包含了handler的三种简单应用 
  1 public class MainActivity extends Activity implements OnClickListener{
  2 
  3 private static String TAG = "tag";
  4 private static ImageView img;
  5 private Handler handler = new Handler();
  6 private static class handler1 extends Handler{
  7 //    handler调用WeakReference来防止内存泄漏
 17 */
 18 private WeakReference<MainActivity> mactivity;
 19 public handler1(MainActivity activity){
 20 Log.v(TAG, "handler1-->handler1");
 21 mactivity = new WeakReference<MainActivity>(activity);
 22 }
 23 @Override
 24 public void handleMessage(Message msg) {
 25 // TODO Auto-generated method stub
 26 MainActivity activity = mactivity.get();
 27 Log.v(TAG, "activity"+activity);
 28 if (activity!=null) {
 29 Log.v(TAG, "handler1-->handleMessage()");
 30 imgrandom();
 31 Log.v(TAG, "imgrandom()--msg.arg1:"+msg.arg1);
 32 img.setBackgroundResource(images[msg.arg1]);
 33 }
 34 }
 35 }
 36 private handler1 hand = new handler1(MainActivity.this);
 37 private    MyRunable myranble = new MyRunable();
 38 // 图片的位置数组
 39 private static int[] images = {R.drawable.t_a,R.drawable.t_asd,R.drawable.t_be,R.drawable.t_beaks,
 40 R.drawable.t_beaksk,R.drawable.t_beasfke,R.drawable.t_beask,R.drawable.t_bebas,R.drawable.t_bebsfkkw,
 41 R.drawable.t_beias,R.drawable.t_beisdfw,R.drawable.t_beisk,R.drawable.t_meksbbbgt,R.drawable.t_menbs,
 42 R.drawable.t_mesdf,R.drawable.t_nebs,R.drawable.t_sd,R.drawable.t_weba,R.drawable.t_wiimmed,R.drawable.t_xifn};
 43 private static int index,baths = 1;

 47 @Override
 48 protected void onCreate(Bundle savedInstanceState) {
 49 super.onCreate(savedInstanceState);
 50 setContentView(R.layout.activity_main);
 51 img = (ImageView) findViewById(R.id.img1);
 52 Log.v(TAG, "onCreate");

 54 }
 55 // 按钮的监听事件
 56 @Override
 57 public void onClick(View v) {
 58 // TODO Auto-generated method stub
 59 switch (v.getId()) {
 60 case R.id.btn1:
 61 Log.v(TAG, "btn1");
 62 changimg();
 63 break;
 64 case R.id.btn2:
 65 Log.v(TAG, "btn2");
 66 if (baths == 1) {
 67 loopimg();
 68 baths++;
 69 Log.v(TAG, "baths:"+baths);
 70 }
 71 break;
 72 case R.id.btn3:
 73 Log.v(TAG, "btn3");
 74 threadchangimg();
 75 break;
 76 case R.id.btn4:
 77 Log.v(TAG, "btn4--baths:"+baths);
 78 handler.removeCallbacks(myranble);
 79 baths = 1;
 80 break;
 81 }
 82 }
 83 private void threadchangimg() {
 84 // TODO Auto-generated method stub
 85 //    创建一个子线程
 86 new Thread(){
 87 @Override
 88 public void run() {
 89 // TODO Auto-generated method stub
 90 Log.v(TAG, "threadchangimg()-->Thread()-->run()");
 91 /*
 92 * 创建一个消息对象 把需要发送的消息放进对象中 通过sendMessage把此对象放
 93 * 入系统的消息池中等待调用
 94 */
 95 Message msg = new Message();
 96 imgrandom();
 97 msg.arg1 = index;
 98 Log.v(TAG, "msg.arg1:"+msg.arg1);
 99 hand.sendMessage(msg);
100 }
101 }.start();
102 }
103 private void loopimg() {
104 // TODO Auto-generated method stub
105 Log.v(TAG, "loopimg()");
106 //    延迟一秒通过主线程绑定的handler调用myranble
107 //    要先实例化MyRunable对象
108 handler.postDelayed(myranble, 1000);
109 }
110 class MyRunable implements Runnable{
111 @Override
112 public void run() {
113 // TODO Auto-generated method stub
114 Log.v(TAG, "MyRunable-->run()");
115 index++;
116 index = index%20;
117 Log.v(TAG, "index:"+index);
118 img.setBackgroundResource(images[index]);
119 handler.postDelayed(myranble, 1000);
120 }
121 
122 }
123 private void changimg() {
124 // TODO Auto-generated method stub
125 /*
126 * 在子线程中不可以直接更新UI
127 * 需要通过主线程绑定的handler来更新UI
128 */
129 Log.v(TAG, "changimg()");
130 new Thread(){
131 public void run() {
132 Log.v(TAG, "Thread()-->run()");
133 handler.post(new Runnable() {
134 @Override
135 public void run() {
136 // TODO Auto-generated method stub
137 Log.v(TAG, "handler-->Runnable()-->run()");
138 imgrandom();
139 Log.v(TAG, "index:"+index);
140 img.setBackgroundResource(images[index]);
141 }
142 
143 });
144 };
145 }.start();
146 }
147 private static void imgrandom() {
148 // TODO Auto-generated method stub
149 //    实现Random方法来实现随机数 实例化一个Random对象 Random对象是int类型的
150 Log.v(TAG, "imgrandom()");
151 Random random = new Random();
152 index = random.nextInt(20);
153 }
154 }
对应的布局文件

 1 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     android:orientation="vertical"
 6     tools:context=".MainActivity" >
 7 
 8     <Button
 9         android:id="@+id/btn1"
10         android:layout_width="match_parent"
11         android:layout_height="wrap_content"
12         android:onClick="onClick"
13         android:text="在子线程中更新UI" />
14 
15     <Button
16         android:id="@+id/btn2"
17         android:layout_width="match_parent"
18         android:layout_height="wrap_content"
19         android:onClick="onClick"
20         android:text="安卓中的图片轮播" />
21 
22     <Button
23         android:id="@+id/btn3"
24         android:layout_width="match_parent"
25         android:layout_height="wrap_content"
26         android:onClick="onClick"
27         android:text="通过消息队列实现图片更改" />
28 
29     <Button
30         android:id="@+id/btn4"
31         android:layout_width="match_parent"
32         android:layout_height="wrap_content"
33         android:onClick="onClick"
34         android:text="停止正在运行的线程" />
35 <RelativeLayout 
36         android:layout_width="match_parent"
37         android:layout_height="match_parent">
38       <ImageView
39         android:id="@+id/img1"
40         android:layout_centerHorizontal="true"
41         android:layout_centerVertical="true"
42         android:layout_width="wrap_content"
43         android:layout_height="wrap_content"
44         android:background="@drawable/t_beaksk"/>
45 </RelativeLayout>
46 
47 </LinearLayout>