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

標籤：

在Android開發過程中，常需要更新介面的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.只有原始建立這個視圖層次(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)中建立一個Handler類的執行個體， 在這個Handler執行個體的handleMessage回呼函數中調用更新介面顯示的函數。介面：

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);                         }      }  }

更新後：

方法二：利用Activity.runOnUiThread(Runnable)把更新ui的代碼建立在Runnable中，然後在需要更新 ui時，把這個Runnable對象傳給Activity.runOnUiThread(Runnable)。 這樣Runnable對像就能在ui程式中被調用。如果當前線程是UI線程,那麼行動是立即執行。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");                 }            });

 

 

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