[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.

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;
@@ -107,7 +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;
@@ -121,9 +121,9 @@ 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.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.ATTACHMENTS;
 import static org.briarproject.briar.android.conversation.ImageActivity.NAME;
 import static org.briarproject.briar.android.settings.SettingsFragment.SETTINGS_NAMESPACE;
 import static org.briarproject.briar.android.util.UiUtils.getAvatarTransitionName;
@@ -194,6 +194,8 @@ public class ConversationActivity extends BriarActivity
 	ViewModelProvider.Factory viewModelFactory;
 
 	private volatile ContactId contactId;
+	@Nullable
+	private Parcelable layoutManagerState;
 
 	private final Observer<String> contactNameObserver = name -> {
 		requireNonNull(name);
@@ -309,6 +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
@@ -428,8 +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();
@@ -471,7 +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);
 			}
@@ -502,7 +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);
 			}
@@ -553,7 +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);
@@ -820,15 +844,11 @@ public class ConversationActivity extends BriarActivity
 		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/ImageActivity.java

@@ -82,7 +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();
@@ -298,13 +298,18 @@ public class ImageActivity extends BriarActivity
 
 	private class ImagePagerAdapter extends FragmentStatePagerAdapter {
 
+		private boolean isFirst = true;
+
 		private ImagePagerAdapter(FragmentManager fm) {
 			super(fm);
 		}
 
 		@Override
 		public Fragment getItem(int position) {
-			return ImageFragment.newInstance(attachments.get(position));
+			Fragment f = ImageFragment
+					.newInstance(attachments.get(position), isFirst);
+			isFirst = false;
+			return f;
 		}
 
 		@Override

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

@@ -35,17 +35,21 @@ import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHME
 @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) {
+	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;
 	}
@@ -63,6 +67,7 @@ public class ImageFragment extends Fragment {
 
 		Bundle args = requireNonNull(getArguments());
 		attachment = requireNonNull(args.getParcelable(ATTACHMENT_POSITION));
+		isFirst = args.getBoolean(IS_FIRST);
 	}
 
 	@Nullable
@@ -85,7 +90,7 @@ public class ImageFragment extends Fragment {
 			public boolean onLoadFailed(@Nullable GlideException e,
 					Object model, Target<Drawable> target,
 					boolean isFirstResource) {
-				if (getActivity() != null)
+				if (getActivity() != null && isFirst)
 					getActivity().supportStartPostponedEnterTransition();
 				return false;
 			}
@@ -104,8 +109,9 @@ public class ImageFragment extends Fragment {
 				if (viewModel.isOverlappingToolbar(photoView, resource)) {
 					photoView.setScaleType(FIT_START);
 				}
-				if (getActivity() != null)
+				if (getActivity() != null && isFirst) {
 					getActivity().supportStartPostponedEnterTransition();
+				}
 				return false;
 			}
 		};

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

@@ -15,6 +15,7 @@ import org.briarproject.briar.android.conversation.glide.BriarImageTransformatio
 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;
 
@@ -42,6 +43,9 @@ class ImageViewHolder extends ViewHolder {
 		} else {
 			setImageViewDimensions(attachment, single, needsStretch);
 			loadImage(attachment, r);
+			if (SDK_INT >= 21) {
+				imageView.setTransitionName(attachment.getTransitionName());
+			}
 		}
 	}
 

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

@@ -32,11 +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.io.ByteArrayInputStream;
 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;
 
@@ -44,7 +44,7 @@ import javax.annotation.concurrent.Immutable;
 import javax.inject.Inject;
 
 import static java.util.Collections.emptyList;
-import static org.briarproject.bramble.util.StringUtils.fromHexString;
+import static java.util.logging.Logger.getLogger;
 import static org.briarproject.briar.client.MessageTrackerConstants.MSG_KEY_READ;
 
 @Immutable
@@ -219,8 +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);
 			}
@@ -241,11 +251,30 @@ class MessagingManagerImpl extends ConversationClientImpl
 	@Override
 	public Attachment getAttachment(MessageId m) {
 		// TODO add real implementation
-		byte[] bytes = fromHexString("89504E470D0A1A0A0000000D49484452" +
-				"000000010000000108060000001F15C4" +
-				"890000000A49444154789C6300010000" +
-				"0500010D0A2DB40000000049454E44AE426082");
-		return new Attachment(new ByteArrayInputStream(bytes));
+		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);
 	}
 
 }