Report loading on/off changes via ExoPlayer.

Also attempt to clear up naming a little, using "buffering" to
mean the user visible buffering state, and "loading" to mean a
source being loaded.
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=126693592

demo/src/main/java/com/google/android/exoplayer/demo/EventLogger.java

@@ -67,6 +67,11 @@ public class EventLogger implements ExoPlayer.EventListener, SimpleExoPlayer.Deb
   // ExoPlayer.EventListener
 
   @Override
+  public void onLoadingChanged(boolean isLoading) {
+    Log.d(TAG, "loading [" + isLoading + "]");
+  }
+
+  @Override
   public void onPlayerStateChanged(boolean playWhenReady, int state) {
     Log.d(TAG, "state [" + getSessionTimeString() + ", " + playWhenReady + ", "
         + getStateString(state) + "]");

demo/src/main/java/com/google/android/exoplayer/demo/PlayerActivity.java

@@ -18,7 +18,7 @@ package com.google.android.exoplayer.demo;
 import com.google.android.exoplayer.AspectRatioFrameLayout;
 import com.google.android.exoplayer.C;
 import com.google.android.exoplayer.ConcatenatingSampleSourceProvider;
-import com.google.android.exoplayer.DefaultBufferingControl;
+import com.google.android.exoplayer.DefaultLoadControl;
 import com.google.android.exoplayer.DefaultTrackSelectionPolicy;
 import com.google.android.exoplayer.DefaultTrackSelector;
 import com.google.android.exoplayer.DefaultTrackSelector.TrackInfo;
@@ -268,8 +268,8 @@ public class PlayerActivity extends Activity implements SurfaceHolder.Callback,
       trackSelector.addListener(this);
       trackSelector.addListener(eventLogger);
       trackSelectionHelper = new TrackSelectionHelper(trackSelector);
-      player = ExoPlayerFactory.newSimpleInstance(this, trackSelector,
-          new DefaultBufferingControl(), drmSessionManager, preferExtensionDecoders);
+      player = ExoPlayerFactory.newSimpleInstance(this, trackSelector, new DefaultLoadControl(),
+          drmSessionManager, preferExtensionDecoders);
       player.addListener(this);
       player.addListener(eventLogger);
       player.setDebugListener(eventLogger);
@@ -389,6 +389,11 @@ public class PlayerActivity extends Activity implements SurfaceHolder.Callback,
   // ExoPlayer.EventListener implementation
 
   @Override
+  public void onLoadingChanged(boolean isLoading) {
+    // Do nothing.
+  }
+
+  @Override
   public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
     if (playbackState == ExoPlayer.STATE_ENDED) {
       showControls();

extensions/flac/src/androidTest/java/com/google/android/exoplayer/ext/flac/FlacPlaybackTest.java

@@ -89,6 +89,11 @@ public class FlacPlaybackTest extends InstrumentationTestCase {
     }
 
     @Override
+    public void onLoadingChanged(boolean isLoading) {
+      // Do nothing.
+    }
+
+    @Override
     public void onPlayWhenReadyCommitted () {
       // Do nothing.
     }

extensions/opus/src/androidTest/java/com/google/android/exoplayer/ext/opus/OpusPlaybackTest.java

@@ -89,6 +89,11 @@ public class OpusPlaybackTest extends InstrumentationTestCase {
     }
 
     @Override
+    public void onLoadingChanged(boolean isLoading) {
+      // Do nothing.
+    }
+
+    @Override
     public void onPlayWhenReadyCommitted () {
       // Do nothing.
     }

extensions/vp9/src/androidTest/java/com/google/android/exoplayer/ext/vp9/VpxPlaybackTest.java

@@ -108,6 +108,11 @@ public class VpxPlaybackTest extends InstrumentationTestCase {
     }
 
     @Override
+    public void onLoadingChanged(boolean isLoading) {
+      // Do nothing.
+    }
+
+    @Override
     public void onPlayWhenReadyCommitted () {
       // Do nothing.
     }

library/src/main/java/com/google/android/exoplayer/DefaultBufferingControl.java → library/src/main/java/com/google/android/exoplayer/DefaultLoadControl.java

@@ -19,26 +19,10 @@ import com.google.android.exoplayer.upstream.Allocator;
 import com.google.android.exoplayer.upstream.DefaultAllocator;
 import com.google.android.exoplayer.util.Util;
 
-import android.os.Handler;
-
 /**
- * The default {@link BufferingControl} implementation.
+ * The default {@link LoadControl} implementation.
  */
-public final class DefaultBufferingControl implements BufferingControl {
-
-  /**
-   * Interface definition for a callback to be notified of {@link DefaultBufferingControl} events.
-   */
-  public interface EventListener {
-
-    /**
-     * Invoked when the control transitions from a buffering to a draining state or vice versa.
-     *
-     * @param buffering Whether the control is now in the buffering state.
-     */
-    void onBufferingChanged(boolean buffering);
-
-  }
+public final class DefaultLoadControl implements LoadControl {
 
   /**
    * The default minimum duration of media that the player will attempt to ensure is buffered at all
@@ -69,8 +53,6 @@ public final class DefaultBufferingControl implements BufferingControl {
   private static final int BELOW_LOW_WATERMARK = 2;
 
   private final DefaultAllocator allocator;
-  private final Handler eventHandler;
-  private final EventListener eventListener;
 
   private final long minBufferUs;
   private final long maxBufferUs;
@@ -83,7 +65,7 @@ public final class DefaultBufferingControl implements BufferingControl {
   /**
    * Constructs a new instance, using the {@code DEFAULT_*} constants defined in this class.
    */
-  public DefaultBufferingControl() {
+  public DefaultLoadControl() {
     this(new DefaultAllocator(C.DEFAULT_BUFFER_SEGMENT_SIZE));
   }
 
@@ -92,22 +74,9 @@ public final class DefaultBufferingControl implements BufferingControl {
    *
    * @param allocator The {@link DefaultAllocator} used by the loader.
    */
-  public DefaultBufferingControl(DefaultAllocator allocator) {
-    this(allocator, null, null);
-  }
-
-  /**
-   * Constructs a new instance, using the {@code DEFAULT_*} constants defined in this class.
-   *
-   * @param allocator The {@link DefaultAllocator} used by the loader.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
-   */
-  public DefaultBufferingControl(DefaultAllocator allocator, Handler eventHandler,
-      EventListener eventListener) {
+  public DefaultLoadControl(DefaultAllocator allocator) {
     this(allocator, DEFAULT_MIN_BUFFER_MS, DEFAULT_MAX_BUFFER_MS, DEFAULT_BUFFER_FOR_PLAYBACK_MS,
-        DEFAULT_BUFFER_FOR_PLAYBACK_AFTER_REBUFFER_MS, eventHandler, eventListener);
+        DEFAULT_BUFFER_FOR_PLAYBACK_AFTER_REBUFFER_MS);
   }
 
   /**
@@ -123,16 +92,10 @@ public final class DefaultBufferingControl implements BufferingControl {
    * @param bufferForPlaybackAfterRebufferMs The default duration of media that must be buffered for
    *     playback to resume after a player-invoked rebuffer (i.e. a rebuffer that occurs due to
    *     buffer depletion rather than a user action), in milliseconds.
-   * @param eventHandler A handler to use when delivering events to {@code eventListener}. May be
-   *     null if delivery of events is not required.
-   * @param eventListener A listener of events. May be null if delivery of events is not required.
    */
-  public DefaultBufferingControl(DefaultAllocator allocator, int minBufferMs, int maxBufferMs,
-      long bufferForPlaybackMs, long bufferForPlaybackAfterRebufferMs, Handler eventHandler,
-      EventListener eventListener) {
+  public DefaultLoadControl(DefaultAllocator allocator, int minBufferMs, int maxBufferMs,
+      long bufferForPlaybackMs, long bufferForPlaybackAfterRebufferMs) {
     this.allocator = allocator;
-    this.eventHandler = eventHandler;
-    this.eventListener = eventListener;
     minBufferUs = minBufferMs * 1000L;
     maxBufferUs = maxBufferMs * 1000L;
     bufferForPlaybackUs = bufferForPlaybackMs * 1000L;
@@ -154,7 +117,7 @@ public final class DefaultBufferingControl implements BufferingControl {
   @Override
   public void reset() {
     targetBufferSize = 0;
-    setBuffering(false);
+    isBuffering = false;
   }
 
   @Override
@@ -169,20 +132,12 @@ public final class DefaultBufferingControl implements BufferingControl {
   }
 
   @Override
-  public boolean shouldContinueBuffering(long bufferedDurationUs) {
+  public boolean shouldContinueLoading(long bufferedDurationUs) {
     int bufferTimeState = getBufferTimeState(bufferedDurationUs);
     boolean targetBufferSizeReached = allocator.getTotalBytesAllocated() >= targetBufferSize;
-    boolean shouldBuffer = bufferTimeState == BELOW_LOW_WATERMARK
+    isBuffering = bufferTimeState == BELOW_LOW_WATERMARK
         || (bufferTimeState == BETWEEN_WATERMARKS && isBuffering && !targetBufferSizeReached);
-    setBuffering(shouldBuffer);
-    return shouldBuffer;
-  }
-
-  private void setBuffering(boolean isBuffering) {
-    if (this.isBuffering != isBuffering) {
-      this.isBuffering = isBuffering;
-      notifyBufferingChanged(isBuffering);
-    }
+    return isBuffering;
   }
 
   private int getBufferTimeState(long bufferedDurationUs) {
@@ -190,15 +145,4 @@ public final class DefaultBufferingControl implements BufferingControl {
         : (bufferedDurationUs < minBufferUs ? BELOW_LOW_WATERMARK : BETWEEN_WATERMARKS);
   }
 
-  private void notifyBufferingChanged(final boolean buffering) {
-    if (eventHandler != null && eventListener != null) {
-      eventHandler.post(new Runnable()  {
-        @Override
-        public void run() {
-          eventListener.onBufferingChanged(buffering);
-        }
-      });
-    }
-  }
-
 }

library/src/main/java/com/google/android/exoplayer/ExoPlayer.java

@@ -98,6 +98,13 @@ public interface ExoPlayer {
   interface EventListener {
 
     /**
+     * Invoked when the player starts or stops loading the source.
+     *
+     * @param isLoading Whether the source is currently being loaded.
+     */
+    void onLoadingChanged(boolean isLoading);
+
+    /**
      * Invoked when the value returned from either {@link ExoPlayer#getPlayWhenReady()} or
      * {@link ExoPlayer#getPlaybackState()} changes.
      *
@@ -270,6 +277,13 @@ public interface ExoPlayer {
   boolean isPlayWhenReadyCommitted();
 
   /**
+   * Whether the player is currently loading the source.
+   *
+   * @return True if the player is currently loading the source. False otherwise.
+   */
+  boolean isLoading();
+
+  /**
    * Seeks to a position specified in milliseconds in the current source.
    *
    * @param positionMs The seek position.

library/src/main/java/com/google/android/exoplayer/ExoPlayerFactory.java

@@ -42,7 +42,7 @@ public final class ExoPlayerFactory {
    * @param trackSelector The {@link TrackSelector} that will be used by the instance.
    */
   public static SimpleExoPlayer newSimpleInstance(Context context, TrackSelector trackSelector) {
-    return newSimpleInstance(context, trackSelector, new DefaultBufferingControl(), null);
+    return newSimpleInstance(context, trackSelector, new DefaultLoadControl(), null);
   }
 
   /**
@@ -52,13 +52,13 @@ public final class ExoPlayerFactory {
    *
    * @param context A {@link Context}.
    * @param trackSelector The {@link TrackSelector} that will be used by the instance.
-   * @param bufferingControl The {@link BufferingControl} that will be used by the instance.
+   * @param loadControl The {@link LoadControl} that will be used by the instance.
    * @param drmSessionManager An optional {@link DrmSessionManager}. May be null if the instance
    *     will not be used for DRM protected playbacks.
    */
   public static SimpleExoPlayer newSimpleInstance(Context context, TrackSelector trackSelector,
-      BufferingControl bufferingControl, DrmSessionManager drmSessionManager) {
-    return newSimpleInstance(context, trackSelector, bufferingControl, drmSessionManager, false);
+      LoadControl loadControl, DrmSessionManager drmSessionManager) {
+    return newSimpleInstance(context, trackSelector, loadControl, drmSessionManager, false);
   }
 
   /**
@@ -68,7 +68,7 @@ public final class ExoPlayerFactory {
    *
    * @param context A {@link Context}.
    * @param trackSelector The {@link TrackSelector} that will be used by the instance.
-   * @param bufferingControl The {@link BufferingControl} that will be used by the instance.
+   * @param loadControl The {@link LoadControl} that will be used by the instance.
    * @param drmSessionManager An optional {@link DrmSessionManager}. May be null if the instance
    *     will not be used for DRM protected playbacks.
    * @param preferExtensionDecoders True to prefer {@link TrackRenderer} instances defined in
@@ -76,9 +76,9 @@ public final class ExoPlayerFactory {
    *     included in the application build for setting this flag to have any effect.
    */
   public static SimpleExoPlayer newSimpleInstance(Context context, TrackSelector trackSelector,
-      BufferingControl bufferingControl, DrmSessionManager drmSessionManager,
+      LoadControl loadControl, DrmSessionManager drmSessionManager,
       boolean preferExtensionDecoders) {
-    return newSimpleInstance(context, trackSelector, bufferingControl, drmSessionManager,
+    return newSimpleInstance(context, trackSelector, loadControl, drmSessionManager,
         preferExtensionDecoders, DEFAULT_ALLOWED_VIDEO_JOINING_TIME_MS);
   }
 
@@ -89,7 +89,7 @@ public final class ExoPlayerFactory {
    *
    * @param context A {@link Context}.
    * @param trackSelector The {@link TrackSelector} that will be used by the instance.
-   * @param bufferingControl The {@link BufferingControl} that will be used by the instance.
+   * @param loadControl The {@link LoadControl} that will be used by the instance.
    * @param drmSessionManager An optional {@link DrmSessionManager}. May be null if the instance
    *     will not be used for DRM protected playbacks.
    * @param preferExtensionDecoders True to prefer {@link TrackRenderer} instances defined in
@@ -99,9 +99,9 @@ public final class ExoPlayerFactory {
    *     seamlessly join an ongoing playback.
    */
   public static SimpleExoPlayer newSimpleInstance(Context context, TrackSelector trackSelector,
-      BufferingControl bufferingControl, DrmSessionManager drmSessionManager,
+      LoadControl loadControl, DrmSessionManager drmSessionManager,
       boolean preferExtensionDecoders, long allowedVideoJoiningTimeMs) {
-    return new SimpleExoPlayer(context, trackSelector, bufferingControl, drmSessionManager,
+    return new SimpleExoPlayer(context, trackSelector, loadControl, drmSessionManager,
         preferExtensionDecoders, allowedVideoJoiningTimeMs);
   }
 
@@ -114,7 +114,7 @@ public final class ExoPlayerFactory {
    * @param trackSelector The {@link TrackSelector} that will be used by the instance.
    */
   public static ExoPlayer newInstance(TrackRenderer[] renderers, TrackSelector trackSelector) {
-    return newInstance(renderers, trackSelector, new DefaultBufferingControl());
+    return newInstance(renderers, trackSelector, new DefaultLoadControl());
   }
 
   /**
@@ -124,11 +124,11 @@ public final class ExoPlayerFactory {
    *
    * @param renderers The {@link TrackRenderer}s that will be used by the instance.
    * @param trackSelector The {@link TrackSelector} that will be used by the instance.
-   * @param bufferingControl The {@link BufferingControl} that will be used by the instance.
+   * @param loadControl The {@link LoadControl} that will be used by the instance.
    */
   public static ExoPlayer newInstance(TrackRenderer[] renderers, TrackSelector trackSelector,
-      BufferingControl bufferingControl) {
-    return new ExoPlayerImpl(renderers, trackSelector, bufferingControl);
+      LoadControl loadControl) {
+    return new ExoPlayerImpl(renderers, trackSelector, loadControl);
   }
 
 }

library/src/main/java/com/google/android/exoplayer/ExoPlayerImpl.java

@@ -41,6 +41,7 @@ import java.util.concurrent.CopyOnWriteArraySet;
   private int playbackState;
   private int pendingPlayWhenReadyAcks;
   private int pendingSetSourceProviderAndSeekAcks;
+  private boolean isLoading;
 
   // Playback information when there is no pending seek/set source operation.
   private PlaybackInfo playbackInfo;
@@ -55,11 +56,11 @@ import java.util.concurrent.CopyOnWriteArraySet;
    *
    * @param renderers The {@link TrackRenderer}s that will be used by the instance.
    * @param trackSelector The {@link TrackSelector} that will be used by the instance.
-   * @param bufferingControl The {@link BufferingControl} that will be used by the instance.
+   * @param loadControl The {@link LoadControl} that will be used by the instance.
    */
   @SuppressLint("HandlerLeak")
   public ExoPlayerImpl(TrackRenderer[] renderers, TrackSelector trackSelector,
-      BufferingControl bufferingControl) {
+      LoadControl loadControl) {
     Log.i(TAG, "Init " + ExoPlayerLibraryInfo.VERSION);
     Assertions.checkNotNull(renderers);
     Assertions.checkState(renderers.length > 0);
@@ -72,8 +73,8 @@ import java.util.concurrent.CopyOnWriteArraySet;
         ExoPlayerImpl.this.handleEvent(msg);
       }
     };
-    internalPlayer = new ExoPlayerImplInternal(renderers, trackSelector, bufferingControl,
-        playWhenReady, eventHandler);
+    internalPlayer = new ExoPlayerImplInternal(renderers, trackSelector, loadControl, playWhenReady,
+        eventHandler);
     playbackInfo = new ExoPlayerImplInternal.PlaybackInfo(0);
   }
 
@@ -133,6 +134,11 @@ import java.util.concurrent.CopyOnWriteArraySet;
   }
 
   @Override
+  public boolean isLoading() {
+    return isLoading;
+  }
+
+  @Override
   public void seekTo(long positionMs) {
     seekTo(getCurrentSourceIndex(), positionMs);
   }
@@ -221,6 +227,13 @@ import java.util.concurrent.CopyOnWriteArraySet;
         }
         break;
       }
+      case ExoPlayerImplInternal.MSG_LOADING_CHANGED: {
+        isLoading = msg.arg1 != 0;
+        for (EventListener listener : listeners) {
+          listener.onLoadingChanged(isLoading);
+        }
+        break;
+      }
       case ExoPlayerImplInternal.MSG_SET_PLAY_WHEN_READY_ACK: {
         pendingPlayWhenReadyAcks--;
         if (pendingPlayWhenReadyAcks == 0) {

library/src/main/java/com/google/android/exoplayer/ExoPlayerImplInternal.java

@@ -35,8 +35,6 @@ import java.util.ArrayList;
 /**
  * Implements the internal behavior of {@link ExoPlayerImpl}.
  */
-// TODO[REFACTOR]: Make sure renderer errors that will prevent prepare from being called again are
-// always propagated properly.
 /* package */ final class ExoPlayerImplInternal implements Handler.Callback, SampleSource.Callback,
     InvalidationListener {
 
@@ -63,11 +61,12 @@ import java.util.ArrayList;
 
   // External messages
   public static final int MSG_STATE_CHANGED = 1;
-  public static final int MSG_SET_PLAY_WHEN_READY_ACK = 2;
-  public static final int MSG_SET_SOURCE_PROVIDER_ACK = 3;
-  public static final int MSG_SEEK_ACK = 4;
-  public static final int MSG_SOURCE_CHANGED = 5;
-  public static final int MSG_ERROR = 6;
+  public static final int MSG_LOADING_CHANGED = 2;
+  public static final int MSG_SET_PLAY_WHEN_READY_ACK = 3;
+  public static final int MSG_SET_SOURCE_PROVIDER_ACK = 4;
+  public static final int MSG_SEEK_ACK = 5;
+  public static final int MSG_SOURCE_CHANGED = 6;
+  public static final int MSG_ERROR = 7;
 
   // Internal messages
   private static final int MSG_SET_SOURCE_PROVIDER = 0;
@@ -93,7 +92,7 @@ import java.util.ArrayList;
   private static final int MAXIMUM_BUFFER_AHEAD_SOURCES = 100;
 
   private final TrackSelector trackSelector;
-  private final BufferingControl bufferingControl;
+  private final LoadControl loadControl;
   private final StandaloneMediaClock standaloneMediaClock;
   private final Handler handler;
   private final HandlerThread internalPlaybackThread;
@@ -108,6 +107,7 @@ import java.util.ArrayList;
   private boolean released;
   private boolean playWhenReady;
   private boolean rebuffering;
+  private boolean isLoading;
   private int state;
   private int customMessagesSent;
   private int customMessagesProcessed;
@@ -116,9 +116,9 @@ import java.util.ArrayList;
   private long internalPositionUs;
 
   public ExoPlayerImplInternal(TrackRenderer[] renderers, TrackSelector trackSelector,
-      BufferingControl bufferingControl, boolean playWhenReady, Handler eventHandler) {
+      LoadControl loadControl, boolean playWhenReady, Handler eventHandler) {
     this.trackSelector = trackSelector;
-    this.bufferingControl = bufferingControl;
+    this.loadControl = loadControl;
     this.playWhenReady = playWhenReady;
     this.eventHandler = eventHandler;
     this.state = ExoPlayer.STATE_IDLE;
@@ -294,6 +294,13 @@ import java.util.ArrayList;
     }
   }
 
+  private void setIsLoading(boolean isLoading) {
+    if (this.isLoading != isLoading) {
+      this.isLoading = isLoading;
+      eventHandler.obtainMessage(MSG_LOADING_CHANGED, isLoading ? 1 : 0, 0).sendToTarget();
+    }
+  }
+
   private void setSourceProviderInternal(SampleSourceProvider sourceProvider) {
     try {
       resetInternal();
@@ -524,7 +531,8 @@ import java.util.ArrayList;
     enabledRenderers = new TrackRenderer[0];
     sampleSourceProvider = null;
     timeline.reset();
-    bufferingControl.reset();
+    loadControl.reset();
+    setIsLoading(false);
   }
 
   private void sendMessagesInternal(ExoPlayerMessage[] messages) throws ExoPlaybackException {
@@ -572,7 +580,7 @@ import java.util.ArrayList;
 
     private Source playingSource;
     private Source readingSource;
-    private Source bufferingSource;
+    private Source loadingSource;
 
     private int pendingSourceIndex;
     private long playingSourceEndPositionUs;
@@ -587,62 +595,65 @@ import java.util.ArrayList;
     }
 
     public boolean haveSufficientBuffer(boolean rebuffering) {
-      if (bufferingSource == null) {
+      if (loadingSource == null) {
         return false;
       }
-      long positionUs = internalPositionUs - bufferingSource.offsetUs;
-      long bufferedPositionUs = !bufferingSource.prepared ? 0
-          : bufferingSource.sampleSource.getBufferedPositionUs();
+      long positionUs = internalPositionUs - loadingSource.offsetUs;
+      long bufferedPositionUs = !loadingSource.prepared ? 0
+          : loadingSource.sampleSource.getBufferedPositionUs();
       if (bufferedPositionUs == C.END_OF_SOURCE_US) {
         int sourceCount = sampleSourceProvider.getSourceCount();
         if (sourceCount != SampleSourceProvider.UNKNOWN_SOURCE_COUNT
-            && bufferingSource.index == sourceCount - 1) {
+            && loadingSource.index == sourceCount - 1) {
           return true;
         }
-        bufferedPositionUs = bufferingSource.sampleSource.getDurationUs();
+        bufferedPositionUs = loadingSource.sampleSource.getDurationUs();
       }
-      return bufferingControl.shouldStartPlayback(bufferedPositionUs - positionUs, rebuffering);
+      return loadControl.shouldStartPlayback(bufferedPositionUs - positionUs, rebuffering);
     }
 
     public void maybeThrowSourcePrepareError() throws IOException {
-      if (bufferingSource != null && !bufferingSource.prepared
-          && (readingSource == null || readingSource.nextSource == bufferingSource)) {
+      if (loadingSource != null && !loadingSource.prepared
+          && (readingSource == null || readingSource.nextSource == loadingSource)) {
         for (TrackRenderer renderer : enabledRenderers) {
           if (!renderer.hasReadStreamToEnd()) {
             return;
           }
         }
-        bufferingSource.sampleSource.maybeThrowPrepareError();
+        loadingSource.sampleSource.maybeThrowPrepareError();
       }
     }
 
     public void updateSources() throws ExoPlaybackException, IOException {
-      // TODO[playlists]: Let sample source providers invalidate sources that are already buffering.
+      // TODO[playlists]: Let sample source providers invalidate sources that are already loaded.
 
-      // Update the buffering source.
+      // Update the loading source.
       int sourceCount = sampleSourceProvider.getSourceCount();
-      if (bufferingSource == null
-          || (bufferingSource.isFullyBuffered() && bufferingSource.index
+      if (loadingSource == null
+          || (loadingSource.isFullyBuffered() && loadingSource.index
               - (playingSource != null ? playingSource.index : 0) < MAXIMUM_BUFFER_AHEAD_SOURCES)) {
-        // Try and obtain the next source to start buffering.
-        int sourceIndex = bufferingSource == null ? pendingSourceIndex : bufferingSource.index + 1;
+        // Try and obtain the next source to start loading.
+        int sourceIndex = loadingSource == null ? pendingSourceIndex : loadingSource.index + 1;
         if (sourceCount == SampleSourceProvider.UNKNOWN_SOURCE_COUNT || sourceIndex < sourceCount) {
           // Attempt to create the next source.
           SampleSource sampleSource = sampleSourceProvider.createSource(sourceIndex);
           if (sampleSource != null) {
             Source newSource = new Source(renderers, trackSelector, sampleSource, sourceIndex);
-            if (bufferingSource != null) {
-              bufferingSource.setNextSource(newSource);
+            if (loadingSource != null) {
+              loadingSource.setNextSource(newSource);
             }
-            bufferingSource = newSource;
+            loadingSource = newSource;
             long startPositionUs = playingSource == null ? playbackInfo.positionUs : 0;
-            bufferingSource.sampleSource.prepare(ExoPlayerImplInternal.this,
-                bufferingControl.getAllocator(), startPositionUs);
+            setIsLoading(true);
+            loadingSource.sampleSource.prepare(ExoPlayerImplInternal.this,
+                loadControl.getAllocator(), startPositionUs);
           }
         }
       }
 
-      if (bufferingSource != null && bufferingSource.needsContinueLoading) {
+      if (loadingSource == null || loadingSource.isFullyBuffered()) {
+        setIsLoading(false);
+      } else if (loadingSource != null && loadingSource.needsContinueLoading) {
         maybeContinueLoading();
       }
 
@@ -713,15 +724,15 @@ import java.util.ArrayList;
     }
 
     public void handleSourcePrepared(SampleSource source) throws ExoPlaybackException {
-      if (bufferingSource == null || bufferingSource.sampleSource != source) {
+      if (loadingSource == null || loadingSource.sampleSource != source) {
         // Stale event.
         return;
       }
       long startPositionUs = playingSource == null ? playbackInfo.positionUs : 0;
-      bufferingSource.handlePrepared(startPositionUs, bufferingControl);
+      loadingSource.handlePrepared(startPositionUs, loadControl);
       if (playingSource == null) {
         // This is the first prepared source, so start playing it.
-        readingSource = bufferingSource;
+        readingSource = loadingSource;
         setPlayingSource(readingSource);
         updateTimelineState();
       }
@@ -729,24 +740,27 @@ import java.util.ArrayList;
     }
 
     public void handleContinueLoadingRequested(SampleSource source) {
-      if (bufferingSource == null || bufferingSource.sampleSource != source) {
+      if (loadingSource == null || loadingSource.sampleSource != source) {
         return;
       }
       maybeContinueLoading();
     }
 
     private void maybeContinueLoading() {
-      long nextLoadPositionUs = bufferingSource.sampleSource.getNextLoadPositionUs();
+      long nextLoadPositionUs = loadingSource.sampleSource.getNextLoadPositionUs();
       if (nextLoadPositionUs != C.END_OF_SOURCE_US) {
-        long positionUs = internalPositionUs - bufferingSource.offsetUs;
+        long positionUs = internalPositionUs - loadingSource.offsetUs;
         long bufferedDurationUs = nextLoadPositionUs - positionUs;
-        boolean continueBuffering = bufferingControl.shouldContinueBuffering(bufferedDurationUs);
-        if (continueBuffering) {
-          bufferingSource.needsContinueLoading = false;
-          bufferingSource.sampleSource.continueLoading(positionUs);
+        boolean continueLoading = loadControl.shouldContinueLoading(bufferedDurationUs);
+        setIsLoading(continueLoading);
+        if (continueLoading) {
+          loadingSource.needsContinueLoading = false;
+          loadingSource.sampleSource.continueLoading(positionUs);
         } else {
-          bufferingSource.needsContinueLoading = true;
+          loadingSource.needsContinueLoading = true;
         }
+      } else {
+        setIsLoading(false);
       }
     }
 
@@ -768,7 +782,7 @@ import java.util.ArrayList;
         setPlayingSource(newPlayingSource);
         updateTimelineState();
         readingSource = playingSource;
-        bufferingSource = playingSource;
+        loadingSource = playingSource;
         if (playingSource.hasEnabledTracks) {
           seekPositionUs = playingSource.sampleSource.seekToUs(seekPositionUs);
         }
@@ -782,7 +796,7 @@ import java.util.ArrayList;
         enabledRenderers = new TrackRenderer[0];
         playingSource = null;
         readingSource = null;
-        bufferingSource = null;
+        loadingSource = null;
         pendingSourceIndex = sourceIndex;
         resetInternalPosition(seekPositionUs);
       }
@@ -818,13 +832,13 @@ import java.util.ArrayList;
         }
         playingSource.nextSource = null;
         readingSource = playingSource;
-        bufferingSource = playingSource;
+        loadingSource = playingSource;
         playingSourceEndPositionUs = C.UNSET_TIME_US;
 
         // Update streams for the new selection, recreating all streams if reading ahead.
         boolean recreateStreams = readingSource != playingSource;
         TrackSelectionArray playingSourceOldTrackSelections = playingSource.sourceTrackSelections;
-        playingSource.updateSourceTrackSelection(playbackInfo.positionUs, bufferingControl,
+        playingSource.updateSourceTrackSelection(playbackInfo.positionUs, loadControl,
             recreateStreams);
 
         int enabledRendererCount = 0;
@@ -858,21 +872,21 @@ import java.util.ArrayList;
         enableRenderers(rendererWasEnabledFlags, enabledRendererCount);
       } else {
         // Release and re-prepare/buffer sources after the one whose selection changed.
-        bufferingSource = source;
-        source = bufferingSource.nextSource;
+        loadingSource = source;
+        source = loadingSource.nextSource;
         while (source != null) {
           source.release();
           source = source.nextSource;
         }
-        bufferingSource.nextSource = null;
-        long positionUs = Math.max(0, internalPositionUs - bufferingSource.offsetUs);
-        bufferingSource.updateSourceTrackSelection(positionUs, bufferingControl, false);
+        loadingSource.nextSource = null;
+        long positionUs = Math.max(0, internalPositionUs - loadingSource.offsetUs);
+        loadingSource.updateSourceTrackSelection(positionUs, loadControl, false);
       }
       maybeContinueLoading();
     }
 
     public void reset() {
-      Source source = playingSource != null ? playingSource : bufferingSource;
+      Source source = playingSource != null ? playingSource : loadingSource;
       while (source != null) {
         source.release();
         source = source.nextSource;
@@ -881,7 +895,7 @@ import java.util.ArrayList;
       isEnded = false;
       playingSource = null;
       readingSource = null;
-      bufferingSource = null;
+      loadingSource = null;
       playingSourceEndPositionUs = C.UNSET_TIME_US;
       pendingSourceIndex = 0;
       playbackInfo = new PlaybackInfo(0);
@@ -995,7 +1009,6 @@ import java.util.ArrayList;
         int index) {
       this.renderers = renderers;
       this.trackSelector = trackSelector;
-
       this.sampleSource = sampleSource;
       this.index = index;
       trackStreams = new TrackStream[renderers.length];
@@ -1011,11 +1024,11 @@ import java.util.ArrayList;
           || sampleSource.getBufferedPositionUs() == C.END_OF_SOURCE_US);
     }
 
-    public void handlePrepared(long positionUs, BufferingControl bufferingControl)
+    public void handlePrepared(long positionUs, LoadControl loadControl)
         throws ExoPlaybackException {
       prepared = true;
       selectTracks();
-      updateSourceTrackSelection(positionUs, bufferingControl, false);
+      updateSourceTrackSelection(positionUs, loadControl, false);
     }
 
     public boolean selectTracks() throws ExoPlaybackException {
@@ -1030,7 +1043,7 @@ import java.util.ArrayList;
       return true;
     }
 
-    public void updateSourceTrackSelection(long positionUs, BufferingControl bufferingControl,
+    public void updateSourceTrackSelection(long positionUs, LoadControl loadControl,
         boolean forceRecreateStreams) throws ExoPlaybackException {
       // Populate lists of streams that are being disabled/newly enabled.
       ArrayList<TrackStream> oldStreams = new ArrayList<>();
@@ -1069,7 +1082,7 @@ import java.util.ArrayList;
       }
 
       // The track selection has changed.
-      bufferingControl.onTrackSelections(renderers, sampleSource.getTrackGroups(), trackSelections);
+      loadControl.onTrackSelections(renderers, sampleSource.getTrackGroups(), trackSelections);
     }
 
     public void release() {

library/src/main/java/com/google/android/exoplayer/BufferingControl.java → library/src/main/java/com/google/android/exoplayer/LoadControl.java

@@ -20,7 +20,7 @@ import com.google.android.exoplayer.upstream.Allocator;
 /**
  * Controls buffering of media.
  */
-public interface BufferingControl {
+public interface LoadControl {
 
   /**
    * Invoked by the player when a track selection occurs.
@@ -55,11 +55,11 @@ public interface BufferingControl {
   boolean shouldStartPlayback(long bufferedDurationUs, boolean rebuffering);
 
   /**
-   * Invoked by the player to determine whether buffering should continue.
+   * Invoked by the player to determine whether it should continue to load the source.
    *
    * @param bufferedDurationUs The duration of media that's currently buffered.
-   * @return True if the buffering should continue. False otherwise.
+   * @return True if the loading should continue. False otherwise.
    */
-  boolean shouldContinueBuffering(long bufferedDurationUs);
+  boolean shouldContinueLoading(long bufferedDurationUs);
 
 }

library/src/main/java/com/google/android/exoplayer/SimpleExoPlayer.java

@@ -111,7 +111,7 @@ public final class SimpleExoPlayer implements ExoPlayer {
   private CodecCounters audioCodecCounters;
 
   /* package */ SimpleExoPlayer(Context context, TrackSelector trackSelector,
-      BufferingControl bufferingControl, DrmSessionManager drmSessionManager,
+      LoadControl loadControl, DrmSessionManager drmSessionManager,
       boolean preferExtensionDecoders, long allowedVideoJoiningTimeMs) {
     mainHandler = new Handler();
     bandwidthMeter = new DefaultBandwidthMeter();
@@ -145,7 +145,7 @@ public final class SimpleExoPlayer implements ExoPlayer {
     this.audioRendererCount = audioRendererCount;
 
     // Build the player and associated objects.
-    player = new ExoPlayerImpl(renderers, trackSelector, bufferingControl);
+    player = new ExoPlayerImpl(renderers, trackSelector, loadControl);
   }
 
   /**
@@ -339,6 +339,11 @@ public final class SimpleExoPlayer implements ExoPlayer {
   }
 
   @Override
+  public boolean isLoading() {
+    return player.isLoading();
+  }
+
+  @Override
   public void seekTo(long positionMs) {
     player.seekTo(positionMs);
   }

library/src/main/java/com/google/android/exoplayer/util/DebugTextViewHelper.java

@@ -154,6 +154,11 @@ public final class DebugTextViewHelper implements Runnable, ExoPlayer.EventListe
   // ExoPlayer.EventListener implementation
 
   @Override
+  public void onLoadingChanged(boolean isLoading) {
+    // Do nothing.
+  }
+
+  @Override
   public void onPlayerStateChanged(boolean playWhenReady, int playbackState) {
     updateTextView();
   }

playbacktests/src/main/java/com/google/android/exoplayer/playbacktests/util/ExoHostedTest.java

@@ -174,7 +174,12 @@ public abstract class ExoHostedTest implements HostedTest, ExoPlayer.EventListen
     assertPassed(audioCodecCounters, videoCodecCounters);
   }
 
-  // ExoPlayer.Listener
+  // ExoPlayer.EventListener
+
+  @Override
+  public void onLoadingChanged(boolean isLoading) {
+    // Do nothing.
+  }
 
   @Override
   public final void onPlayerStateChanged(boolean playWhenReady, int playbackState) {