我的Android最佳實踐之—— Android更新UI的兩種方法:handler與runOnUiThread()

在Android開發過程中，常需要更新界面的UI。而更新UI是要主線程來更新的，即UI線程更新。如果在主線線程之外的線程中直接更新頁面 顯示常會報錯。拋出異常：android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.

只有原始創建這個視圖層次(view hierachy)的線程才能修改它的視圖(view)

話不多說，貼出下面的代碼

方法一：

在Activity.onCreate(Bundle savedInstanceState)中創建一個Handler類的實例， 在這個Handler實例的handleMessage回調函數中調用更新界面顯示的函數。

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", "黃色");  
            msg.setData(bundle);  
            MainActivity.this.UIhandler.sendMessage(msg);  
               
        }  
    }  
}

更新后：

方法二：利用Activity.runOnUiThread(Runnable)把更新ui的代碼創建在Runnable中，然后在需要更新 ui時，把這個Runnable對象傳給Activity.runOnUiThread(Runnable)。 這樣Runnable對像就能在ui程序中被調用。如果當前線程是UI線程,那么行動是立即執行。如果當前線程不是UI線程,操作是發布到事件隊列的UI 線程.

    private class UIThread2 extends Thread {
        @Override
        public void run() {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    UITxt.setText("黃色"); 
                }
            });