Chapter02

Introduction: Sample for stop FinalizerWatchdogDaemon
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简介

该例子主要演示了如何通过关闭FinalizerWatchdogDaemon来减少TimeoutException的触发

需要注意的是,此种方法并不是去解决问题,而是为了避免上报异常采取的一种 hack 方案,并没有真正的解决引起 finialize() 超时的问题。

界面

screen

操作步骤

  1. 最好在模拟器下执行例子,因为各个手机设置的超时时长不同,不容易观看效果。
  2. 点击触发 Timeout按钮,等待 10 多秒后,应用会触发 TimeOut Crash,产生如下日志
D/ghost: =============fire finalize=============FinalizerDaemon
I/.watchdogkille: Thread[3,tid=4369,WaitingInMainSignalCatcherLoop,Thread*=0x76e6ece16400,peer=0x149802d0,"Signal Catcher"]: reacting to signal 3
I/.watchdogkille: Wrote stack traces to '[tombstoned]'
E/AndroidRuntime: FATAL EXCEPTION: FinalizerWatchdogDaemon
    Process: com.dodola.watchdogkiller, PID: 4363
    java.util.concurrent.TimeoutException: com.dodola.watchdogkiller.GhostObject.finalize() timed out after 10 seconds
        at java.lang.Thread.sleep(Native Method)
        at java.lang.Thread.sleep(Thread.java:373)
        at java.lang.Thread.sleep(Thread.java:314)
        at com.dodola.watchdogkiller.GhostObject.finalize(GhostObject.java:13)
        at java.lang.Daemons$FinalizerDaemon.doFinalize(Daemons.java:250)
        at java.lang.Daemons$FinalizerDaemon.runInternal(Daemons.java:237)
        at java.lang.Daemons$Daemon.run(Daemons.java:103)
        at java.lang.Thread.run(Thread.java:764)
I/Process: Sending signal. PID: 4363 SIG: 9
  1. 点击Kill WatchDog 按钮可以关闭 Timeout watchdog,然后点击触发 TimeOut 按钮观察情况,正常情况下不会产生 crash

疑问点

如果直接调用 Daemons$FinalizerWatchdogDaemon 的 stop 方法,在 Android 6.0 之前的版本可能会有问题。

final Class clazz = Class.forName("java.lang.Daemons$FinalizerWatchdogDaemon");
final Field field = clazz.getDeclaredField("INSTANCE");
field.setAccessible(true);
final Object watchdog = field.get(null);
final Method method = clazz.getSuperclass().getDeclaredMethod("stop");
method.setAccessible(true);
method.invoke(watchdog);

这是为什么,你能告诉我们吗?

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