RemoteController在API 19 引进，用来给音乐控制提供标准接口。长久以来，音乐播放在Android平台没有一个标准的接口，所有播放器都使用自己的方式实现对音乐的控制，最常见的方式是在Service中进行音乐播放，通过PendingIntent进行播放事件的传递及控制，因此就带来了一个问题。任何一个第三方app无法通过标准方式获取到当前正在播放的音乐的信息，更无法进行控制。RemoteController的出现恰好解决了这个问题，RemoteController需要和RemoteControlClient配合使用，从命名上能够看出，RemoteController是控制及信息获取端的接口，用来进行音乐信息的获取以及音乐播放动作的发送。RemoteControlClient是播放器端的接口，用来获取并执行播放动作，同时讲当前播放状态信息进行同步。
1.继承 NotificationListenerService 并实现RemoteController.OnClientUpdateListener接口来创建remoteController对象并获取播放进度
@TargetApi(Build.VERSION_CODES.KITKAT) public class MusicStateListener extends NotificationListenerService implements RemoteController.OnClientUpdateListener { }NotificationListenerService的主要作用是用来获取和操作通知栏通知，由于很奇葩的原因，为了获取合法的remoteController对象，必须实现这样一个NotificationListenerService并作为onClientUpdateListener传入remoteController来实现。
public void registerRemoteController() { remoteController = new RemoteController(this, this); boolean registered; try { registered = ((AudioManager) getSystemService(AUDIO_SERVICE)) .registerRemoteController(remoteController); } catch (NullPointerException e) { registered = false; } if (registered) { try { remoteController.setArtworkConfiguration( getResources().getDimensionPixelSize(R.dimen.remote_artwork_bitmap_width), getResources().getDimensionPixelSize(R.dimen.remote_artwork_bitmap_height)); remoteController.setSynchronizationMode(RemoteController.POSITION_SYNCHRONIZATION_CHECK); } catch (IllegalArgumentException e) { e.printStackTrace(); } } }RemoteController的初始化传入的两个参数分别是context和updateListener，而且此处的context必须是notificationListenerService
2.获取播放信息
合法register之后在回调中会接收到播放信息，包括播放/暂停等动作信息以及歌曲的meta信息
/** * Interface definition for the callbacks to be invoked whenever media events, metadata * and playback status are available. */ public interface OnClientUpdateListener { /** * Called whenever all information, previously received through the other * methods of the listener, is no longer valid and is about to be refreshed. * This is typically called whenever a new {@link RemoteControlClient} has been selected * by the system to have its media information published. * @param clearing true if there is no selected RemoteControlClient and no information * is available. */ public void onClientChange(boolean clearing); /** * Called whenever the playback state has changed. * It is called when no information is known about the playback progress in the media and * the playback speed. * @param state one of the playback states authorized * in {@link RemoteControlClient#setPlaybackState(int)}. */ public void onClientPlaybackStateUpdate(int state); /** * Called whenever the playback state has changed, and playback position * and speed are known. * @param state one of the playback states authorized * in {@link RemoteControlClient#setPlaybackState(int)}. * @param stateChangeTimeMs the system time at which the state change was reported, * expressed in ms. Based on {@link android.os.SystemClock#elapsedRealtime()}. * @param currentPosMs a positive value for the current media playback position expressed * in ms, a negative value if the position is temporarily unknown. * @param speed a value expressed as a ratio of 1x playback: 1.0f is normal playback, * 2.0f is 2x, 0.5f is half-speed, -2.0f is rewind at 2x speed. 0.0f means nothing is * playing (e.g. when state is {@link RemoteControlClient#PLAYSTATE_ERROR}). */ public void onClientPlaybackStateUpdate(int state, long stateChangeTimeMs, long currentPosMs, float speed); /** * Called whenever the transport control flags have changed. * @param transportControlFlags one of the flags authorized * in {@link RemoteControlClient#setTransportControlFlags(int)}. */ public void onClientTransportControlUpdate(int transportControlFlags); /** * Called whenever new metadata is available. * See the {@link MediaMetadataEditor#putLong(int, long)}, * {@link MediaMetadataEditor#putString(int, String)}, * {@link MediaMetadataEditor#putBitmap(int, Bitmap)}, and * {@link MediaMetadataEditor#putObject(int, Object)} methods for the various keys that * can be queried. * @param metadataEditor the container of the new metadata. */ public void onClientMetadataUpdate(MetadataEditor metadataEditor); };音乐的meta信息从onClientMetadataUpdate回调中获取，能够获取到的字段包括歌手、名称、专辑名称、专辑封面等。注意此处获取到的专辑封面bitmap的尺寸是由注册remoteController时setArtworkConfiguration (int, int)来决定的
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3.音乐控制
音乐的控制主要通过remoteController的sendMediaKeyEvent来实现 需要注意的是音乐的控制在逻辑上是模拟按钮的点击动作来实现的，所以在send一个keyCode时需要先后send KEY_ACTION_DOWN和KEY_ACTION_UP两个event来实现，所以我的实现是这样的
public boolean sendMusicKeyEvent(int keyCode) { if (!clientIdLost && remoteController != null) { // send "down" and "up" key events. KeyEvent keyEvent = new KeyEvent(KeyEvent.ACTION_DOWN, keyCode); boolean down = remoteController.sendMediaKeyEvent(keyEvent); keyEvent = new KeyEvent(KeyEvent.ACTION_UP, keyCode); boolean up = remoteController.sendMediaKeyEvent(keyEvent); return down && up; } else { long eventTime = SystemClock.uptimeMillis(); KeyEvent key = new KeyEvent(eventTime, eventTime, KeyEvent.ACTION_DOWN, keyCode, 0); dispatchMediaKeyToAudioService(key); dispatchMediaKeyToAudioService(KeyEvent.changeAction(key, KeyEvent.ACTION_UP)); } return false; } private void dispatchMediaKeyToAudioService(KeyEvent event) { AudioManager audioManager = (AudioManager) getSystemService(AUDIO_SERVICE); if (audioManager != null) { try { audioManager.dispatchMediaKeyEvent(event); } catch (Exception e) { e.printStackTrace(); } } }前面一部分是刚才讲到的通过remoteController来sendMediaKeyEvent，后面一部分是当remoteClient发生变化时remoteController的传递会失效，此时可以通过AudioManager来传递事件，
注意事项
1.注册RemoteController时OnClientUpdateListener必须是NotificationListenerService 2.发送KeyEvent时先发送ACTION_DOWN再发送ACTION_UP才是一个完整的事件；
2014年10月08日发布 更多 0 推荐 收藏