RecyclerView.onMeasure(...) 的空指针异常

Question

我正在尝试修复运行停止我的 Android 应用程序的 exception。我用谷歌搜索了这个异常，发现其他人也有同样的问题。一些人通过在他们的 RecycledView 中包含一个 LinearLayoutManager 解决了这个问题，其他人在 onCreate() 方法中包含了这个管理器的代码，还有一些人在他们的 'com.android.support:recyclerview-v7:21.0.0' 方法中包含了 compile 'com.android.support:recyclerview-v7:21.0.0' build.gradle 文件。

三个都试过了，问题依旧。我想知道为什么。

这是我来自 onCreate():

的代码

// gets recyclerView
mRecyclerView = (RecyclerView) findViewById(R.id.list);
// manager for recyclerView
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
// animations for recyclerViews
mRecyclerView.setItemAnimator(new DefaultItemAnimator());
mAdapter = new GameAdapter(GameManager.getInstance().getGamesFromParse(), R.layout.card_view, this);
mRecyclerView.setAdapter(mAdapter);

你觉得哪里不对？

这是 exception 堆栈：

05-27 11:56:50.386    7756-7756/games.picup.com.picup E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: games.picup.com.picup, PID: 7756
java.lang.NullPointerException
        at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1694)
        at android.view.View.measure(View.java:17619)
        at android.support.v4.widget.SwipeRefreshLayout.onMeasure(SwipeRefreshLayout.java:559)
        at android.view.View.measure(View.java:17619)
        at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
        at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
        at android.view.View.measure(View.java:17619)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5428)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:17619)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5428)
        at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1410)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
        at android.view.View.measure(View.java:17619)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5428)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2588)
        at android.view.View.measure(View.java:17619)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2317)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1412)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1613)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1270)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6691)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:813)
        at android.view.Choreographer.doCallbacks(Choreographer.java:613)
        at android.view.Choreographer.doFrame(Choreographer.java:583)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:799)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:146)
        at android.app.ActivityThread.main(ActivityThread.java:5731)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
        at dalvik.system.NativeStart.main(Native Method)

编辑：已解决，请看我的回答。

Answer 1

试试这个，

  mRecyclerView .setLayoutManager(new LinearLayoutManager(mRecyclerView.getContext()));

看起来问题出在上下文

Answer 2

添加

// gets recyclerView
   mRecyclerView = (RecyclerView) findViewById(R.id.list);
// manager for recyclerView
   recyclerView.setLayoutManager(new LinearLayoutManager(recyclerView.getContext()));

Answer 3

我的 XML 文件中似乎在 LinearLayout 标记之外包含了一个额外的 RecyclerView。通过简单地删除这个额外的 RecyclerView，应用程序运行时没有 exception.

RecyclerView.onMeasure(...) 的空指针异常

Null Pointer Exception for RecyclerView.onMeasure(...)

java

android

nullpointerexception

android-recyclerview