Android异步处理系列文章四篇之三

 1 package com.zhuozhuo;
 2 
 3 import android.app.Activity;
 4 import android.os.Bundle;
 5 import android.os.Handler;
 6 import android.os.Looper;
 7 import android.os.Message;
 8 import android.util.Log;
 9 import android.view.View;
10 import android.view.View.OnClickListener;
11 
12 public class LooperThreadActivity extends Activity{
13     /** Called when the activity is first created. */
14     
15     private final int MSG_HELLO = 0;
16     private Handler mHandler;
17     
18     @Override
19     public void onCreate(Bundle savedInstanceState) {
20         super.onCreate(savedInstanceState);
21         setContentView(R.layout.main);
22         new CustomThread().start();//新建并启动CustomThread实例
23         
24         findViewById(R.id.send_btn).setOnClickListener(new OnClickListener() {
25             
26             @Override
27             public void onClick(View v) {//点击界面时发送消息
28                 String str = "hello";
29                 Log.d("Test", "MainThread is ready to send msg:" + str);
30                 mHandler.obtainMessage(MSG_HELLO, str).sendToTarget();//发送消息到CustomThread实例
31                 
32             }
33         });
34         
35     }
36     
37     
38     
39     
40     
41     class CustomThread extends Thread {
42         @Override
43         public void run() {
44             //建立消息循环的步骤
45             Looper.prepare();//1、初始化Looper
46             mHandler = new Handler(){//2、绑定handler到CustomThread实例的Looper对象
47                 public void handleMessage (Message msg) {//3、定义处理消息的方法
48                     switch(msg.what) {
49                     case MSG_HELLO:
50                         Log.d("Test", "CustomThread receive msg:" + (String) msg.obj);
51                     }
52                 }
53             };
54             Looper.loop();//4、启动消息循环
55         }
56     }
57 }

 1 xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     android:orientation="vertical"
 4     android:layout_width="fill_parent"
 5     android:layout_height="fill_parent"
 6     >
 7 <TextView  
 8     android:layout_width="fill_parent" 
 9     android:layout_height="wrap_content" 
10     android:text="@string/hello"
11     />
12 <Button android:text="发送消息" android:id="@+id/send_btn" android:layout_width="wrap_content" android:layout_height="wrap_content">Button>
13 LinearLayout>

1 private static final ThreadLocal sThreadLocal = new ThreadLocal();
2 public static final void prepare() {
3         if (sThreadLocal.get() != null) {
4             throw new RuntimeException("Only one Looper may be created per thread");
5         }
6         sThreadLocal.set(new Looper());
7 }

1 final MessageQueue mQueue;
2 private Looper() {
3         mQueue = new MessageQueue();
4         mRun = true;
5         mThread = Thread.currentThread();
6     }

 1 final MessageQueue mQueue;
 2  final Looper mLooper;
 3 public Handler() {
 4         if (FIND_POTENTIAL_LEAKS) {
 5             final Classextends Handler> klass = getClass();
 6             if ((klass.isAnonymousClass() || klass.isMemberClass() || klass.isLocalClass()) &&
 7                     (klass.getModifiers() & Modifier.STATIC) == 0) {
 8                 Log.w(TAG, "The following Handler class should be static or leaks might occur: " +
 9                     klass.getCanonicalName());
10             }
11         }
12 
13         mLooper = Looper.myLooper();
14         if (mLooper == null) {
15             throw new RuntimeException(
16                 "Can't create handler inside thread that has not called Looper.prepare()");
17         }
18         mQueue = mLooper.mQueue;
19         mCallback = null;
20 }

 1  public static final void loop() {
 2         Looper me = myLooper();
 3         MessageQueue queue = me.mQueue;
 4         
 5         // Make sure the identity of this thread is that of the local process,
 6         // and keep track of what that identity token actually is.
 7         Binder.clearCallingIdentity();
 8         final long ident = Binder.clearCallingIdentity();
 9         
10         while (true) {
11             Message msg = queue.next(); // might block
12             //if (!me.mRun) {
13             //    break;
14             //}
15             if (msg != null) {
16                 if (msg.target == null) {
17                     // No target is a magic identifier for the quit message.
18                     return;
19                 }
20                 if (me.mLogging!= null) me.mLogging.println(
21                         ">>>>> Dispatching to " + msg.target + " "
22                         + msg.callback + ": " + msg.what
23                         );
24                 msg.target.dispatchMessage(msg);
25                 if (me.mLogging!= null) me.mLogging.println(
26                         "<<<<27                         + msg.callback);
28                 
29                 // Make sure that during the course of dispatching the
30                 // identity of the thread wasn't corrupted.
31                 final long newIdent = Binder.clearCallingIdentity();
32                 if (ident != newIdent) {
33                     Log.wtf("Looper", "Thread identity changed from 0x"
34                             + Long.toHexString(ident) + " to 0x"
35                             + Long.toHexString(newIdent) + " while dispatching to "
36                             + msg.target.getClass().getName() + " "
37                             + msg.callback + " what=" + msg.what);
38                 }
39                 
40                 msg.recycle();
41             }
42         }
43     }

 1 public void dispatchMessage(Message msg) {
 2         if (msg.callback != null) {
 3             handleCallback(msg);
 4         } else {
 5             if (mCallback != null) {
 6                 if (mCallback.handleMessage(msg)) {
 7                     return;
 8                 }
 9             }
10             handleMessage(msg);
11         }
12 }