handler异步更新UI-优快云博客

本文通过一个具体的Android应用程序实例，详细介绍了如何使用Handler机制来更新UI。该应用利用Handler在主线程与子线程间传递消息，实现了每隔两秒更换一次ImageView中显示的图片。

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废话少说,直接进入代码

package com.pms.myhandle;

import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;

public class MyHandle extends Activity {

private ImageView iv;
int what = 0;

//创建Handle对象
private Handler handler = new Handler(){

//实现方法用来接收消息
@Override
public void handleMessage(Message msg) {
switch(msg.what){ //判断接收的消息
case 0:
iv.setImageResource(R.drawable.photo1);
break;
case 1:
iv.setImageResource(R.drawable.photo2);
break;
case 2:
iv.setImageResource(R.drawable.photo3);
break;

}
super.handleMessage(msg);
}

};
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

//取得ImageView对象
iv = (ImageView) findViewById(R.id.iv);

thread.start(); //启动线程

}

//新建一个线程
Thread thread = new Thread(new Runnable() {

//实现run方法
@Override
public void run() {
while(true)
{
Message msg = handler.obtainMessage();
msg.what = (what++)%3;
handler.sendMessage(msg); //发送消息
try {
Thread.sleep(2000);//停止2秒
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}){

};
}

main.xml

<?xml version="1.0" encoding="UTF-8"?>
-<LinearLayout android:layout_height="fill_parent" android:layout_width="fill_parent" android:orientation="vertical" xmlns:android="http://schemas.android.com/apk/res/android"> <TextView android:layout_height="wrap_content" android:layout_width="fill_parent" android:text="@string/hello"/> <ImageView android:layout_height="wrap_content" android:layout_width="wrap_content" android:src="@drawable/photo1" android:id="@+id/iv"/> </LinearLayout>