Get rid of DownloadState.STATE_REMOVED

It's a transient state whose only use is when passing a removed
download to onDownloadStateChanged. It's a bit strange to have it
as a proper state, since we end up asserting that it's an invalid
value in other places.

This change adds an explicit onDownloadRemoved, which allows
removal of the transient STATE_REMOVED, related assertions, and
uncertainty when dealing with an @State variable whether it's
necessary to handle it being STATE_REMOVED.

PiperOrigin-RevId: 242444128

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

@@ -124,13 +124,18 @@ public class DownloadTracker implements DownloadManager.Listener {
 
   @Override
   public void onDownloadStateChanged(DownloadManager downloadManager, DownloadState downloadState) {
-    boolean downloaded = isDownloaded(downloadState.uri);
+    boolean downloadAdded = downloadStates.put(downloadState.uri, downloadState) == null;
-    if (downloadState.state == DownloadState.STATE_REMOVED) {
+    if (downloadAdded) {
-      downloadStates.remove(downloadState.uri);
+      for (Listener listener : listeners) {
-    } else {
+        listener.onDownloadsChanged();
-      downloadStates.put(downloadState.uri, downloadState);
+      }
     }
-    if (downloaded != isDownloaded(downloadState.uri)) {
+  }
+
+  @Override
+  public void onDownloadRemoved(DownloadManager downloadManager, DownloadState downloadState) {
+    boolean downloadRemoved = downloadStates.remove(downloadState.uri) != null;
+    if (downloadRemoved) {
       for (Listener listener : listeners) {
         listener.onDownloadsChanged();
       }

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

@@ -192,7 +192,6 @@ public final class DefaultDownloadIndex implements DownloadIndex {
    */
   public void putDownloadState(DownloadState downloadState) throws DatabaseIOException {
     ensureInitialized();
-    Assertions.checkState(downloadState.state != DownloadState.STATE_REMOVED);
     try {
       ContentValues values = new ContentValues();
       values.put(COLUMN_ID, downloadState.id);

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

@@ -23,7 +23,6 @@ import static com.google.android.exoplayer2.offline.DownloadState.STATE_COMPLETE
 import static com.google.android.exoplayer2.offline.DownloadState.STATE_DOWNLOADING;
 import static com.google.android.exoplayer2.offline.DownloadState.STATE_FAILED;
 import static com.google.android.exoplayer2.offline.DownloadState.STATE_QUEUED;
-import static com.google.android.exoplayer2.offline.DownloadState.STATE_REMOVED;
 import static com.google.android.exoplayer2.offline.DownloadState.STATE_REMOVING;
 import static com.google.android.exoplayer2.offline.DownloadState.STATE_RESTARTING;
 import static com.google.android.exoplayer2.offline.DownloadState.STATE_STOPPED;
@@ -81,6 +80,14 @@ public final class DownloadManager {
     default void onDownloadStateChanged(
         DownloadManager downloadManager, DownloadState downloadState) {}
 
+    /**
+     * Called when a download is removed.
+     *
+     * @param downloadManager The reporting instance.
+     * @param downloadState The last state of the download before it was removed.
+     */
+    default void onDownloadRemoved(DownloadManager downloadManager, DownloadState downloadState) {}
+
     /**
      * Called when there is no active download left.
      *
@@ -114,6 +121,7 @@ public final class DownloadManager {
   private static final int MSG_INITIALIZED = 0;
   private static final int MSG_PROCESSED = 1;
   private static final int MSG_DOWNLOAD_STATE_CHANGED = 2;
+  private static final int MSG_DOWNLOAD_REMOVED = 3;
 
   // Messages posted to the background handler.
   private static final int MSG_INITIALIZE = 0;
@@ -470,6 +478,10 @@ public final class DownloadManager {
         DownloadState state = (DownloadState) message.obj;
         onDownloadStateChanged(state);
         break;
+      case MSG_DOWNLOAD_REMOVED:
+        state = (DownloadState) message.obj;
+        onDownloadRemoved(state);
+        break;
       case MSG_PROCESSED:
         int processedMessageCount = message.arg1;
         int activeDownloadCount = message.arg2;
@@ -495,7 +507,7 @@ public final class DownloadManager {
   }
 
   private void onDownloadStateChanged(DownloadState downloadState) {
-    if (isFinished(downloadState.state)) {
+    if (downloadState.state == STATE_COMPLETED || downloadState.state == STATE_FAILED) {
       downloadStates.remove(downloadState.id);
     } else {
       downloadStates.put(downloadState.id, downloadState);
@@ -505,6 +517,13 @@ public final class DownloadManager {
     }
   }
 
+  private void onDownloadRemoved(DownloadState downloadState) {
+    downloadStates.remove(downloadState.id);
+    for (Listener listener : listeners) {
+      listener.onDownloadRemoved(this, downloadState);
+    }
+  }
+
   private void onMessageProcessed(int processedMessageCount, int activeDownloadCount) {
     this.pendingMessages -= processedMessageCount;
     this.activeDownloadCount = activeDownloadCount;
@@ -615,15 +634,30 @@ public final class DownloadManager {
     }
   }
 
-  private void onDownloadStateChange(Download download, DownloadState downloadState) {
+  private void onDownloadStateChangedInternal(Download download, DownloadState downloadState) {
     logd("Download state is changed", download);
-    updateDownloadIndex(downloadState);
+    try {
-    if (isFinished(download.state)) {
+      downloadIndex.putDownloadState(downloadState);
+    } catch (DatabaseIOException e) {
+      Log.e(TAG, "Failed to update index", e);
+    }
+    if (download.state == STATE_COMPLETED || download.state == STATE_FAILED) {
       downloads.remove(download);
     }
     mainHandler.obtainMessage(MSG_DOWNLOAD_STATE_CHANGED, downloadState).sendToTarget();
   }
 
+  private void onDownloadRemovedInternal(Download download, DownloadState downloadState) {
+    logd("Download is removed", download);
+    try {
+      downloadIndex.removeDownloadState(downloadState.id);
+    } catch (DatabaseIOException e) {
+      Log.e(TAG, "Failed to remove from index", e);
+    }
+    downloads.remove(download);
+    mainHandler.obtainMessage(MSG_DOWNLOAD_REMOVED, downloadState).sendToTarget();
+  }
+
   private void setNotMetRequirementsInternal(
       @Requirements.RequirementFlags int notMetRequirements) {
     if (this.notMetRequirements == notMetRequirements) {
@@ -687,18 +721,6 @@ public final class DownloadManager {
     download.initialize();
   }
 
-  private void updateDownloadIndex(DownloadState downloadState) {
-    try {
-      if (downloadState.state == DownloadState.STATE_REMOVED) {
-        downloadIndex.removeDownloadState(downloadState.id);
-      } else {
-        downloadIndex.putDownloadState(downloadState);
-      }
-    } catch (DatabaseIOException e) {
-      Log.e(TAG, "updateDownloadIndex failed", e);
-    }
-  }
-
   private static void logd(String message) {
     if (DEBUG) {
       Log.d(TAG, message);
@@ -779,10 +801,6 @@ public final class DownloadManager {
     }
   }
 
-  private static boolean isFinished(@DownloadState.State int state) {
-    return state == STATE_FAILED || state == STATE_COMPLETED || state == STATE_REMOVED;
-  }
-
   private static final class Download {
     private final DownloadManager downloadManager;
 
@@ -867,7 +885,6 @@ public final class DownloadManager {
     }
 
     public DownloadAction getAction() {
-      Assertions.checkState(state != STATE_REMOVED);
       return DownloadAction.createDownloadAction(
           downloadState.type,
           downloadState.uri,
@@ -897,7 +914,7 @@ public final class DownloadManager {
         }
       }
       if (oldDownloadState == downloadState) {
-        downloadManager.onDownloadStateChange(this, getUpdatedDownloadState());
+        downloadManager.onDownloadStateChangedInternal(this, getUpdatedDownloadState());
       }
     }
 
@@ -913,7 +930,7 @@ public final class DownloadManager {
         setState(STATE_STOPPED);
       }
       if (state == initialState) {
-        downloadManager.onDownloadStateChange(this, getUpdatedDownloadState());
+        downloadManager.onDownloadStateChangedInternal(this, getUpdatedDownloadState());
       }
     }
 
@@ -935,7 +952,7 @@ public final class DownloadManager {
     private void setState(@DownloadState.State int newState) {
       if (state != newState) {
         state = newState;
-        downloadManager.onDownloadStateChange(this, getUpdatedDownloadState());
+        downloadManager.onDownloadStateChangedInternal(this, getUpdatedDownloadState());
       }
     }
 
@@ -945,10 +962,10 @@ public final class DownloadManager {
       }
       if (isCanceled) {
         downloadManager.startDownloadThread(this);
+      } else if (state == STATE_REMOVING) {
+        downloadManager.onDownloadRemovedInternal(this, getUpdatedDownloadState());
       } else if (state == STATE_RESTARTING) {
         initialize(STATE_QUEUED);
-      } else if (state == STATE_REMOVING) {
-        setState(STATE_REMOVED);
       } else { // STATE_DOWNLOADING
         if (error != null) {
           Log.e(TAG, "Download failed: " + downloadState.id, error);

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

@@ -509,6 +509,15 @@ public abstract class DownloadService extends Service {
     // Do nothing.
   }
 
+  /**
+   * Called when a download is removed. The default implementation is a no-op.
+   *
+   * @param downloadState The last state of the download before it was removed.
+   */
+  protected void onDownloadRemoved(DownloadState downloadState) {
+    // Do nothing.
+  }
+
   private void notifyDownloadStateChange(DownloadState downloadState) {
     onDownloadStateChanged(downloadState);
     if (foregroundNotificationUpdater != null) {
@@ -522,6 +531,13 @@ public abstract class DownloadService extends Service {
     }
   }
 
+  private void notifyDownloadRemoved(DownloadState downloadState) {
+    onDownloadRemoved(downloadState);
+    if (foregroundNotificationUpdater != null) {
+      foregroundNotificationUpdater.update();
+    }
+  }
+
   private void stop() {
     if (foregroundNotificationUpdater != null) {
       foregroundNotificationUpdater.stopPeriodicUpdates();
@@ -642,6 +658,13 @@ public abstract class DownloadService extends Service {
       }
     }
 
+    @Override
+    public void onDownloadRemoved(DownloadManager downloadManager, DownloadState downloadState) {
+      if (downloadService != null) {
+        downloadService.notifyDownloadRemoved(downloadState);
+      }
+    }
+
     @Override
     public final void onIdle(DownloadManager downloadManager) {
       if (downloadService != null) {

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

@@ -34,8 +34,8 @@ public final class DownloadState {
 
   /**
    * Download states. One of {@link #STATE_QUEUED}, {@link #STATE_STOPPED}, {@link
-   * #STATE_DOWNLOADING}, {@link #STATE_COMPLETED}, {@link #STATE_FAILED}, {@link #STATE_REMOVING},
+   * #STATE_DOWNLOADING}, {@link #STATE_COMPLETED}, {@link #STATE_FAILED}, {@link #STATE_REMOVING}
-   * {@link #STATE_REMOVED} or {@link #STATE_RESTARTING}.
+   * or {@link #STATE_RESTARTING}.
    */
   @Documented
   @Retention(RetentionPolicy.SOURCE)
@@ -46,10 +46,10 @@ public final class DownloadState {
     STATE_COMPLETED,
     STATE_FAILED,
     STATE_REMOVING,
-    STATE_REMOVED,
     STATE_RESTARTING
   })
   public @interface State {}
+  // Important: These constants are persisted into DownloadIndex. Do not change them.
   /** The download is waiting to be started. */
   public static final int STATE_QUEUED = 0;
   /** The download is stopped. */
@@ -62,8 +62,6 @@ public final class DownloadState {
   public static final int STATE_FAILED = 4;
   /** The download is being removed. */
   public static final int STATE_REMOVING = 5;
-  /** The download is removed. */
-  public static final int STATE_REMOVED = 6;
   /** The download will restart after all downloaded data is removed. */
   public static final int STATE_RESTARTING = 7;
 
@@ -97,8 +95,6 @@ public final class DownloadState {
         return "FAILED";
       case STATE_REMOVING:
         return "REMOVING";
-      case STATE_REMOVED:
-        return "REMOVED";
       case STATE_RESTARTING:
         return "RESTARTING";
       default:

library/core/src/test/java/com/google/android/exoplayer2/offline/DownloadManagerTest.java

@@ -565,10 +565,6 @@ public class DownloadManagerTest {
       return assertState(DownloadState.STATE_REMOVING);
     }
 
-    private TaskWrapper assertRemoved() {
-      return assertState(DownloadState.STATE_REMOVED);
-    }
-
     private TaskWrapper assertFailed() {
       return assertState(DownloadState.STATE_FAILED);
     }
@@ -586,6 +582,11 @@ public class DownloadManagerTest {
       return this;
     }
 
+    private TaskWrapper assertRemoved() {
+      downloadManagerListener.assertRemoved(taskId, ASSERT_TRUE_TIMEOUT);
+      return this;
+    }
+
     @Override
     public boolean equals(Object o) {
       if (this == o) {

library/ui/src/main/java/com/google/android/exoplayer2/ui/DownloadNotificationHelper.java

@@ -65,8 +65,7 @@ public final class DownloadNotificationHelper {
     boolean haveRemoveTasks = false;
     for (DownloadState downloadState : downloadStates) {
       if (downloadState.state == DownloadState.STATE_REMOVING
-          || downloadState.state == DownloadState.STATE_RESTARTING
+          || downloadState.state == DownloadState.STATE_RESTARTING) {
-          || downloadState.state == DownloadState.STATE_REMOVED) {
         haveRemoveTasks = true;
         continue;
       }

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

@@ -34,6 +34,7 @@ public final class TestDownloadManagerListener implements DownloadManager.Listen
 
   private static final int TIMEOUT = 1000;
   private static final int INITIALIZATION_TIMEOUT = 10000;
+  private static final int STATE_REMOVED = -1;
 
   private final DownloadManager downloadManager;
   private final DummyMainThread dummyMainThread;
@@ -79,6 +80,11 @@ public final class TestDownloadManagerListener implements DownloadManager.Listen
     getStateQueue(downloadState.id).add(downloadState.state);
   }
 
+  @Override
+  public void onDownloadRemoved(DownloadManager downloadManager, DownloadState downloadState) {
+    getStateQueue(downloadState.id).add(STATE_REMOVED);
+  }
+
   @Override
   public synchronized void onIdle(DownloadManager downloadManager) {
     if (downloadFinishedCondition != null) {
@@ -120,7 +126,15 @@ public final class TestDownloadManagerListener implements DownloadManager.Listen
     }
   }
 
+  public void assertRemoved(String taskId, int timeoutMs) {
+    assertStateInternal(taskId, STATE_REMOVED, timeoutMs);
+  }
+
   public void assertState(String taskId, @State int expectedState, int timeoutMs) {
+    assertStateInternal(taskId, expectedState, timeoutMs);
+  }
+
+  private void assertStateInternal(String taskId, int expectedState, int timeoutMs) {
     ArrayList<Integer> receivedStates = new ArrayList<>();
     while (true) {
       Integer state = null;
@@ -140,7 +154,12 @@ public final class TestDownloadManagerListener implements DownloadManager.Listen
           if (i > 0) {
             sb.append(',');
           }
-          sb.append(DownloadState.getStateString(receivedStates.get(i)));
+          int receivedState = receivedStates.get(i);
+          String receivedStateString =
+              receivedState == STATE_REMOVED
+                  ? "REMOVED"
+                  : DownloadState.getStateString(receivedState);
+          sb.append(receivedStateString);
         }
         fail(
             String.format(