Activity和Service之间通过handler传递数据

在写音乐播放器的时候用到了这个东西，相当于Activity中把mHandler用Messenger这个信封包裹着传递到了到了Service。Service拿到这个信封，信封里面装着mHandler，告诉service往里面装信息，然后信封再邮寄给mHandler。

Activity中的主要代码：

1.开启我的服务的方法

private void startMyService(String option, String path) {
Intent service = new Intent(this, MyService.class);
service.putExtra("option", option);
service.putExtra("messenger", new Messenger(mHandler));
service.putExtra("path", path);
startService(service);
}

2,Activity中的handler

private Handler mHandler = new Handler() {
// 接收结果，刷新界面
public void handleMessage(Message msg) {
switch (msg.what) {
case 1:
break;

case 2:

break;
}
};
};

Service中接收Activity中传递过来的messager信封，在Service的的startCommand()方法中：

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
String option = intent.getStringExtra("option");
if (mMessenger == null) {
mMessenger = (Messenger) intent.getExtras().get("messenger");
}
return super.onStartCommand(intent, flags, startId);
}

下面这个方法里面用到了Timer，在里面一直执行向Activity中的mHandler发送数据。

public void onPrepared(MediaPlayer mp) {
if (mTimer == null) {
mTimer = new Timer();
}
/**
* @Params task the task to schedule. delay amount of time in
*         milliseconds before first execution. @Params period amount of
*         time in milliseconds between subsequent executions.
*/
mTimer.schedule(new TimerTask() {

@Override
public void run() {
// 1.准备好的时候告诉activity，当前歌曲的总时长
int currentPosition = mPlayer.getCurrentPosition();
int duration = mPlayer.getDuration();
Message message = Message.obtain();
message.what = Constants.MSG_ONPREPARED;
message.arg1 = currentPosition;
message.arg2 = duration;
try {
mMessenger.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
}, 0, 1000);

}