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; |
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 |
12 | * Email:fengcunhan@gmail.com |
15 | public class HandlerTestActivity extends Activity { |
16 | private Handler uiHandler; |
17 | private ThreadWithLooper thread; |
18 | private Runnable showRunable; |
20 | public void onCreate(Bundle savedInstanceState) { |
21 | super .onCreate(savedInstanceState); |
22 | setContentView(R.layout.main); |
23 | uiHandler= new Handler(){ |
25 | public void handleMessage(Message msg) { |
27 | case Messages.MSG_HELLO: |
28 | Toast.makeText(HandlerTestActivity. this , (String)msg.obj, Toast.LENGTH_SHORT).show(); |
34 | thread= new ThreadWithLooper(uiHandler); |
37 | showRunable= new Runnable() { |
42 | thread.getHandler().sendEmptyMessage(Messages.MSG_HELLO); |
43 | uiHandler.postDelayed( this , 2 * 1000 ); |
46 | uiHandler.post(showRunable); |
51 | protected void onStop() { |
53 | uiHandler.removeCallbacks(showRunable); |
01 | import android.os.Handler; |
02 | import android.os.Looper; |
03 | import android.os.Message; |
07 | * org.fneg.ThreadWithLooper.java |
08 | * Create at: 2012-6-4 下午4:58:11 |
10 | * Email:fengcunhan@gmail.com |
13 | public class ThreadWithLooper extends Thread { |
14 | private Handler handler; |
16 | private Handler uiHandler; |
18 | public ThreadWithLooper(Handler mHandler){ |
19 | this .uiHandler=mHandler; |
21 | handler = new Handler(){ |
24 | public void handleMessage(Message msg) { |
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); |
39 | public Handler getHandler() { |
43 | public void setHandler(Handler handler) { |
44 | this .handler = handler; |
03 | * org.fneg.Messages.java |
04 | * Create at: 2012-6-4 下午4:51:20 |
06 | * Email:fengcunhan@gmail.com |
09 | public class Messages { |
10 | public static final int MSG_HELLO= 0X1 ; |
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