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.
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("黄色");
}
});