Fix ANR when leaving MediaPreviewActivity.

app/src/main/java/org/thoughtcrime/securesms/MediaPreviewActivity.java

@@ -73,6 +73,7 @@ import org.thoughtcrime.securesms.sharing.ShareActivity;
 import org.thoughtcrime.securesms.util.AttachmentUtil;
 import org.thoughtcrime.securesms.util.DateUtils;
 import org.thoughtcrime.securesms.util.FullscreenHelper;
+import org.thoughtcrime.securesms.util.LifecycleCursorWrapper;
 import org.thoughtcrime.securesms.util.SaveAttachmentTask;
 import org.thoughtcrime.securesms.util.SaveAttachmentTask.Attachment;
 import org.thoughtcrime.securesms.util.StorageUtil;
@@ -128,7 +129,7 @@ public final class MediaPreviewActivity extends PassphraseRequiredActivity
   private MediaDatabase.Sorting sorting;
   private FullscreenHelper      fullscreenHelper;
 
-  private @Nullable Cursor cursor = null;
+  private @Nullable LifecycleCursorWrapper cursor = null;
 
   public static @NonNull Intent intentFromMediaRecord(@NonNull Context context,
                                                       @NonNull MediaRecord mediaRecord,
@@ -248,10 +249,7 @@ public final class MediaPreviewActivity extends PassphraseRequiredActivity
 
   @Override
   protected void onDestroy() {
-    if (cursor != null) {
+    cursor = null;
-      cursor.close();
-      cursor = null;
-    }
     super.onDestroy();
   }
 
@@ -549,9 +547,11 @@ public final class MediaPreviewActivity extends PassphraseRequiredActivity
       }
 
       if (cursor != null) {
+        getLifecycle().removeObserver(cursor);
         cursor.close();
       }
-      cursor = Objects.requireNonNull(data.first);
+      cursor = new LifecycleCursorWrapper(Objects.requireNonNull(data.first));
+      getLifecycle().addObserver(cursor);
 
       int mediaPosition = Objects.requireNonNull(data.second);
 

app/src/main/java/org/thoughtcrime/securesms/util/LifecycleCursorWrapper.java

@@ -8,6 +8,8 @@ import androidx.lifecycle.DefaultLifecycleObserver;
 import androidx.lifecycle.Lifecycle;
 import androidx.lifecycle.LifecycleOwner;
 
+import org.signal.core.util.concurrent.SignalExecutors;
+
 /**
  * Wraps a {@link Cursor} that will be closed automatically when the {@link Lifecycle.Event}.ON_DESTROY
  * is fired from the lifecycle this object is observing.
@@ -22,4 +24,9 @@ public class LifecycleCursorWrapper extends CursorWrapper implements DefaultLife
   public void onDestroy(@NonNull LifecycleOwner owner) {
     close();
   }
+
+  @Override
+  public void close() {
+    SignalExecutors.BOUNDED.execute(super::close);
+  }
 }