学步园

Android 更新UI的两种方法——handler和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();  
                }  
      
            });