[android] Create attachments before showing previews

briar-android/src/main/java/org/briarproject/briar/android/blog/ReblogFragment.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.blog;
 
-import android.net.Uri;
 import android.os.Bundle;
 import android.view.LayoutInflater;
 import android.view.View;
@@ -21,6 +20,7 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 
@@ -121,7 +121,8 @@ public class ReblogFragment extends BaseFragment implements SendListener {
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		ui.input.hideSoftKeyboard();
 		feedController.repeatPost(item, text,
 				new UiExceptionHandler<DbException>(this) {

briar-android/src/main/java/org/briarproject/briar/android/blog/WriteBlogPostActivity.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.blog;
 
 import android.content.Intent;
-import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.view.KeyEvent;
@@ -27,6 +26,7 @@ import org.briarproject.briar.api.android.AndroidNotificationManager;
 import org.briarproject.briar.api.blog.BlogManager;
 import org.briarproject.briar.api.blog.BlogPost;
 import org.briarproject.briar.api.blog.BlogPostFactory;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.security.GeneralSecurityException;
 import java.util.List;
@@ -120,7 +120,8 @@ public class WriteBlogPostActivity extends BriarActivity
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		if (isNullOrEmpty(text)) throw new AssertionError();
 
 		// hide publish button, show progress bar

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

@@ -1,8 +1,11 @@
 package org.briarproject.briar.android.conversation;
 
+import android.content.ContentResolver;
 import android.graphics.BitmapFactory;
 import android.graphics.BitmapFactory.Options;
+import android.net.Uri;
 import android.support.annotation.Nullable;
+import android.support.annotation.VisibleForTesting;
 import android.support.media.ExifInterface;
 import android.webkit.MimeTypeMap;
 
@@ -12,6 +15,7 @@ import org.briarproject.bramble.api.Pair;
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.GroupId;
 import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.android.conversation.ImageHelper.DecodeResult;
 import org.briarproject.briar.api.messaging.Attachment;
@@ -25,6 +29,7 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.logging.Logger;
 
 import static android.support.media.ExifInterface.ORIENTATION_ROTATE_270;
@@ -54,6 +59,7 @@ class AttachmentController {
 	private final int minWidth, maxWidth;
 	private final int minHeight, maxHeight;
 
+	private final List<AttachmentHeader> unsent = new CopyOnWriteArrayList<>();
 	private final Map<MessageId, List<AttachmentItem>> attachmentCache =
 			new ConcurrentHashMap<>();
 
@@ -114,6 +120,54 @@ class AttachmentController {
 		return attachments;
 	}
 
+	@DatabaseExecutor
+	AttachmentHeader createAttachmentHeader(ContentResolver contentResolver,
+			GroupId groupId, Uri uri)
+			throws IOException, DbException {
+		InputStream is = contentResolver.openInputStream(uri);
+		if (is == null) throw new IOException();
+		String contentType = contentResolver.getType(uri);
+		if (contentType == null) throw new IOException("null content type");
+		long timestamp = System.currentTimeMillis();
+		AttachmentHeader h = messagingManager
+				.addLocalAttachment(groupId, timestamp, contentType, is);
+		tryToClose(is, LOG, WARNING);
+		unsent.add(h);
+		return h;
+	}
+
+	@DatabaseExecutor
+	void deleteUnsentAttachments() {
+		for (AttachmentHeader h : unsent) {
+			try {
+				messagingManager.removeAttachment(h);
+			} catch (DbException e) {
+				logException(LOG, WARNING, e);
+			}
+		}
+	}
+
+	List<AttachmentHeader> getUnsentAttachments() {
+		return new ArrayList<>(unsent);
+	}
+
+	void markAttachmentsSent() {
+		unsent.clear();
+	}
+
+	@DatabaseExecutor
+	AttachmentItem getAttachmentItem(ContentResolver contentResolver, Uri uri,
+			AttachmentHeader h, boolean needsSize) throws IOException {
+		InputStream is = null;
+		try {
+			is = contentResolver.openInputStream(uri);
+			if (is == null) throw new IOException();
+			return getAttachmentItem(h, new Attachment(is), needsSize);
+		} finally {
+			if (is != null) tryToClose(is, LOG, WARNING);
+		}
+	}
+
 	/**
 	 * Creates {@link AttachmentItem}s from the passed headers and Attachments.
 	 * <p>
@@ -135,6 +189,7 @@ class AttachmentController {
 	 * Creates an {@link AttachmentItem} from the {@link Attachment}'s
 	 * {@link InputStream} which will be closed when this method returns.
 	 */
+	@VisibleForTesting
 	AttachmentItem getAttachmentItem(AttachmentHeader h, Attachment a,
 			boolean needsSize) {
 		MessageId messageId = h.getMessageId();

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

@@ -6,7 +6,6 @@ import android.arch.lifecycle.ViewModelProvider;
 import android.arch.lifecycle.ViewModelProviders;
 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;
@@ -264,7 +263,7 @@ public class ConversationActivity extends BriarActivity
 		if (FEATURE_FLAG_IMAGE_ATTACHMENTS) {
 			ImagePreview imagePreview = findViewById(R.id.imagePreview);
 			sendController = new TextAttachmentController(textInputView,
-					imagePreview, this, this);
+					imagePreview, this, this, viewModel);
 			observeOnce(viewModel.hasImageSupport(), this, hasSupport -> {
 				if (hasSupport != null && hasSupport) {
 					// remove cast when removing FEATURE_FLAG_IMAGE_ATTACHMENTS
@@ -658,12 +657,13 @@ public class ConversationActivity extends BriarActivity
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
-		if (isNullOrEmpty(text) && imageUris.isEmpty())
+			List<AttachmentHeader> attachmentHeaders) {
+		if (isNullOrEmpty(text) && attachmentHeaders.isEmpty())
 			throw new AssertionError();
 		long timestamp = System.currentTimeMillis();
 		timestamp = Math.max(timestamp, getMinTimestampForNewMessage());
-		viewModel.sendMessage(text, imageUris, timestamp);
+		viewModel.sendMessage(text, attachmentHeaders, timestamp);
 		textInputView.clearText();
 	}
 

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

@@ -11,7 +11,6 @@ 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;
@@ -27,10 +26,11 @@ 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.system.AndroidExecutor;
 import org.briarproject.briar.android.util.UiUtils;
+import org.briarproject.briar.android.view.TextAttachmentController.AttachmentManager;
 import org.briarproject.briar.android.viewmodel.LiveEvent;
 import org.briarproject.briar.android.viewmodel.MutableLiveEvent;
-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;
@@ -38,10 +38,11 @@ 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.Collection;
+import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.Executor;
 import java.util.logging.Logger;
 
@@ -50,7 +51,6 @@ 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;
@@ -59,7 +59,8 @@ import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_
 import static org.briarproject.briar.android.util.UiUtils.observeForeverOnce;
 
 @NotNullByDefault
-public class ConversationViewModel extends AndroidViewModel {
+public class ConversationViewModel extends AndroidViewModel implements
+		AttachmentManager {
 
 	private static Logger LOG =
 			getLogger(ConversationViewModel.class.getName());
@@ -73,6 +74,7 @@ public class ConversationViewModel extends AndroidViewModel {
 	@CryptoExecutor
 	private final Executor cryptoExecutor;
 	private final TransactionManager db;
+	private final AndroidExecutor androidExecutor;
 	private final MessagingManager messagingManager;
 	private final ContactManager contactManager;
 	private final SettingsManager settingsManager;
@@ -100,17 +102,20 @@ public class ConversationViewModel extends AndroidViewModel {
 			new MutableLiveData<>();
 	private final MutableLiveData<PrivateMessageHeader> addedHeader =
 			new MutableLiveData<>();
+	// TODO move to AttachmentController
+	private final Map<Uri, AttachmentItem> unsentItems = new HashMap<>();
 
 	@Inject
 	ConversationViewModel(Application application,
 			@DatabaseExecutor Executor dbExecutor,
 			@CryptoExecutor Executor cryptoExecutor, TransactionManager db,
-			MessagingManager messagingManager, ContactManager contactManager,
+			AndroidExecutor androidExecutor, MessagingManager messagingManager,
-			SettingsManager settingsManager,
+			ContactManager contactManager, SettingsManager settingsManager,
 			PrivateMessageFactory privateMessageFactory) {
 		super(application);
 		this.dbExecutor = dbExecutor;
 		this.cryptoExecutor = cryptoExecutor;
+		this.androidExecutor = androidExecutor;
 		this.db = db;
 		this.messagingManager = messagingManager;
 		this.contactManager = contactManager;
@@ -121,6 +126,12 @@ public class ConversationViewModel extends AndroidViewModel {
 		contactDeleted.setValue(false);
 	}
 
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		attachmentController.deleteUnsentAttachments();
+	}
+
 	/**
 	 * Setting the {@link ContactId} automatically triggers loading of other
 	 * data.
@@ -176,15 +187,56 @@ public class ConversationViewModel extends AndroidViewModel {
 		});
 	}
 
-	void sendMessage(@Nullable String text, List<Uri> uris, long timestamp) {
+	void sendMessage(@Nullable String text,
+			List<AttachmentHeader> attachmentHeaders, long timestamp) {
 		if (messagingGroupId.getValue() == null) loadGroupId();
 		observeForeverOnce(messagingGroupId, groupId -> {
 			if (groupId == null) return;
-			// calls through to creating and storing the message
+			createMessage(groupId, text, attachmentHeaders, timestamp);
-			storeAttachments(groupId, text, uris, timestamp);
 		});
 	}
 
+	@Override
+	public void storeAttachment(Uri uri, boolean needsSize, Runnable onSuccess,
+			Runnable onError) {
+		if (unsentItems.containsKey(uri)) {
+			// This can happen due to configuration (screen orientation) change.
+			// So don't create a new attachment, if we have one already.
+			androidExecutor.runOnUiThread(onSuccess);
+			return;
+		}
+		if (messagingGroupId.getValue() == null) loadGroupId();
+		observeForeverOnce(messagingGroupId, groupId -> dbExecutor.execute(()
+				-> {
+			if (groupId == null) throw new IllegalStateException();
+			long start = now();
+			try {
+				ContentResolver contentResolver =
+						getApplication().getContentResolver();
+				AttachmentHeader h = attachmentController
+						.createAttachmentHeader(contentResolver, groupId, uri);
+				unsentItems.put(uri, attachmentController
+						.getAttachmentItem(contentResolver, uri, h, needsSize));
+				androidExecutor.runOnUiThread(onSuccess);
+			} catch (DbException | IOException e) {
+				logException(LOG, WARNING, e);
+				androidExecutor.runOnUiThread(onError);
+			}
+			logDuration(LOG, "Storing attachment", start);
+		}));
+	}
+
+	@Override
+	public List<AttachmentHeader> getAttachments() {
+		return attachmentController.getUnsentAttachments();
+	}
+
+	@Override
+	public void removeAttachments() {
+		unsentItems.clear();
+		dbExecutor.execute(attachmentController::deleteUnsentAttachments);
+	}
+
 	private void loadGroupId() {
 		if (contactId == null) throw new IllegalStateException();
 		dbExecutor.execute(() -> {
@@ -252,58 +304,8 @@ public class ConversationViewModel extends AndroidViewModel {
 		});
 	}
 
-	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,
+			List<AttachmentHeader> attachments, long timestamp) {
-			long timestamp) {
 		cryptoExecutor.execute(() -> {
 			try {
 				// TODO remove when text can be null in the backend
@@ -311,7 +313,6 @@ public class ConversationViewModel extends AndroidViewModel {
 				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);
@@ -331,6 +332,10 @@ public class ConversationViewModel extends AndroidViewModel {
 						message.getId(), message.getGroupId(),
 						message.getTimestamp(), true, true, false, false,
 						text != null, attachments);
+				attachmentController.put(m.getMessage().getId(),
+						new ArrayList<>(unsentItems.values()));
+				unsentItems.clear();
+				attachmentController.markAttachmentsSent();
 				// TODO add text to cache when available here
 				addedHeader.postValue(h);
 			} catch (DbException e) {

briar-android/src/main/java/org/briarproject/briar/android/introduction/IntroductionMessageFragment.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.introduction;
 
 import android.content.Context;
-import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.v7.app.ActionBar;
@@ -26,6 +25,7 @@ import org.briarproject.briar.android.view.TextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
 import org.briarproject.briar.api.introduction.IntroductionManager;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 import java.util.logging.Logger;
@@ -193,7 +193,8 @@ public class IntroductionMessageFragment extends BaseFragment
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		// disable button to prevent accidental double invitations
 		ui.message.setReady(false);
 

briar-android/src/main/java/org/briarproject/briar/android/sharing/BaseMessageFragment.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.sharing;
 
 import android.content.Context;
-import android.net.Uri;
 import android.os.Bundle;
 import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
@@ -19,6 +18,7 @@ import org.briarproject.briar.android.fragment.BaseFragment;
 import org.briarproject.briar.android.view.LargeTextInputView;
 import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 
@@ -83,7 +83,8 @@ public abstract class BaseMessageFragment extends BaseFragment
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		// disable button to prevent accidental double actions
 		sendController.setReady(false);
 		message.hideSoftKeyboard();

briar-android/src/main/java/org/briarproject/briar/android/threaded/ThreadListActivity.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.threaded;
 
 import android.content.Intent;
-import android.net.Uri;
 import android.os.Bundle;
 import android.os.Parcelable;
 import android.support.annotation.CallSuper;
@@ -34,6 +33,7 @@ import org.briarproject.briar.android.view.TextSendController;
 import org.briarproject.briar.android.view.TextSendController.SendListener;
 import org.briarproject.briar.android.view.UnreadMessageButton;
 import org.briarproject.briar.api.client.NamedGroup;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.Collection;
 import java.util.List;
@@ -341,7 +341,8 @@ public abstract class ThreadListActivity<G extends NamedGroup, I extends ThreadI
 	}
 
 	@Override
-	public void onSendClick(@Nullable String text, List<Uri> imageUris) {
+	public void onSendClick(@Nullable String text,
+			List<AttachmentHeader> headers) {
 		if (isNullOrEmpty(text)) throw new AssertionError();
 
 		I replyItem = adapter.getHighlightedItem();

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreview.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.view;
 
 import android.content.Context;
-import android.net.Uri;
 import android.support.annotation.Nullable;
 import android.support.constraint.ConstraintLayout;
 import android.support.v7.widget.RecyclerView;
@@ -60,21 +59,22 @@ public class ImagePreview extends ConstraintLayout {
 		this.listener = listener;
 	}
 
-	void showPreview(Collection<Uri> imageUris) {
+	void showPreview(Collection<ImagePreviewItem> items) {
 		if (listener == null) throw new IllegalStateException();
-		if (imageUris.size() == 1) {
+		if (items.size() == 1) {
 			LayoutParams params = (LayoutParams) imageList.getLayoutParams();
 			params.width = MATCH_PARENT;
 			imageList.setLayoutParams(params);
 		}
 		setVisibility(VISIBLE);
-		imageList.setAdapter(new ImagePreviewAdapter(imageUris, listener));
+		ImagePreviewAdapter adapter = new ImagePreviewAdapter(items, listener);
+		imageList.setAdapter(adapter);
 	}
 
-	void removeUri(Uri uri) {
+	void loadPreviewImage(ImagePreviewItem item) {
 		ImagePreviewAdapter adapter =
-				(ImagePreviewAdapter) imageList.getAdapter();
+				((ImagePreviewAdapter) imageList.getAdapter());
-		requireNonNull(adapter).removeUri(uri);
+		requireNonNull(adapter).loadItemPreview(item);
 	}
 
 	interface ImagePreviewListener {
@@ -86,7 +86,7 @@ public class ImagePreview extends ConstraintLayout {
 		 *
 		 * Warning: Glide may call this multiple times.
 		 */
-		void onUriError(Uri uri);
+		void onError();
 
 		void onCancel();
 	}

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreviewAdapter.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.view;
 
-import android.net.Uri;
 import android.support.annotation.LayoutRes;
 import android.support.v7.widget.RecyclerView.Adapter;
 import android.view.LayoutInflater;
@@ -15,17 +14,19 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
+import static android.support.v7.widget.RecyclerView.NO_POSITION;
 import static java.util.Objects.requireNonNull;
 
 @NotNullByDefault
 class ImagePreviewAdapter extends Adapter<ImagePreviewViewHolder> {
 
-	private final List<Uri> items;
+	private final List<ImagePreviewItem> items;
 	private final ImagePreviewListener listener;
 	@LayoutRes
 	private final int layout;
 
-	ImagePreviewAdapter(Collection<Uri> items, ImagePreviewListener listener) {
+	ImagePreviewAdapter(Collection<ImagePreviewItem> items,
+			ImagePreviewListener listener) {
 		this.items = new ArrayList<>(items);
 		this.listener = listener;
 		this.layout = items.size() == 1 ?
@@ -52,11 +53,12 @@ class ImagePreviewAdapter extends Adapter<ImagePreviewViewHolder> {
 		return items.size();
 	}
 
-	void removeUri(Uri uri) {
+	void loadItemPreview(ImagePreviewItem item) {
-		int pos = items.indexOf(uri);
+		int pos = items.indexOf(item);
-		if (pos == -1) return;
+		if (pos == NO_POSITION) throw new AssertionError();
-		items.remove(uri);
+		ImagePreviewItem newItem = items.get(pos);
-		notifyItemRemoved(pos);
+		newItem.setWaitForLoading(false);
+		notifyItemChanged(pos, newItem);
 	}
 
 }

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreviewItem.java

@@ -0,0 +1,53 @@
+package org.briarproject.briar.android.view;
+
+import android.net.Uri;
+import android.support.annotation.Nullable;
+
+import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+
+@NotNullByDefault
+class ImagePreviewItem {
+
+	private final Uri uri;
+	private boolean waitForLoading = true;
+
+	private ImagePreviewItem(Uri uri) {
+		this.uri = uri;
+	}
+
+	Uri getUri() {
+		return uri;
+	}
+
+	void setWaitForLoading(boolean waitForLoading) {
+		this.waitForLoading = waitForLoading;
+	}
+
+	boolean waitForLoading() {
+		return waitForLoading;
+	}
+
+	static List<ImagePreviewItem> fromUris(Collection<Uri> uris) {
+		List<ImagePreviewItem> items = new ArrayList<>(uris.size());
+		for (Uri uri : uris) {
+			items.add(new ImagePreviewItem(uri));
+		}
+		return items;
+	}
+
+	@Override
+	public boolean equals(@Nullable Object o) {
+		return o instanceof ImagePreviewItem &&
+				uri.equals(((ImagePreviewItem) o).uri);
+	}
+
+	@Override
+	public int hashCode() {
+		return uri.hashCode();
+	}
+
+}

briar-android/src/main/java/org/briarproject/briar/android/view/ImagePreviewViewHolder.java

@@ -1,7 +1,6 @@
 package org.briarproject.briar.android.view;
 
 import android.graphics.drawable.Drawable;
-import android.net.Uri;
 import android.support.annotation.DrawableRes;
 import android.support.annotation.Nullable;
 import android.support.v7.widget.RecyclerView.ViewHolder;
@@ -42,9 +41,10 @@ class ImagePreviewViewHolder extends ViewHolder {
 		this.progressBar = v.findViewById(R.id.progressBar);
 	}
 
-	void bind(Uri uri) {
+	void bind(ImagePreviewItem item) {
+		if (item.waitForLoading()) return;
 		GlideApp.with(imageView)
-				.load(uri)
+				.load(item.getUri())
 				.diskCacheStrategy(NONE)
 				.error(ERROR_RES)
 				.downsample(FIT_CENTER)
@@ -55,7 +55,7 @@ class ImagePreviewViewHolder extends ViewHolder {
 							Object model, Target<Drawable> target,
 							boolean isFirstResource) {
 						progressBar.setVisibility(INVISIBLE);
-						listener.onUriError(uri);
+						listener.onError();
 						return false;
 					}
 

briar-android/src/main/java/org/briarproject/briar/android/view/TextAttachmentController.java

@@ -16,6 +16,7 @@ import android.widget.Toast;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.view.ImagePreview.ImagePreviewListener;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.ArrayList;
 import java.util.List;
@@ -46,6 +47,7 @@ public class TextAttachmentController extends TextSendController
 	private final ImagePreview imagePreview;
 	private final AttachImageListener imageListener;
 	private final CompositeSendButton sendButton;
+	private final AttachmentManager attachmentManager;
 
 	private CharSequence textHint;
 	private List<Uri> imageUris = emptyList();
@@ -53,10 +55,12 @@ public class TextAttachmentController extends TextSendController
 	private boolean loadingPreviews = false;
 
 	public TextAttachmentController(TextInputView v, ImagePreview imagePreview,
-			SendListener listener, AttachImageListener imageListener) {
+			SendListener listener, AttachImageListener imageListener,
+			AttachmentManager attachmentManager) {
 		super(v, listener, false);
 		this.imageListener = imageListener;
 		this.imagePreview = imagePreview;
+		this.attachmentManager = attachmentManager;
 		this.imagePreview.setImagePreviewListener(this);
 
 		sendButton = (CompositeSendButton) compositeSendButton;
@@ -84,7 +88,8 @@ public class TextAttachmentController extends TextSendController
 	@Override
 	public void onSendEvent() {
 		if (canSend()) {
-			listener.onSendClick(textInput.getText(), imageUris);
+			listener.onSendClick(textInput.getText(),
+					attachmentManager.getAttachments());
 			reset();
 		}
 	}
@@ -139,7 +144,15 @@ public class TextAttachmentController extends TextSendController
 		loadingPreviews = true;
 		updateViewState();
 		textInput.setHint(R.string.image_caption_hint);
-		imagePreview.showPreview(imageUris);
+		List<ImagePreviewItem> items = ImagePreviewItem.fromUris(imageUris);
+		imagePreview.showPreview(items);
+		// store attachments and show preview when successful
+		boolean needsSize = items.size() == 1;
+		for (ImagePreviewItem item : items) {
+			attachmentManager.storeAttachment(item.getUri(), needsSize,
+					() -> imagePreview.loadPreviewImage(item),
+					this::onError);
+		}
 	}
 
 	private void reset() {
@@ -180,22 +193,16 @@ public class TextAttachmentController extends TextSendController
 	}
 
 	@Override
-	public void onUriError(Uri uri) {
+	public void onError() {
-		boolean removed = imageUris.remove(uri);
-		if (!removed) {
-			// we have removed this Uri already, do not remove it again
-			return;
-		}
-		imagePreview.removeUri(uri);
-		if (imageUris.isEmpty()) onCancel();
 		Toast.makeText(textInput.getContext(), R.string.image_attach_error,
 				LENGTH_LONG).show();
-		checkAllPreviewsLoaded();
+		onCancel();
 	}
 
 	@Override
 	public void onCancel() {
 		textInput.clearText();
+		attachmentManager.removeAttachments();
 		reset();
 	}
 
@@ -265,4 +272,20 @@ public class TextAttachmentController extends TextSendController
 		void onAttachImage(Intent intent);
 	}
 
+	public interface AttachmentManager {
+		/**
+		 * Stores a new attachment in the database.
+		 *
+		 * @param uri The Uri of the attachment to store.
+		 * @param onSuccess will be run on the UiThread when the attachment was stored successfully.
+		 * @param onError will be run on the UiThread when the attachment could not be stored.
+		 */
+		void storeAttachment(Uri uri, boolean needsSize, Runnable onSuccess,
+				Runnable onError);
+
+		List<AttachmentHeader> getAttachments();
+
+		void removeAttachments();
+	}
+
 }

briar-android/src/main/java/org/briarproject/briar/android/view/TextSendController.java

@@ -1,6 +1,5 @@
 package org.briarproject.briar.android.view;
 
-import android.net.Uri;
 import android.os.Parcelable;
 import android.support.annotation.Nullable;
 import android.support.annotation.UiThread;
@@ -10,6 +9,7 @@ import android.view.View;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
 import org.briarproject.briar.R;
 import org.briarproject.briar.android.view.EmojiTextInputView.TextInputListener;
+import org.briarproject.briar.api.messaging.AttachmentHeader;
 
 import java.util.List;
 
@@ -85,7 +85,7 @@ public class TextSendController implements TextInputListener {
 	}
 
 	public interface SendListener {
-		void onSendClick(@Nullable String text, List<Uri> imageUris);
+		void onSendClick(@Nullable String text, List<AttachmentHeader> headers);
 	}
 
 }

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

@@ -129,7 +129,7 @@
 	<string name="message_hint">Type message</string>
 	<string name="image_caption_hint">Add a caption (optional)</string>
 	<string name="image_attach">Attach image</string>
-	<string name="image_attach_error">Could not attach image</string>
+	<string name="image_attach_error">Could not attach image(s)</string>
 	<string name="set_contact_alias">Change contact name</string>
 	<string name="set_contact_alias_hint">Contact name</string>
 	<string name="set_alias_button">Change</string>

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

@@ -25,4 +25,15 @@ public class AttachmentHeader {
 		return contentType;
 	}
 
+	@Override
+	public boolean equals(Object o) {
+		return o instanceof AttachmentHeader &&
+				messageId.equals(((AttachmentHeader) o).messageId);
+	}
+
+	@Override
+	public int hashCode() {
+		return messageId.hashCode();
+	}
+
 }

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

@@ -8,4 +8,19 @@ public interface MessagingConstants {
 	 * The maximum length of a private message's text in UTF-8 bytes.
 	 */
 	int MAX_PRIVATE_MESSAGE_TEXT_LENGTH = MAX_MESSAGE_BODY_LENGTH - 1024;
+
+	/**
+	 * The supported mime types for image attachments.
+	 */
+	String[] IMAGE_MIME_TYPES = {
+			"image/jpeg",
+			"image/png",
+			"image/gif",
+	};
+
+	/**
+	 * The maximum allowed size of image attachments.
+	 */
+	int MAX_IMAGE_SIZE = 6 * 1024 * 1024;
+
 }

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

@@ -41,6 +41,11 @@ public interface MessagingManager extends ConversationClient {
 	AttachmentHeader addLocalAttachment(GroupId groupId, long timestamp,
 			String contentType, InputStream is) throws DbException, IOException;
 
+	/**
+	 * Removes an unsent attachment.
+	 */
+	void removeAttachment(AttachmentHeader header) throws DbException;
+
 	/**
 	 * Returns the ID of the contact with the given private conversation.
 	 */

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

@@ -166,6 +166,11 @@ class MessagingManagerImpl extends ConversationClientImpl
 		return new AttachmentHeader(new MessageId(b), "image/png");
 	}
 
+	@Override
+	public void removeAttachment(AttachmentHeader header) throws DbException {
+		// TODO add real implementation
+	}
+
 	private ContactId getContactId(Transaction txn, GroupId g)
 			throws DbException {
 		try {