+		Intent i = getIntent();
+		attachments = i.getParcelableArrayListExtra(ATTACHMENTS);
+		int position = i.getIntExtra(ATTACHMENT_POSITION, -1);
+		if (position == -1) throw new IllegalStateException();
+		String name = i.getStringExtra(NAME);
+		long time = i.getLongExtra(DATE, 0);
 		String date = formatDateAbsolute(this, time);
 		contactName.setText(name);
 		dateView.setText(date);
 
-		// Image View
-		photoView = findViewById(R.id.photoView);
+		// Set up image ViewPager
+		viewPager = findViewById(R.id.viewPager);
+		ImagePagerAdapter pagerAdapter =
+				new ImagePagerAdapter(getSupportFragmentManager());
+		viewPager.setAdapter(pagerAdapter);
+		viewPager.setCurrentItem(position);
+
 		if (SDK_INT >= 16) {
-			photoView.setOnClickListener(view -> toggleSystemUi());
+			viewModel.getOnImageClicked().observe(this, this::onImageClicked);
 			window.getDecorView().setSystemUiVisibility(
 					SYSTEM_UI_FLAG_LAYOUT_STABLE |
 							SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN);
 		}
-
-		// Request Listener
-		RequestListener<Drawable> listener = new RequestListener<Drawable>() {
-			@Override
-			public boolean onLoadFailed(@Nullable GlideException e,
-					Object model, Target<Drawable> target,
-					boolean isFirstResource) {
-				supportStartPostponedEnterTransition();
-				return false;
-			}
-
-			@Override
-			public boolean onResourceReady(Drawable resource, Object model,
-					Target<Drawable> target, DataSource dataSource,
-					boolean isFirstResource) {
-				if (SDK_INT >= 21 && !(resource instanceof Animatable)) {
-					// set transition name only when not animatable,
-					// because the animation won't start otherwise
-					photoView.setTransitionName(
-							attachment.getTransitionName());
-				}
-				// Move image to the top if overlapping toolbar
-				if (isOverlappingToolbar(resource)) {
-					photoView.setScaleType(FIT_START);
-				}
-				supportStartPostponedEnterTransition();
-				return false;
-			}
-		};
-
-		// Load Image
-		GlideApp.with(this)
-				.load(attachment)
-				.diskCacheStrategy(NONE)
-				.error(R.drawable.ic_image_broken)
-				.dontTransform()
-				.addListener(listener)
-				.into(photoView);
 	}
 
 	@Override
@@ -193,11 +161,23 @@ public class ImageActivity extends BriarActivity
 		}
 	}
 
+	@Override
+	public void onGlobalLayout() {
+		viewModel.setToolbarPosition(
+				appBarLayout.getTop(), appBarLayout.getBottom()
+		);
+		if (SDK_INT >= 16) {
+			layout.getViewTreeObserver().removeOnGlobalLayoutListener(this);
+		} else {
+			layout.getViewTreeObserver().removeGlobalOnLayoutListener(this);
+		}
+	}
+
 	@Override
 	protected void onActivityResult(int request, int result, Intent data) {
 		super.onActivityResult(request, result, data);
 		if (request == REQUEST_SAVE_ATTACHMENT && result == RESULT_OK) {
-			viewModel.saveImage(attachment, data.getData());
+			viewModel.saveImage(getVisibleAttachment(), data.getData());
 		}
 	}
 
@@ -225,6 +205,14 @@ public class ImageActivity extends BriarActivity
 		supportFinishAfterTransition();
 	}
 
+	@RequiresApi(api = 16)
+	private void onImageClicked(@Nullable Boolean clicked) {
+		if (clicked != null && clicked) {
+			toggleSystemUi();
+			viewModel.onOnImageClickSeen();
+		}
+	}
+
 	@RequiresApi(api = 16)
 	private void toggleSystemUi() {
 		View decorView = getWindow().getDecorView();
@@ -259,29 +247,13 @@ public class ImageActivity extends BriarActivity
 				.start();
 	}
 
-	private boolean isOverlappingToolbar(Drawable drawable) {
-		int width = drawable.getIntrinsicWidth();
-		int height = drawable.getIntrinsicHeight();
-		float widthPercentage = photoView.getWidth() / (float) width;
-		float heightPercentage = photoView.getHeight() / (float) height;
-		float scaleFactor = Math.min(widthPercentage, heightPercentage);
-		int realWidth = (int) (width * scaleFactor);
-		int realHeight = (int) (height * scaleFactor);
-		// return if photo doesn't use the full width,
-		// because it will be moved to the right otherwise
-		if (realWidth < photoView.getWidth()) return false;
-		int drawableTop = (photoView.getHeight() - realHeight) / 2;
-		return drawableTop < appBarLayout.getBottom() &&
-				drawableTop != appBarLayout.getTop();
-	}
-
 	private void showSaveImageDialog() {
 		OnClickListener okListener = (dialog, which) -> {
 			if (SDK_INT >= 19) {
 				Intent intent = getCreationIntent();
 				startActivityForResult(intent, REQUEST_SAVE_ATTACHMENT);
 			} else {
-				viewModel.saveImage(attachment);
+				viewModel.saveImage(getVisibleAttachment());
 			}
 		};
 		Builder builder = new Builder(this, R.style.BriarDialogTheme);
@@ -303,7 +275,7 @@ public class ImageActivity extends BriarActivity
 		String fileName = sdf.format(new Date());
 		Intent intent = new Intent(ACTION_CREATE_DOCUMENT);
 		intent.addCategory(CATEGORY_OPENABLE);
-		intent.setType(attachment.getMimeType());
+		intent.setType(getVisibleAttachment().getMimeType());
 		intent.putExtra(EXTRA_TITLE, fileName);
 		return intent;
 	}
@@ -320,4 +292,31 @@ public class ImageActivity extends BriarActivity
 		viewModel.onSaveStateSeen();
 	}
 
+	AttachmentItem getVisibleAttachment() {
+		return attachments.get(viewPager.getCurrentItem());
+	}
+
+	private class ImagePagerAdapter extends FragmentStatePagerAdapter {
+
+		private boolean isFirst = true;
+
+		private ImagePagerAdapter(FragmentManager fm) {
+			super(fm);
+		}
+
+		@Override
+		public Fragment getItem(int position) {
+			Fragment f = ImageFragment
+					.newInstance(attachments.get(position), isFirst);
+			isFirst = false;
+			return f;
+		}
+
+		@Override
+		public int getCount() {
+			return attachments.size();
+		}
+
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageAdapter.java

@@ -0,0 +1,155 @@
+package org.briarproject.briar.android.conversation;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.support.annotation.Nullable;
+import android.support.v7.widget.RecyclerView.Adapter;
+import android.util.DisplayMetrics;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+import android.view.WindowManager;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.conversation.glide.Radii;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static android.content.Context.WINDOW_SERVICE;
+import static java.util.Objects.requireNonNull;
+import static org.briarproject.briar.android.util.UiUtils.isRtl;
+
+@NotNullByDefault
+class ImageAdapter extends Adapter<ImageViewHolder> {
+
+	private final List<AttachmentItem> items = new ArrayList<>();
+	private final ConversationListener listener;
+	private final int imageSize;
+	private final int radiusBig, radiusSmall;
+	private final boolean isRtl;
+	@Nullable
+	private ConversationMessageItem conversationItem;
+
+	ImageAdapter(Context ctx, ConversationListener listener) {
+		this.listener = listener;
+		imageSize = getImageSize(ctx);
+		Resources res = ctx.getResources();
+		radiusBig =
+				res.getDimensionPixelSize(R.dimen.message_bubble_radius_big);
+		radiusSmall =
+				res.getDimensionPixelSize(R.dimen.message_bubble_radius_small);
+		isRtl = isRtl(ctx);
+	}
+
+	@Override
+	public ImageViewHolder onCreateViewHolder(ViewGroup viewGroup, int type) {
+		View v = LayoutInflater.from(viewGroup.getContext()).inflate(
+				R.layout.list_item_image, viewGroup, false);
+		return new ImageViewHolder(v, imageSize);
+	}
+
+	@Override
+	public void onBindViewHolder(ImageViewHolder imageViewHolder,
+			int position) {
+		// get item
+		requireNonNull(conversationItem);
+		AttachmentItem item = items.get(position);
+		// set onClick listener
+		imageViewHolder.itemView.setOnClickListener(v ->
+				listener.onAttachmentClicked(v, conversationItem, item)
+		);
+		// bind view holder
+		int size = items.size();
+		boolean isIncoming = conversationItem.isIncoming();
+		boolean hasText = conversationItem.getText() != null;
+		Radii r = getRadii(position, size, isIncoming, hasText);
+		imageViewHolder.bind(item, r, size == 1, singleInRow(position, size));
+	}
+
+	@Override
+	public int getItemCount() {
+		return items.size();
+	}
+
+	void setConversationItem(ConversationMessageItem item) {
+		this.conversationItem = item;
+		this.items.clear();
+		this.items.addAll(item.getAttachments());
+		notifyDataSetChanged();
+	}
+
+	private int getImageSize(Context ctx) {
+		Resources res = ctx.getResources();
+		WindowManager windowManager =
+				(WindowManager) ctx.getSystemService(WINDOW_SERVICE);
+		DisplayMetrics displayMetrics = new DisplayMetrics();
+		if (windowManager == null) {
+			return res.getDimensionPixelSize(
+					R.dimen.message_bubble_image_default);
+		}
+		windowManager.getDefaultDisplay().getMetrics(displayMetrics);
+		int imageSize = displayMetrics.widthPixels / 3;
+		int maxSize = res.getDimensionPixelSize(
+				R.dimen.message_bubble_image_max_width);
+		return Math.min(imageSize, maxSize);
+	}
+
+	private Radii getRadii(int pos, int num, boolean isIncoming,
+			boolean hasText) {
+		boolean left = isLeft(pos);
+		boolean single = num == 1;
+		// Top Row
+		int topLeft;
+		int topRight;
+		if (single) {
+			topLeft = isIncoming ? radiusSmall : radiusBig;
+			topRight = !isIncoming ? radiusSmall : radiusBig;
+		} else if (isTopRow(pos)) {
+			topLeft = left ? (isIncoming ? radiusSmall : radiusBig) : 0;
+			topRight = !left ? (!isIncoming ? radiusSmall : radiusBig) : 0;
+		} else {
+			topLeft = 0;
+			topRight = 0;
+		}
+		// Bottom Row
+		boolean singleInRow = singleInRow(pos, num);
+		int bottomLeft;
+		int bottomRight;
+		if (!hasText && isBottomRow(pos, num)) {
+			bottomLeft = singleInRow || left ? radiusBig : 0;
+			bottomRight = singleInRow || !left ? radiusBig : 0;
+		} else {
+			bottomLeft = 0;
+			bottomRight = 0;
+		}
+		if (isRtl) return new Radii(topRight, topLeft, bottomRight, bottomLeft);
+		return new Radii(topLeft, topRight, bottomLeft, bottomRight);
+	}
+
+	void clear() {
+		items.clear();
+		notifyDataSetChanged();
+	}
+
+	static boolean isTopRow(int pos) {
+		return pos < 2;
+	}
+
+	static boolean isLeft(int pos) {
+		return pos % 2 == 0;
+	}
+
+	static boolean isBottomRow(int pos, int num) {
+		return num % 2 == 0 ?
+				pos >= num - 2 : // last two, if even
+				pos > num - 2;   // last one, if odd
+	}
+
+	static boolean singleInRow(int pos, int num) {
+		// last item of an odd number
+		return num % 2 != 0 && pos == num -1;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageFragment.java

@@ -0,0 +1,131 @@
+package org.briarproject.briar.android.conversation;
+
+import android.arch.lifecycle.ViewModelProvider;
+import android.arch.lifecycle.ViewModelProviders;
+import android.graphics.drawable.Animatable;
+import android.graphics.drawable.Drawable;
+import android.os.Bundle;
+import android.support.annotation.Nullable;
+import android.support.v4.app.Fragment;
+import android.view.LayoutInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+import com.bumptech.glide.load.DataSource;
+import com.bumptech.glide.load.engine.GlideException;
+import com.bumptech.glide.request.RequestListener;
+import com.bumptech.glide.request.target.Target;
+import com.github.chrisbanes.photoview.PhotoView;
+
+import org.briarproject.bramble.api.nullsafety.MethodsNotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.activity.BaseActivity;
+import org.briarproject.briar.android.conversation.glide.GlideApp;
+
+import javax.annotation.ParametersAreNonnullByDefault;
+import javax.inject.Inject;
+
+import static android.os.Build.VERSION.SDK_INT;
+import static android.widget.ImageView.ScaleType.FIT_START;
+import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
+import static org.briarproject.bramble.api.nullsafety.NullSafety.requireNonNull;
+import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENT_POSITION;
+
+@MethodsNotNullByDefault
+@ParametersAreNonnullByDefault
+public class ImageFragment extends Fragment {
+
+	private final static String IS_FIRST = "isFirst";
+
+	@Inject
+	ViewModelProvider.Factory viewModelFactory;
+
+	private AttachmentItem attachment;
+	private boolean isFirst;
+	private ImageViewModel viewModel;
+	private PhotoView photoView;
+
+	static ImageFragment newInstance(AttachmentItem a, boolean isFirst) {
+		ImageFragment f = new ImageFragment();
+		Bundle args = new Bundle();
+		args.putParcelable(ATTACHMENT_POSITION, a);
+		args.putBoolean(IS_FIRST, isFirst);
+		f.setArguments(args);
+		return f;
+	}
+
+	@Override
+	public void onActivityCreated(@Nullable Bundle savedInstanceState) {
+		super.onActivityCreated(savedInstanceState);
+		BaseActivity a = (BaseActivity) requireNonNull(getActivity());
+		a.getActivityComponent().inject(this);
+	}
+
+	@Override
+	public void onCreate(@Nullable Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+
+		Bundle args = requireNonNull(getArguments());
+		attachment = requireNonNull(args.getParcelable(ATTACHMENT_POSITION));
+		isFirst = args.getBoolean(IS_FIRST);
+	}
+
+	@Nullable
+	@Override
+	public View onCreateView(LayoutInflater inflater,
+			@Nullable ViewGroup container,
+			@Nullable Bundle savedInstanceState) {
+		View v = inflater.inflate(R.layout.fragment_image, container,
+				false);
+
+		viewModel = ViewModelProviders.of(requireNonNull(getActivity()),
+				viewModelFactory).get(ImageViewModel.class);
+
+		photoView = v.findViewById(R.id.photoView);
+		photoView.setOnClickListener(view -> viewModel.clickImage());
+
+		// Request Listener
+		RequestListener<Drawable> listener = new RequestListener<Drawable>() {
+			@Override
+			public boolean onLoadFailed(@Nullable GlideException e,
+					Object model, Target<Drawable> target,
+					boolean isFirstResource) {
+				if (getActivity() != null && isFirst)
+					getActivity().supportStartPostponedEnterTransition();
+				return false;
+			}
+
+			@Override
+			public boolean onResourceReady(Drawable resource, Object model,
+					Target<Drawable> target, DataSource dataSource,
+					boolean isFirstResource) {
+				if (SDK_INT >= 21 && !(resource instanceof Animatable)) {
+					// set transition name only when not animatable,
+					// because the animation won't start otherwise
+					photoView.setTransitionName(
+							attachment.getTransitionName());
+				}
+				// Move image to the top if overlapping toolbar
+				if (viewModel.isOverlappingToolbar(photoView, resource)) {
+					photoView.setScaleType(FIT_START);
+				}
+				if (getActivity() != null && isFirst) {
+					getActivity().supportStartPostponedEnterTransition();
+				}
+				return false;
+			}
+		};
+
+		// Load Image
+		GlideApp.with(this)
+				.load(attachment)
+				.diskCacheStrategy(NONE)
+				.error(R.drawable.ic_image_broken)
+				.dontTransform()
+				.addListener(listener)
+				.into(photoView);
+
+		return v;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageItemDecoration.java

@@ -0,0 +1,54 @@
+package org.briarproject.briar.android.conversation;
+
+import android.content.Context;
+import android.content.res.Resources;
+import android.graphics.Rect;
+import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.RecyclerView.ItemDecoration;
+import android.support.v7.widget.RecyclerView.State;
+import android.view.View;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.util.UiUtils;
+
+import static org.briarproject.briar.android.conversation.ImageAdapter.isBottomRow;
+import static org.briarproject.briar.android.conversation.ImageAdapter.isLeft;
+import static org.briarproject.briar.android.conversation.ImageAdapter.isTopRow;
+import static org.briarproject.briar.android.conversation.ImageAdapter.singleInRow;
+
+@NotNullByDefault
+class ImageItemDecoration extends ItemDecoration {
+
+	private final int border;
+	private final boolean isRtl;
+
+	ImageItemDecoration(Context ctx) {
+		Resources res = ctx.getResources();
+
+		// for pixel perfection, add a pixel to the border if it has an odd size
+		int b = res.getDimensionPixelSize(R.dimen.message_bubble_border);
+		int realBorderSize = b % 2 == 0 ? b : b + 1;
+
+		// we are applying half the border around the insides of each image
+		// to prevent differently sized images looking slightly broken
+		border = realBorderSize / 2;
+
+		// find out if we are showing a RTL language
+		isRtl = UiUtils.isRtl(ctx);
+	}
+
+	@Override
+	public void getItemOffsets(Rect outRect, View view, RecyclerView parent,
+			State state) {
+		if (state.getItemCount() == 1) return;
+		int pos = parent.getChildAdapterPosition(view);
+		int num = state.getItemCount();
+		boolean start = isLeft(pos) ^ isRtl;
+		outRect.top = isTopRow(pos) ? 0 : border;
+		outRect.left = start ? 0 : border;
+		outRect.right = start && !singleInRow(pos, num) ? border : 0;
+		outRect.bottom = isBottomRow(pos, num) ? 0 : border;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewHolder.java

@@ -0,0 +1,74 @@
+package org.briarproject.briar.android.conversation;
+
+import android.graphics.Bitmap;
+import android.support.annotation.DrawableRes;
+import android.support.v7.widget.RecyclerView.ViewHolder;
+import android.support.v7.widget.StaggeredGridLayoutManager.LayoutParams;
+import android.view.View;
+import android.widget.ImageView;
+
+import com.bumptech.glide.load.Transformation;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.briar.R;
+import org.briarproject.briar.android.conversation.glide.BriarImageTransformation;
+import org.briarproject.briar.android.conversation.glide.GlideApp;
+import org.briarproject.briar.android.conversation.glide.Radii;
+
+import static android.os.Build.VERSION.SDK_INT;
+import static com.bumptech.glide.load.engine.DiskCacheStrategy.NONE;
+import static com.bumptech.glide.load.resource.drawable.DrawableTransitionOptions.withCrossFade;
+
+@NotNullByDefault
+class ImageViewHolder extends ViewHolder {
+
+	@DrawableRes
+	private static final int ERROR_RES = R.drawable.ic_image_broken;
+
+	protected final ImageView imageView;
+	private final int imageSize;
+
+	ImageViewHolder(View v, int imageSize) {
+		super(v);
+		imageView = v.findViewById(R.id.imageView);
+		this.imageSize = imageSize;
+	}
+
+	void bind(AttachmentItem attachment, Radii r, boolean single,
+			boolean needsStretch) {
+		if (attachment.hasError()) {
+			GlideApp.with(imageView)
+					.clear(imageView);
+			imageView.setImageResource(ERROR_RES);
+		} else {
+			setImageViewDimensions(attachment, single, needsStretch);
+			loadImage(attachment, r);
+			if (SDK_INT >= 21) {
+				imageView.setTransitionName(attachment.getTransitionName());
+			}
+		}
+	}
+
+	private void setImageViewDimensions(AttachmentItem a, boolean single,
+			boolean needsStretch) {
+		LayoutParams params = (LayoutParams) imageView.getLayoutParams();
+		int width = needsStretch ? imageSize * 2 : imageSize;
+		params.width = single ? a.getThumbnailWidth() : width;
+		params.height = single ? a.getThumbnailHeight() : imageSize;
+		params.setFullSpan(!single && needsStretch);
+		imageView.setLayoutParams(params);
+	}
+
+	private void loadImage(AttachmentItem a, Radii r) {
+		Transformation<Bitmap> transformation = new BriarImageTransformation(r);
+		GlideApp.with(imageView)
+				.load(a)
+				.diskCacheStrategy(NONE)
+				.error(ERROR_RES)
+				.transform(transformation)
+				.transition(withCrossFade())
+				.into(imageView)
+				.waitForLayout();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/ImageViewModel.java

@@ -4,9 +4,11 @@ import android.app.Application;
 import android.arch.lifecycle.AndroidViewModel;
 import android.arch.lifecycle.LiveData;
 import android.arch.lifecycle.MutableLiveData;
+import android.graphics.drawable.Drawable;
 import android.net.Uri;
 import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
+import android.view.View;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
@@ -48,10 +50,13 @@ public class ImageViewModel extends AndroidViewModel {
 	@IoExecutor
 	private final Executor ioExecutor;
 
-	private MutableLiveData<Boolean> saveState = new MutableLiveData<>();
+	private final MutableLiveData<Boolean> imageClicked =
+			new MutableLiveData<>();
+	private final MutableLiveData<Boolean> saveState = new MutableLiveData<>();
+	private int toolbarTop, toolbarBottom;
 
 	@Inject
-	public ImageViewModel(Application application,
+	ImageViewModel(Application application,
 			MessagingManager messagingManager,
 			@DatabaseExecutor Executor dbExecutor,
 			@IoExecutor Executor ioExecutor) {
@@ -61,6 +66,45 @@ public class ImageViewModel extends AndroidViewModel {
 		this.ioExecutor = ioExecutor;
 	}
 
+	void clickImage() {
+		imageClicked.setValue(true);
+	}
+
+	/**
+	 * A LiveData that is true if the image was clicked,
+	 * false if it wasn't.
+	 *
+	 * Call {@link #onOnImageClickSeen()} after consuming an update.
+	 */
+	LiveData<Boolean> getOnImageClicked() {
+		return imageClicked;
+	}
+
+	@UiThread
+	void onOnImageClickSeen() {
+		imageClicked.setValue(false);
+	}
+
+	void setToolbarPosition(int top, int bottom) {
+		toolbarTop = top;
+		toolbarBottom = bottom;
+	}
+
+	boolean isOverlappingToolbar(View screenView, Drawable drawable) {
+		int width = drawable.getIntrinsicWidth();
+		int height = drawable.getIntrinsicHeight();
+		float widthPercentage = screenView.getWidth() / (float) width;
+		float heightPercentage = screenView.getHeight() / (float) height;
+		float scaleFactor = Math.min(widthPercentage, heightPercentage);
+		int realWidth = (int) (width * scaleFactor);
+		int realHeight = (int) (height * scaleFactor);
+		// return if image doesn't use the full width,
+		// because it will be moved to the right otherwise
+		if (realWidth < screenView.getWidth()) return false;
+		int drawableTop = (screenView.getHeight() - realHeight) / 2;
+		return drawableTop < toolbarBottom && drawableTop != toolbarTop;
+	}
+
 	/**
 	 * A LiveData that is true if the image was saved,
 	 * false if there was an error and null otherwise.

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/BriarImageTransformation.java

@@ -7,10 +7,8 @@ import com.bumptech.glide.load.resource.bitmap.CenterCrop;
 
 public class BriarImageTransformation extends MultiTransformation<Bitmap> {
 
-	public BriarImageTransformation(int smallRadius, int radius,
-			boolean leftCornerSmall, boolean bottomRound) {
-		super(new CenterCrop(), new ImageCornerTransformation(
-				smallRadius, radius, leftCornerSmall, bottomRound));
+	public BriarImageTransformation(Radii r) {
+		super(new CenterCrop(), new CustomCornersTransformation(r));
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/CustomCornersTransformation.java

@@ -0,0 +1,128 @@
+package org.briarproject.briar.android.conversation.glide;
+
+import android.graphics.Bitmap;
+import android.graphics.BitmapShader;
+import android.graphics.Canvas;
+import android.graphics.Paint;
+import android.graphics.RectF;
+import android.support.annotation.NonNull;
+
+import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
+import com.bumptech.glide.load.resource.bitmap.BitmapTransformation;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.security.MessageDigest;
+
+import javax.annotation.concurrent.Immutable;
+
+import static android.graphics.Bitmap.Config.ARGB_8888;
+import static android.graphics.Shader.TileMode.CLAMP;
+
+@Immutable
+@NotNullByDefault
+public class CustomCornersTransformation extends BitmapTransformation {
+
+	private static final String ID = CustomCornersTransformation.class.getName();
+
+	private final Radii radii;
+
+	public CustomCornersTransformation(Radii radii) {
+		this.radii = radii;
+	}
+
+	@Override
+	protected Bitmap transform(BitmapPool pool, Bitmap toTransform,
+			int outWidth, int outHeight) {
+		int width = toTransform.getWidth();
+		int height = toTransform.getHeight();
+
+		Bitmap bitmap = pool.get(width, height, ARGB_8888);
+		bitmap.setHasAlpha(true);
+
+		Canvas canvas = new Canvas(bitmap);
+		Paint paint = new Paint();
+		paint.setAntiAlias(true);
+		paint.setShader(new BitmapShader(toTransform, CLAMP, CLAMP));
+		drawRect(canvas, paint, width, height);
+		return bitmap;
+	}
+
+	private void drawRect(Canvas canvas, Paint paint, float width,
+			float height) {
+		drawTopLeft(canvas, paint, radii.topLeft, width, height);
+		drawTopRight(canvas, paint, radii.topRight, width, height);
+		drawBottomLeft(canvas, paint, radii.bottomLeft, width, height);
+		drawBottomRight(canvas, paint, radii.bottomRight, width, height);
+	}
+
+	private void drawTopLeft(Canvas canvas, Paint paint, int radius,
+			float width, float height) {
+		RectF rect = new RectF(
+				0,
+				0,
+				width / 2 + radius + 1,
+				height / 2 + radius + 1
+		);
+		if (radius == 0) canvas.drawRect(rect, paint);
+		else canvas.drawRoundRect(rect, radius, radius, paint);
+	}
+
+	private void drawTopRight(Canvas canvas, Paint paint, int radius,
+			float width, float height) {
+		RectF rect = new RectF(
+				width / 2 - radius,
+				0,
+				width,
+				height / 2 + radius + 1
+		);
+		if (radius == 0) canvas.drawRect(rect, paint);
+		else canvas.drawRoundRect(rect, radius, radius, paint);
+	}
+
+	private void drawBottomLeft(Canvas canvas, Paint paint, int radius,
+			float width, float height) {
+		RectF rect = new RectF(
+				0,
+				height / 2 - radius,
+				width / 2 + radius + 1,
+				height
+		);
+		if (radius == 0) canvas.drawRect(rect, paint);
+		else canvas.drawRoundRect(rect, radius, radius, paint);
+	}
+
+	private void drawBottomRight(Canvas canvas, Paint paint, int radius,
+			float width, float height) {
+		RectF rect = new RectF(
+				width / 2 - radius,
+				height / 2 - radius,
+				width,
+				height
+		);
+		if (radius == 0) canvas.drawRect(rect, paint);
+		else canvas.drawRoundRect(rect, radius, radius, paint);
+	}
+
+	@Override
+	public String toString() {
+		return "ImageCornerTransformation(" + radii + ")";
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof CustomCornersTransformation &&
+				radii.equals(((CustomCornersTransformation) o).radii);
+	}
+
+	@Override
+	public int hashCode() {
+		return ID.hashCode() + radii.hashCode();
+	}
+
+	@Override
+	public void updateDiskCacheKey(@NonNull MessageDigest messageDigest) {
+		messageDigest.update((ID + radii).getBytes(CHARSET));
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/ImageCornerTransformation.java

@@ -1,111 +0,0 @@
-package org.briarproject.briar.android.conversation.glide;
-
-import android.graphics.Bitmap;
-import android.graphics.BitmapShader;
-import android.graphics.Canvas;
-import android.graphics.Paint;
-import android.graphics.RectF;
-import android.support.annotation.NonNull;
-
-import com.bumptech.glide.load.engine.bitmap_recycle.BitmapPool;
-import com.bumptech.glide.load.resource.bitmap.BitmapTransformation;
-
-import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
-
-import java.security.MessageDigest;
-
-import javax.annotation.concurrent.Immutable;
-
-import static android.graphics.Bitmap.Config.ARGB_8888;
-import static android.graphics.Shader.TileMode.CLAMP;
-
-@Immutable
-@NotNullByDefault
-class ImageCornerTransformation extends BitmapTransformation {
-
-	private static final String ID = ImageCornerTransformation.class.getName();
-
-	private final int smallRadius, radius;
-	private final boolean leftCornerSmall, bottomRound;
-
-	ImageCornerTransformation(int smallRadius, int radius,
-			boolean leftCornerSmall, boolean bottomRound) {
-		this.smallRadius = smallRadius;
-		this.radius = radius;
-		this.leftCornerSmall = leftCornerSmall;
-		this.bottomRound = bottomRound;
-	}
-
-	@Override
-	protected Bitmap transform(BitmapPool pool, Bitmap toTransform,
-			int outWidth, int outHeight) {
-		int width = toTransform.getWidth();
-		int height = toTransform.getHeight();
-
-		Bitmap bitmap = pool.get(width, height, ARGB_8888);
-		bitmap.setHasAlpha(true);
-
-		Canvas canvas = new Canvas(bitmap);
-		Paint paint = new Paint();
-		paint.setAntiAlias(true);
-		paint.setShader(new BitmapShader(toTransform, CLAMP, CLAMP));
-		drawRect(canvas, paint, width, height);
-		return bitmap;
-	}
-
-	private void drawRect(Canvas canvas, Paint paint, float width,
-			float height) {
-		drawSmallCorner(canvas, paint, width);
-		drawBigCorners(canvas, paint, width, height);
-	}
-
-	private void drawSmallCorner(Canvas canvas, Paint paint, float width) {
-		float left = leftCornerSmall ? 0 : width - radius;
-		float right = leftCornerSmall ? radius : width;
-		canvas.drawRoundRect(new RectF(left, 0, right, radius),
-				smallRadius, smallRadius, paint);
-	}
-
-	private void drawBigCorners(Canvas canvas, Paint paint, float width,
-			float height) {
-		float top = bottomRound ? 0 : radius;
-		RectF rect = new RectF(0, top, width, height);
-		if (bottomRound) {
-			canvas.drawRoundRect(rect, radius, radius, paint);
-		} else {
-			canvas.drawRect(rect, paint);
-			canvas.drawRoundRect(new RectF(0, 0, width, radius * 2),
-					radius, radius, paint);
-		}
-	}
-
-	@Override
-	public String toString() {
-		return "ImageCornerTransformation(smallRadius=" + smallRadius +
-				", radius=" + radius + ", leftCornerSmall=" + leftCornerSmall +
-				", bottomRound=" + bottomRound + ")";
-	}
-
-	@Override
-	public boolean equals(Object o) {
-		return o instanceof ImageCornerTransformation &&
-				((ImageCornerTransformation) o).smallRadius == smallRadius &&
-				((ImageCornerTransformation) o).radius == radius &&
-				((ImageCornerTransformation) o).leftCornerSmall ==
-						leftCornerSmall &&
-				((ImageCornerTransformation) o).bottomRound == bottomRound;
-	}
-
-	@Override
-	public int hashCode() {
-		return ID.hashCode() + (smallRadius << 16) ^ (radius << 2) ^
-				(leftCornerSmall ? 2 : 0) ^ (bottomRound ? 1 : 0);
-	}
-
-	@Override
-	public void updateDiskCacheKey(@NonNull MessageDigest messageDigest) {
-		messageDigest.update((ID + '|' + smallRadius + '|' + radius + '|' +
-				leftCornerSmall + '|' + bottomRound).getBytes(CHARSET));
-	}
-
-}

briar-android/src/main/java/org/briarproject/briar/android/conversation/glide/Radii.java

@@ -0,0 +1,41 @@
+package org.briarproject.briar.android.conversation.glide;
+
+import android.support.annotation.Nullable;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+@NotNullByDefault
+public class Radii {
+
+	public final int topLeft, topRight, bottomLeft, bottomRight;
+
+	public Radii(int topLeft, int topRight, int bottomLeft, int bottomRight) {
+		this.topLeft = topLeft;
+		this.topRight = topRight;
+		this.bottomLeft = bottomLeft;
+		this.bottomRight = bottomRight;
+	}
+
+	@Override
+	public boolean equals(@Nullable Object o) {
+		return o instanceof Radii &&
+				topLeft == ((Radii) o).topLeft &&
+				topRight == ((Radii) o).topRight &&
+				bottomLeft == ((Radii) o).bottomLeft &&
+				bottomRight == ((Radii) o).bottomRight;
+	}
+
+	@Override
+	public int hashCode() {
+		return topLeft << 24 ^ topRight << 16 ^ bottomLeft << 8 ^ bottomRight;
+	}
+
+	@Override
+	public String toString() {
+		return "Radii(topLeft=" + topLeft +
+				",topRight=" + topRight +
+				",bottomLeft=" + bottomLeft +
+				",bottomRight=" + bottomRight;
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/util/UiUtils.java

@@ -14,9 +14,9 @@ import android.os.PowerManager;
 import android.support.annotation.AttrRes;
 import android.support.annotation.ColorInt;
 import android.support.annotation.ColorRes;
-import android.support.annotation.MainThread;
 import android.support.annotation.Nullable;
 import android.support.annotation.RequiresApi;
+import android.support.annotation.UiThread;
 import android.support.design.widget.TextInputLayout;
 import android.support.v4.app.FragmentManager;
 import android.support.v4.content.ContextCompat;
@@ -56,6 +56,7 @@ import static android.content.Intent.FLAG_ACTIVITY_NEW_TASK;
 import static android.os.Build.MANUFACTURER;
 import static android.os.Build.VERSION.SDK_INT;
 import static android.provider.Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS;
+import static android.support.v4.view.ViewCompat.LAYOUT_DIRECTION_RTL;
 import static android.support.v7.app.AppCompatDelegate.MODE_NIGHT_AUTO;
 import static android.support.v7.app.AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM;
 import static android.support.v7.app.AppCompatDelegate.MODE_NIGHT_NO;
@@ -342,7 +343,7 @@ public class UiUtils {
 	 * If the LiveData's value is available, the {@link Observer} will be
 	 * called right away.
 	 */
-	@MainThread
+	@UiThread
 	public static <T> void observeOnce(LiveData<T> liveData,
 			LifecycleOwner owner, Observer<T> observer) {
 		liveData.observe(owner, new Observer<T>() {
@@ -354,4 +355,28 @@ public class UiUtils {
 		});
 	}
 
+	/**
+	 * Same as {@link #observeOnce(LiveData, LifecycleOwner, Observer)},
+	 * but without a {@link LifecycleOwner}.
+	 *
+	 * Warning: Do NOT call from objects that have a lifecycle.
+	 */
+	@UiThread
+	public static <T> void observeForeverOnce(LiveData<T> liveData,
+			Observer<T> observer) {
+		liveData.observeForever(new Observer<T>() {
+			@Override
+			public void onChanged(@Nullable T t) {
+				observer.onChanged(t);
+				liveData.removeObserver(this);
+			}
+		});
+	}
+
+	public static boolean isRtl(Context ctx) {
+		if (SDK_INT < 17) return false;
+		return ctx.getResources().getConfiguration().getLayoutDirection() ==
+				LAYOUT_DIRECTION_RTL;
+	}
+
 }

briar-android/src/main/res/layout/activity_conversation.xml

@@ -49,7 +49,8 @@
 		android:id="@+id/conversationView"
 		android:layout_width="match_parent"
 		android:layout_height="0dp"
-		android:layout_weight="2"/>
+		android:layout_weight="2"
+		app:scrollToEnd="false"/>
 
 	<org.briarproject.briar.android.view.ImagePreview
 		android:id="@+id/imagePreview"

briar-android/src/main/res/layout/activity_image.xml

@@ -8,12 +8,11 @@
 	android:background="@color/briar_black"
 	tools:context=".android.conversation.ImageActivity">
 
-	<com.github.chrisbanes.photoview.PhotoView
-		android:id="@+id/photoView"
+	<android.support.v4.view.ViewPager
+		android:id="@+id/viewPager"
 		android:layout_width="match_parent"
 		android:layout_height="match_parent"
-		tools:ignore="ContentDescription"
-		tools:srcCompat="@tools:sample/backgrounds/scenic"/>
+		tools:background="@color/briar_green_light"/>
 
 	<android.support.design.widget.AppBarLayout
 		android:id="@+id/appBarLayout"

briar-android/src/main/res/layout/fragment_image.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<com.github.chrisbanes.photoview.PhotoView
+	android:id="@+id/photoView"
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	tools:ignore="ContentDescription"
+	tools:srcCompat="@tools:sample/backgrounds/scenic"/>

briar-android/src/main/res/layout/list_item_conversation_msg_image.xml

@@ -15,15 +15,19 @@
 	android:background="@drawable/msg_in"
 	android:elevation="@dimen/message_bubble_elevation">
 
-	<ImageView
-		android:id="@+id/imageView"
+	<android.support.v7.widget.RecyclerView
+		android:id="@+id/imageList"
 		android:layout_width="@dimen/message_bubble_image_default"
 		android:layout_height="@dimen/message_bubble_image_default"
+		android:orientation="vertical"
+		app:layoutManager="android.support.v7.widget.StaggeredGridLayoutManager"
 		app:layout_constraintBottom_toTopOf="@+id/text"
+		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintStart_toStartOf="parent"
 		app:layout_constraintTop_toTopOf="parent"
+		app:spanCount="2"
 		tools:ignore="ContentDescription"
-		tools:src="@drawable/alerts_and_states_error"/>
+		tools:listitem="@layout/list_item_image"/>
 
 	<com.vanniktech.emoji.EmojiTextView
 		android:id="@+id/text"
@@ -38,10 +42,10 @@
 		android:visibility="gone"
 		app:layout_constrainedWidth="true"
 		app:layout_constraintBottom_toTopOf="@+id/statusLayout"
-		app:layout_constraintEnd_toEndOf="@+id/imageView"
+		app:layout_constraintEnd_toEndOf="@+id/imageList"
 		app:layout_constraintHorizontal_bias="0.0"
 		app:layout_constraintStart_toStartOf="parent"
-		app:layout_constraintTop_toBottomOf="@+id/imageView"
+		app:layout_constraintTop_toBottomOf="@+id/imageList"
 		tools:text="The text of a message which can sometimes be a bit longer as well"/>
 
 	<LinearLayout
@@ -53,7 +57,7 @@
 		android:layout_marginRight="@dimen/message_bubble_padding_sides_inner"
 		android:background="@drawable/msg_status_bubble"
 		android:orientation="horizontal"
-		app:layout_constraintBottom_toBottomOf="@+id/imageView"
+		app:layout_constraintBottom_toBottomOf="@+id/imageList"
 		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintHorizontal_bias="1.0"
 		app:layout_constraintStart_toStartOf="parent">

briar-android/src/main/res/layout/list_item_conversation_msg_image_text.xml

@@ -15,15 +15,19 @@
 	android:background="@drawable/msg_in"
 	android:elevation="@dimen/message_bubble_elevation">
 
-	<ImageView
-		android:id="@+id/imageView"
+	<android.support.v7.widget.RecyclerView
+		android:id="@+id/imageList"
 		android:layout_width="@dimen/message_bubble_image_default"
 		android:layout_height="@dimen/message_bubble_image_default"
+		android:orientation="vertical"
+		app:layoutManager="android.support.v7.widget.StaggeredGridLayoutManager"
 		app:layout_constraintBottom_toTopOf="@+id/text"
+		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintStart_toStartOf="parent"
 		app:layout_constraintTop_toTopOf="parent"
+		app:spanCount="2"
 		tools:ignore="ContentDescription"
-		tools:src="@drawable/alerts_and_states_error"/>
+		tools:listitem="@layout/list_item_image"/>
 
 	<com.vanniktech.emoji.EmojiTextView
 		android:id="@+id/text"
@@ -37,10 +41,10 @@
 		android:textColor="?android:attr/textColorPrimary"
 		app:layout_constrainedWidth="true"
 		app:layout_constraintBottom_toTopOf="@+id/statusLayout"
-		app:layout_constraintEnd_toEndOf="@+id/imageView"
+		app:layout_constraintEnd_toEndOf="@+id/imageList"
 		app:layout_constraintHorizontal_bias="0.0"
 		app:layout_constraintStart_toStartOf="parent"
-		app:layout_constraintTop_toBottomOf="@+id/imageView"
+		app:layout_constraintTop_toBottomOf="@+id/imageList"
 		tools:text="The text of a message which can sometimes be a bit longer as well"/>
 
 	<LinearLayout

briar-android/src/main/res/layout/list_item_conversation_msg_in.xml

@@ -15,15 +15,20 @@
 	android:background="@drawable/msg_in"
 	android:elevation="@dimen/message_bubble_elevation">
 
-	<ImageView
-		android:id="@+id/imageView"
+	<android.support.v7.widget.RecyclerView
+		android:id="@+id/imageList"
 		android:layout_width="@dimen/message_bubble_image_default"
 		android:layout_height="@dimen/message_bubble_image_default"
+		android:orientation="vertical"
 		android:visibility="gone"
+		app:layoutManager="android.support.v7.widget.StaggeredGridLayoutManager"
 		app:layout_constraintBottom_toTopOf="@+id/text"
+		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintStart_toStartOf="parent"
 		app:layout_constraintTop_toTopOf="parent"
-		tools:ignore="ContentDescription"/>
+		app:spanCount="2"
+		tools:ignore="ContentDescription"
+		tools:listitem="@layout/list_item_image"/>
 
 	<com.vanniktech.emoji.EmojiTextView
 		android:id="@+id/text"
@@ -40,7 +45,7 @@
 		app:layout_constraintEnd_toEndOf="parent"
 		app:layout_constraintHorizontal_bias="0.0"
 		app:layout_constraintStart_toStartOf="parent"
-		app:layout_constraintTop_toBottomOf="@+id/imageView"
+		app:layout_constraintTop_toBottomOf="@+id/imageList"
 		tools:text="The text of a message which can sometimes be a bit longer as well"/>
 
 	<LinearLayout

briar-android/src/main/res/layout/list_item_conversation_msg_out.xml

@@ -21,14 +21,18 @@
 		android:background="@drawable/msg_out"
 		android:elevation="@dimen/message_bubble_elevation">
 
-		<ImageView
-			android:id="@+id/imageView"
+		<android.support.v7.widget.RecyclerView
+			android:id="@+id/imageList"
 			android:layout_width="@dimen/message_bubble_image_default"
 			android:layout_height="@dimen/message_bubble_image_default"
+			android:orientation="vertical"
 			android:visibility="gone"
+			app:layoutManager="android.support.v7.widget.StaggeredGridLayoutManager"
 			app:layout_constraintBottom_toTopOf="@+id/text"
+			app:layout_constraintEnd_toEndOf="parent"
 			app:layout_constraintStart_toStartOf="parent"
 			app:layout_constraintTop_toTopOf="parent"
+			app:spanCount="2"
 			tools:ignore="ContentDescription"
 			tools:src="@drawable/alerts_and_states_error"/>
 
@@ -47,7 +51,7 @@
 			app:layout_constraintEnd_toEndOf="parent"
 			app:layout_constraintHorizontal_bias="0.0"
 			app:layout_constraintStart_toStartOf="parent"
-			app:layout_constraintTop_toBottomOf="@+id/imageView"
+			app:layout_constraintTop_toBottomOf="@+id/imageList"
 			tools:text="This is a long long long message that spans over several lines.\n\nIt ends here."/>
 
 		<LinearLayout

briar-android/src/main/res/layout/list_item_image.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<ImageView
+	android:id="@+id/imageView"
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="@dimen/message_bubble_image_default"
+	android:layout_height="@dimen/message_bubble_image_default"
+	android:scaleType="centerCrop"
+	tools:ignore="ContentDescription"
+	tools:srcCompat="@tools:sample/avatars"/>

briar-android/src/main/res/values/dimens.xml

@@ -43,7 +43,7 @@
 	<dimen name="message_bubble_radius_top_inner">@dimen/message_bubble_radius_small</dimen>
 	<dimen name="message_bubble_radius_top_outer">@dimen/message_bubble_radius_big</dimen>
 	<dimen name="message_bubble_margin">6dp</dimen>
-	<dimen name="message_bubble_image_default">210dp</dimen>
+	<dimen name="message_bubble_image_default">115dp</dimen>
 	<dimen name="message_bubble_image_min_width">150dp</dimen>
 	<dimen name="message_bubble_image_max_width">240dp</dimen>
 	<dimen name="message_bubble_image_min_height">100dp</dimen>

briar-api/src/main/java/org/briarproject/briar/api/messaging/MessagingManager.java

@@ -8,7 +8,8 @@ import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.api.conversation.ConversationManager.ConversationClient;
 
-import java.nio.ByteBuffer;
+import java.io.IOException;
+import java.io.InputStream;
 
 @NotNullByDefault
 public interface MessagingManager extends ConversationClient {
@@ -37,7 +38,7 @@ public interface MessagingManager extends ConversationClient {
 	 * Stores a local attachment message.
 	 */
 	AttachmentHeader addLocalAttachment(GroupId groupId, long timestamp,
-			String contentType, ByteBuffer data) throws DbException;
+			String contentType, InputStream is) throws DbException, IOException;
 
 	/**
 	 * Returns the ID of the contact with the given private conversation.

briar-core/src/main/java/org/briarproject/briar/messaging/MessagingManagerImpl.java

@@ -32,9 +32,11 @@ import org.briarproject.briar.api.messaging.PrivateMessageHeader;
 import org.briarproject.briar.api.messaging.event.PrivateMessageReceivedEvent;
 import org.briarproject.briar.client.ConversationClientImpl;
 
-import java.nio.ByteBuffer;
+import java.io.IOException;
+import java.io.InputStream;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.List;
 import java.util.Map;
 import java.util.Random;
 
@@ -42,6 +44,7 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.Collections.emptyList;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.client.MessageTrackerConstants.MSG_KEY_READ;
 
 @Immutable
@@ -152,8 +155,9 @@ class MessagingManagerImpl extends ConversationClientImpl
 
 	@Override
 	public AttachmentHeader addLocalAttachment(GroupId groupId, long timestamp,
-			String contentType, ByteBuffer data) {
+			String contentType, InputStream is) throws IOException {
 		// TODO add real implementation
+		if (is.available() == 0) throw new IOException();
 		byte[] b = new byte[MessageId.LENGTH];
 		new Random().nextBytes(b);
 		return new AttachmentHeader(new MessageId(b), "image/png");
@@ -215,8 +219,18 @@ class MessagingManagerImpl extends ConversationClientImpl
 				long timestamp = meta.getLong("timestamp");
 				boolean local = meta.getBoolean("local");
 				boolean read = meta.getBoolean("read");
+				// TODO replace fake attachments by real ones
+				int num = (int) (timestamp % 5);
+				boolean hasText = num == 0 || id.hashCode() % 2 == 0;
+				List<AttachmentHeader> attachments = new ArrayList<>(num);
+				for (int i = 0; i < num; i++) {
+					byte[] aIdBytes = id.getBytes().clone();
+					aIdBytes[0] = (byte) i;
+					MessageId aId = new MessageId(aIdBytes);
+					attachments.add(new AttachmentHeader(aId, "image/jpeg"));
+				}
 				headers.add(new PrivateMessageHeader(id, g, timestamp, local,
-						read, s.isSent(), s.isSeen(), true, emptyList()));
+						read, s.isSent(), s.isSeen(), hasText, attachments));
 			} catch (FormatException e) {
 				throw new DbException(e);
 			}
@@ -237,7 +251,30 @@ class MessagingManagerImpl extends ConversationClientImpl
 	@Override
 	public Attachment getAttachment(MessageId m) {
 		// TODO add real implementation
-		throw new IllegalStateException("Not yet implemented");
+		String[] files = new String[] {
+//				"error_animated.gif",
+//				"error_high.jpg",
+//				"error_wide.jpg",
+//				"error_huge.gif",
+//				"error_large.gif",
+//				"error_malformed.jpg",
+//				"wide.jpg",
+//				"high.jpg",
+//				"small.png",
+				"kitten1.jpg",
+				"kitten2.jpg",
+				"kitten3.gif",
+				"kitten4.jpg",
+				"kitten5.jpg",
+				"kitten6.png",
+		};
+		int index = Math.abs(m.hashCode() % files.length);
+		String file = files[index];
+		getLogger(MessagingManagerImpl.class.getName())
+				.warning("Loading file: " + file);
+
+		InputStream is = getClass().getClassLoader().getResourceAsStream(file);
+		return new Attachment(is);
 	}
 
 }