ViewDragHelper.getTouchSlop() 上的 NullPointerException

【问题标题】：NullPointerException on ViewDragHelper.getTouchSlop()ViewDragHelper.getTouchSlop() 上的 NullPointerException
【发布时间】：2019-10-24 16:02:17
【问题描述】：

我有一个问题，一个我无法复制的奇怪问题，但我发现很多用户都存在这个问题。崩溃发生在 Crashitycs 中。问题是：

致命异常：java.lang.NullPointerException 尝试在空对象引用上调用虚拟方法“int android.support.v4.widget.ViewDragHelper.getTouchSlop()”

目前我已将支持库设置为 28.0.0。

我不知道接下来要尝试什么，因为我不明白这个错误来自哪里，我无法重现它

final SUPPORT_LIBRARY_VERSION = '28.0.0'

// Support
implementation "com.android.support:design:$SUPPORT_LIBRARY_VERSION"
implementation "com.android.support:appcompat-v7:$SUPPORT_LIBRARY_VERSION"
implementation "com.android.support:cardview-v7:$SUPPORT_LIBRARY_VERSION"
implementation "com.android.support:recyclerview-v7:$SUPPORT_LIBRARY_VERSION"
implementation 'com.android.support.constraint:constraint-layout:1.1.1'
implementation "com.android.support:exifinterface:$SUPPORT_LIBRARY_VERSION"
implementation "com.android.support:support-media-compat:$SUPPORT_LIBRARY_VERSION"
implementation "com.android.support:support-v4:$SUPPORT_LIBRARY_VERSION"

这是我的 Logcat

       at android.support.design.widget.BottomSheetBehavior.onTouchEvent(BottomSheetBehavior.java:350)
       at android.support.design.widget.CoordinatorLayout.performIntercept(CoordinatorLayout.java:476)
       at android.support.design.widget.CoordinatorLayout.onTouchEvent(CoordinatorLayout.java:527)
       at android.view.View.dispatchTouchEvent(View.java:9390)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2549)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2240)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at com.android.internal.policy.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2461)
       at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1777)
       at android.app.Activity.dispatchTouchEvent(Activity.java:2865)
       at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
       at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
       at com.android.internal.policy.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2422)
       at android.view.View.dispatchPointerEvent(View.java:9610)
       at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4447)
       at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4313)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3900)
       at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3866)
       at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3992)
       at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3874)
       at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4049)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3900)
       at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3866)
       at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3874)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6146)
       at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6120)
       at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6081)
       at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6262)
       at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:192)
       at android.os.MessageQueue.nativePollOnce(MessageQueue.java)
       at android.os.MessageQueue.next(MessageQueue.java:330)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:5621)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:684)

--

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.support.v4.widget.ViewDragHelper.getTouchSlop()' on a null object reference
       at android.support.design.widget.BottomSheetBehavior.onTouchEvent(BottomSheetBehavior.java:350)
       at android.support.design.widget.CoordinatorLayout.performIntercept(CoordinatorLayout.java:476)
       at android.support.design.widget.CoordinatorLayout.onTouchEvent(CoordinatorLayout.java:527)
       at android.view.View.dispatchTouchEvent(View.java:9390)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2549)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2240)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at com.android.internal.policy.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2461)
       at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1777)
       at android.app.Activity.dispatchTouchEvent(Activity.java:2865)
       at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
       at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
       at com.android.internal.policy.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2422)
       at android.view.View.dispatchPointerEvent(View.java:9610)
       at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4447)
       at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4313)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3900)
       at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3866)
       at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3992)
       at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3874)
       at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4049)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3900)
       at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3866)
       at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3874)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6146)
       at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6120)
       at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6081)
       at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6262)
       at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:192)
       at android.os.MessageQueue.nativePollOnce(MessageQueue.java)
       at android.os.MessageQueue.next(MessageQueue.java:330)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:5621)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:684)

#0. Crashed: main
       at android.support.design.widget.BottomSheetBehavior.onTouchEvent(BottomSheetBehavior.java:350)
       at android.support.design.widget.CoordinatorLayout.performIntercept(CoordinatorLayout.java:476)
       at android.support.design.widget.CoordinatorLayout.onTouchEvent(CoordinatorLayout.java:527)
       at android.view.View.dispatchTouchEvent(View.java:9390)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2549)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2240)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2555)
       at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2254)
       at com.android.internal.policy.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2461)
       at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1777)
       at android.app.Activity.dispatchTouchEvent(Activity.java:2865)
       at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
       at android.support.v7.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
       at com.android.internal.policy.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2422)
       at android.view.View.dispatchPointerEvent(View.java:9610)
       at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4447)
       at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:4313)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3900)
       at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3866)
       at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3992)
       at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3874)
       at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:4049)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3900)
       at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3866)
       at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3874)
       at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3847)
       at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:6146)
       at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:6120)
       at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:6081)
       at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:6262)
       at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:192)
       at android.os.MessageQueue.nativePollOnce(MessageQueue.java)
       at android.os.MessageQueue.next(MessageQueue.java:330)
       at android.os.Looper.loop(Looper.java:137)
       at android.app.ActivityThread.main(ActivityThread.java:5621)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:684)

目前我为很多片段（嗯，几乎所有片段）扩展BottomSheetDialogFragment

【问题讨论】：

  • 注意潜在的亲密选民：我不相信“什么是 NullPointerException？”重复适用于这种情况，因为它是 Android SDK 的内部类的问题。在堆栈跟踪中似乎没有对 OP 应用程序的任何直接引用。
  • 通过调用堆栈跟踪中的BottomSheetBehavior 来猜测，您是否在应用程序的任何位置使用BottomSheet 的任何实例？如果是这样，您可以尝试拖动它，看看会发生什么？
  • @MichaelDodd 是的，我确实在应用程序中使用它。其实很多。我为很多片段扩展了BottomSheetDialogFragment。我无法复制它，我尝试拖动、单击、关闭等...，没有任何效果，我无法复制它，但我可以看到某些百分比的用户确实有这个问题

标签： java android nullpointerexception


【解决方案1】：

在源代码中检查以前读取的行：

return action == MotionEvent.ACTION_MOVE
        && scroll != null
        && !ignoreEvents
        && state != STATE_DRAGGING
        && !parent.isPointInChildBounds(scroll, (int) event.getX(), (int) event.getY())
        && Math.abs(initialY - event.getY()) > viewDragHelper.getTouchSlop();
  }

在以后的版本中似乎可以阅读：

 return action == MotionEvent.ACTION_MOVE
        && scroll != null
        && !ignoreEvents
        && state != STATE_DRAGGING
        && !parent.isPointInChildBounds(scroll, (int) event.getX(), (int) event.getY())
        && viewDragHelper != null
        && Math.abs(initialY - event.getY()) > viewDragHelper.getTouchSlop();
  }

似乎应该修复它。尽管其他一些函数似乎可以清除 viewDragHelper 值，但一般情况下可能很难重现。

在某些版本中，如果在调用 onLayoutChild() 之前执行触摸移动，您可能会收到空指针错误。看起来这可能很难做到。但是，没有明确检查它。

显然应该修复它，但我没有在源代码中看到明确的检查，无论如何它们的复制步骤可能会对您有所帮助。

https://github.com/material-components/material-components-android/issues/43

“这可能发生在较旧/较慢的设备上，通过向触摸事件发送垃圾邮件到 正在构建布局时的底部工作表。”

【讨论】：

    猜你喜欢
    • 2013-04-21
    • 2014-03-18
    • 2016-03-26
    • 2012-10-03
    • 1970-01-01
    • 2013-09-12
    • 2013-02-21
    • 1970-01-01
    • 1970-01-01
    相关资源
    最近更新 更多
    热门标签
    Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode