简单运行图:
名词解析:
Message(消息):定义了一个包含描述以及随意的数据对象可以被发送到Hanlder的消息,获得消息的最好方法是Message.obtain或者Handler.obtainMessage方法;
MessageQueue (消息队列):是looper中的一个消息队列;
Looper:用于使一个消息队列在线程中循环,线程中默认是没有消息队列循环的,创建方法demo:
classLooperThreadextendsThread{
publicHandler mHandler; publicvoid run(){
Looper.prepare(); mHandler =newHandler(){
publicvoid handleMessage(Message msg){
// process incoming messages here
}
}; Looper.loop();
}
}
Looper方法 | |||||||||||
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void | dump(Printer pw, String prefix) | ||||||||||
synchronized static Looper |
getMainLooper() 获得主线程的Looper Returns the application's main looper, which lives in the main thread of the application.
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Thread |
getThread()
Return the Thread associated with this Looper.
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static void |
loop()
Run the message queue in this thread.
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static Looper |
myLooper() 获得当前线程关联的Looper Return the Looper object associated with the current thread.
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static MessageQueue |
myQueue() 获得当前线程关联的消息队列 Return the
MessageQueue object associated with the current thread. |
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static void |
prepare()
Initialize the current thread as a looper.
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static void |
prepareMainLooper()
Initialize the current thread as a looper, marking it as an application's main looper.
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Handler(消息控制器):一个处理程序允许您发送或者处理消息以及与线程的MessageQueue相关联的可执行对象,每个Handler实例与单个线程以及该线程的消息队列想关联。当你创建一个新的Handler 实例的时候,该实例将被绑定到线程消息队列,该实例将传递messages消息或者可运行的对象到 message queue消息队列并且在当消息被获取的时候执行他们。
Handler的两个主要用途:
- 安排消息或者可执行对象在未来的某个时间点执行。
- 将一个在子线程执行的动作放到消息队列中
处理消息通过 post(Runnable), postAtTime(Runnable, long), postDelayed(Runnable, long), sendEmptyMessage(int),sendMessage(Message), sendMessageAtTime(Message, long), and sendMessageDelayed(Message, long) 方法来完成。post系列方法允许你队列一个可执行对象,当消息被handler所在线程接收的时候会执行;sendMessage允许你队列一个包含一捆数据的Message对象,到消息handler所在线程接收的时候将调用handler实例的handleMessage(Message)方法,Massage 就是在另一个线程发送的消息。
当你使用handler发送消息或者可执行对象的时候你可以选择handler所在线程获得消息就执行或延迟一定的时间再执行,当应用程序创建一个线程的时候,它的主线程专门运行一个message queue 消息队列用于维护应用程序*组件 。我们可以创建子线程通过Handler实例与主线程通信。
Handler 方法介绍 | |||||||||||
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void |
dispatchMessage(Message msg)
Handle system messages here.
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final void | dump(Printer pw, String prefix) | ||||||||||
final Looper | getLooper() | ||||||||||
String |
getMessageName(Message message)
Returns a string representing the name of the specified message.
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void |
handleMessage(Message msg) 子类必须实现这个方法来接收消息 |
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final boolean |
hasMessages(int what, Object object)
Check if there are any pending posts of messages with code 'what' and whose obj is 'object' in the message queue.
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final boolean |
hasMessages(int what)
Check if there are any pending posts of messages with code 'what' in the message queue.
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final Message |
obtainMessage(int what, int arg1, int arg2)
Same as
obtainMessage() , except that it also sets the what, arg1 and arg2 members of the returned Message. |
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final Message |
obtainMessage()
Returns a new
Message from the global message pool. |
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final Message |
obtainMessage(int what, int arg1, int arg2, Object obj)
Same as
obtainMessage() , except that it also sets the what, obj, arg1,and arg2 values on the returned Message. |
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final Message |
obtainMessage(int what)
Same as
obtainMessage() , except that it also sets the what member of the returned Message. |
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final Message |
obtainMessage(int what, Object obj)
Same as
obtainMessage() , except that it also sets the what and obj members of the returned Message. |
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final boolean |
post(Runnable r) 使可执行的r被添加到消息队列 Causes the Runnable r to be added to the message queue.
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final boolean |
postAtFrontOfQueue(Runnable r)
Posts a message to an object that implements Runnable.
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final boolean |
postAtTime(Runnable r, Object token, long uptimeMillis) 在规定的时间点执行 Causes the Runnable r to be added to the message queue, to be run at a specific time given by uptimeMillis.
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final boolean |
postAtTime(Runnable r, long uptimeMillis)
Causes the Runnable r to be added to the message queue, to be run at a specific time given by uptimeMillis.
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final boolean |
postDelayed(Runnable r, long delayMillis) 延迟执行规定的时间长度 Causes the Runnable r to be added to the message queue, to be run after the specified amount of time elapses.
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final void |
removeCallbacks(Runnable r)
Remove any pending posts of Runnable r that are in the message queue.
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final void |
removeCallbacks(Runnable r, Object token)
Remove any pending posts of Runnable r with Object token that are in the message queue.
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final void |
removeCallbacksAndMessages(Object token)
Remove any pending posts of callbacks and sent messages whose obj is token.
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final void |
removeMessages(int what)
Remove any pending posts of messages with code 'what' that are in the message queue.
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final void |
removeMessages(int what, Object object)
Remove any pending posts of messages with code 'what' and whose obj is 'object' that are in the message queue.
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final boolean |
sendEmptyMessage(int what)
Sends a Message containing only the what value.
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final boolean |
sendEmptyMessageAtTime(int what, long uptimeMillis)
Sends a Message containing only the what value, to be delivered at a specific time.
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final boolean |
sendEmptyMessageDelayed(int what, long delayMillis)
Sends a Message containing only the what value, to be delivered after the specified amount of time elapses.
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final boolean |
sendMessage(Message msg) 将一个消息添加到消息队列的末尾 Pushes a message onto the end of the message queue after all pending messages before the current time.
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final boolean |
sendMessageAtFrontOfQueue(Message msg) 将一个消息添加到消息队列的最前面 Enqueue a message at the front of the message queue, to be processed on the next iteration of the message loop.
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boolean |
sendMessageAtTime(Message msg, long uptimeMillis) 在规定的时间点添加消息到队列 Enqueue a message into the message queue after all pending messages before the absolute time (in milliseconds) uptimeMillis.
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final boolean |
sendMessageDelayed(Message msg, long delayMillis) 延迟规定的时间再消息添加到消息队列 Enqueue a message into the message queue after all pending messages before (current time + delayMillis).
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String |
toString()
Returns a string containing a concise, human-readable description of this object.
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