Handler详解系列(六)——View的post()方法详解

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MainActivity如下:

package cc.testui2;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.TextView;import android.app.Activity;/** * Demo描述: * 在子线程中更改UI的方式二 *  * 在子线程中采用View的post()方法. * 依据源码可知它在最终还是调用了UI线程的handler的post()方法. * 所以在post方法中勿做耗时操作 *  * 看一下该方法的源码: * * Causes the Runnable to be added to the message queue. * The runnable will be run on the user interface thread. * * @param action The Runnable that will be executed. * * @return Returns true if the Runnable was successfully placed in to the *         message queue.  Returns false on failure, usually because the *         looper processing the message queue is exiting. * * public boolean post(Runnable action) { *      final AttachInfo attachInfo = mAttachInfo; *      if (attachInfo != null) { *         return attachInfo.mHandler.post(action); *      } *      // Assume that post will succeed later *      ViewRootImpl.getRunQueue().post(action); *      return true; * } *  *  * 该方法的英文注释: * 将Runnable放入消息队列,并在UI线程中执行. *  * 参考资料: * http://blog.csdn.net/guolin_blog/article/details/9991569 * Thank you very much */public class MainActivity extends Activity { private TextView mTextView; private TextView mTipTextView; private Button mButton;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.main);init();}    private void init(){    mTextView=(TextView) findViewById(R.id.textView);    mTipTextView=(TextView) findViewById(R.id.tipTextView);    mButton=(Button) findViewById(R.id.button);    mButton.setOnClickListener(new OnClickListenerImpl());    System.out.println("UI线程ID="+Thread.currentThread().getId());    }private class OnClickListenerImpl implements OnClickListener {@Overridepublic void onClick(View v) {mTipTextView.post(new Runnable() {@Overridepublic void run() {mTextView.setText("My number is 9527");System.out.println("view.post(new Runnable())里的run()方法 线程ID="+Thread.currentThread().getId());}});}}}

main.xml如下:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"   >     <TextView        android:id="@+id/textView"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="test"        android:layout_centerHorizontal="true"        android:layout_marginTop="50dip"        />          <Button        android:id="@+id/button"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="Button"        android:layout_centerHorizontal="true"        android:layout_marginTop="120dip"        />        <TextView        android:id="@+id/tipTextView"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="测试在子线程中更新UI"         android:layout_centerInParent="true"        /></RelativeLayout>

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