Add initial version of SimpleBasePlayer

This base class will simplify the implementation of custom
Player classes. The current version only supports
available commands and playWhenReady handling.

PiperOrigin-RevId: 467618021

library/common/src/main/java/com/google/android/exoplayer2/LegacyMediaPlayerWrapper.java

+/*
+ * Copyright 2022 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;
+
+import android.media.MediaPlayer;
+import android.os.Looper;
+import com.google.common.util.concurrent.Futures;
+import com.google.common.util.concurrent.ListenableFuture;
+
+/** A {@link Player} wrapper for the legacy Android platform {@link MediaPlayer}. */
+public final class LegacyMediaPlayerWrapper extends SimpleBasePlayer {
+
+  private final MediaPlayer player;
+
+  private boolean playWhenReady;
+
+  /**
+   * Creates the {@link MediaPlayer} wrapper.
+   *
+   * @param looper The {@link Looper} used to call all methods on.
+   */
+  public LegacyMediaPlayerWrapper(Looper looper) {
+    super(looper);
+    this.player = new MediaPlayer();
+  }
+
+  @Override
+  protected State getState() {
+    return new State.Builder()
+        .setAvailableCommands(new Commands.Builder().addAll(Player.COMMAND_PLAY_PAUSE).build())
+        .setPlayWhenReady(playWhenReady, Player.PLAY_WHEN_READY_CHANGE_REASON_USER_REQUEST)
+        .build();
+  }
+
+  @Override
+  protected ListenableFuture<?> handleSetPlayWhenReady(boolean playWhenReady) {
+    this.playWhenReady = playWhenReady;
+    // TODO: Only call these methods if the player is in Started or Paused state.
+    if (playWhenReady) {
+      player.start();
+    } else {
+      player.pause();
+    }
+    return Futures.immediateVoidFuture();
+  }
+}