Make play button behave differently in IDLE and ENDED states

- In IDLE, the button will now call a preparer. This allows
  removal of the separate retry button from the demo app.
- In ENDED, the button will seek back to the default position
  and play.
- Behavior is made consistent with LeanbackPlayerAdapter.

Issue: #3689

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=182506855

RELEASENOTES.md

@@ -19,12 +19,15 @@
     periods.
   * Replaced `ExoPlayer.sendMessages` with `ExoPlayer.createMessage` to allow
     more customization of the message. Now supports setting a message delivery
-    playback position and/or a delivery handler.
+    playback position and/or a delivery handler
     ([#2189](https://github.com/google/ExoPlayer/issues/2189)).
 * UI components:
   * Generalized player and control views to allow them to bind with any
     `Player`, and renamed them to `PlayerView` and `PlayerControlView`
     respectively.
+  * Made `PlayerView`'s play button behave correctly when the player is ended
+    ([#3689](https://github.com/google/ExoPlayer/issues/3689)), and call a
+    `PlaybackPreparer` when the player is idle.
 * Buffering:
   * Allow a back-buffer of media to be retained behind the current playback
     position, for fast backward seeking. The back-buffer can be configured by

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

@@ -39,6 +39,7 @@ import com.google.android.exoplayer2.C.ContentType;
 import com.google.android.exoplayer2.DefaultRenderersFactory;
 import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.ExoPlayerFactory;
+import com.google.android.exoplayer2.PlaybackPreparer;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.SimpleExoPlayer;
 import com.google.android.exoplayer2.drm.DefaultDrmSessionManager;
@@ -82,7 +83,7 @@ import java.util.UUID;
 
 /** An activity that plays media using {@link SimpleExoPlayer}. */
 public class PlayerActivity extends Activity
-    implements OnClickListener, PlayerControlView.VisibilityListener {
+    implements OnClickListener, PlaybackPreparer, PlayerControlView.VisibilityListener {
 
   public static final String DRM_SCHEME_EXTRA = "drm_scheme";
   public static final String DRM_LICENSE_URL = "drm_license_url";
@@ -114,7 +115,6 @@ public class PlayerActivity extends Activity
   private PlayerView playerView;
   private LinearLayout debugRootView;
   private TextView debugTextView;
-  private Button retryButton;
 
   private DataSource.Factory mediaDataSourceFactory;
   private SimpleExoPlayer player;
@@ -152,8 +152,6 @@ public class PlayerActivity extends Activity
     rootView.setOnClickListener(this);
     debugRootView = findViewById(R.id.controls_root);
     debugTextView = findViewById(R.id.debug_text_view);
-    retryButton = findViewById(R.id.retry_button);
-    retryButton.setOnClickListener(this);
 
     playerView = findViewById(R.id.player_view);
     playerView.setControllerVisibilityListener(this);
@@ -229,9 +227,7 @@ public class PlayerActivity extends Activity
 
   @Override
   public void onClick(View view) {
-    if (view == retryButton) {
-      initializePlayer();
-    } else if (view.getParent() == debugRootView) {
+    if (view.getParent() == debugRootView) {
       MappedTrackInfo mappedTrackInfo = trackSelector.getCurrentMappedTrackInfo();
       if (mappedTrackInfo != null) {
         trackSelectionHelper.showSelectionDialog(
@@ -240,6 +236,13 @@ public class PlayerActivity extends Activity
     }
   }
 
+  // PlaybackControlView.PlaybackPreparer implementation
+
+  @Override
+  public void preparePlayback() {
+    initializePlayer();
+  }
+
   // PlaybackControlView.VisibilityListener implementation
 
   @Override
@@ -301,9 +304,10 @@ public class PlayerActivity extends Activity
       player.addMetadataOutput(eventLogger);
       player.addAudioDebugListener(eventLogger);
       player.addVideoDebugListener(eventLogger);
+      player.setPlayWhenReady(shouldAutoPlay);
 
       playerView.setPlayer(player);
-      player.setPlayWhenReady(shouldAutoPlay);
+      playerView.setPlaybackPreparer(this);
       debugViewHelper = new DebugTextViewHelper(player, debugTextView);
       debugViewHelper.start();
     }
@@ -502,10 +506,6 @@ public class PlayerActivity extends Activity
 
   private void updateButtonVisibilities() {
     debugRootView.removeAllViews();
-
-    retryButton.setVisibility(inErrorState ? View.VISIBLE : View.GONE);
-    debugRootView.addView(retryButton);
-
     if (player == null) {
       return;
     }

demos/main/src/main/res/layout/player_activity.xml

@@ -42,15 +42,7 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:orientation="horizontal"
-        android:visibility="gone">
-
-      <Button android:id="@+id/retry_button"
-          android:layout_width="wrap_content"
-          android:layout_height="wrap_content"
-          android:text="@string/retry"
-          android:visibility="gone"/>
-
-    </LinearLayout>
+        android:visibility="gone"/>
 
   </LinearLayout>
 

demos/main/src/main/res/values/strings.xml

@@ -23,8 +23,6 @@
 
   <string name="text">Text</string>
 
-  <string name="retry">Retry</string>
-
   <string name="selection_disabled">Disabled</string>
 
   <string name="selection_default">Default</string>

extensions/leanback/src/main/java/com/google/android/exoplayer2/ext/leanback/LeanbackPlayerAdapter.java

@@ -30,6 +30,7 @@ import com.google.android.exoplayer2.ControlDispatcher;
 import com.google.android.exoplayer2.DefaultControlDispatcher;
 import com.google.android.exoplayer2.ExoPlaybackException;
 import com.google.android.exoplayer2.ExoPlayerLibraryInfo;
+import com.google.android.exoplayer2.PlaybackPreparer;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Player.DiscontinuityReason;
 import com.google.android.exoplayer2.Player.TimelineChangeReason;
@@ -50,6 +51,7 @@ public final class LeanbackPlayerAdapter extends PlayerAdapter {
   private final ComponentListener componentListener;
   private final Runnable updateProgressRunnable;
 
+  private @Nullable PlaybackPreparer playbackPreparer;
   private ControlDispatcher controlDispatcher;
   private ErrorMessageProvider<? super ExoPlaybackException> errorMessageProvider;
   private SurfaceHolderGlueHost surfaceHolderGlueHost;
@@ -83,6 +85,15 @@ public final class LeanbackPlayerAdapter extends PlayerAdapter {
   }
 
   /**
+   * Sets the {@link PlaybackPreparer}.
+   *
+   * @param playbackPreparer The {@link PlaybackPreparer}.
+   */
+  public void setPlaybackPreparer(@Nullable PlaybackPreparer playbackPreparer) {
+    this.playbackPreparer = playbackPreparer;
+  }
+
+  /**
    * Sets the {@link ControlDispatcher}.
    *
    * @param controlDispatcher The {@link ControlDispatcher}, or null to use
@@ -165,7 +176,11 @@ public final class LeanbackPlayerAdapter extends PlayerAdapter {
 
   @Override
   public void play() {
-    if (player.getPlaybackState() == Player.STATE_ENDED) {
+    if (player.getPlaybackState() == Player.STATE_IDLE) {
+      if (playbackPreparer != null) {
+        playbackPreparer.preparePlayback();
+      }
+    } else if (player.getPlaybackState() == Player.STATE_ENDED) {
       controlDispatcher.dispatchSeekTo(player, player.getCurrentWindowIndex(), C.TIME_UNSET);
     }
     if (controlDispatcher.dispatchSetPlayWhenReady(player, true)) {

library/core/src/main/java/com/google/android/exoplayer2/PlaybackPreparer.java

+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.android.exoplayer2;
+
+/** Called to prepare a playback. */
+public interface PlaybackPreparer {
+
+  /** Called to prepare a playback. */
+  void preparePlayback();
+}

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

@@ -31,6 +31,7 @@ import android.widget.ImageView;
 import android.widget.TextView;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ExoPlayerLibraryInfo;
+import com.google.android.exoplayer2.PlaybackPreparer;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Timeline;
 import com.google.android.exoplayer2.util.Assertions;
@@ -217,6 +218,7 @@ public class PlayerControlView extends FrameLayout {
   private Player player;
   private com.google.android.exoplayer2.ControlDispatcher controlDispatcher;
   private VisibilityListener visibilityListener;
+  private @Nullable PlaybackPreparer playbackPreparer;
 
   private boolean isAttachedToWindow;
   private boolean showMultiWindowTimeBar;
@@ -432,6 +434,15 @@ public class PlayerControlView extends FrameLayout {
   }
 
   /**
+   * Sets the {@link PlaybackPreparer}.
+   *
+   * @param playbackPreparer The {@link PlaybackPreparer}.
+   */
+  public void setPlaybackPreparer(@Nullable PlaybackPreparer playbackPreparer) {
+    this.playbackPreparer = playbackPreparer;
+  }
+
+  /**
    * Sets the {@link com.google.android.exoplayer2.ControlDispatcher}.
    *
    * @param controlDispatcher The {@link com.google.android.exoplayer2.ControlDispatcher}, or null
@@ -599,7 +610,7 @@ public class PlayerControlView extends FrameLayout {
       return;
     }
     boolean requestPlayPauseFocus = false;
-    boolean playing = player != null && player.getPlayWhenReady();
+    boolean playing = isPlaying();
     if (playButton != null) {
       requestPlayPauseFocus |= playing && playButton.isFocused();
       playButton.setVisibility(playing ? View.GONE : View.VISIBLE);
@@ -811,7 +822,7 @@ public class PlayerControlView extends FrameLayout {
   }
 
   private void requestPlayPauseFocus() {
-    boolean playing = player != null && player.getPlayWhenReady();
+    boolean playing = isPlaying();
     if (!playing && playButton != null) {
       playButton.requestFocus();
     } else if (playing && pauseButton != null) {
@@ -985,6 +996,13 @@ public class PlayerControlView extends FrameLayout {
     return true;
   }
 
+  private boolean isPlaying() {
+    return player != null
+        && player.getPlaybackState() != Player.STATE_ENDED
+        && player.getPlaybackState() != Player.STATE_IDLE
+        && player.getPlayWhenReady();
+  }
+
   @SuppressLint("InlinedApi")
   private static boolean isHandledMediaKey(int keyCode) {
     return keyCode == KeyEvent.KEYCODE_MEDIA_FAST_FORWARD
@@ -1085,6 +1103,13 @@ public class PlayerControlView extends FrameLayout {
         } else if (rewindButton == view) {
           rewind();
         } else if (playButton == view) {
+          if (player.getPlaybackState() == Player.STATE_IDLE) {
+            if (playbackPreparer != null) {
+              playbackPreparer.preparePlayback();
+            }
+          } else if (player.getPlaybackState() == Player.STATE_ENDED) {
+            controlDispatcher.dispatchSeekTo(player, player.getCurrentWindowIndex(), C.TIME_UNSET);
+          }
           controlDispatcher.dispatchSetPlayWhenReady(player, true);
         } else if (pauseButton == view) {
           controlDispatcher.dispatchSetPlayWhenReady(player, false);

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

@@ -39,6 +39,7 @@ import android.widget.ImageView;
 import com.google.android.exoplayer2.C;
 import com.google.android.exoplayer2.ControlDispatcher;
 import com.google.android.exoplayer2.DefaultControlDispatcher;
+import com.google.android.exoplayer2.PlaybackPreparer;
 import com.google.android.exoplayer2.Player;
 import com.google.android.exoplayer2.Player.DiscontinuityReason;
 import com.google.android.exoplayer2.metadata.Metadata;
@@ -677,6 +678,16 @@ public class PlayerView extends FrameLayout {
   }
 
   /**
+   * Sets the {@link PlaybackPreparer}.
+   *
+   * @param playbackPreparer The {@link PlaybackPreparer}.
+   */
+  public void setPlaybackPreparer(@Nullable PlaybackPreparer playbackPreparer) {
+    Assertions.checkState(controller != null);
+    controller.setPlaybackPreparer(playbackPreparer);
+  }
+
+  /**
    * Sets the {@link ControlDispatcher}.
    *
    * @param controlDispatcher The {@link ControlDispatcher}, or null to use {@link