Android系列之Message機制的靈活應用 – Android移動開發技術文章_手機開發 Android移動開發教學課程

下面我們會以android實例來展示對應的功能,程序界面於下:


Android系列之Message機制的靈活應用


  程序代碼如下,後面部分有代碼說明:


 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    //主線程要發送消息給other thread, 這裡創建那個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 //主線程發送消息給自己  
 89 Looper looper;  
 90 looper = Looper.myLooper();  //get the Main looper related with the main thread  
 91 //如果不給任何參數的話會用當前線程對應的Looper(這裡就是Main Looper)為Handler裡面的成員mLooper賦值  
 92 mHandler = new EventHandler(looper);  
 93 //mHandler = new EventHandler();  
 94 // 清除整個MessageQueue裡的消息  
 95 mHandler.removeMessages(0);  
 96 String obj = ”This main threads message and received by itself!”;  
 97 //得到Message對象  
 98 Message m = mHandler.obtainMessage(1, 1, 1, obj);  
 99 // 將Message對象送入到main thread的MessageQueue裡面  
100 mHandler.sendMessage(m);  
101 break;  
102  case 102:  
103 //other線程發送消息給主線程  
104 postRunnable = false;  
105 noLooerThread = new NoLooperThread();  
106 noLooerThread.start();  
107 break;  
108  case 103:   
109 //other thread獲取它自己發送的消息  
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通過Post Runnable方式發送消息給主線程  
116 postRunnable = true;  
117 noLooerThread = new NoLooperThread();  
118 noLooerThread.start();  
119 break;  
120  case 105:    
121 //主線程發送消息給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 //可以根據msg.what執行不同的處理,這裡沒有這麼做  
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 //不能在非主線程的線程裡面更新UI,所以這裡通過Log打印收到的消息  
154 Log.e(sTag, (String)msg.obj);  
155 ownLooperThread.stop();  
156 break;  
157 default:  
158 //不能在非主線程的線程裡面更新UI,所以這裡通過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(); 

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