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xjk112:
2015-05-08 13:21
我奋斗了18年才和你坐在一起喝咖啡[转] -
sandy_vv:
给达内广告,收费 ?
Java 利用url下载MP3保存到本地 -
78945612:
哥们
这个对于初学者怎么整呢?
android 定时关机 -
cn23snyga:
请教贵博,用ACE 绘制出的图表,可以捕捉到点击事件的坐标值 ...
使用achartengine开发曲线图相关的Android应用程序(zhuan) -
qi19901212:
楼主你好,我开发的achartengine放在 scrollv ...
Android开发工具之AChartEngine
在网上有许多资料对这三者关系的分析,但都比较笼统不够细致入微.
以下是自己深入源码分析其结果.
Handler 源码:
public class Handler {
private static final boolean FIND_POTENTIAL_LEAKS = false;
private static final String TAG = "Handler";
public interface Callback {
public boolean handleMessage(Message msg);
}
final MessageQueue mQueue;
final Looper mLooper;
final Callback mCallback;
IMessenger mMessenger;
/**
* Subclasses must implement this to receive messages.
*/
public void handleMessage(Message msg) {
}
public Handler() {
if (FIND_POTENTIAL_LEAKS) {
final Class<? extends Handler> klass = getClass();
if ((klass.isAnonymousClass() || klass.isMemberClass() || klass.isLocalClass()) &&
(klass.getModifiers() & Modifier.STATIC) == 0) {
Log.w(TAG, "The following Handler class should be static or leaks might occur: " +
klass.getCanonicalName());
}
}
mLooper = Looper.myLooper();
if (mLooper == null) {
throw new RuntimeException(
"Can't create handler inside thread that has not called Looper.prepare()");
}
mQueue = mLooper.mQueue;
mCallback = null;
}
/**
* Handle system messages here.
*/
public void dispatchMessage(Message msg) {
if (msg.callback != null) {
handleCallback(msg);
} else {
if (mCallback != null) {
if (mCallback.handleMessage(msg)) {
return;
}
}
handleMessage(msg);
}
}
public Handler() {
if (FIND_POTENTIAL_LEAKS) {
final Class<? extends Handler> klass = getClass();
if ((klass.isAnonymousClass() || klass.isMemberClass() || klass.isLocalClass()) &&
(klass.getModifiers() & Modifier.STATIC) == 0) {
Log.w(TAG, "The following Handler class should be static or leaks might occur: " +
klass.getCanonicalName());
}
}
mLooper = Looper.myLooper();
if (mLooper == null) {
throw new RuntimeException(
"Can't create handler inside thread that has not called Looper.prepare()");
}
mQueue = mLooper.mQueue;
mCallback = null;
}
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;
}
从源码分析可以看出:
handler在无参数的构造方法中调用Looper.myLooper()方法,里面就是从当前线程里面获取一个Looper对象,如果没有则创建.这样对Looper就进行初始化,初始化Looper的同时一并初始化MessageQueue,并且从中得到looper的MessageQueue .可以看出Handler就是Looper和MessageQueue的管理者和调度者.
其中最重要的是:sendMessageAtTime(Message msg, long uptimeMillis)这个方法,当你往Handler中发送Message消息的时候,从代码看出他自己并不去处理Message ,而是交给了MessageQueue.由以下从这段代码来处理:
queue.enqueueMessage(msg, uptimeMillis), 其具体实现要看下面的对
MessageQueue的分析
Looper结构关联的内容:
Looper 源码:
public class Looper {
private static final boolean DEBUG = false;
private static final boolean localLOGV = DEBUG ? Config.LOGD : Config.LOGV;
// sThreadLocal.get() will return null unless you've called prepare().
private static final ThreadLocal sThreadLocal = new ThreadLocal();
final MessageQueue mQueue;
volatile boolean mRun;
Thread mThread;
private Printer mLogging = null;
private static Looper mMainLooper = null;
public static final void prepare() {
if (sThreadLocal.get() != null) {
throw new RuntimeException("Only one Looper may be created per thread");
}
sThreadLocal.set(new Looper());
}
public static final void loop() {
Looper me = myLooper();
MessageQueue queue = me.mQueue;
while (true) {
Message msg = queue.next(); // might block
if (msg != null) {
if (msg.target == null) {
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();
}
}
}
从源码可以看出Looper 封装的信息:
Looper实质上是对当前线程, ThreadLocal,MessageQueue的封装,也就是负责在多线程之间传递消息的一个循环器.
当你往Handler中添加消息的时候则,里面这个方法: public static final void loop()死循环的方法就会被系统调用,之后的功能代码是:
msg.target.dispatchMessage(msg),则从MessageQueue中得到一个
Message(msg),之后调用Handler的dispatchMessage(msg),这个方法内部实际调用的就是 Handler.handleMessage(msg)方法,这个就是我们在
activity要重写的方法,所以我们就能够得到其他子线程传递的Message了.
Message的源码分析:
public final class Message implements Parcelable {
public int what;
public int arg1;
public int arg2;
public Object obj;
public Messenger replyTo;
long when;
Bundle data;
Handler target;
Runnable callback;
Message next;
private static Object mPoolSync = new Object();
private static Message mPool;
private static int mPoolSize = 0;
private static final int MAX_POOL_SIZE = 10;
When: 向Handler发送Message生成的时间
Data: 在Bundler 对象上绑定要线程中传递的数据
Next: 当前Message 对一下个Message 的引用
Handler: 处理当前Message 的Handler对象.
mPool: 通过字面理解可能叫他Message池,但是通过分析应该叫有下一个Message引用的Message链更加适合.
其中Message.obtain(),通过源码分析就是获取断掉Message链关系的第一个Message.
MessageQueue
public class MessageQueue {
Message mMessages;
private final ArrayList mIdleHandlers = new ArrayList();
private boolean mQuiting = false;
boolean mQuitAllowed = true;
public static interface IdleHandler {
boolean queueIdle();
}
public final void addIdleHandler(IdleHandler handler) {
if (handler == null) {
throw new NullPointerException("Can't add a null IdleHandler");
}
synchronized (this) {
mIdleHandlers.add(handler);
}
}
final boolean enqueueMessage(Message msg, long when) {
if (msg.when != 0) {
throw new AndroidRuntimeException(msg
+ " This message is already in use.");
}
if (msg.target == null && !mQuitAllowed) {
throw new RuntimeException("Main thread not allowed to quit");
}
synchronized (this) {
if (mQuiting) {
RuntimeException e = new RuntimeException(
msg.target + " sending message to a Handler on a dead thread");
Log.w("MessageQueue", e.getMessage(), e);
return false;
} else if (msg.target == null) {
mQuiting = true;
}
msg.when = when;
//Log.d("MessageQueue", "Enqueing: " + msg);
Message p = mMessages;
if (p == null || when == 0 || when < p.when) {
msg.next = p;
mMessages = msg;
this.notify();
} else {
Message prev = null;
while (p != null && p.when <= when) {
prev = p;
p = p.next;
}
msg.next = prev.next;
prev.next = msg;
this.notify();
}
}
return true;
}
mMessages: 为当前序列的第一个Message, 通过源码分析 MessageQueue并不是对许多Message 之间的关系维护,这样也许可以省去很多事把,而Message 之间的关系
则统统丢给了Message自己去维护,这个可以从对Message源码分析可以理解.
mIdleHandler: 保存的是一系列的handler的集合.
其中final boolean enqueueMessage(Message msg, long when),
这个方法就是上面提到Handler 处理消息时调用到的方法,对她理解了就显
的很重要了,功能代码如下:
msg.when = when;
Message p = mMessages;
if (p == null || when == 0 || when < p.when) {
msg.next = p;
mMessages = msg;
this.notify();
} else {
Message prev = null;
while (p != null && p.when <= when) {
prev = p;
p = p.next;
}
msg.next = prev.next;
prev.next = msg;
this.notify();
}
当向MessageQueue中添加消息的时候,判断当前的Message(mMessage)是否为空,
如果为空或者when=0或者when<p.when: 则把要添加的Message(msg)赋给当
前的Message(mMessage),并且将msg.next属性设为空,
如果不为空: 则循环把当前的Message(mMessage)的下一个Message(next)进行遍历,用prev记住当前的message,直到找到prev的下一个Message为空的时候就退出循环,最后将msg接到prev的屁股后面,
即这段代码: prev.next = msg;
以下是自己深入源码分析其结果.
Handler 源码:
public class Handler {
private static final boolean FIND_POTENTIAL_LEAKS = false;
private static final String TAG = "Handler";
public interface Callback {
public boolean handleMessage(Message msg);
}
final MessageQueue mQueue;
final Looper mLooper;
final Callback mCallback;
IMessenger mMessenger;
/**
* Subclasses must implement this to receive messages.
*/
public void handleMessage(Message msg) {
}
public Handler() {
if (FIND_POTENTIAL_LEAKS) {
final Class<? extends Handler> klass = getClass();
if ((klass.isAnonymousClass() || klass.isMemberClass() || klass.isLocalClass()) &&
(klass.getModifiers() & Modifier.STATIC) == 0) {
Log.w(TAG, "The following Handler class should be static or leaks might occur: " +
klass.getCanonicalName());
}
}
mLooper = Looper.myLooper();
if (mLooper == null) {
throw new RuntimeException(
"Can't create handler inside thread that has not called Looper.prepare()");
}
mQueue = mLooper.mQueue;
mCallback = null;
}
/**
* Handle system messages here.
*/
public void dispatchMessage(Message msg) {
if (msg.callback != null) {
handleCallback(msg);
} else {
if (mCallback != null) {
if (mCallback.handleMessage(msg)) {
return;
}
}
handleMessage(msg);
}
}
public Handler() {
if (FIND_POTENTIAL_LEAKS) {
final Class<? extends Handler> klass = getClass();
if ((klass.isAnonymousClass() || klass.isMemberClass() || klass.isLocalClass()) &&
(klass.getModifiers() & Modifier.STATIC) == 0) {
Log.w(TAG, "The following Handler class should be static or leaks might occur: " +
klass.getCanonicalName());
}
}
mLooper = Looper.myLooper();
if (mLooper == null) {
throw new RuntimeException(
"Can't create handler inside thread that has not called Looper.prepare()");
}
mQueue = mLooper.mQueue;
mCallback = null;
}
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;
}
从源码分析可以看出:
handler在无参数的构造方法中调用Looper.myLooper()方法,里面就是从当前线程里面获取一个Looper对象,如果没有则创建.这样对Looper就进行初始化,初始化Looper的同时一并初始化MessageQueue,并且从中得到looper的MessageQueue .可以看出Handler就是Looper和MessageQueue的管理者和调度者.
其中最重要的是:sendMessageAtTime(Message msg, long uptimeMillis)这个方法,当你往Handler中发送Message消息的时候,从代码看出他自己并不去处理Message ,而是交给了MessageQueue.由以下从这段代码来处理:
queue.enqueueMessage(msg, uptimeMillis), 其具体实现要看下面的对
MessageQueue的分析
Looper结构关联的内容:
Looper 源码:
public class Looper {
private static final boolean DEBUG = false;
private static final boolean localLOGV = DEBUG ? Config.LOGD : Config.LOGV;
// sThreadLocal.get() will return null unless you've called prepare().
private static final ThreadLocal sThreadLocal = new ThreadLocal();
final MessageQueue mQueue;
volatile boolean mRun;
Thread mThread;
private Printer mLogging = null;
private static Looper mMainLooper = null;
public static final void prepare() {
if (sThreadLocal.get() != null) {
throw new RuntimeException("Only one Looper may be created per thread");
}
sThreadLocal.set(new Looper());
}
public static final void loop() {
Looper me = myLooper();
MessageQueue queue = me.mQueue;
while (true) {
Message msg = queue.next(); // might block
if (msg != null) {
if (msg.target == null) {
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();
}
}
}
从源码可以看出Looper 封装的信息:
Looper实质上是对当前线程, ThreadLocal,MessageQueue的封装,也就是负责在多线程之间传递消息的一个循环器.
当你往Handler中添加消息的时候则,里面这个方法: public static final void loop()死循环的方法就会被系统调用,之后的功能代码是:
msg.target.dispatchMessage(msg),则从MessageQueue中得到一个
Message(msg),之后调用Handler的dispatchMessage(msg),这个方法内部实际调用的就是 Handler.handleMessage(msg)方法,这个就是我们在
activity要重写的方法,所以我们就能够得到其他子线程传递的Message了.
Message的源码分析:
public final class Message implements Parcelable {
public int what;
public int arg1;
public int arg2;
public Object obj;
public Messenger replyTo;
long when;
Bundle data;
Handler target;
Runnable callback;
Message next;
private static Object mPoolSync = new Object();
private static Message mPool;
private static int mPoolSize = 0;
private static final int MAX_POOL_SIZE = 10;
When: 向Handler发送Message生成的时间
Data: 在Bundler 对象上绑定要线程中传递的数据
Next: 当前Message 对一下个Message 的引用
Handler: 处理当前Message 的Handler对象.
mPool: 通过字面理解可能叫他Message池,但是通过分析应该叫有下一个Message引用的Message链更加适合.
其中Message.obtain(),通过源码分析就是获取断掉Message链关系的第一个Message.
MessageQueue
public class MessageQueue {
Message mMessages;
private final ArrayList mIdleHandlers = new ArrayList();
private boolean mQuiting = false;
boolean mQuitAllowed = true;
public static interface IdleHandler {
boolean queueIdle();
}
public final void addIdleHandler(IdleHandler handler) {
if (handler == null) {
throw new NullPointerException("Can't add a null IdleHandler");
}
synchronized (this) {
mIdleHandlers.add(handler);
}
}
final boolean enqueueMessage(Message msg, long when) {
if (msg.when != 0) {
throw new AndroidRuntimeException(msg
+ " This message is already in use.");
}
if (msg.target == null && !mQuitAllowed) {
throw new RuntimeException("Main thread not allowed to quit");
}
synchronized (this) {
if (mQuiting) {
RuntimeException e = new RuntimeException(
msg.target + " sending message to a Handler on a dead thread");
Log.w("MessageQueue", e.getMessage(), e);
return false;
} else if (msg.target == null) {
mQuiting = true;
}
msg.when = when;
//Log.d("MessageQueue", "Enqueing: " + msg);
Message p = mMessages;
if (p == null || when == 0 || when < p.when) {
msg.next = p;
mMessages = msg;
this.notify();
} else {
Message prev = null;
while (p != null && p.when <= when) {
prev = p;
p = p.next;
}
msg.next = prev.next;
prev.next = msg;
this.notify();
}
}
return true;
}
mMessages: 为当前序列的第一个Message, 通过源码分析 MessageQueue并不是对许多Message 之间的关系维护,这样也许可以省去很多事把,而Message 之间的关系
则统统丢给了Message自己去维护,这个可以从对Message源码分析可以理解.
mIdleHandler: 保存的是一系列的handler的集合.
其中final boolean enqueueMessage(Message msg, long when),
这个方法就是上面提到Handler 处理消息时调用到的方法,对她理解了就显
的很重要了,功能代码如下:
msg.when = when;
Message p = mMessages;
if (p == null || when == 0 || when < p.when) {
msg.next = p;
mMessages = msg;
this.notify();
} else {
Message prev = null;
while (p != null && p.when <= when) {
prev = p;
p = p.next;
}
msg.next = prev.next;
prev.next = msg;
this.notify();
}
当向MessageQueue中添加消息的时候,判断当前的Message(mMessage)是否为空,
如果为空或者when=0或者when<p.when: 则把要添加的Message(msg)赋给当
前的Message(mMessage),并且将msg.next属性设为空,
如果不为空: 则循环把当前的Message(mMessage)的下一个Message(next)进行遍历,用prev记住当前的message,直到找到prev的下一个Message为空的时候就退出循环,最后将msg接到prev的屁股后面,
即这段代码: prev.next = msg;
发表评论
-
Android开发之Tools
2011-10-02 00:19 897AChartEngine is a charting libr ... -
使用achartengine开发曲线图相关的Android应用程序(zhuan)
2011-10-02 00:10 2955应用程序的开发过程中,经常会遇到和曲线图打交道的情况,相比自己 ... -
或许您还不知道的八款开源Android游戏引擎
2011-09-29 12:38 765很多初学Android游戏开发 ... -
Android开发工具之AChartEngine
2011-09-29 12:11 3024最近在做一个关于股票的软件(for Android),在软件中 ... -
android 事件处理(转)
2011-09-15 12:14 1082android中的事件类型分为按键事件和屏幕触摸事件,Touc ... -
android paint设置字体 中文字体 楷体 和自动换行方法(zhuan)
2011-09-14 16:19 3816Bitmap bmp = BitmapFactory.deco ... -
Android Canvas类介绍(zhuan)
2011-09-14 14:57 934当我们调整好画笔之后,现在需要绘制到画布上,这就得用Can ... -
Android Canvas类介绍(zhuan)
2011-09-14 14:56 0当我们调整好画笔之后,现在需要绘制到画布上,这就得用Can ... -
Android OpenGL之生成FloatBuffer
2011-09-06 08:56 1475public FloatBuffer getFloatBuff ... -
Activity之间的跳转(A-B-A)
2011-09-05 12:29 982Activity A 中: Intent intent ... -
Android OpenGL相关
2011-09-02 15:46 7110x10000是出于OPENGL前期内存节约的考虑, 以INT ... -
Android 返回键
2011-09-01 17:11 1066@Override public boolean onK ... -
android selector(zhuan)
2011-08-30 10:06 536<?xml version="1.0" ... -
android 定时关机
2011-08-29 10:19 1260Calendar calendar = Calendar.ge ... -
android 相关2
2011-08-25 12:31 770AndroidManifest.xml的activity里加a ... -
Android ListView刷新 (Handler/Service)
2011-08-03 21:40 2103本文转自http://blog.sina.com.cn/s/b ... -
Android 中的ListView内容刷新问题(转)
2011-08-03 21:22 1188本文转自http://www.linuxidc.com/Lin ... -
android listview
2011-08-03 21:21 786Android 中的ListView内容刷新 对于ListV ... -
android相关
2011-07-21 12:48 783android:screenOrientation=" ... -
Android中JNI程序的编写(zhuan)
2011-07-15 18:48 948zhuan(http://luco1130.blog.163. ...
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