Show placeholders for missing attachments in ImageActivity

and display attachments as they arrive while ImageActivity is open.

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

@@ -24,6 +24,7 @@ import org.briarproject.briar.android.conversation.glide.GlideApp;
 import javax.annotation.ParametersAreNonnullByDefault;
 import javax.inject.Inject;
 
+import androidx.annotation.DrawableRes;
 import androidx.annotation.Nullable;
 import androidx.fragment.app.Fragment;
 import androidx.lifecycle.ViewModelProvider;
@@ -33,14 +34,19 @@ 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.attachment.AttachmentItem.State.AVAILABLE;
+import static org.briarproject.briar.android.attachment.AttachmentItem.State.ERROR;
 import static org.briarproject.briar.android.conversation.ImageActivity.ATTACHMENT_POSITION;
 import static org.briarproject.briar.android.conversation.ImageActivity.ITEM_ID;
 
 @MethodsNotNullByDefault
 @ParametersAreNonnullByDefault
-public class ImageFragment extends Fragment {
+public class ImageFragment extends Fragment
+		implements RequestListener<Drawable> {
 
 	private final static String IS_FIRST = "isFirst";
+	@DrawableRes
+	private static final int ERROR_RES = R.drawable.ic_image_broken;
 
 	@Inject
 	ViewModelProvider.Factory viewModelFactory;
@@ -89,55 +95,72 @@ public class ImageFragment extends Fragment {
 
 		viewModel = ViewModelProviders.of(requireNonNull(getActivity()),
 				viewModelFactory).get(ImageViewModel.class);
+		viewModel.getOnAttachmentLoaded()
+				.observeEvent(this, this::onAttachmentLoaded);
 
 		photoView = v.findViewById(R.id.photoView);
 		photoView.setScaleLevels(1, 2, 4);
 		photoView.setOnClickListener(view -> viewModel.clickImage());
 
-		// Request Listener
+		if (attachment.getState() == AVAILABLE) {
-		RequestListener<Drawable> listener = new RequestListener<Drawable>() {
+			loadImage();
-
+			// postponed transition will be started when Image was loaded
-			@Override
+		} else if (attachment.getState() == ERROR) {
-			public boolean onLoadFailed(@Nullable GlideException e,
+			photoView.setImageResource(ERROR_RES);
-					Object model, Target<Drawable> target,
+			startPostponedTransition();
-					boolean isFirstResource) {
+		} else {
-				if (getActivity() != null && isFirst)
+			photoView.setImageResource(R.drawable.ic_image_missing);
-					getActivity().supportStartPostponedEnterTransition();
+			startPostponedTransition();
-				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(conversationItemId));
-				}
-				// 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)
-				// TODO allow if size < maxTextureSize ?
-//				.override(SIZE_ORIGINAL)
-				.diskCacheStrategy(NONE)
-				.error(R.drawable.ic_image_broken)
-				.addListener(listener)
-				.into(photoView);
 
 		return v;
 	}
 
+	private void loadImage() {
+		GlideApp.with(this)
+				.load(attachment)
+				// TODO allow if size < maxTextureSize ?
+//					.override(SIZE_ORIGINAL)
+				.diskCacheStrategy(NONE)
+				.error(ERROR_RES)
+				.addListener(this)
+				.into(photoView);
+	}
+
+	private void onAttachmentLoaded(MessageId messageId) {
+		if (attachment.getMessageId().equals(messageId)) loadImage();
+	}
+
+	@Override
+	public boolean onLoadFailed(@Nullable GlideException e,
+			Object model, Target<Drawable> target,
+			boolean isFirstResource) {
+		startPostponedTransition();
+		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(conversationItemId));
+		}
+		// Move image to the top if overlapping toolbar
+		if (viewModel.isOverlappingToolbar(photoView, resource)) {
+			photoView.setScaleType(FIT_START);
+		}
+		startPostponedTransition();
+		return false;
+	}
+
+	private void startPostponedTransition() {
+		if (getActivity() != null && isFirst) {
+			getActivity().supportStartPostponedEnterTransition();
+		}
+	}
+
 }

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

@@ -56,12 +56,12 @@ class ImageViewHolder extends ViewHolder {
 			imageView.setScaleType(FIT_CENTER);
 		} else {
 			loadImage(attachment, r);
-			if (SDK_INT >= 21) {
-				imageView.setTransitionName(
-						attachment.getTransitionName(conversationItemId));
-			}
 			imageView.setScaleType(CENTER_CROP);
 		}
+		if (SDK_INT >= 21) {
+			imageView.setTransitionName(
+					attachment.getTransitionName(conversationItemId));
+		}
 	}
 
 	private void setImageViewDimensions(AttachmentItem a, boolean single,

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

@@ -7,13 +7,18 @@ import android.view.View;
 
 import org.briarproject.bramble.api.db.DatabaseExecutor;
 import org.briarproject.bramble.api.db.DbException;
+import org.briarproject.bramble.api.event.Event;
+import org.briarproject.bramble.api.event.EventBus;
+import org.briarproject.bramble.api.event.EventListener;
 import org.briarproject.bramble.api.lifecycle.IoExecutor;
 import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
+import org.briarproject.bramble.api.sync.MessageId;
 import org.briarproject.briar.android.attachment.AttachmentItem;
 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.MessagingManager;
+import org.briarproject.briar.api.messaging.event.AttachmentReceivedEvent;
 
 import java.io.File;
 import java.io.FileOutputStream;
@@ -41,16 +46,19 @@ import static org.briarproject.bramble.util.IoUtils.copyAndClose;
 import static org.briarproject.bramble.util.LogUtils.logException;
 
 @NotNullByDefault
-public class ImageViewModel extends AndroidViewModel {
+public class ImageViewModel extends AndroidViewModel implements EventListener {
 
 	private static Logger LOG = getLogger(ImageViewModel.class.getName());
 
 	private final MessagingManager messagingManager;
+	private final EventBus eventBus;
 	@DatabaseExecutor
 	private final Executor dbExecutor;
 	@IoExecutor
 	private final Executor ioExecutor;
 
+	private final MutableLiveEvent<MessageId> attachmentLoaded =
+			new MutableLiveEvent<>();
 	/**
 	 * true means there was an error saving the image, false if image was saved.
 	 */
@@ -62,13 +70,34 @@ public class ImageViewModel extends AndroidViewModel {
 
 	@Inject
 	ImageViewModel(Application application,
-			MessagingManager messagingManager,
+			MessagingManager messagingManager, EventBus eventBus,
 			@DatabaseExecutor Executor dbExecutor,
 			@IoExecutor Executor ioExecutor) {
 		super(application);
 		this.messagingManager = messagingManager;
+		this.eventBus = eventBus;
 		this.dbExecutor = dbExecutor;
 		this.ioExecutor = ioExecutor;
+
+		eventBus.addListener(this);
+	}
+
+	@Override
+	protected void onCleared() {
+		super.onCleared();
+		eventBus.removeListener(this);
+	}
+
+	@Override
+	public void eventOccurred(Event e) {
+		if (e instanceof AttachmentReceivedEvent) {
+			attachmentLoaded
+					.postEvent(((AttachmentReceivedEvent) e).getMessageId());
+		}
+	}
+
+	LiveEvent<MessageId> getOnAttachmentLoaded() {
+		return attachmentLoaded;
 	}
 
 	void clickImage() {