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 &n
补充：移动开发 , Android ,
