Android线程中设置控件的值提示报错的解决方法

package com.yarin.android.Examples_04_15;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;
import android.widget.TextView;
public class Activity01 extends Activity
{
 //声明ImageView对象
 ImageView imageview;
 TextView textview;
 //ImageView的alpha值，
 int  image_alpha = 255;
 Handler mHandler = new Handler();
 //控件线程
 boolean isrung = false;
 /** Called when the activity is first created. */
 @Override
 public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 isrung = true;
 //获得ImageView的对象
 imageview = (ImageView) this.findViewById(R.id.ImageView01);
 textview = (TextView) this.findViewById(R.id.TextView01);
 //设置imageview的图片资源。同样可以再xml布局中像下面这样写
 //android:src="@drawable/logo"
 imageview.setImageResource(R.drawable.logo);
 //设置imageview的Alpha值
 imageview.setAlpha(image_alpha);
 //开启一个线程来让Alpha值递减
 new Thread(new Runnable() {
  public void run()
  {
  while (isrung)
  {
   try
   {
   Thread.sleep(200);
   //更新Alpha值
   updateAlpha();
   //如果使用下面注释的代码来直接设置imageview的透明度、textview的值会报错，因为线程中不能对控件进行设置操作，需要使用一个Handler来进行对相关值的设置
//   if (image_alpha - 7 >= 0)
//   {
//    image_alpha -= 7;
//   }
//   else
//   {
//    image_alpha = 0;
//    isrung = false;
//   }
//   imageview.setAlpha(image_alpha);
//   textview.setText("现在alpha值是："+Integer.toString(image_alpha));
   }
   catch (InterruptedException e)
   {
   e.printStackTrace();
   }
  }
  }
 }).start();
 //接受消息之后更新imageview视图
 mHandler = new Handler() {
  @Override
  public void handleMessage(Message msg)
  {
  super.handleMessage(msg);
  imageview.setAlpha(image_alpha);
  textview.setText("现在alpha值是："+Integer.toString(image_alpha));
  //更新
  imageview.invalidate();
  }
 };
 }
 public void updateAlpha()
 {
 if (image_alpha - 7 >= 0)
 {
  image_alpha -= 7;
 }
 else
 {
  image_alpha = 0;
  isrung = false;
 }
 //发送需要更新imageview视图的消息
 mHandler.sendMessage(mHandler.obtainMessage());
 }
}