Android 主线程和线程之间相互发送消息

   通过分析Activity源码，我们知道每个Activity都有一个Looper，所以主线程在接收Message是不需要调用Looper.prepare()和Looper.loop()，但是线程是不带Looper的，当线程要接收来自主线程的消息是就需要调用Looper.prepare()和Looper.loop()。以下我们将通过一个示例，讲述主线程和线程之间如何发送Message。

01	import android.app.Activity;

02	import android.os.Bundle;

03	import android.os.Handler;

04	import android.os.Message;

05	import android.widget.Toast;

06

07

/**

08	* 这个类是主线程，它每隔两秒就发送一个Message给线程，线程收到Message后将发送一个Message给主线程，主线程收到Message后会将Message内容Toast出来。

09	* org.fneg.HandlerTestActivity.java

10	* Create at: 2012-6-4 下午9:39:19

11	* @author:feng

12	* Email:fengcunhan@gmail.com

13

*

14

*/

15	public class HandlerTestActivity extends Activity {

16	private Handler uiHandler;

17	private ThreadWithLooper thread;

18	private Runnable showRunable;

19

@Override

20	public void onCreate(Bundle savedInstanceState) {

21	super.onCreate(savedInstanceState);

22	setContentView(R.layout.main);

23	uiHandler=new Handler(){

24

@Override

25	public void handleMessage(Message msg) {

26	switch(msg.what){

27	case Messages.MSG_HELLO:

28	Toast.makeText(HandlerTestActivity.this, (String)msg.obj, Toast.LENGTH_SHORT).show();

29

break;

30

31

}

32

}

33

};

34	thread=new ThreadWithLooper(uiHandler);

35

36	thread.start();

37	showRunable=new Runnable() {

38

39

@Override

40	public void run() {

41	//給线程发送一个Message

42	thread.getHandler().sendEmptyMessage(Messages.MSG_HELLO);

43	uiHandler.postDelayed(this, 2*1000);

44

}

45

};

46	uiHandler.post(showRunable);

47

48

}

49

50

@Override

51	protected void onStop() {

52	super.onStop();

53	uiHandler.removeCallbacks(showRunable);

54

}

55

}

01	import android.os.Handler;

02	import android.os.Looper;

03	import android.os.Message;

04

05

/**

06	* 从线程发送消息到UI线程（主线程）

07	* org.fneg.ThreadWithLooper.java

08	* Create at: 2012-6-4 下午4:58:11

09	* @author:feng<br/>

10	* Email:fengcunhan@gmail.com

11

*

12

*/

13	public class ThreadWithLooper extends Thread {

14	private Handler handler;

15

16	private Handler uiHandler;

17

18	public ThreadWithLooper(Handler mHandler){

19	this.uiHandler=mHandler;

20	//初始化Handler，接收到主线程发送过来的Message就回复一个Message给主线程，消息内容是 一个字符串和当前时间

21	handler =new Handler(){

22

23

@Override

24	public void handleMessage(Message msg) {

25	switch(msg.what){

26	case Messages.MSG_HELLO:

27	Message message=new Message();

28	message.what=Messages.MSG_HELLO;

29	message.obj="Yes!I get a hello"+System.currentTimeMillis();

30	uiHandler.sendMessage(message);

31

break;

32

33

}

34

}

35

36

};

37

}

38

39	public Handler getHandler() {

40	return handler;

41

}

42

43	public void setHandler(Handler handler) {

44	this.handler = handler;

45

}

46

47

@Override

48	public void run() {

49	Looper.prepare();

50

51	Looper.loop();

52

}

53

54

55

}

01

/**

02

*

03	* org.fneg.Messages.java

04	* Create at: 2012-6-4 下午4:51:20

05	* @author:feng

06	* Email:fengcunhan@gmail.com

07

*

08

*/

09	public class Messages {

10	public static final int MSG_HELLO=0X1;

11

}