NullPointerException的原因android.support.v7.widget.RecyclerView.onMeasure

我得到以下exception

01-27 11:15:15.756 18348-18348/com.example.pnimje.newswipelistview E/AndroidRuntime﹕ FATAL EXCEPTION: main java.lang.NullPointerException at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1764) at android.view.View.measure(View.java:15848) at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:728) at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:477) at android.view.View.measure(View.java:15848) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:15848) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008) at android.support.v7.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:453) at android.view.View.measure(View.java:15848) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at android.view.View.measure(View.java:15848) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404) at android.widget.LinearLayout.measureVertical(LinearLayout.java:695) at android.widget.LinearLayout.onMeasure(LinearLayout.java:588) at android.view.View.measure(View.java:15848) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5008) at android.widget.FrameLayout.onMeasure(FrameLayout.java:310) at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2189) at android.view.View.measure(View.java:15848) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1905) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1104) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1284) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749) at android.view.Choreographer.doCallbacks(Choreographer.java:562) at android.view.Choreographer.doFrame(Choreographer.java:532) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735) at android.os.Handler.handleCallback(Handler.java:730) at android.os.Handler.dispatchMessage(Handler.java:92) at android.os.Looper.loop(Looper.java:137) at android.app.ActivityThread.main(ActivityThread.java:5103) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:525) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) at dalvik.system.NativeStart.main(Native Method) 

和RecyclerView.java:1764是

  mLayout.onMeasure(mRecycler, mState, widthSpec, heightSpec); 

为什么mLayout(LayoutManager)为空?

Solutions Collecting From Web of "NullPointerException的原因android.support.v7.widget.RecyclerView.onMeasure"

因为您尚未将LinearLayoutManager设置为RecyclerView。

例如:

  mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView); LinearLayoutManager layoutManager = new LinearLayoutManager(context); mRecyclerView.setLayoutManager(layoutManager); mRecyclerView.setAdapter(new CustomAdapter()); 

这些错误通常源于不设置RecyclerView的布局管理器 。 Bein’匆忙自己,我忘了设置一个结束于以下错误:

 java.lang.NullPointerException at android.support.v7.widget.RecyclerView.onInterceptTouchEvent(RecyclerView.java:1636) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1820) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2177) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1878) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2177) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1878) at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2177) at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1878) 

以下行应该解决它:

 mRecyclerView.setLayoutManager(new LinearLayoutManager((Activity)this)); 

Antón的反应很好,但在像我这样的初学者中可能会让人感到困惑,这有助于澄清一些疑问。

 RecyclerView rv; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_buscar); rv = (RecyclerView) findViewById(R.id.RecViewTest); LinearLayoutManager llm = new LinearLayoutManager(this); rv.setLayoutManager(llm); } 

您需要validation发送到适配器的内容不是空List 。 我建议您按代码创建RecyclerView ,稍后在获取信息时添加它,或者在将空对象传递给适配器的构造函数之前放置空NULL对象。