这是我的mainactivity

package com.example.handler_012;

import android.app.Activity;

import android.os.Bundle;

import android.os.Handler;

import android.view.Menu;

import android.view.MenuItem;

import android.widget.ImageView;

import android.widget.TextView;

public class MainActivity extends Activity {

private TextView tv;

private Handler handler1=new Handler();

private ImageView imv;

private MyRunnable myRunnable=new MyRunnable();

private int images[]={R.drawable.image_1,R.drawable.image_2,R.drawable.image_3};

private int i;

class MyRunnable implements Runnable{

public void run(){

i++;

i=i%3;

imv.setImageResource(images[i]);

handler1.postDelayed(myRunnable, 1000);

}

}

@Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        tv=(TextView) findViewById(R.id.textview);

        imv=(ImageView) findViewById(R.id.imageView1);

       // handler1=new Handler();

        handler1.postDelayed(myRunnable, 1000);

//        new Thread(){

//         public void run() {

//         try {

// Thread.sleep(1000);

// handler1.post(new Runnable() {

//

// @Override

// public void run() {

// // TODO Auto-generated method stub

// tv.setText("update thread");

// }

// });

//

// } catch (InterruptedException e) {

// // TODO Auto-generated catch block

// e.printStackTrace();

// }

//        

//         };

//        }.start();

    }

}

这是activity.xml文档：

<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"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.example.handler_012.MainActivity" >

    <TextView

        android:id="@+id/textview"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="@string/hello_world" />

    <ImageView

        android:id="@+id/imageView1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_below="@+id/textview"

        android:layout_centerHorizontal="true"

        android:layout_marginTop="132dp"

        android:src="@drawable/ic_launcher" />

</RelativeLayout>