在 android 5.0上使用回收视图时应用程序崩溃

我正在尝试破坏新的回收视图,每当我尝试运行它,我的应用程序立即崩溃。它为尝试从 android.support.v7.widget.RecyclerView访问方法提供了 NullPointerException。我看过其他的帖子,发现大多数人都没有 compile 'com.android.support:recyclerview-v7:+',但是我试过了,一点用都没有。我不知道现在该怎么办,如果你能帮忙我会很感激的。这里的错误日志: (我会张贴图片,但我还没有10代表)

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)
108845 次浏览

This issue usually occurs when no LayoutManager was provided for the RecyclerView. You can do it like so:

final LinearLayoutManager layoutManager = new LinearLayoutManager(context);
layoutManager.setOrientation(LinearLayoutManager.VERTICAL);
recyclerView.setLayoutManager(layoutManager);

In my case it was not connected to 'final', but to the issue mentioned in @NemanjaKovačević comment to @aga answer. I was setting a layoutManager on data load and that was the cause of the same crash. After moving the layoutManager setup to onCreateView of my fragment the issue was fixed.

Something like this:

@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);

I experienced this crash even though I had the RecyclerView.LayoutManager properly set. I had to move the RecyclerView initialization code into the onViewCreated(...) callback to fix this issue.

@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);
}

Since LinearLayoutManager is vertical by default, an easier way to do this is:

recyclerView.setLayoutManager(new LinearLayoutManager(context));

If you want to change the orientation you could use this constructor:

public LinearLayoutManager(Context context, int orientation, boolean reverseLayout);

For me, I was having the same issue, the issue was that there was an unused RecyclerView in xml with view gone but I am not binding it to any adapter in Activity, hence the issue. It was solved as soon as I removed such unused recycler views in xml

i.e - I removed this view as this was not called in code or any adapter has been set

<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/rv_profileview_allactivities"
android:visibility="gone" />

You need to use setLayoutManager in the RecyclerView#onCreate() method. Before adding recyclerView to a view, it must have the LayoutManager set.

 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));


}

I got this issue due to wrong reference of RecyclerView id.

recyclerView = (RecyclerView) findViewById(R.id.rv_followers_list);

to

recyclerView = (RecyclerView) findViewById(R.id.rv_search_list);
recyclerView =
(RecyclerView) findViewById(R.id.recycler_view2);

Check with you recycler view ID, pointing to actual recycler view solved my issue

I think the problem in your Adapter. Make sure you have returned ViewHolder in onCreateViewHolder(). Like below:

@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;
}

My problem was in my XML lyout I have an android:animateLayoutChanges set to true and I've called notifyDataSetChanged() on the RecyclerView's adapter in the Java code.

So, I've just removed android:animateLayoutChanges from my layout and that resloved my problem.

I had this problem when using Butterknife library. I had:

View rootView = inflater.inflate
(R.layout.fragment_recipe_detail_view, container, false);
ButterKnife.bind(rootView);

But the correct version is:

View rootView = inflater.inflate
(R.layout.fragment_recipe_detail_view, container, false);
ButterKnife.bind(this, rootView);

If I where you I will do this. onView(withId(android.R.id.list)).perform(RecyclerViewActions.scrollToPosition(3)); android.R.id.list change it to your list id and position will be your position inside your array.

For me the problem was with my activity_main.xml(21) in which the recycleView didn't have an id.

activity_main.xml(21)

 <android.support.v7.widget.RecyclerView
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button3"
tools:listitem="@layout/transaction_list_row" />

activity_main.xml

<android.support.v7.widget.RecyclerView


android:id="@+id/transac_recycler_view"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginLeft="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp"
android:layout_marginRight="8dp"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/button3"
/>

It worked when i added a android:id="@+id/transac_recycler_view" to the activity_main.xml(21) recycleView

In Gradle implement this library :

implementation 'com.android.support:appcompat-v7:SDK_VER'
implementation 'com.android.support:design:SDK_VER'
implementation 'com.android.support:support-v4:SDK_VER'
implementation 'com.android.support:support-v13:SDK_VER'
implementation 'com.android.support:recyclerview-v7:SDK_VER'

In XML mention like this :

<android.support.v7.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/recyclerView"/>

In Fragment we use recyclerView like this :

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View rootView = inflater.inflate(R.layout.YOUR_LAYOUT_NAME, container, false);


RecyclerView recyclerView = (RecyclerView) rootView.findViewById(R.id.recyclerView);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
recyclerView.setLayoutManager(layoutManager);
APICallMethod();
YOURADAPTER = new YOURADAPTER(getActivity(), YOUR_LIST); // you can use that adapter after for loop in response(APICALLMETHOD)
recyclerView.setAdapter(YOURADAPTER);
return rootView;
}

In Activity we use RecyclerView like this :

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.YOUR_LAYOUT_NAME);


RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.VERTICAL, false);
recyclerView.setLayoutManager(layoutManager);
APICallMethod();
YOURADAPTER = new YOURADAPTER(ACTIVITY_NAME.this, YOUR_LIST); // you can use that adapter after for loop in response(APICALLMETHOD)
recyclerView.setAdapter(YOURADAPTER);
}

if you need horizontal RecyclerView do this :

RecyclerView recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(getActivity(), LinearLayoutManager.HORIZONTAL, false);
recyclerView.setLayoutManager(layoutManager);
APICallMethod();
YOURADAPTER = new YOURADAPTER(ACTIVITY_NAME.this, YOUR_LIST); // you can use that adapter after for loop in response(APICALLMETHOD)
recyclerView.setAdapter(YOURADAPTER);

if you want to use GridLayoutManager using RecyclerView use like this :

        RecyclerView recyclerView = findViewById(R.id.rvNumbers);
recyclerView.setLayoutManager(new GridLayoutManager(this, 3)); // 3 is number of columns.
adapter = new MyRecyclerViewAdapter(this, data);
recyclerView.setAdapter(adapter);

I was using a Dependency Injection - ButterKnife and this problem arised because I had not binded the view.

So inside onCreate() I just inserted this line:

ButterKnife.bind(this);

My RecyclerView declaration with Dependency Injection:

@BindView(R.id.recyclerview)
RecyclerView recyclerView;

using fragment

writing code in onCreateView()

RecyclerView recyVideo = view.findViewById(R.id.recyVideoFag);

using activity

writing code in onCreate() RecyclerView recyVideo = findViewById(R.id.recyVideoFag);

In my case, I added only butterknife library and forget to add annotationProcessor. By adding below line to build.gradle (App module), solved my problem.

    annotationProcessor 'com.jakewharton:butterknife-compiler:10.1.0'

Recyclerview recylerview = findbyid(R.id.recyclerview) May be you have missed it

For those who are using: implementation 'androidx.recyclerview:recyclerview:1.1.0-beta05'

make sure you are using this in your xml layout

I also experienced a crash when running my app below API 27. Here's a link to the message

Originally, I have created a style to change the font size of my textview inside the recyclerview that's why I created this code below: (I could have just called @dimen when changing the font size based on screen sizes)

Inside style.xml

and added this in my theme

themes.xml

After investigating, I found out that this is the one causing me an error and after removing the style, I no longer experiencing a crash.

I tried all the possible solutions I found here in stack overflow and almost gave up on this, thankfully in my curiosity I thought why not removing the style maybe this causes the crash and then boom the crash is gone.

I had similar problem when I test my application on GenyMotion. After restart the device in GenyMotion problem was solved

I faced the same issue cause I had the RecyclerView in another layout and not on activity_main.xml.

By searching on some sites I got something and felt like sharing here

  1. Add Id to Include tag in Activity_main.xml

    <include id="includedRecyclerLayout" .... </include>

  2. call this layout before Searching view by ID in MainActivity.java

    `ConstraintLayout includedLayout = findViewById(R.id.inckudedRecyclerLayout);

    RecyclerViewrecyclerview=includedLayout.findViewById(R.id.RECYCLER_VIEW_ID)`;

I had this problem when using Butterknife , I was using fragment

For Fragment, it should be ButterKnife.bind(this,view);

For Activity ButterKnife.bind(this);