Android 更新UI的兩種方法——handler和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.
隻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：
[html]
<span style="font-size:14px;">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);
}
}
}</span>
更新後：www.aiwalls.com
方法二：利用Activity.runOnUiThread(Runnable)把更新ui的代碼創建在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程序中被調用。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,操作是發佈到事件隊列的UI線程
[html]
FusionField.currentActivity.runOnUiThread(new Runnable()
{
public void run()
{
Toast.makeText(getApplicationContext(), , "Update My UI",
Toast.LENGTH_LONG).show();
}
});