Android线程间通信的Message机制
1.1.Message 代码在frameworks\base\core\java\android\Os\Message.java中。
Message.obtain函数:有多个obtain函数,主要功能一样,只是参数不一样。作用是从Message Pool中取出一个Message,如果Message Pool中已经没有Message可取则新建一个Message返回,同时用对应的参数给得到的Message对象赋值。
Message Pool:大小为10个;通过Message.mPool->(Message并且Message.next)-> (Message并且Message.next)-> (Message并且Message.next)...构造一个Message Pool。Message Pool的第一个元素直接new出来,然后把Message.mPool(static类的static变量)指向它。其他的元素都是使用完的 Message通过Message的recycle函数清理后放到Message Pool(通过Message Pool最后一个Message的next指向需要回收的Message的方式实现)。下图为Message Pool的结构:
1.2.MessageQueue MessageQueue里面有一个收到的Message的对列:
MessageQueue.mMessages(static变量)->( Message并且Message.next)-> ( Message并且Message.next)->...,下图为接收消息的消息队列:
上层代码通过Handler的sendMessage等函数放入一个message到MessageQueue里面时最终会调用 MessageQueue的 enqueueMessage函数。enqueueMessage根据上面的接收的Message的队列的构造把接收到的Message放入队列中。
MessageQueue的removeMessages函数根据上面的接收的Message的队列的构造把接收到的Message从队列中删除,并且调用对应Message对象的recycle函数把不用的Message放入Message Pool中。
1.3.Looper Looper对象的创建是通过prepare函数,而且每一个Looper对象会和一个线程关联
Java代码
- 1. public static final void prepare() {
- 2. if (sThreadLocal.get() != null) {
- 3. throw new RuntimeException("Only one Looper may be created per thread");
- 4. }
- 5. sThreadLocal.set(new Looper());
- 6. }
复制代码
- public static final void prepare() {
- if (sThreadLocal.get() != null) {
- throw new RuntimeException("Only one Looper may be created per thread");
- }
- sThreadLocal.set(new Looper());
- }
复制代码
Looper对象创建时会创建一个MessageQueue,主线程默认会创建一个Looper从而有MessageQueue,其他线程默认是没有 MessageQueue的不能接收Message,如果需要接收Message则需要通过prepare函数创建一个MessageQueue。具体操作请见示例代码。
Java代码
- 1. private Looper() {
- 2. mQueue = new MessageQueue();
- 3. mRun = true;
- 4. mThread = Thread.currentThread();
- 5. }
复制代码
private Looper() { mQueue = new MessageQueue(); mRun = true; mThread = Thread.currentThread(); }
prepareMainLooper函数只给主线程调用(系统处理,程序员不用处理),它会调用prepare建立Looper对象和MessageQueue。
Java代码
1. public static final void prepareMainLooper() { 2. prepare(); 3. setMainLooper(myLooper()); 4. if (Process.supportsProcesses()) { 5. myLooper().mQueue.mQuitAllowed = false; 6. } 7. }
public static final void prepareMainLooper() { prepare(); setMainLooper(myLooper()); if (Process.supportsProcesses()) { myLooper().mQueue.mQuitAllowed = false; } }
Loop函数从MessageQueue中从前往后取出Message,然后通过Handler的dispatchMessage函数进行消息的处理(可见消息的处理是Handler负责的),消息处理完了以后通过Message对象的recycle函数放到Message Pool中,以便下次使用,通过Pool的处理提供了一定的内存管理从而加速消息对象的获取。至于需要定时处理的消息如何做到定时处理,请见 MessageQueue的next函数,它在取Message来进行处理时通过判断MessageQueue里面的Message是否符合时间要求来决定是否需要把Message取出来做处理,通过这种方式做到消息的定时处理。
Java代码
- 1. public static final void loop() {
- 2. Looper me = myLooper();
- 3. MessageQueue queue = me.mQueue;
- 4. while (true) {
- 5. Message msg = queue.next(); // might block
- 6. //if (!me.mRun) {
- 7. // break;
- 8. //}
- 9. if (msg != null) {
- 10. if (msg.target == null) {
- 11. // No target is a magic identifier for the quit message
- 12. return;
- 13. }
- 14.
- 15. if (me.mLogging!= null)
- 16. me.mLogging.println(">>>>> Dispatching to " + msg.target + " "+ msg.callback + ": " + msg.what);
- 17. msg.target.dispatchMessage(msg);
- 18. if (me.mLogging!= null)
- 19. me.mLogging.println("<<<<< Finished to" + msg.target + " "+ msg.callback);
- 20. msg.recycle();
- 21. }
- 22. }
- 23. }
- public static final void loop() {
- Looper me = myLooper();
- MessageQueue queue = me.mQueue;
- while (true) {
- Message msg = queue.next(); // might block
- //if (!me.mRun) {
- // break;
- //}
- if (msg != null) {
- if (msg.target == null) {
- // No target is a magic identifier for the quit message
- return;
- }
- if (me.mLogging!= null)
- me.mLogging.println(">>>>> Dispatching to " + msg.target + " "+ msg.callback + ": " + msg.what);
- msg.target.dispatchMessage(msg);
- if (me.mLogging!= null)
- me.mLogging.println("<<<<< Finished to" + msg.target + " "+ msg.callback);
- msg.recycle();
- }
- }
- }
复制代码
1.4.Handler
Handler的构造函数表示Handler会有成员变量指向Looper和MessageQueue,后面我们会看到没什么需要这些引用;至于callback是实现了Callback接口的对象,后面会看到这个对象的作用。
Java代码
1. public Handler(Looper looper, Callback callback) { 2. mLooper = looper; 3. mQueue = looper.mQueue; 4. mCallback = callback; 5. } 6. 7. public interface Callback { 8. public boolean handleMessage(Message msg); 9. }
public Handler(Looper looper, Callback callback) { mLooper = looper; mQueue = looper.mQueue; mCallback = callback; }
public interface Callback { public boolean handleMessage(Message msg); }
获取消息:直接通过Message的obtain方法获取一个Message对象。
Java代码
1. public final Message obtainMessage(int what, int arg1, int arg2, Object obj){ 2. return Message.obtain(this, what, arg1, arg2, obj); 3. }
public final Message obtainMessage(int what, int arg1, int arg2, Object obj){ return Message.obtain(this, what, arg1, arg2, obj); }
发送消息:通过MessageQueue的enqueueMessage把Message对象放到MessageQueue的接收消息队列中
Java代码
1. public boolean sendMessageAtTime(Message msg, long uptimeMillis){ 2. boolean sent = false; 3. MessageQueue queue = mQueue; 4. if (queue != null) { 5. msg.target = this; 6. sent = queue.enqueueMessage(msg, uptimeMillis); 7. } else { 8. RuntimeException e = new RuntimeException(this + " sendMessageAtTime() called with no mQueue"); 9. Log.w("Looper", e.getMessage(), e); 10. } 11. return sent; 12. }
public boolean sendMessageAtTime(Message msg, long uptimeMillis){ boolean sent = false; MessageQueue queue = mQueue; if (queue != null) { msg.target = this; sent = queue.enqueueMessage(msg, uptimeMillis); } else { RuntimeException e = new RuntimeException(this + " sendMessageAtTime() called with no mQueue"); Log.w("Looper", e.getMessage(), e); } return sent; }
线程如何处理MessageQueue中接收的消息:在Looper的loop函数中循环取出MessageQueue的接收消息队列中的消息,然后调用 Hander的dispatchMessage函数对消息进行处理,至于如何处理(相应消息)则由用户指定(三个方法,优先级从高到低:Message里面的Callback,一个实现了Runnable接口的对象,其中run函数做处理工作;Handler里面的mCallback指向的一个实现了 Callback接口的对象,里面的handleMessage进行处理;处理消息Handler对象对应的类继承并实现了其中 handleMessage函数,通过这个实现的handleMessage函数处理消息)。
Java代码
1. public void dispatchMessage(Message msg) { 2. if (msg.callback != null) { 3. handleCallback(msg); 4. } else { 5. if (mCallback != null) { 6. if (mCallback.handleMessage(msg)) { 7. return; 8. } 9. } 10. handleMessage(msg); 11. } 12. }
public void dispatchMessage(Message msg) { if (msg.callback != null) { handleCallback(msg); } else { if (mCallback != null) { if (mCallback.handleMessage(msg)) { return; } } handleMessage(msg); } }
Runnable说明:Runnable只是一个接口,实现了这个接口的类对应的对象也只是个普通的对象,并不是一个Java中的Thread。Thread类经常使用Runnable,很多人有误解,所以这里澄清一下。
从上可知以下关系图:
其中清理Message是Looper里面的loop函数指把处理过的Message放到Message的Pool里面去,如果里面已经超过最大值10个,则丢弃这个Message对象。
调用Handler是指Looper里面的loop函数从MessageQueue的接收消息队列里面取出消息,然后根据消息指向的Handler对象调用其对应的处理方法。 1.5.代码示例
下面我们会以android实例来展示对应的功能,程序界面于下: g。 |
- 1
评分人数
-
|
|
|
|
|
|
- UID
- 16560
- 帖子
- 42
- 精华
- 0
- 积分
- 152
- e望
- 3 点
- e币
- 31 元
- e脉
- 0 条
- 来自
- 澳大利亚
- 在线时间
- 69 小时
|
2#
发表于 2010-1-29 08:01 | 只看该作者
程序代码如下,后面部分有代码说明:
Java代码
- 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 thread's 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 thread's 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();
- 170. mainLooper = Looper.getMainLooper(); //这是一个static函数
- 171. String obj;
- 172. if(myLooper == null){
- 173. mNoLooperThreadHandler = new EventHandler(mainLooper);
- 174. obj = "NoLooperThread has no looper and handleMessage function executed in main thread!";
- 175. }
- 176. else {
- 177. mNoLooperThreadHandler = new EventHandler(myLooper);
- 178. obj = "This is from NoLooperThread self and handleMessage function executed in NoLooperThread!";
- 179. }
- 180. mNoLooperThreadHandler.removeMessages(0);
- 181. if(false == postRunnable){
- 182. //send message to main thread
- 183. Message m = mNoLooperThreadHandler.obtainMessage(2, 1, 1, obj);
- 184. mNoLooperThreadHandler.sendMessage(m);
- 185. Log.e(sTag, "NoLooperThread id:" + this.getId());
- 186. }else{
- 187. //下面new出来的实现了Runnable接口的对象中run函数是在Main Thread中执行,不是在NoLooperThread中执行
- 188. //注意Runnable是一个接口,它里面的run函数被执行时不会再新建一个线程
- 189. //您可以在run上加断点然后在eclipse调试中看它在哪个线程中执行
- 190. mNoLooperThreadHandler.post(new Runnable(){
- 191. @Override
- 192. public void run() {
- 193. tv.setText("update UI through handler post runnalbe mechanism!");
- 194. noLooerThread.stop();
- 195. }
- 196. });
- 197. }
- 198. }
- 199. }
- 200.
- 201. //OwnLooperThread has his own message queue by execute Looper.prepare();
- 202. class OwnLooperThread extends Thread{
- 203. private EventHandler mOwnLooperThreadHandler;
- 204. public void run() {
- 205. Looper.prepare();
- 206. Looper myLooper, mainLooper;
- 207. myLooper = Looper.myLooper();
- 208. mainLooper = Looper.getMainLooper(); //这是一个static函数
- 209. String obj;
- 210. if(myLooper == null){
- 211. mOwnLooperThreadHandler = new EventHandler(mainLooper);
- 212. obj = "OwnLooperThread has no looper and handleMessage function executed in main thread!";
- 213. }
- 214. else {
- 215. mOwnLooperThreadHandler = new EventHandler(myLooper);
- 216. obj = "This is from OwnLooperThread self and handleMessage function executed in NoLooperThread!";
- 217. }
- 218. mOwnLooperThreadHandler.removeMessages(0);
- 219. //给自己发送消息
- 220. Message m = mOwnLooperThreadHandler.obtainMessage(3, 1, 1, obj);
- 221. mOwnLooperThreadHandler.sendMessage(m);
- 222. Looper.loop();
- 223. }
- 224. }
- 225.
- 226. //ReceiveMessageThread has his own message queue by execute Looper.prepare();
- 227. class ReceiveMessageThread extends Thread{
- 228. public void run() {
- 229. Looper.prepare();
- 230. mOtherThreadHandler = new Handler(){
- 231. public void handleMessage(Message msg) {
- 232. Log.e(sTag, (String)msg.obj);
- 233. }
- 234. };
- 235. Looper.loop();
- 236. }
- 237. }
- 238.
- 239. }
- package com.android.messageexample;
- import android.app.Activity;
- import android.content.Context;
- import android.graphics.Color;
- import android.os.Bundle;
- import android.os.Handler;
- import android.os.Looper;
- import android.os.Message;
- import android.util.Log;
- import android.view.View;
- import android.view.View.OnClickListener;
- import android.widget.Button;
- import android.widget.LinearLayout;
- import android.widget.TextView;
- public class MessageExample extends Activity implements OnClickListener {
- private final int WC = LinearLayout.LayoutParams.WRAP_CONTENT;
- private final int FP = LinearLayout.LayoutParams.FILL_PARENT;
- public TextView tv;
- private EventHandler mHandler;
- private Handler mOtherThreadHandler=null;
- private Button btn, btn2, btn3, btn4, btn5, btn6;
- private NoLooperThread noLooerThread = null;
- private OwnLooperThread ownLooperThread = null;
- private ReceiveMessageThread receiveMessageThread =null;
- private Context context = null;
- private final String sTag = "MessageExample";
- private boolean postRunnable = false;
- /** Called when the activity is first created. */
- @Override
- public void onCreate(Bundle savedInstanceState) {
- super.onCreate(savedInstanceState);
- context = this.getApplicationContext();
- LinearLayout layout = new LinearLayout(this);
- layout.setOrientation(LinearLayout.VERTICAL);
- btn = new Button(this);
- btn.setId(101);
- btn.setText("message from main thread self");
- btn.setOnClickListener(this);
- LinearLayout.LayoutParams param =
- new LinearLayout.LayoutParams(250,50);
- param.topMargin = 10;
- layout.addView(btn, param);
- btn2 = new Button(this);
- btn2.setId(102);
- btn2.setText("message from other thread to main thread");
- btn2.setOnClickListener(this);
- layout.addView(btn2, param);
- btn3 = new Button(this);
- btn3.setId(103);
- btn3.setText("message to other thread from itself");
- btn3.setOnClickListener(this);
- layout.addView(btn3, param);
- btn4 = new Button(this);
- btn4.setId(104);
- btn4.setText("message with Runnable as callback from other thread to main thread");
- btn4.setOnClickListener(this);
- layout.addView(btn4, param);
- btn5 = new Button(this);
- btn5.setId(105);
- btn5.setText("main thread's message to other thread");
- btn5.setOnClickListener(this);
- layout.addView(btn5, param);
- btn6 = new Button(this);
- btn6.setId(106);
- btn6.setText("exit");
- btn6.setOnClickListener(this);
- layout.addView(btn6, param);
- tv = new TextView(this);
- tv.setTextColor(Color.WHITE);
- tv.setText("");
- LinearLayout.LayoutParams param2 =
- new LinearLayout.LayoutParams(FP, WC);
- param2.topMargin = 10;
- layout.addView(tv, param2);
- setContentView(layout);
-
- //主线程要发送消息给other thread, 这里创建那个other thread
- receiveMessageThread = new ReceiveMessageThread();
- receiveMessageThread.start();
- }
- //implement the OnClickListener interface
- @Override
- public void onClick(View v) {
- switch(v.getId()){
- case 101:
- //主线程发送消息给自己
- Looper looper;
- looper = Looper.myLooper(); //get the Main looper related with the main thread
- //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
- mHandler = new EventHandler(looper);
- //mHandler = new EventHandler();
- // 清除整个MessageQueue里的消息
- mHandler.removeMessages(0);
- String obj = "This main thread's message and received by itself!";
- //得到Message对象
- Message m = mHandler.obtainMessage(1, 1, 1, obj);
- // 将Message对象送入到main thread的MessageQueue里面
- mHandler.sendMessage(m);
- break;
- case 102:
- //other线程发送消息给主线程
- postRunnable = false;
- noLooerThread = new NoLooperThread();
- noLooerThread.start();
- break;
- case 103:
- //other thread获取它自己发送的消息
- tv.setText("please look at the error level log for other thread received message");
- ownLooperThread = new OwnLooperThread();
- ownLooperThread.start();
- break;
- case 104:
- //other thread通过Post Runnable方式发送消息给主线程
- postRunnable = true;
- noLooerThread = new NoLooperThread();
- noLooerThread.start();
- break;
- case 105:
- //主线程发送消息给other thread
- if(null!=mOtherThreadHandler){
- tv.setText("please look at the error level log for other thread received message from main thread");
- String msgObj = "message from mainThread";
- Message mainThreadMsg = mOtherThreadHandler.obtainMessage(1, 1, 1, msgObj);
- mOtherThreadHandler.sendMessage(mainThreadMsg);
- }
- break;
- case 106:
- finish();
- break;
- }
- }
- class EventHandler extends Handler
- {
- public EventHandler(Looper looper) {
- super(looper);
- }
- public EventHandler() {
- super();
- }
- public void handleMessage(Message msg) {
- //可以根据msg.what执行不同的处理,这里没有这么做
- switch(msg.what){
- case 1:
- tv.setText((String)msg.obj);
- break;
- case 2:
- tv.setText((String)msg.obj);
- noLooerThread.stop();
- break;
- case 3:
- //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
- Log.e(sTag, (String)msg.obj);
- ownLooperThread.stop();
- break;
- default:
- //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
- Log.e(sTag, (String)msg.obj);
- break;
- }
- }
- }
- //NoLooperThread
- class NoLooperThread extends Thread{
- private EventHandler mNoLooperThreadHandler;
- public void run() {
- Looper myLooper, mainLooper;
- myLooper = Looper.myLooper();
- mainLooper = Looper.getMainLooper(); //这是一个static函数
- String obj;
- if(myLooper == null){
- mNoLooperThreadHandler = new EventHandler(mainLooper);
- obj = "NoLooperThread has no looper and handleMessage function executed in main thread!";
- }
- else {
- mNoLooperThreadHandler = new EventHandler(myLooper);
- obj = "This is from NoLooperThread self and handleMessage function executed in NoLooperThread!";
- }
- mNoLooperThreadHandler.removeMessages(0);
- if(false == postRunnable){
- //send message to main thread
- Message m = mNoLooperThreadHandler.obtainMessage(2, 1, 1, obj);
- mNoLooperThreadHandler.sendMessage(m);
- Log.e(sTag, "NoLooperThread id:" + this.getId());
- }else{
- //下面new出来的实现了Runnable接口的对象中run函数是在Main Thread中执行,不是在NoLooperThread中执行
- //注意Runnable是一个接口,它里面的run函数被执行时不会再新建一个线程
- //您可以在run上加断点然后在eclipse调试中看它在哪个线程中执行
- mNoLooperThreadHandler.post(new Runnable(){
- @Override
- public void run() {
- tv.setText("update UI through handler post runnalbe mechanism!");
- noLooerThread.stop();
- }
- });
- }
- }
- }
- //OwnLooperThread has his own message queue by execute Looper.prepare();
- class OwnLooperThread extends Thread{
- private EventHandler mOwnLooperThreadHandler;
- public void run() {
- Looper.prepare();
- Looper myLooper, mainLooper;
- myLooper = Looper.myLooper();
- mainLooper = Looper.getMainLooper(); //这是一个static函数
- String obj;
- if(myLooper == null){
- mOwnLooperThreadHandler = new EventHandler(mainLooper);
- obj = "OwnLooperThread has no looper and handleMessage function executed in main thread!";
- }
- else {
- mOwnLooperThreadHandler = new EventHandler(myLooper);
- obj = "This is from OwnLooperThread self and handleMessage function executed in NoLooperThread!";
- }
- mOwnLooperThreadHandler.removeMessages(0);
- //给自己发送消息
- Message m = mOwnLooperThreadHandler.obtainMessage(3, 1, 1, obj);
- mOwnLooperThreadHandler.sendMessage(m);
- Looper.loop();
- }
- }
- //ReceiveMessageThread has his own message queue by execute Looper.prepare();
- class ReceiveMessageThread extends Thread{
- public void run() {
- Looper.prepare();
- mOtherThreadHandler = new Handler(){
- public void handleMessage(Message msg) {
- Log.e(sTag, (String)msg.obj);
- }
- };
- Looper.loop();
- }
- }
- }
复制代码
说明(代码详细解释请见后文):
使用Looper.myLooper静态方法可以取得当前线程的Looper对象。
使用mHandler = new EevntHandler(Looper.myLooper()); 可建立用来处理当前线程的Handler对象;其中,EevntHandler是Handler的子类。
使用mHandler = new EevntHandler(Looper.getMainLooper()); 可建立用来处理main线程的Handler对象;其中,EevntHandler是Handler的子类。 |
|
|