Android ANR初探

前言

记得之前换工作面试的时候，面试官问我知道ANR吗？我说知道，然后让我讲了一下ANR出现的原因，我就把ANR出现的原因一通说。然后，面试官又问我那么怎么分析和解决ANR问题呢？这时候我就傻眼了，只能说分析代码了。然后面试官笑了一下，又问我：那么你知道ANR会生成一个ANR文件吗？当时的我该怎么形容呢？硬着头皮说不知道。当然，那次也就GG了。

首先

那么什么是ANR呢？

1、解释

Application Not Responding即应用无响应。

当操作在一段时间内，系统无法处理是，就会发生ANR。弹出对应的无响应的对话框。

2、ANR的类型

1）KeyDispatchTimeout
这个Key事件分发超时的时间，Android默认是5秒，主要是定义在ActivityManagerService.java

// How long we wait until we timeout on key dispatching.
static final int KEY_DISPATCHING_TIMEOUT = 5*1000;

2）BroadcastTimeOut
广播的超时时间，分为FG和BG，分别是10秒和60秒。同样是定义在ActivitManagerService.java

// How long we allow a receiver to run before giving up on it.
static final int BROADCAST_FG_TIMEOUT = 10*1000;
static final int BROADCAST_BG_TIMEOUT = 60*1000;

3）ServiceTimeOut
Service的超时时间为20秒，定义在ActiveServices.java

// How long we wait for a service to finish executing.
static final int SERVICE_TIMEOUT = 20*1000;

// How long we wait for a service to finish executing.
static final int SERVICE_BACKGROUND_TIMEOUT = SERVICE_TIMEOUT * 10;

其次

上面说了那么多，那么我们来模拟一下ANR并且分析一下
1、首先创建一个activity，里面放两个按钮，当我们点击选择相册的按钮的时候先让主线程休眠50s，然后看看

class MainActivity : AppCompatActivity() {


override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    btn_album.setOnClickListener {
        Thread.sleep(50*1000)
        CameraUtil.openAlbum(this, REQUEST_CODE_OPEN_PHOTO_ALBUM)
    }
    btn_take_photo.setOnClickListener {
        CameraUtil.takePhoto(this, REQUEST_CODE_TAKE_PHOTO)
    }
  }





override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    super.onActivityResult(requestCode, resultCode, data)
    CameraUtil.onActivityResult(
        this,
        requestCode,
        resultCode,
        data,
        object : CameraUtil.OnCameraResultListener {
            override fun onAlbumResult(path: String) {
                Log.e("TAG", path)
            }

            override fun onCameraResult(uri: Uri) {
                Log.e("TAG", uri.toString())
            }
        })
}


}

ANR.png

分析:可以看到上面我们在主线程中让主线程休眠50s，那么界面长时间无响应就会出现ANR了，如上图所示。那么当我们不知道为什么会出现ANR的时候该怎么处理呢？其实，当出现ANR的时候会在data/anr/目录下生成anr日志文件，这里以as为例。

ANR文件.png

1、如上图所示，我们先点击DeviceFile Explorer选项，然后打开data/anr文件，里面的anr_2020-08-10-18-17-42就是我们所需要的anr文件。然后，右击保存到电脑上，找到我们保存的地方打开ANR文件看看里面的具体内容。

2、ANR文件具体内容

suspend all histogram:  Sum: 1.413ms 99% C.I. 2us-243.199us Avg: 13.586us Max: 352us
DALVIK THREADS (16):
"Signal Catcher" daemon prio=5 tid=3 Runnable
  | group="system" sCount=0 dsCount=0 flags=0 obj=0x15700020 self=0x7b7b016400
  | sysTid=13715 nice=0 cgrp=default sched=0/0 handle=0x7b5c6054f0
  | state=R schedstat=( 30247917 1431772 18 ) utm=1 stm=1 core=0 HZ=100
  | stack=0x7b5c50a000-0x7b5c50c000 stackSize=1009KB
  | held mutexes= "mutator lock"(shared held)
  native: #00 pc 00000000003c7d4c  /system/lib64/libart.so     (art::DumpNativeStack(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, int,         BacktraceMap*, char const*, art::ArtMethod*, void*, bool)+220)
  native: #01 pc 00000000004a5b64  /system/lib64/libart.so     (art::Thread::DumpStack(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, bool,     BacktraceMap*, bool) const+352)
  native: #02 pc 00000000004bf780  /system/lib64/libart.so (art::DumpCheckpoint::Run(art::Thread*)+844)
  native: #03 pc 00000000004b84fc  /system/lib64/libart.so (art::ThreadList::RunCheckpoint(art::Closure*, art::Closure*)+484)
  native: #04 pc 00000000004b798c  /system/lib64/libart.so (art::ThreadList::Dump(std::__1::basic_ostream<char, std::__1::char_traits<char>>&, bool)+1036)
  native: #05 pc 00000000004b74ac  /system/lib64/libart.so (art::ThreadList::DumpForSigQuit(std::__1::basic_ostream<char, std::__1::char_traits<char>>&)+884)
  native: #06 pc 00000000004878a0  /system/lib64/libart.so (art::Runtime::DumpForSigQuit(std::__1::basic_ostream<char, std::__1::char_traits<char>>&)+188)
  native: #07 pc 0000000000493610  /system/lib64/libart.so (art::SignalCatcher::HandleSigQuit()+1372)
  native: #08 pc 00000000004922e8  /system/lib64/libart.so (art::SignalCatcher::Run(void*)+256)
  native: #09 pc 0000000000082e10  /system/lib64/libc.so (__pthread_start(void*)+36)
  native: #10 pc 0000000000024080  /system/lib64/libc.so (__start_thread+68)
  (no managed stack frames)

"main" prio=5 tid=1 Sleeping
| group="main" sCount=1 dsCount=0 flags=1 obj=0x75771ba0 self=0x7b7b014c00
| sysTid=13709 nice=-10 cgrp=default sched=0/0 handle=0x7c0184d548
| state=S schedstat=( 569303132 16322390 301 ) utm=51 stm=5 core=2 HZ=100
| stack=0x7ff5ac9000-0x7ff5acb000 stackSize=8MB
| held mutexes=
at java.lang.Thread.sleep(Native method)
- sleeping on <0x0808d0f6> (a java.lang.Object)
at java.lang.Thread.sleep(Thread.java:386)
- locked <0x0808d0f6> (a java.lang.Object)
at java.lang.Thread.sleep(Thread.java:327)
at com.yk.silence.customcamera.MainActivity$onCreate$1.onClick(MainActivity.kt:18)
at android.view.View.performClick(View.java:6652)
at android.view.View.performClickInternal(View.java:6624)
at android.view.View.access$3100(View.java:787)
at android.view.View$PerformClick.run(View.java:26213)
at android.os.Handler.handleCallback(Handler.java:891)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:207)
at android.app.ActivityThread.main(ActivityThread.java:7470)
at java.lang.reflect.Method.invoke(Native method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:958)

"Jit thread pool worker thread 0" daemon prio=5 tid=2 Native
| group="main" sCount=1 dsCount=0 flags=1 obj=0x156c0030 self=0x7b72033000
| sysTid=13714 nice=9 cgrp=default sched=0/0 handle=0x7b5c7064f0
| state=S schedstat=( 75499990 5454172 203 ) utm=5 stm=2 core=1 HZ=100
| stack=0x7b5c608000-0x7b5c60a000 stackSize=1021KB
| held mutexes=
kernel: (couldn't read /proc/self/task/13714/stack stderr:Permission denied)
native: #00 pc 000000000001f3ec  /system/lib64/libc.so (syscall+28)
native: #01 pc 00000000000dbd94  /system/lib64/libart.so (art::ConditionVariable::WaitHoldingLocks(art::Thread*)+148)
native: #02 pc 00000000004c0fc4  /system/lib64/libart.so (art::ThreadPool::GetTask(art::Thread*)+260)
native: #03 pc 00000000004c052c  /system/lib64/libart.so (art::ThreadPoolWorker::Run()+124)
native: #04 pc 00000000004bffec  /system/lib64/libart.so (art::ThreadPoolWorker::Callback(void*)+148)
native: #05 pc 0000000000082e10  /system/lib64/libc.so (__pthread_start(void*)+36)
native: #06 pc 0000000000024080  /system/lib64/libc.so (__start_thread+68)
(no managed stack frames)

分析:既然我们已经拿到了ANR日志文件的内容了，那么怎么分析呢？不可能一通乱找吧。这个是当然的，有两个可以参考的点，一个就是我们应用程序的包名，另外一个就是main方法。这里我截取了一部分主要的日志文件，但是也够了。我们首先看一下"main"方法，并且找一下我们应用对应的包名com.yk.silence.customcamera,那么很容易就定位到了at com.yk.silence.customcamera.MainActivity$onCreate$1.onClick(MainActivity.kt:18),这一行，然后我们看一下我们的源码。在第18行的休眠50S的代码，所以找对应规律会事半功倍。

image.png

最后

好了，这个就是关于ANR初探的文章，如果有写的不到位的地方还请大佬不吝赐教。当然，如果你有更好的建议欢迎进群（493180098）探讨。