Enhance Loader API.

library/src/main/java/com/google/android/exoplayer/chunk/ChunkSampleSource.java

@@ -24,6 +24,7 @@ import com.google.android.exoplayer.SampleSource;
 import com.google.android.exoplayer.TrackInfo;
 import com.google.android.exoplayer.TrackRenderer;
 import com.google.android.exoplayer.upstream.Loader;
+import com.google.android.exoplayer.upstream.Loader.Loadable;
 import com.google.android.exoplayer.util.Assertions;
 
 import android.os.Handler;
@@ -39,7 +40,7 @@ import java.util.List;
  * A {@link SampleSource} that loads media in {@link Chunk}s, which are themselves obtained from a
  * {@link ChunkSource}.
  */
-public class ChunkSampleSource implements SampleSource, Loader.Listener {
+public class ChunkSampleSource implements SampleSource, Loader.Callback {
 
   /**
    * Interface definition for a callback to be notified of {@link ChunkSampleSource} events.
@@ -199,7 +200,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
   @Override
   public boolean prepare() {
     Assertions.checkState(state == STATE_UNPREPARED);
-    loader = new Loader("Loader:" + chunkSource.getTrackInfo().mimeType, this);
+    loader = new Loader("Loader:" + chunkSource.getTrackInfo().mimeType);
     state = STATE_PREPARED;
     return true;
   }
@@ -413,7 +414,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
   }
 
   @Override
-  public void onLoaded() {
+  public void onLoadCompleted(Loadable loadable) {
     Chunk currentLoadable = currentLoadableHolder.chunk;
     notifyLoadCompleted(currentLoadable.bytesLoaded());
     try {
@@ -436,7 +437,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
   }
 
   @Override
-  public void onCanceled() {
+  public void onLoadCanceled(Loadable loadable) {
     Chunk currentLoadable = currentLoadableHolder.chunk;
     notifyLoadCanceled(currentLoadable.bytesLoaded());
     if (!isMediaChunk(currentLoadable)) {
@@ -452,7 +453,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
   }
 
   @Override
-  public void onError(IOException e) {
+  public void onLoadError(Loadable loadable, IOException e) {
     currentLoadableException = e;
     currentLoadableExceptionCount++;
     currentLoadableExceptionTimestamp = SystemClock.elapsedRealtime();
@@ -553,7 +554,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
       discardUpstreamMediaChunks(currentLoadableHolder.queueSize);
       if (currentLoadableHolder.chunk == backedOffChunk) {
         // Chunk was unchanged. Resume loading.
-        loader.startLoading(backedOffChunk);
+        loader.startLoading(backedOffChunk, this);
       } else {
         backedOffChunk.release();
         maybeStartLoading();
@@ -564,7 +565,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
     if (backedOffChunk == mediaChunks.getFirst()) {
       // We're not able to clear the first media chunk, so we have no choice but to continue
       // loading it.
-      loader.startLoading(backedOffChunk);
+      loader.startLoading(backedOffChunk, this);
       return;
     }
 
@@ -579,7 +580,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
 
     if (currentLoadableHolder.chunk == backedOffChunk) {
       // Chunk was unchanged. Resume loading.
-      loader.startLoading(backedOffChunk);
+      loader.startLoading(backedOffChunk, this);
     } else {
       // This call will remove and release at least one chunk from the end of mediaChunks. Since
       // the current loadable is the last media chunk, it is guaranteed to be removed.
@@ -609,7 +610,7 @@ public class ChunkSampleSource implements SampleSource, Loader.Listener {
       notifyLoadStarted(currentLoadable.format.id, currentLoadable.trigger, true, -1, -1,
           currentLoadable.getLength());
     }
-    loader.startLoading(currentLoadable);
+    loader.startLoading(currentLoadable, this);
   }
 
   /**

library/src/main/java/com/google/android/exoplayer/upstream/Loader.java

@@ -20,6 +20,7 @@ import com.google.android.exoplayer.util.Util;
 
 import android.annotation.SuppressLint;
 import android.os.Handler;
+import android.os.Looper;
 import android.os.Message;
 import android.util.Log;
 
@@ -72,22 +73,28 @@ public final class Loader {
   /**
    * Interface definition for a callback to be notified of {@link Loader} events.
    */
-  public interface Listener {
+  public interface Callback {
 
     /**
      * Invoked when loading has been canceled.
+     *
+     * @param loadable The loadable whose load has been canceled.
      */
-    void onCanceled();
+    void onLoadCanceled(Loadable loadable);
 
     /**
      * Invoked when the data source has been fully loaded.
+     *
+     * @param loadable The loadable whose load has completed.
      */
-    void onLoaded();
+    void onLoadCompleted(Loadable loadable);
 
     /**
      * Invoked when the data source is stopped due to an error.
+     *
+     * @param loadable The loadable whose load has failed.
      */
-    void onError(IOException exception);
+    void onLoadError(Loadable loadable, IOException exception);
 
   }
 
@@ -95,18 +102,29 @@ public final class Loader {
   private static final int MSG_ERROR = 1;
 
   private final ExecutorService downloadExecutorService;
-  private final Listener listener;
 
   private LoadTask currentTask;
   private boolean loading;
 
   /**
    * @param threadName A name for the loader's thread.
-   * @param listener A listener to invoke when state changes occur.
    */
-  public Loader(String threadName, Listener listener) {
+  public Loader(String threadName) {
     this.downloadExecutorService = Util.newSingleThreadExecutor(threadName);
-    this.listener = listener;
+  }
+
+  /**
+   * Invokes {@link #startLoading(Looper, Loadable, Callback)}, using the {@link Looper}
+   * associated with the calling thread.
+   *
+   * @param loadable The {@link Loadable} to load.
+   * @param callback A callback to invoke when the load ends.
+   * @throws IllegalStateException If the calling thread does not have an associated {@link Looper}.
+   */
+  public void startLoading(Loadable loadable, Callback callback) {
+    Looper myLooper = Looper.myLooper();
+    Assertions.checkState(myLooper != null);
+    startLoading(myLooper, loadable, callback);
   }
 
   /**
@@ -115,12 +133,14 @@ public final class Loader {
    * A {@link Loader} instance can only load one {@link Loadable} at a time, and so this method
    * must not be called when another load is in progress.
    *
+   * @param looper The looper of the thread on which the callback should be invoked.
    * @param loadable The {@link Loadable} to load.
+   * @param callback A callback to invoke when the load ends.
    */
-  public void startLoading(Loadable loadable) {
+  public void startLoading(Looper looper, Loadable loadable, Callback callback) {
     Assertions.checkState(!loading);
     loading = true;
-    currentTask = new LoadTask(loadable);
+    currentTask = new LoadTask(looper, loadable, callback);
     downloadExecutorService.submit(currentTask);
   }
 
@@ -161,11 +181,14 @@ public final class Loader {
     private static final String TAG = "LoadTask";
 
     private final Loadable loadable;
+    private final Loader.Callback callback;
 
     private volatile Thread executorThread;
 
-    public LoadTask(Loadable loadable) {
+    public LoadTask(Looper looper, Loadable loadable, Loader.Callback callback) {
+      super(looper);
       this.loadable = loadable;
+      this.callback = callback;
     }
 
     public void quit() {
@@ -200,15 +223,15 @@ public final class Loader {
     public void handleMessage(Message msg) {
       onFinished();
       if (loadable.isLoadCanceled()) {
-        listener.onCanceled();
+        callback.onLoadCanceled(loadable);
         return;
       }
       switch (msg.what) {
         case MSG_END_OF_SOURCE:
-          listener.onLoaded();
+          callback.onLoadCompleted(loadable);
           break;
         case MSG_ERROR:
-          listener.onError((IOException) msg.obj);
+          callback.onLoadError(loadable, (IOException) msg.obj);
           break;
       }
     }