安卓ApiDemos学习 app/Alarm/AlarmService

使用alarm机制定时启动service，并让service显示Notification的例子

首先创建待定意图

mAlarmSender = PendingIntent.getService(AlarmService.this,0, new Intent(AlarmService.this, AlarmService_Service.class), 0);

注册alarm,30秒启动一次

AlarmManager am = (AlarmManager)getSystemService(ALARM_SERVICE);am.setRepeating(AlarmManager.ELAPSED_REALTIME_WAKEUP,firstTime, 30*1000, mAlarmSender);

AlarmService_Service是接收intent的service

service首先显示Notification

mNM = (NotificationManager)getSystemService(NOTIFICATION_SERVICE);showNotification();private void showNotification() {        CharSequence text = getText(R.string.alarm_service_started);        Notification notification = new Notification(R.drawable.stat_sample, text,                System.currentTimeMillis());        PendingIntent contentIntent = PendingIntent.getActivity(this, 0,                new Intent(this, AlarmService.class), 0);        notification.setLatestEventInfo(this, getText(R.string.alarm_service_label),                       text, contentIntent);        mNM.notify(R.string.alarm_service_started, notification);}

Notification的第1个参数，用来表示通知发出时，状态栏显示的的图标

Notification的第2个参数，用来表示通知发出时，状态栏显示的滚动文字

Notification的第3个参数，用来表示通知的时间

notification.setLatestEventInfo的参数2，里面设置的文字对应Sample Alarm Service这句话

notification.setLatestEventInfo的参数3，里面设置的文字对应The alarm service has started running这句话

mNM.notify(R.string.alarm_service_started, notification);

notify的第一个参数表示Notification的唯一ID,cancel通知的时候要用到这个ID

service退出的时候，就会将通知消除

    public void onDestroy() {        // Cancel the notification -- we use the same ID that we had used to start it        mNM.cancel(R.string.alarm_service_started);        // Tell the user we stopped.        Toast.makeText(this, R.string.alarm_service_finished, Toast.LENGTH_SHORT).show();    }

点击通知的时候，会执行传入的待定意图，启动画面

        PendingIntent contentIntent = PendingIntent.getActivity(this, 0,                new Intent(this, AlarmService.class), 0);        notification.setLatestEventInfo(this, getText(R.string.alarm_service_label),                       text, contentIntent);

注意：PendingIntent.getService是用来启动service的待定意图，PendingIntent.getActivity是用来启动Activity的待定意图

service接着启动一个线程，用来暂停15秒

        Thread thr = new Thread(null, mTask, "AlarmService_Service");        thr.start();

在线程中，等待15秒后，会停止service

            long endTime = System.currentTimeMillis() + 15*1000;            while (System.currentTimeMillis() < endTime) {                synchronized (mBinder) {                    try {                        mBinder.wait(endTime - System.currentTimeMillis());                    } catch (Exception e) {                    }                }            }            // Done with our work...  stop the service!            AlarmService_Service.this.stopSelf();

最后分析下Binder运用。按照我的理解，Binder就像是service提供的一个远程调用的插座。

其他进程可以通过这个插座连接到service上，并调用Binder提供的一些方法。ServiceConnection就像是其他进程的插头，用来取得service提供的Binder。

private ServiceConnection mConnection = new ServiceConnection(){    public void onServiceConnected(ComponentName className, IBinder service) {    // Called when the connection is made.    serviceBinder = ((MyService.MyBinder)service).getService();    }     public void onServiceDisconnected(ComponentName className) {    // Received when the service unexpectedly disconnects.    serviceBinder = null;    }};

绑定service，需要指定目的service以及ServiceConnection

Intent bindIntent = new Intent(MyActivity.this, MyService.class);bindService(bindIntent, mConnection, Context.BIND_AUTO_CREATE);

当然，本例并没有其他进程连接过来，只是利用binder对象作为同步lock的对象而已

因为没有人调用binder的notify，所以它只能老老实实的等待wait函数超时了