Handler制作簡(jiǎn)單相冊(cè)查看器的實(shí)例代碼

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:gravity="center">
  <ImageView
    android:id="@+id/myImageView"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"/>
</LinearLayout>

package com.example.sample_9_9;
public class MyTread extends Thread{    //繼承自線程類
  HandlerSampleActivity activity;     //activity引用
  int what = 1;              //發(fā)送消息的what值
  public MyTread(HandlerSampleActivity activity){ //構(gòu)造器
    this.activity = activity;    //得到activity的引用
  }
  @Override
  public void run(){
    while(true){       //循環(huán)
      activity.myHandler.sendEmptyMessage((what++)%4);
      //發(fā)送消息，%4是因?yàn)橹挥兴膹垐D進(jìn)行輪換
      try{
        Thread.sleep(2000);    //睡眠兩秒鐘
      }
      catch (Exception e){     //捕獲異常
        e.printStackTrace();   //打印異常
      }
    }
  }
}

package com.example.sample_9_9;
import android.os.Handler;
import android.os.Message;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.ImageView;
public class HandlerSampleActivity extends AppCompatActivity {
  ImageView myImageView;
  Handler myHandler = new Handler() { //創(chuàng)建一個(gè)Handler對(duì)象
    @Override
    public void handleMessage(Message msg) {  //重寫接收消息的方法
      switch (msg.what) { //判斷what值
        case 0:
          myImageView.setImageResource(R.drawable .a);
          break;
        case 1:
          myImageView.setImageResource(R.drawable .b);
          break;
        case 2:
          myImageView.setImageResource(R.drawable .c);
          break;
        case 3:
          myImageView.setImageResource(R.drawable .d);
          break;
      }
      super.handleMessage(msg);
    }
  };
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_handler_sample);
    myImageView = (ImageView) findViewById(R.id.myImageView);
    MyTread myThread = new MyTread(this);  //初始化線程
    myThread.start(); //啟動(dòng)線程
  }
}