Fix MediaRailAdapter request counting.

app/src/main/java/org/thoughtcrime/securesms/components/ThumbnailView.java

@@ -26,6 +26,7 @@ import com.bumptech.glide.load.resource.bitmap.BitmapTransformation;
 import com.bumptech.glide.load.resource.bitmap.CenterCrop;
 import com.bumptech.glide.load.resource.bitmap.FitCenter;
 import com.bumptech.glide.load.resource.bitmap.RoundedCorners;
+import com.bumptech.glide.request.Request;
 import com.bumptech.glide.request.RequestListener;
 import com.bumptech.glide.request.RequestOptions;
 
@@ -422,7 +423,7 @@ public class ThumbnailView extends FrameLayout {
     return setImageResource(glideRequests, uri, width, height, true, null);
   }
 
-  public ListenableFuture<Boolean> setImageResource(@NonNull GlideRequests glideRequests, @NonNull Uri uri, int width, int height, boolean animate, @Nullable RequestListener<Drawable> listener) {
+  public ListenableFuture<Boolean> setImageResource(@NonNull GlideRequests glideRequests, @NonNull Uri uri, int width, int height, boolean animate, @Nullable ThumbnailRequestListener listener) {
     SettableFuture<Boolean> future = new SettableFuture<>();
 
     if (transferControls.isPresent()) getTransferControls().setVisibility(View.GONE);
@@ -445,7 +446,17 @@ public class ThumbnailView extends FrameLayout {
       request = request.transforms(new CenterCrop());
     }
 
-    request.into(new GlideDrawableListeningTarget(image, future));
+    GlideDrawableListeningTarget target = new GlideDrawableListeningTarget(image, future);
+    Request previousRequest = target.getRequest();
+    boolean previousRequestRunning = previousRequest != null && previousRequest.isRunning();
+    request.into(target);
+    if (listener != null) {
+      listener.onLoadScheduled();
+      if (previousRequestRunning) {
+        listener.onLoadCanceled();
+      }
+    }
+
     blurhash.setImageDrawable(null);
 
     return future;
@@ -572,6 +583,11 @@ public class ThumbnailView extends FrameLayout {
     return 0;
   }
 
+  public interface ThumbnailRequestListener extends RequestListener<Drawable> {
+    void onLoadCanceled();
+    void onLoadScheduled();
+  }
+
   private class ThumbnailClickDispatcher implements View.OnClickListener {
     @Override
     public void onClick(View view) {

app/src/main/java/org/thoughtcrime/securesms/mediapreview/mediarail/MediaRailAdapter.kt

@@ -6,7 +6,6 @@ import android.widget.ImageView
 import androidx.recyclerview.widget.RecyclerView
 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 org.thoughtcrime.securesms.R
 import org.thoughtcrime.securesms.components.ThumbnailView
@@ -78,7 +77,6 @@ class MediaRailAdapter(
     }
 
     override fun bind(model: MediaRailItem) {
-      imageLoadingListener.onRequest()
       image.setImageResource(glideRequests, model.media.uri, 0, 0, false, imageLoadingListener)
       image.setOnClickListener { onRailItemSelected(model.media) }
       captionIndicator.visibility = if (model.media.caption.isPresent) View.VISIBLE else View.GONE
@@ -88,12 +86,16 @@ class MediaRailAdapter(
     }
   }
 
-  abstract class ImageLoadingListener : RequestListener<Drawable?> {
+  abstract class ImageLoadingListener : ThumbnailView.ThumbnailRequestListener {
     private val activeJobs = AtomicInteger()
-    fun onRequest() {
+    final override fun onLoadScheduled() {
       activeJobs.incrementAndGet()
     }
 
+    final override fun onLoadCanceled() {
+      activeJobs.decrementAndGet()
+    }
+
     final override fun onLoadFailed(e: GlideException?, model: Any, target: Target<Drawable?>, isFirstResource: Boolean): Boolean {
       val count = activeJobs.decrementAndGet()
       if (count == 0) {