android-looper

问题 This is the code in ActivityThread.main(): public static void main(String[] args) { ...... Looper.prepareMainLooper(); ... Looper.loop(); throw new RuntimeException("Main thread loop unexpectedly exited"); } It made the Looper running. There is a loop running in the Looper.loop() all the time. Why does Looper.loop() not block the UI thread? 回答1: Looper.loop() prepares the Looper to run the messages that are passed to the thread. It doesn't blindly keep iterating over itself, rather it uses a

问题 This is the code in ActivityThread.main(): public static void main(String[] args) { ...... Looper.prepareMainLooper(); ... Looper.loop(); throw new RuntimeException("Main thread loop unexpectedly exited"); } It made the Looper running. There is a loop running in the Looper.loop() all the time. Why does Looper.loop() not block the UI thread? 回答1: Looper.loop() prepares the Looper to run the messages that are passed to the thread. It doesn't blindly keep iterating over itself, rather it uses a

问题 Today I read some blogs and source code about how Handler & Looper work together. Based on what I've learnt, we can have only one Looper on each thread by using the ThreadLocal magic. Usually Handler is initiated in main thread, or else you must manually start or saying, prepare the Looper on a separate thread and then loop it up. class LooperThread extends Thread { public Handler mHandler; public void run() { Looper.prepare(); mHandler = new Handler() { public void handleMessage(Message msg)

问题 Today I read some blogs and source code about how Handler & Looper work together. Based on what I've learnt, we can have only one Looper on each thread by using the ThreadLocal magic. Usually Handler is initiated in main thread, or else you must manually start or saying, prepare the Looper on a separate thread and then loop it up. class LooperThread extends Thread { public Handler mHandler; public void run() { Looper.prepare(); mHandler = new Handler() { public void handleMessage(Message msg)

问题 Is a Handler a Thread or not? If yes, how can we update the UI from this Handler(thread)? If we use the Looper concept, it may be possible. In this case, does it apply to any threads? I am very much confused about these Threads, Handlers and Loopers. Could anyone please explain them with an example? Is a Handler a Thread or not? If yes, how can we update the UI from this Handler(thread). If we use the Looper concept, it may be possible, in this case does it apply to any threads? I am very

问题 Is a Handler a Thread or not? If yes, how can we update the UI from this Handler(thread)? If we use the Looper concept, it may be possible. In this case, does it apply to any threads? I am very much confused about these Threads, Handlers and Loopers. Could anyone please explain them with an example? Is a Handler a Thread or not? If yes, how can we update the UI from this Handler(thread). If we use the Looper concept, it may be possible, in this case does it apply to any threads? I am very

问题 This bug baffled me for hours. I am getting the NullPointerException . The problem is this error is not consistent. It happens when I launch the app, but only occasionally. So I am not sure what is causing it. I apologize for the verbose question with the error log, but I could not find another way of asking. The error log is as follows: FATAL EXCEPTION: main Process: com.myproject.android, PID: 22175 java.lang.NullPointerException at com.myproject.android.ImageDownloaderThread.queueImage

问题 This bug baffled me for hours. I am getting the NullPointerException . The problem is this error is not consistent. It happens when I launch the app, but only occasionally. So I am not sure what is causing it. I apologize for the verbose question with the error log, but I could not find another way of asking. The error log is as follows: FATAL EXCEPTION: main Process: com.myproject.android, PID: 22175 java.lang.NullPointerException at com.myproject.android.ImageDownloaderThread.queueImage

问题 I am new to Android. I want to know what the Looper class does and also how to use it. I have read the Android Looper class documentation but I am unable to completely understand it. I have seen it in a lot of places but unable to understand its purpose. Can anyone help me by defining the purpose of Looper and also by giving a simple example if possible? 回答1: What is Looper? Looper is a class which is used to execute the Messages(Runnables) in a queue. Normal threads have no such queue, e.g.

问题 Just clarifying but in an Android activity on MAIN Thread if I call Looper.myLooper() vs Looper.getMainLooper() the return the same reference, right? they are the same thing? I know I would never have to call these usually as Android takes care of this but I'd like to know how they differ when being called from the main thread? if from the main thread I call Looper.myLooper().quit(); // or Looper.getMainLooper().quit(); They both give the same runtime exception so I'm assuming they are the