Android更新UI的两种方法——handler与runOnUiThread()

在Android开发过程中，常需要更新界面的UI。而更新UI是要主线程来更新的，即UI线程更新。如果在主线线程之外的线程中直接更新页面显示常会报错。抛出异常：android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

只有原始创建这个视图层次(view hierachy)的线程才能修改它的视图(view)

话不多说，贴出下面的代码

方法一：

在Activity.onCreate(Bundle savedInstanceState)中创建一个Handler类的实例，在这个Handler实例的handleMessage回调函数中调用更新界面显示的函数。

界面：

public class MainActivity extends Activity {  
    private EditText UITxt;  
    private Button updateUIBtn;  
    private UIHandler UIhandler;  
   
    @Override  
    public void onCreate(Bundle savedInstanceState) {  
        super.onCreate(savedInstanceState);  
        setContentView(R.layout.activity_main);  
        UITxt = (EditText)findViewById(R.id.ui_txt);  
        updateUIBtn = (Button)findViewById(R.id.update_ui_btn);  
        updateUIBtn.setOnClickListener(new View.OnClickListener() {  
               
            public void onClick(View v) {  
                // TODO Auto-generated method stub  
                UIhandler = new UIHandler();  
                UIThread thread = new UIThread();  
                thread.start();  
            }  
        });  
    }  
   
    @Override  
    public boolean onCreateOptionsMenu(Menu menu) {  
        getMenuInflater().inflate(R.menu.activity_main, menu);  
        return true;  
    }  
    private class UIHandler extends Handler{  
        @Override  
        public void handleMessage(Message msg) {  
            // TODO Auto-generated method stub  
            super.handleMessage(msg);  
            Bundle bundle = msg.getData();  
            String color = bundle.getString("color");  
            UITxt.setText(color);  
        }  
    }  
    private class UIThread extends Thread{  
        @Override  
        public void run() {  
            try {  
                Thread.sleep(3000);  
            } catch (InterruptedException e) {  
                // TODO Auto-generated catch block  
                e.printStackTrace();  
            }  
            Message msg = new Message();  
            Bundle bundle = new Bundle();  
            bundle.putString("color", "黄色");  
            msg.setData(bundle);  
            MainActivity.this.UIhandler.sendMessage(msg);  
               
        }  
    }  
}

更新后：

方法二：利用Activity.runOnUiThread(Runnable)把更新ui的代码创建在Runnable中，然后在需要更新 ui时，把这个Runnable对象传给Activity.runOnUiThread(Runnable)。这样Runnable对像就能在ui程序中被调用。如果当前线程是UI线程,那么行动是立即执行。如果当前线程不是UI线程,操作是发布到事件队列的UI 线程

FusionField.currentActivity.runOnUiThread(new Runnable()    
        {    
            public void run()    
            {    
                Toast.makeText(getApplicationContext(), , "Update My UI",    
                        Toast.LENGTH_LONG).show();    
            }    
     
        });