浅析Android中的消息机制（转）

 1 public class MainActivity extends Activity implements View.OnClickListener { 
 2     private TextView stateText; 
 3     private Button btn; 
 4     
 5     @Override 
 6     public void onCreate(Bundle savedInstanceState) { 
 7         super.onCreate(savedInstanceState); 
 8         setContentView(R.layout.main); 
 9         stateText = (TextView) findViewById(R.id.tv); 
10         btn = (Button) findViewById(R.id.btn); 
11         btn.setOnClickListener(this); 
12     } 
13     
14     @Override 
15     public void onClick(View v) {
16         new WorkThread().start(); 
17     } 
18     
19     //工作线程 
20     private class WorkThread extends Thread { 
21         @Override 
22         public void run() { 
23             //......处理比较耗时的操作 
24             //处理完成后改变状态 
25             stateText.setText("completed"); 
26         } 
27     } 
28     
29 }

ERROR/AndroidRuntime(421): FATAL EXCEPTION: Thread-8 ERROR/AndroidRuntime(421): android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. 

 1 public class MainActivity extends Activity implements View.OnClickListener { 
 2     private static final int COMPLETED = 0; 
 3     private TextView stateText; 
 4     private Button btn; 
 5     
 6     private Handler handler = new Handler() { 
 7         @Override 
 8         public void handleMessage(Message msg) { 
 9             if (msg.what == COMPLETED) { 
10                 stateText.setText("completed"); 
11             }
12         } 
13     }
14         
15     @Override 
16     public void onCreate(Bundle savedInstanceState) { 
17         super.onCreate(savedInstanceState); 
18         setContentView(R.layout.main); 
19         stateText = (TextView) findViewById(R.id.tv); 
20         btn = (Button) findViewById(R.id.btn); 
21         btn.setOnClickListener(this); 
22     } 
23         
24     @Override 
25     public void onClick(View v) {
26         new WorkThread().start();
27     } 
28     
29     //工作线程 
30     private class WorkThread extends Thread { 
31         @Override 
32         public void run() { 
33             //......处理比较耗时的操作 
34             //处理完成后给handler发送消息 
35             Message msg = new Message(); 
36             msg.what = COMPLETED; 
37             handler.sendMessage(msg); 
38         }
39     }         
40 }

 1 class WorkThread extends Thread { 
 2     public Handler mHandler; 
 3     public void run() { 
 4         Looper.prepare(); 
 5         mHandler = new Handler() { 
 6             public void handleMessage(Message msg) { 
 7                 // 处理收到的消息 
 8             } 
 9         }; 
10         Looper.loop();
11     }         
12 }