android - BoringLayout.isBoring 的 NullPointerException 一点也不无聊

Question

下面的堆栈跟踪通常不会发生，但会在这里和那里发生在某些用户身上。

在 Android 2.3.3 上，异常发生在 BoringLayout.isBoring:240
在 Android 4.1.2 上相同，第 260 行

任何帮助，将不胜感激。:-)

java.lang.NullPointerException
at android.text.BoringLayout.isBoring(BoringLayout.java:260)
at android.widget.TextView.onMeasure(TextView.java:6322)
at android.view.View.measure(View.java:15473)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5056)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1396)
at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1038)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:576)
at android.view.View.measure(View.java:15473)
at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:1223)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:576)
at android.view.View.measure(View.java:15473)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5056)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1396)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
at android.view.View.measure(View.java:15473)
at android.widget.ListView.setupChild(ListView.java:1853)
at android.widget.ListView.makeAndAddView(ListView.java:1778)
at android.widget.ListView.fillDown(ListView.java:678)
at android.widget.ListView.fillFromTop(ListView.java:739)
at android.widget.ListView.layoutChildren(ListView.java:1614)
at android.widget.AbsListView.onLayout(AbsListView.java:2296)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:948)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.support.v4.view.ViewPager.onLayout(ViewPager.java:1589)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.widget.RelativeLayout.onLayout(RelativeLayout.java:948)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1655)
at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1513)
at android.widget.LinearLayout.onLayout(LinearLayout.java:1426)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
at android.view.View.layout(View.java:14055)
at android.view.ViewGroup.layout(ViewGroup.java:4604)
at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1992)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1813)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1112)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4472)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
at android.view.Choreographer.doCallbacks(Choreographer.java:555)
at android.view.Choreographer.doFrame(Choreographer.java:525)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4898)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1006)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:773)
at dalvik.system.NativeStart.main(Native Method)

Answer 1

Ok found it. I'm not deleting the question because maybe it would help someone some day.

So my mistake was: I have extended TextView to create a class that manipulates the text, and look depending on the value set.

My error was that in some cases I chose not to set the text, and simply called 'return'. In those cases the 'text' was null, which caused the above NPE.

Lesson: If you override setText, a value MUST be set when it is called.

This is one of those points in time I remember 'design by contract', preconditions, invariants etc. This could have been helpful here.

To all those that tried to help, you have my thanks. @Deylan - special thanks, you were the one that gave me the nudge in the right direction.