//继续完善音乐播放器demo
相关文章:
android:使用Messenger进行进程间通信(一):http://www.cnblogs.com/happyhacking/p/5318418.html
android:使用RemoteView自定义Notification:http://www.cnblogs.com/happyhacking/p/5318529.html
activity => service => notification
在添加了Notification之后,出现一个问题,即通过activity和notification都可以实现对service中方法的调用,
然而目前两者并不能同步.由于之前已经实现了从activity到service的进程间通信,所以当在activtiy中进行操作时,
相应的在service中使用handler更新notification的内容即可.
class IncomingHandler extends Handler {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
mActivityMessenger = msg.replyTo;
switch (msg.what) {
case 0:
mMediaPlayer.stop();
i = msg.arg1;
mMediaPlayer = MediaPlayer.create(MusicService.this, mMusicDatas.get(i).getSrc());
if(isPlaying) {
mMediaPlayer.start();
}
//更新notification显示的内容
mRemoteViews.setTextViewText(R.id.music_name, mMusicDatas.get(i).getName());
mRemoteViews.setTextViewText(R.id.singer_name, mMusicDatas.get(i).getSinger());
mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
break;
case 1:
if(msg.arg1==1){
isPlaying =false;
mMediaPlayer.pause();
//更新notification显示的内容
mRemoteViews.setImageViewResource(R.id.btn_play, R.drawable.note_btn_play);
mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
} else {
isPlaying = true;
i = msg.arg2;
mMediaPlayer = MediaPlayer.create(MusicService.this, mMusicDatas.get(i).getSrc());
mMediaPlayer.start();
//更新notification显示的内容
mRemoteViews.setImageViewResource(R.id.btn_play, R.drawable.note_btn_pause);
mNotificationManager.notify(NOTIFICATION_ID, mBuilder.build());
}
break;
default:
break;
}
}
}
notification => service => activity
在谷歌的官方文档中有以下描述:
If you want the service to respond, then you need to also create a Messenger in the client.
Then when the client receives the onServiceConnected() callback, it sends a Message to the service
that includes the client's Messenger in the replyTo parameter of the send() method.
个人理解是:
要实现service到activity的通信,需要在activity(client)也创建一个Messenger,并且在onServiceConnected()
方法中将这个messenger实例作为replyTo的参数send到service.
activity中的处理:
①创建activity自身的messenger,用来处理service发送过来的message
②在ServiceConnection实例的onServiceConnected()回调方法中将activity的messenger作为msg.replyTo的参数send给service
//创建activity自身的messenger
private Messenger mActivityMessenger = new Messenger(new Handler() {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
switch (msg.what) {
case CODE:
mIndex = msg.arg1;
setMusicNameAndSingerName(mIndex);
if(msg.arg2 == 1) {
mPlayBtn.setBackgroundResource(R.drawable.desk_pause);
} else {
mPlayBtn.setBackgroundResource(R.drawable.desk_play);
}
}
}
});
private ServiceConnection mServiceConnection = new ServiceConnection() {
@Override
public void onServiceConnected(ComponentName name, IBinder service) {
mMessenger = new Messenger(service);
//注意这里紧接着要send一次,目的是防止首先操作的是notification,而这时service还没有得到activity的messenger,导致service->activity的通信失败.
Message message = Message.obtain();
message.replyTo = mActivityMessenger;
try {
mMessenger.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
@Override
public void onServiceDisconnected(ComponentName name) {
}
};
service中的处理
在自定义hangdler中接收activity发送过来的messenger.
class IncomingHandler extends Handler {
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
//获取client的messenger
mActivityMessenger = msg.replyTo;
switch (msg.what) {
//...
}
}
}
当notification中的点击事件发生时,调用以下方法,向activity发送msg
//service->activity
private void sendToActivity() {
Message message = Message.obtain();
message.what = MainActivity.CODE;
message.arg1 = i;
message.arg2 = (isPlaying == true)?1:2;
try {
mActivityMessenger.send(message);
} catch (RemoteException e) {
e.printStackTrace();
}
}
如此一来,就实现了activity和service之间的进程间的双向通信.
基本原理如下图所示:
图中:黑字实线是activity和service的绑定过程中相互发送messenger的过程.
红字虚线是进程间相互通信的过程.
需要强调的是:
在bindService()成功后,要立即将activity的messenger发送给service,否则,如果在此操作之前,操作notification,
由于此时service中还没有activity的messenger,将无法将notification的操作同步到activity中.
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