尝试在Android 5.0上使用RecyclerView时，应用程序崩溃
我试图搞砸新的RecyclerView，每当我尝试运行它，我的应用程序立即崩溃。 它给我NullPointerException尝试从android.support.v7.widget.RecyclerView访问方法。 我看了其他post，看到大多数人没有compile 'com.android.support:recyclerview-v7:+'但我试过，它根本没有帮助。 真的不知道该怎么做，任何帮助，将不胜感激。 这里的错误日志:(我会张贴图片，但我没有10代表呢）
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView$LayoutManager.onMeasure(android.support.v7.widget.RecyclerView$Recycler, android.support.v7.widget.RecyclerView$State, int, int)' on a null object reference at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1764) at android.view.View.measure(View.java:17430) at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727) at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) at android.view.View.measure(View.java:17430) at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:851) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) at android.view.View.measure(View.java:17430) at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560) at android.view.View.measure(View.java:17430) at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001) at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166) at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372) at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054) at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5786) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767) at android.view.Choreographer.doCallbacks(Choreographer.java:580) at android.view.Choreographer.doFrame(Choreographer.java:550) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
当没有为RecyclerView提供LayoutManager时，通常会发生此问题。 你可以这样做：
final LinearLayoutManager layoutManager = new LinearLayoutManager(context); layoutManager.setOrientation(LinearLayoutManager.VERTICAL); recyclerView.setLayoutManager(layoutManager);
在我的情况下，它没有连接到“最终”，而是@ @NemanjaKovačević对@aga答复中提到的问题。 我正在设置一个layoutManager的数据加载，这是相同的崩溃的原因。 将layoutManager设置移动到我的片段的onCreateView之后，问题就解决了。
像这样的东西：
@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { ... mRecyclerView = (RecyclerView) rootView.findViewById(R.id.recycler); mLayoutManager = new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL); mRecyclerView.setLayoutManager(mLayoutManager);
对我来说，我遇到了同样的问题，问题是在XML中有一个未使用的RecyclerView，但是我没有将它绑定到Activity中的任何适配器，因此是问题。 一旦我在xml中删除了这样的未使用的回收站视图，它就解决了
即 – 我删除了这个视图，因为这不是在代码中调用或任何适配器已被设置
<android.support.v7.widget.RecyclerView android:layout_width="match_parent" android:layout_height="match_parent" android:id="@+id/rv_profileview_allactivities" android:visibility="gone" />
即使我已经正确设置了RecyclerView.LayoutManager我也遇到了这个崩溃。 我不得不将RecyclerView初始化代码移动到onViewCreated(...)callback来解决这个问题。
@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View rootView = inflater.inflate(R.layout.fragment_listing, container, false); rootView.setTag(TAG); return inflater.inflate(R.layout.fragment_listing, container, false); } @Override public void onViewCreated(View view, Bundle savedInstanceState) { super.onViewCreated(view, savedInstanceState); mLayoutManager = new LinearLayoutManager(getActivity()); mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL); mRecyclerView = (RecyclerView) view.findViewById(R.id.recyclerView); mRecyclerView.setItemAnimator(new DefaultItemAnimator()); mRecyclerView.setLayoutManager(mLayoutManager); mAdapter = new ListingAdapter(mListing); mRecyclerView.setAdapter(mAdapter); }
您需要在RecyclerView#onCreate()方法中使用setLayoutManager 。 在将recyclerView添加到视图之前，必须先设置LayoutManager 。
private RecyclerView menuAsList; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_home); menuAsList = (RecyclerView) findViewById(R.id.recyclerView_mainMenu); menuAsList.setLayoutManager(new LinearLayoutManager(Home.this)); }
由于LinearLayoutManager默认是垂直的，因此更简单的方法是：
recyclerView.setLayoutManager(new LinearLayoutManager(context));
如果你想改变方向，你可以使用这个构造函数：
public LinearLayoutManager(Context context, int orientation, boolean reverseLayout);
recyclerView = (RecyclerView) findViewById(R.id.recycler_view2);
检查你的回收者视图ID，指向实际的回收站视图解决了我的问题
package com.example.om.recycler_view; import android.support.v7.app.AppCompatActivity; import android.os.Bundle; import android.support.v7.widget.DefaultItemAnimator; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView; import android.support.v7.widget.Toolbar; import java.util.ArrayList; import java.util.List; public class MainActivity extends AppCompatActivity { private List<Movie>movieList= new ArrayList<>(); private RecyclerView recyclerView; private MoviesAdapter mAdapter; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Toolbar toolbar=(Toolbar)findViewById(R.id.toolbar); setSupportActionBar(toolbar); recyclerView=(RecyclerView)findViewById(R.id.recycler_view); mAdapter=new MoviesAdapter(movieList); RecyclerView.LayoutManager mLayoutManager= new LinearLayoutManager(this); recyclerView.setLayoutManager(mLayoutManager); recyclerView.setItemAnimator(new DefaultItemAnimator()); recyclerView.setAdapter(mAdapter); prepareMovieData(); } private void prepareMovieData() { Movie movie=new Movie("Mad Max: Fury Road", "Action & Adventure", "2015"); movieList.add(movie); movie = new Movie("Star Wars: Episode VII - The Force Awakens", "Action", "2015"); movieList.add(movie); movie = new Movie("Shaun the Sheep", "Animation", "2015"); movieList.add(movie); movie = new Movie("The Martian", "Science Fiction & Fantasy", "2015"); movieList.add(movie); movie = new Movie("Mission: Impossible Rogue Nation", "Action", "2015"); movieList.add(movie); movie = new Movie("Up", "Animation", "2009"); movieList.add(movie); movie = new Movie("Star Trek", "Science Fiction", "2009"); movieList.add(movie); movie = new Movie("The LEGO Movie", "Animation", "2014"); movieList.add(movie); movie = new Movie("Iron Man", "Action & Adventure", "2008"); movieList.add(movie); movie = new Movie("Aliens", "Science Fiction", "1986"); movieList.add(movie); movie = new Movie("Chicken Run", "Animation", "2000"); movieList.add(movie); movie = new Movie("Back to the Future", "Science Fiction", "1985"); movieList.add(movie); movie = new Movie("Raiders of the Lost Ark", "Action & Adventure", "1981"); movieList.add(movie); movie = new Movie("Goldfinger", "Action & Adventure", "1965"); movieList.add(movie); movie = new Movie("Guardians of the Galaxy", "Science Fiction & Fantasy", "2014"); movieList.add(movie); mAdapter.notifyDataSetChanged(); } } ERROR is: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.om.recycler_view/com.example.om.recycler_view.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2348) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2410) at android.app.ActivityThread.access$800(ActivityThread.java:151) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1313) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5345) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:947) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:742) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference at com.example.om.recycler_view.MainActivity.onCreate(MainActivity.java:28) at android.app.Activity.performCreate(Activity.java:6012) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2410) at android.app.ActivityThread.access$800(ActivityThread.java:151) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1313) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5345) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) How can solve???????
我认为你的Adapter的问题。 确保你已经在onCreateViewHolder()返回了ViewHolder 。 如下所示：
@Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View v; v = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_leaderboard, parent, false); ViewHolder view_holder = new ViewHolder(v); return view_holder; }
由于RecyclerView id的引用错误，我得到了这个问题。
recyclerView = (RecyclerView) findViewById(R.id.rv_followers_list);
至
recyclerView = (RecyclerView) findViewById(R.id.rv_search_list);
