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

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);    		    	}    }}

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();                  }                    });