Android系列之Message机制的灵活应用
下面我们会以android实例来展示对应的功能，程序界面于下：
程序代码如下，后面部分有代码说明：
1 package com.android.messageexample;
2 import android.app.Activity;
3 import android.content.Context;
4 import android.graphics.Color;
5 import android.os.Bundle;
6 import android.os.Handler;
7 import android.os.Looper;
8 import android.os.Message;
9 import android.util.Log;
10 import android.view.View;
11 import android.view.View.OnClickListener;
12 import android.widget.Button;
13 import android.widget.LinearLayout;
14 import android.widget.TextView;
15 public class MessageExample extends Activity implements OnClickListener {
16 private final int WC = LinearLayout.LayoutParams.WRAP_CONTENT;
17 private final int FP = LinearLayout.LayoutParams.FILL_PARENT;
18 public TextView tv;
19 private EventHandler mHandler;
20 private Handler mOtherThreadHandler=null;
21 private Button btn, btn2, btn3, btn4, btn5, btn6;
22 private NoLooperThread noLooerThread = null;
23 private OwnLooperThread ownLooperThread = null;
24 private ReceiveMessageThread receiveMessageThread =null;
25 private Context context = null;
26 private final String sTag = "MessageExample";
27 private boolean postRunnable = false;
28
29 /** Called when the activity is first created. */
30 @Override
31 public void onCreate(Bundle savedInstanceState) {
32 super.onCreate(savedInstanceState);
33 context = this.getApplicationContext();
34 LinearLayout layout = new LinearLayout(this);
35 layout.setOrientation(LinearLayout.VERTICAL);
36 btn = new Button(this);
37 btn.setId(101);
38 btn.setText("message from main thread self");
39 btn.setOnClickListener(this);
40 LinearLayout.LayoutParams param =
41 new LinearLayout.LayoutParams(250,50);
42 param.topMargin = 10;
43 layout.addView(btn, param);
44 btn2 = new Button(this);
45 btn2.setId(102);
46 btn2.setText("message from other thread to main thread");
47 btn2.setOnClickListener(this);
48 layout.addView(btn2, param);
49 btn3 = new Button(this);
50 btn3.setId(103);
51 btn3.setText("message to other thread from itself");
52 btn3.setOnClickListener(this);
53 layout.addView(btn3, param);
54 btn4 = new Button(this);
55 btn4.setId(104);
56 btn4.setText("message with Runnable as callback from other thread to main thread");
57 btn4.setOnClickListener(this);
58 layout.addView(btn4, param);
59 btn5 = new Button(this);
60 btn5.setId(105);
61 btn5.setText("main threads message to other thread");
62 btn5.setOnClickListener(this);
63 layout.addView(btn5, param);
64 btn6 = new Button(this);
65 btn6.setId(106);
66 btn6.setText("exit");
67 btn6.setOnClickListener(this);
68 layout.addView(btn6, param);
69 tv = new TextView(this);
70 tv.setTextColor(Color.WHITE);
71 tv.setText("");
72 LinearLayout.LayoutParams param2 =
73 new LinearLayout.LayoutParams(FP, WC);
74 param2.topMargin = 10;
75 layout.addView(tv, param2);
76 setContentView(layout);
77
78 //主线程要发送消息给other thread， 这里创建那个other thread
79 receiveMessageThread = new ReceiveMessageThread();
80 receiveMessageThread.start();
81 }
82
83 //implement the OnClickListener interface
84 @Override
85 public void onClick(View v) {
86 switch(v.getId()){
87 case 101:
88 //主线程发送消息给自己
89 Looper looper;
90 looper = Looper.myLooper(); //get the Main looper related with the main thread
91 //如果不给任何参数的话会用当前线程对应的Looper(这里就是Main Looper)为Handler里面的成员mLooper赋值
92 mHandler = new EventHandler(looper);
93 //mHandler = new EventHandler();
94 // 清除整个MessageQueue里的消息
95 mHandler.removeMessages(0);
96 String obj = "This main threads message and received by itself!";
97 //得到Message对象
98 Message m = mHandler.obtainMessage(1, 1, 1, obj);
99 // 将Message对象送入到main thread的MessageQueue里面
100 mHandler.sendMessage(m);
101 break;
102 case 102:
103 //other线程发送消息给主线程
104 postRunnable = false;
105 noLooerThread = new NoLooperThread();
106 noLooerThread.start();
107 break;
108 case 103:
109 //other thread获取它自己发送的消息
110 tv.setText("please look at the error level log for other thread received message");
111 ownLooperThread = new OwnLooperThread();
112 ownLooperThread.start();
113 break;
114 case 104:
115 //other thread通过Post Runnable方式发送消息给主线程
116 postRunnable = true;
117 noLooerThread = new NoLooperThread();
118 noLooerThread.start();
119 break;
120 case 105:
121 //主线程发送消息给other thread
122 if(null!=mOtherThreadHandler){
123 tv.setText("please look at the error level log for other thread received message from main thread");
124 String msgObj = "message from mainThread";
125 Message mainThreadMsg = mOtherThreadHandler.obtainMessage(1, 1, 1, msgObj);
126 mOtherThreadHandler.sendMessage(mainThreadMsg);
127 }
128 break;
129 case 106:
130 finish();
131 break;
132 }
133 }
134 class EventHandler extends Handler
135 {
136 public EventHandler(Looper looper) {
137 super(looper);
138 }
139 public EventHandler() {
140 super();
141 }
142 public void handleMessage(Message msg) {
143 //可以根据msg.what执行不同的处理，这里没有这么做
144 switch(msg.what){
145 case 1:
146 tv.setText((String)msg.obj);
147 break;
148 case 2:
149 tv.setText((String)msg.obj);
150 noLooerThread.stop();
151 break;
152 case 3:
153 //不能在非主线程的线程里面更新UI，所以这里通过Log打印收到的消息
154 Log.e(sTag, (String)msg.obj);
155 ownLooperThread.stop();
156 break;
157 default:
158 //不能在非主线程的线程里面更新UI，所以这里通过Log打印收到的消息
159 Log.e(sTag, (String)msg.obj);
160 break;
161 }
162 }
163 }
164 //NoLooperThread
165 class NoLooperThread extends Thread{
166 private EventHandler mNoLooperThreadHandler;
167 public void run() {
168 Looper myLooper, mainLooper;
169 myLooper = Looper.myLooper();
补充：移动开发 , Android ,
