Propagate download exception through onDownloadChanged callback

demos/main/src/main/java/com/google/android/exoplayer2/demo/DemoDownloadService.java

@@ -20,6 +20,7 @@ import static com.google.android.exoplayer2.demo.DemoApplication.DOWNLOAD_NOTIFI
 import android.app.Notification;
 import android.content.Context;
 import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
 import com.google.android.exoplayer2.offline.Download;
 import com.google.android.exoplayer2.offline.DownloadManager;
 import com.google.android.exoplayer2.offline.DownloadService;
@@ -94,7 +95,8 @@ public class DemoDownloadService extends DownloadService {
     }
 
     @Override
-    public void onDownloadChanged(@NonNull DownloadManager manager, @NonNull Download download) {
+    public void onDownloadChanged(
+        DownloadManager downloadManager, Download download, @Nullable Throwable error) {
       Notification notification;
       if (download.state == Download.STATE_COMPLETED) {
         notification =

demos/main/src/main/java/com/google/android/exoplayer2/demo/DownloadTracker.java

@@ -126,7 +126,9 @@ public class DownloadTracker {
 
     @Override
     public void onDownloadChanged(
-        @NonNull DownloadManager downloadManager, @NonNull Download download) {
+        @NonNull DownloadManager downloadManager,
+        @NonNull Download download,
+        @Nullable Throwable error) {
       downloads.put(download.request.uri, download);
       for (Listener listener : listeners) {
         listener.onDownloadsChanged();

library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadManager.java

@@ -93,8 +93,10 @@ public final class DownloadManager {
      *
      * @param downloadManager The reporting instance.
      * @param download The state of the download.
+     * @param error exception occurred when a download is failed
      */
-    default void onDownloadChanged(DownloadManager downloadManager, Download download) {}
+    default void onDownloadChanged(
+        DownloadManager downloadManager, Download download, @Nullable Throwable error) {}
 
     /**
      * Called when a download is removed.
@@ -614,7 +616,7 @@ public final class DownloadManager {
       }
     } else {
       for (Listener listener : listeners) {
-        listener.onDownloadChanged(this, updatedDownload);
+        listener.onDownloadChanged(this, updatedDownload, update.error);
       }
     }
     if (waitingForRequirementsChanged) {
@@ -906,7 +908,7 @@ public final class DownloadManager {
       ArrayList<Download> updateList = new ArrayList<>(downloads);
       for (int i = 0; i < downloads.size(); i++) {
         DownloadUpdate update =
-            new DownloadUpdate(downloads.get(i), /* isRemove= */ false, updateList);
+            new DownloadUpdate(downloads.get(i), /* isRemove= */ false, updateList, null);
         mainHandler.obtainMessage(MSG_DOWNLOAD_UPDATE, update).sendToTarget();
       }
       syncTasks();
@@ -1121,7 +1123,11 @@ public final class DownloadManager {
         Log.e(TAG, "Failed to update index.", e);
       }
       DownloadUpdate update =
-          new DownloadUpdate(download, /* isRemove= */ false, new ArrayList<>(downloads));
+          new DownloadUpdate(
+              download,
+              /* isRemove= */ false,
+              new ArrayList<>(downloads),
+              finalError);
       mainHandler.obtainMessage(MSG_DOWNLOAD_UPDATE, update).sendToTarget();
     }
 
@@ -1139,7 +1145,7 @@ public final class DownloadManager {
           Log.e(TAG, "Failed to remove from database");
         }
         DownloadUpdate update =
-            new DownloadUpdate(download, /* isRemove= */ true, new ArrayList<>(downloads));
+            new DownloadUpdate(download, /* isRemove= */ true, new ArrayList<>(downloads), null);
         mainHandler.obtainMessage(MSG_DOWNLOAD_UPDATE, update).sendToTarget();
       }
     }
@@ -1194,7 +1200,7 @@ public final class DownloadManager {
         Log.e(TAG, "Failed to update index.", e);
       }
       DownloadUpdate update =
-          new DownloadUpdate(download, /* isRemove= */ false, new ArrayList<>(downloads));
+          new DownloadUpdate(download, /* isRemove= */ false, new ArrayList<>(downloads), null);
       mainHandler.obtainMessage(MSG_DOWNLOAD_UPDATE, update).sendToTarget();
       return download;
     }
@@ -1355,11 +1361,14 @@ public final class DownloadManager {
     public final Download download;
     public final boolean isRemove;
     public final List<Download> downloads;
+    @Nullable public final Throwable error;
 
-    public DownloadUpdate(Download download, boolean isRemove, List<Download> downloads) {
+    public DownloadUpdate(
+        Download download, boolean isRemove, List<Download> downloads, @Nullable Throwable error) {
       this.download = download;
       this.isRemove = isRemove;
       this.downloads = downloads;
+      this.error = error;
     }
   }
 }

library/core/src/main/java/com/google/android/exoplayer2/offline/DownloadService.java

@@ -974,7 +974,8 @@ public abstract class DownloadService extends Service {
     }
 
     @Override
-    public void onDownloadChanged(DownloadManager downloadManager, Download download) {
+    public void onDownloadChanged(
+        DownloadManager downloadManager, Download download, @Nullable Throwable throwable) {
       if (downloadService != null) {
         downloadService.notifyDownloadChanged(download);
       }

testutils/src/main/java/com/google/android/exoplayer2/testutil/TestDownloadManagerListener.java

@@ -100,7 +100,8 @@ public final class TestDownloadManagerListener implements DownloadManager.Listen
   }
 
   @Override
-  public void onDownloadChanged(DownloadManager downloadManager, Download download) {
+  public void onDownloadChanged(
+      DownloadManager downloadManager, Download download, @Nullable Throwable error) {
     if (download.state == Download.STATE_FAILED) {
       failureReason = download.failureReason;
     }