Add convenience methods to query current window

- Support querying whether the current window is dynamic
  and seekable. The new methods are similar to getDuration,
  which is also a convenience method for the current window.
- Improve demo app to restore positions in VOD items within
  playlists where the last item is live. Also restore the
  position within the window for live items unless the player
  failed with BehindLiveWindowException.

Issue: #2320

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=144443898

demo/src/main/java/com/google/android/exoplayer2/demo/PlayerActivity.java

@@ -45,6 +45,7 @@
 import com.google.android.exoplayer2.extractor.DefaultExtractorsFactory;
 import com.google.android.exoplayer2.mediacodec.MediaCodecRenderer.DecoderInitializationException;
 import com.google.android.exoplayer2.mediacodec.MediaCodecUtil.DecoderQueryException;
+import com.google.android.exoplayer2.source.BehindLiveWindowException;
 import com.google.android.exoplayer2.source.ConcatenatingMediaSource;
 import com.google.android.exoplayer2.source.ExtractorMediaSource;
 import com.google.android.exoplayer2.source.MediaSource;
@@ -100,7 +101,6 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
   }
 
   private Handler mainHandler;
-  private Timeline.Window window;
   private EventLogger eventLogger;
   private SimpleExoPlayerView simpleExoPlayerView;
   private LinearLayout debugRootView;
@@ -115,19 +115,18 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
   private boolean playerNeedsSource;
 
   private boolean shouldAutoPlay;
-  private boolean isTimelineStatic;
-  private int playerWindow;
-  private long playerPosition;
+  private int resumeWindow;
+  private long resumePosition;
 
   // Activity lifecycle
 
   @Override
   public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     shouldAutoPlay = true;
+    clearResumePosition();
     mediaDataSourceFactory = buildDataSourceFactory(true);
     mainHandler = new Handler();
-    window = new Timeline.Window();
     if (CookieHandler.getDefault() != DEFAULT_COOKIE_MANAGER) {
       CookieHandler.setDefault(DEFAULT_COOKIE_MANAGER);
     }
@@ -148,7 +147,8 @@ public void onCreate(Bundle savedInstanceState) {
   @Override
   public void onNewIntent(Intent intent) {
     releasePlayer();
-    isTimelineStatic = false;
+    shouldAutoPlay = true;
+    clearResumePosition();
     setIntent(intent);
   }
 
@@ -264,7 +264,7 @@ private void initializePlayer() {
       @SimpleExoPlayer.ExtensionRendererMode int extensionRendererMode =
           ((DemoApplication) getApplication()).useExtensionRenderers()
               ? (preferExtensionDecoders ? SimpleExoPlayer.EXTENSION_RENDERER_MODE_PREFER
-                  : SimpleExoPlayer.EXTENSION_RENDERER_MODE_ON)
+              : SimpleExoPlayer.EXTENSION_RENDERER_MODE_ON)
               : SimpleExoPlayer.EXTENSION_RENDERER_MODE_OFF;
       TrackSelection.Factory videoTrackSelectionFactory =
           new AdaptiveVideoTrackSelection.Factory(BANDWIDTH_METER);
@@ -281,13 +281,6 @@ private void initializePlayer() {
       player.setMetadataOutput(eventLogger);
 
       simpleExoPlayerView.setPlayer(player);
-      if (isTimelineStatic) {
-        if (playerPosition == C.TIME_UNSET) {
-          player.seekToDefaultPosition(playerWindow);
-        } else {
-          player.seekTo(playerWindow, playerPosition);
-        }
-      }
       player.setPlayWhenReady(shouldAutoPlay);
       debugViewHelper = new DebugTextViewHelper(player, debugTextView);
       debugViewHelper.start();
@@ -324,7 +317,8 @@ private void initializePlayer() {
       }
       MediaSource mediaSource = mediaSources.length == 1 ? mediaSources[0]
           : new ConcatenatingMediaSource(mediaSources);
-      player.prepare(mediaSource, !isTimelineStatic, !isTimelineStatic);
+      player.seekTo(resumeWindow, resumePosition);
+      player.prepare(mediaSource, false, false);
       playerNeedsSource = false;
       updateButtonVisibilities();
     }
@@ -367,12 +361,7 @@ private void releasePlayer() {
       debugViewHelper.stop();
       debugViewHelper = null;
       shouldAutoPlay = player.getPlayWhenReady();
-      playerWindow = player.getCurrentWindowIndex();
-      playerPosition = C.TIME_UNSET;
-      Timeline timeline = player.getCurrentTimeline();
-      if (!timeline.isEmpty() && timeline.getWindow(playerWindow, window).isSeekable) {
-        playerPosition = player.getCurrentPosition();
-      }
+      updateResumePosition();
       player.release();
       player = null;
       trackSelector = null;
@@ -381,6 +370,17 @@ private void releasePlayer() {
     }
   }
 
+  private void updateResumePosition() {
+    resumeWindow = player.getCurrentWindowIndex();
+    resumePosition = player.isCurrentWindowSeekable() ? Math.max(0, player.getCurrentPosition())
+        : C.TIME_UNSET;
+  }
+
+  private void clearResumePosition() {
+    resumeWindow = 0;
+    resumePosition = C.TIME_UNSET;
+  }
+
   /**
    * Returns a new DataSource factory.
    *
@@ -427,8 +427,7 @@ public void onPositionDiscontinuity() {
 
   @Override
   public void onTimelineChanged(Timeline timeline, Object manifest) {
-    isTimelineStatic = !timeline.isEmpty()
-        && !timeline.getWindow(timeline.getWindowCount() - 1, window).isDynamic;
+    // Do nothing.
   }
 
   @Override
@@ -460,6 +459,11 @@ public void onPlayerError(ExoPlaybackException e) {
       showToast(errorString);
     }
     playerNeedsSource = true;
+    if (isBehindLiveWindow(e)) {
+      clearResumePosition();
+    } else {
+      updateResumePosition();
+    }
     updateButtonVisibilities();
     showControls();
   }
@@ -535,4 +539,18 @@ private void showToast(String message) {
     Toast.makeText(getApplicationContext(), message, Toast.LENGTH_LONG).show();
   }
 
+  private static boolean isBehindLiveWindow(ExoPlaybackException e) {
+    if (e.type != ExoPlaybackException.TYPE_SOURCE) {
+      return false;
+    }
+    Throwable cause = e.getSourceException();
+    while (cause != null) {
+      if (cause instanceof BehindLiveWindowException) {
+        return true;
+      }
+      cause = cause.getCause();
+    }
+    return false;
+  }
+
 }

library/src/main/java/com/google/android/exoplayer2/ExoPlayer.java

@@ -447,4 +447,20 @@ public ExoPlayerMessage(ExoPlayerComponent target, int messageType, Object messa
    */
   int getBufferedPercentage();
 
+  /**
+   * Returns whether the current window is dynamic, or {@code false} if the {@link Timeline} is
+   * empty.
+   *
+   * @see Timeline.Window#isDynamic
+   */
+  boolean isCurrentWindowDynamic();
+
+  /**
+   * Returns whether the current window is seekable, or {@code false} if the {@link Timeline} is
+   * empty.
+   *
+   * @see Timeline.Window#isSeekable
+   */
+  boolean isCurrentWindowSeekable();
+
 }

library/src/main/java/com/google/android/exoplayer2/ExoPlayerImpl.java

@@ -271,6 +271,22 @@ public int getBufferedPercentage() {
         : (int) (duration == 0 ? 100 : (bufferedPosition * 100) / duration);
   }
 
+  @Override
+  public boolean isCurrentWindowDynamic() {
+    if (timeline.isEmpty()) {
+      return false;
+    }
+    return timeline.getWindow(getCurrentWindowIndex(), window).isDynamic;
+  }
+
+  @Override
+  public boolean isCurrentWindowSeekable() {
+    if (timeline.isEmpty()) {
+      return false;
+    }
+    return timeline.getWindow(getCurrentWindowIndex(), window).isSeekable;
+  }
+
   @Override
   public int getRendererCount() {
     return renderers.length;

library/src/main/java/com/google/android/exoplayer2/SimpleExoPlayer.java

@@ -546,63 +546,73 @@ public void blockingSendMessages(ExoPlayerMessage... messages) {
   }
 
   @Override
-  public int getCurrentPeriodIndex() {
-    return player.getCurrentPeriodIndex();
+  public int getRendererCount() {
+    return player.getRendererCount();
   }
 
   @Override
-  public int getCurrentWindowIndex() {
-    return player.getCurrentWindowIndex();
+  public int getRendererType(int index) {
+    return player.getRendererType(index);
   }
 
   @Override
-  public long getDuration() {
-    return player.getDuration();
+  public TrackGroupArray getCurrentTrackGroups() {
+    return player.getCurrentTrackGroups();
   }
 
   @Override
-  public long getCurrentPosition() {
-    return player.getCurrentPosition();
+  public TrackSelectionArray getCurrentTrackSelections() {
+    return player.getCurrentTrackSelections();
   }
 
   @Override
-  public long getBufferedPosition() {
-    return player.getBufferedPosition();
+  public Timeline getCurrentTimeline() {
+    return player.getCurrentTimeline();
   }
 
   @Override
-  public int getBufferedPercentage() {
-    return player.getBufferedPercentage();
+  public Object getCurrentManifest() {
+    return player.getCurrentManifest();
   }
 
   @Override
-  public int getRendererCount() {
-    return player.getRendererCount();
+  public int getCurrentPeriodIndex() {
+    return player.getCurrentPeriodIndex();
   }
 
   @Override
-  public int getRendererType(int index) {
-    return player.getRendererType(index);
+  public int getCurrentWindowIndex() {
+    return player.getCurrentWindowIndex();
   }
 
   @Override
-  public TrackGroupArray getCurrentTrackGroups() {
-    return player.getCurrentTrackGroups();
+  public long getDuration() {
+    return player.getDuration();
   }
 
   @Override
-  public TrackSelectionArray getCurrentTrackSelections() {
-    return player.getCurrentTrackSelections();
+  public long getCurrentPosition() {
+    return player.getCurrentPosition();
   }
 
   @Override
-  public Timeline getCurrentTimeline() {
-    return player.getCurrentTimeline();
+  public long getBufferedPosition() {
+    return player.getBufferedPosition();
   }
 
   @Override
-  public Object getCurrentManifest() {
-    return player.getCurrentManifest();
+  public int getBufferedPercentage() {
+    return player.getBufferedPercentage();
+  }
+
+  @Override
+  public boolean isCurrentWindowDynamic() {
+    return player.isCurrentWindowDynamic();
+  }
+
+  @Override
+  public boolean isCurrentWindowSeekable() {
+    return player.isCurrentWindowSeekable();
   }
 
   // Renderer building.