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.drm.UnsupportedDrmException;
 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;
@@ -115,9 +115,8 @@ 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
 
@@ -125,9 +124,9 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
   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 class PlayerActivity extends Activity implements OnClickListener, ExoPlay
   @Override
   public void onNewIntent(Intent intent) {
     releasePlayer();
-    isTimelineStatic = false;
+    shouldAutoPlay = true;
+    clearResumePosition();
     setIntent(intent);
   }
 
@@ -281,13 +281,6 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
       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 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
       }
       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 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
       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 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
     }
   }
 
+  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 class PlayerActivity extends Activity implements OnClickListener, ExoPlay
 
   @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 class PlayerActivity extends Activity implements OnClickListener, ExoPlay
       showToast(errorString);
     }
     playerNeedsSource = true;
+    if (isBehindLiveWindow(e)) {
+      clearResumePosition();
+    } else {
+      updateResumePosition();
+    }
     updateButtonVisibilities();
     showControls();
   }
@@ -535,4 +539,18 @@ public class PlayerActivity extends Activity implements OnClickListener, ExoPlay
     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 interface ExoPlayer {
    */
   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 @@ import java.util.concurrent.CopyOnWriteArraySet;
         : (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

@@ -545,6 +545,36 @@ public class SimpleExoPlayer implements ExoPlayer {
     player.blockingSendMessages(messages);
   }
 
+  @Override
+  public int getRendererCount() {
+    return player.getRendererCount();
+  }
+
+  @Override
+  public int getRendererType(int index) {
+    return player.getRendererType(index);
+  }
+
+  @Override
+  public TrackGroupArray getCurrentTrackGroups() {
+    return player.getCurrentTrackGroups();
+  }
+
+  @Override
+  public TrackSelectionArray getCurrentTrackSelections() {
+    return player.getCurrentTrackSelections();
+  }
+
+  @Override
+  public Timeline getCurrentTimeline() {
+    return player.getCurrentTimeline();
+  }
+
+  @Override
+  public Object getCurrentManifest() {
+    return player.getCurrentManifest();
+  }
+
   @Override
   public int getCurrentPeriodIndex() {
     return player.getCurrentPeriodIndex();
@@ -576,33 +606,13 @@ public class SimpleExoPlayer implements ExoPlayer {
   }
 
   @Override
-  public int getRendererCount() {
-    return player.getRendererCount();
+  public boolean isCurrentWindowDynamic() {
+    return player.isCurrentWindowDynamic();
   }
 
   @Override
-  public int getRendererType(int index) {
-    return player.getRendererType(index);
-  }
-
-  @Override
-  public TrackGroupArray getCurrentTrackGroups() {
-    return player.getCurrentTrackGroups();
-  }
-
-  @Override
-  public TrackSelectionArray getCurrentTrackSelections() {
-    return player.getCurrentTrackSelections();
-  }
-
-  @Override
-  public Timeline getCurrentTimeline() {
-    return player.getCurrentTimeline();
-  }
-
-  @Override
-  public Object getCurrentManifest() {
-    return player.getCurrentManifest();
+  public boolean isCurrentWindowSeekable() {
+    return player.isCurrentWindowSeekable();
   }
 
   // Renderer building.