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This article mainly introduces "what is the essential difference between Android main thread crash and child thread crash". In daily operation, I believe that many people have doubts about the essential difference between Android main thread crash and child thread crash. The editor consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the question of "what is the essential difference between Android main thread crash and child thread crash"! Next, please follow the editor to study!

Question and answer session

Q: what is the essential difference between an Android main thread crash and a child thread crash?

A: a child thread crash is like a normal Java thread. Through setDefaultUncaughtExceptionHandler, you can catch the exception of the corresponding child thread in the ThreadGroup for subsequent processing (start an independent process to remind the user and report to the platform, etc., or ignore a specific exception through policy distribution as if it did not occur). There is a slight difference between the Crash of the main thread and the Crash of the child thread in Android, although both can be captured through setDefaultUncaughtExceptionHandler in nature, but there is actually a little trick behind this. Since the Android main thread keeps a pipeline blocking production consumer loop through MainHandler's Looper.loop () after startup, all the main thread code is dispatched in the MainLooper through this loop, so when the main thread crash scenario, the loop will be jumped out, resulting in Looper can not continue to execute other Message, so when the main thread crash will appear several different performance One kind of scenario is that crash in the onCreate of Activity will cause the interface black screen (note that this crash is not anr, because the subsequent code cannot be executed because an exception is thrown in the onCreate, that is, the Activity lifecycle framework code cannot continue, and the subsequent Message cannot be distributed normally, so the interface will be black before it comes out), while the crash may not go black in the View click event response (it may also, depending on what you do). But the subsequent Message can not be distributed normally.

Expansion link

Q: what do you think of the above description?

A: there is nothing to say about the collapse of the subthread. Because the main thread crashes and causes the Looper to exit, we can start a Looper.loop () with our own try-catch in the main thread to execute the main thread task, which is equivalent to replacing the Looper.loop () in the ActivityThread main through the loop () with try-catch, so that the loop will not exit after the main thread crashes and can continue to execute the code. It's just that the crash scene may not be valid. For example, if the user clicks the button to set the copy crash, it may not respond. At the same time, clicking the button to start the onCreate of Activity and other methods such as crash will cause a black screen, so this kind of crash needs to be treated differently (such as reporting an exception and popping a box to remind and directly kill the process, etc.).

Here is a simple implementation of the core code (Activity lifecycle handling is sketchy, for demo only):

/ / Application starts to replace new Handler (getMainLooper ()) .post (new Runnable () {@ Override public void run () {/ / continue to cycle every time you jump, ensuring that you can always loop while (true) {try {Looper.loop ();} catch (Throwable e) {e.printStackTrace () / / TODO manually reports errors to the exception management platform, performs interactive processing, etc. If (e.getMessage ()! = null & & e.getMessage (). StartsWith ("Unable to start activity")) {/ / TODO comes from Activity life cycle crash, killing process android.os.Process.killProcess (android.os.Process.myPid ()) Break;})

Of course, for the crash black screen in the Activity lifecycle method, in addition to judging the stack log, we can also use the mH main Handler implementation of hook ActivityThread, trust the Message handle function in it for our implementation, and then capture the try-catch. If we find an exception, the close corresponds to Activity or kill app.

At this point, the study on "what is the essential difference between Android main thread crash and child thread crash" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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