Service、BroadcastReceiver、Activity之间的通信

public class MyService extends Service {
private Timer timer;//声明计时器
private TimerTask task;//声明计时器Task
private int index = 101;//倒计时起点变量
@Override
public IBinder onBind(Intent intent) {
return null;
}
@Override
public void onCreate() {
super.onCreate();
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
startTimer();//启动计时器
return super.onStartCommand(intent, flags, startId);
}
@Override
public void onDestroy() {
stopTimer();//停止计时器
super.onDestroy();
}
public void startTimer() {
timer = new Timer();//实例化Timer对象
task = new TimerTask() {//实例化TimerTask
@Override
public void run() {
index--;
Intent i1 = new Intent();// 不能进行页面的跳转，只能实例化成这样
i1.setAction("action111");// 设置Intent对象的action属性，以便于在主界面做匹配
i1.putExtra("name", index);// 携带数据
sendBroadcast(i1);// 发送广播
}
};
timer.schedule(task, 1000, 1000);// 启动计时器
}
// 停止计时器
public void stopTimer() {
timer.cancel();
}
}

<service android:name="MyService"></service>

public class MainActivity extends Activity implements OnClickListener {
private Button startBtn, stopBtn;//声明主界面的按钮
private Intent intent;//声明Intent对象
private TextView tv;//声明主界面显示区
//创建BroadcastReceiver对象，用来接受Service发过来的消息并处理
private BroadcastReceiver receiver =new BroadcastReceiver() {

@Override
public void onReceive(Context context, Intent intent) {
int num = intent.getIntExtra("name", 0);//获得后台传过来的，键值为name对应的值
tv.setText(num+"");//更新主界面UI
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
//找到资源
startBtn = (Button) findViewById(R.id.start);
stopBtn = (Button) findViewById(R.id.stop);
//为按钮加载监听
startBtn.setOnClickListener(this);
stopBtn.setOnClickListener(this);
//找到资源
tv = (TextView) findViewById(R.id.textView1);
//动态注册BroadcastReceiver对象，并添加要接收数据的action，匹配成功处理数据，否则不处理
registerReceiver(receiver, new IntentFilter("action111"));
//实例化Intent对象
intent = new Intent(MainActivity.this, MyService.class);

}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.start:
startService(intent);//启动Service
break;
case R.id.stop:
stopService(intent);//停止Service
break;
}
}

@Override
protected void onStop() {
unregisterReceiver(receiver);//取消动态注册
super.onStop();
}
}