调用 getVisibility() 时的 ContentFrameLayout.onMeasure NPE

Question

我的应用程序的 Crashlytics 数据在 FrameLayout.onMeasure() 上显示空指针异常崩溃。

我在日志中看不到我的应用程序跟踪，因此无法确定哪个 Activity 正在崩溃，但主要 Activity 由带有 5 个片段的 TabLayout + Viewpager 组成。 崩溃日志如下：

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getVisibility()' on a null object reference
   at android.widget.FrameLayout.onMeasure(FrameLayout.java:193)
   at android.support.v7.widget.ContentFrameLayout.onMeasure(SourceFile:135)
   at android.view.View.measure(View.java:18866)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
   at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
   at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
   at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
   at android.view.View.measure(View.java:18866)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
   at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
   at android.view.View.measure(View.java:18866)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
   at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)
   at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)
   at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)
   at android.view.View.measure(View.java:18866)
   at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5951)
   at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)
   at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2650)
   at android.view.View.measure(View.java:18866)
   at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2104)
   at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1220)
   at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1456)
   at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1111)
   at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6017)
   at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)
   at android.view.Choreographer.doCallbacks(Choreographer.java:670)
   at android.view.Choreographer.doFrame(Choreographer.java:606)
   at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)
   at android.os.Handler.handleCallback(Handler.java:739)
   at android.os.Handler.dispatchMessage(Handler.java:95)
   at android.os.Looper.loop(Looper.java:224)
   at android.app.ActivityThread.main(ActivityThread.java:5526)
   at java.lang.reflect.Method.invoke(Method.java)
   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

这可能是 AppCompat v7 库中的一些错误吗？ 还是我在 Tablayout + Viewpager 组合上做错了什么

任何帮助将不胜感激。

Answer 1

从日志中可以清楚地看出错误：

Attempt to invoke virtual method 'int android.view.View.getVisibility()' on a null object reference

您正试图调用空对象上的方法，这会引发空指针异常。
我的疯狂猜测是，您正试图在您的 onMeasure() 方法上使用 getVisiblity() 获取对象的可见性，并且由于该对象尚未实例化（换句话说，持有空引用），因此它会抛出例外。

我在 ViewPager 上遇到过类似情况。基本上，我还没有滑动/移动到特定视图，并且由于该视图尚未构建，我正在调用它的方法，从而使应用程序崩溃。

您能否发布包含 onMeasure() 部分的代码 sn-p，以便我可以帮助您调试它？

问候，