<Android's research training project seven> Pictures Countdown

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     xmlns:app="http://schemas.android.com/apk/res-auto"
 4     xmlns:tools="http://schemas.android.com/tools"
 5     android:layout_width="match_parent"
 6     android:layout_height="match_parent"
 7     tools:context=".MainActivity">
 8 
 9     <ImageView
10         android:id="@+id/imageview"
11         android:layout_width="match_parent"
12         android:layout_height="match_parent"
13         tools:layout_editor_absoluteX="50dp"
14         tools:layout_editor_absoluteY="-25dp" />
15 
16 </android.support.constraint.ConstraintLayout>

activity_main.xml

 1 package com.example.daojishi;
 2 
 3 import android.os.Handler;
 4 import android.os.Message;
 5 import android.support.v7.app.AppCompatActivity;
 6 import android.os.Bundle;
 7 import android.widget.ImageView;
 8 
 9 public class MainActivity extends AppCompatActivity {
10 
11     private ImageView imageview;
12     private Handler handler;
13     @Override
14     protected void onCreate(Bundle savedInstanceState) {
15         super.onCreate(savedInstanceState);
16         setContentView(R.layout.activity_main);
17         imageview = (ImageView)findViewById(R.id.imageview);
18         handler = new Handler(){
19             @Override
20             public void dispatchMessage(Message msg) {
21                 super.dispatchMessage(msg);
22                 if(msg.what==1){
23                     String pic = "p" + msg.obj;
24                     int resID = getResources().getIdentifier(pic,"mipmap",getPackageName());
25                     imageview.setImageResource(resID);
26                 }
27             }
28         };
29         new Thread(){
30             @Override
31             public void run() {
32                 super.run();
33                 int num = 9;
34                 while(num>=0)
35                 {
36                     try{
37                         Thread.sleep(1000);
38                     }catch(Exception e ){
39                         e.printStackTrace();
40                     }
41                     Message msg = new Message();
42                     msg.what=1;
43                     msg.obj=num;
44                     handler.sendMessage(msg);
45                     num--;
46                 }
47             }
48         }.start();
49     }
50 }

MainActivity.java