RecyclerView+GridLayoutManger in the ViewPager+Fragment cause NullPointerException

Question

09-24 19:27:06.711    3474-3474/com.mstation.firstblood E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.mstation.firstblood, PID: 3474
    java.lang.NullPointerException
            at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1764)
            at android.view.View.measure(View.java:17221)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5156)
            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:17221)
            at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
            at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
            at android.view.View.measure(View.java:17221)
            at android.widget.ScrollView.measureChildWithMargins(ScrollView.java:1613)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
            at android.widget.ScrollView.onMeasure(ScrollView.java:563)
            at android.view.View.measure(View.java:17221)
            at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1488)
            at android.view.View.measure(View.java:17221)
            at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:719)
            at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:455)
            at android.view.View.measure(View.java:17221)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5156)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
            at android.view.View.measure(View.java:17221)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5156)
            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:17221)
            at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5156)
            at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
            at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2481)
            at android.view.View.measure(View.java:17221)
            at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2317)
            at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1179)
            at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1554)
            at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1066)
            at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6245)
            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:733)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5117)
            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:785)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
            at dalvik.system.NativeStart.main(Native Method)

i have search a lot of answer, most of them was because LayoutManager was not been set. but this is not my reason.

my condition is a fragment in the viewpager ,and the layout is

<ScrollView>
    <RecyclerView></RecyclerView>
</ScrollView>

here is the java code

public class CartoonFragment extends BaseLazyFragment {

    private AutoScrollViewPager autoScrollViewPager;

    private ArrayList<AdvertiseFragment> advertiseList = new ArrayList<>();

    private RecyclerView latestRecyclerView;

    private RecyclerView.LayoutManager layoutManager;

    private LatestCartoonAdapter latestCartoonAdapter;

    private LinearLayout waveLineLayout;//分类布局的 波浪线

    private int POINTER_WIDTH = 20;//波浪线圆点的宽度  单位：dp

    private boolean isPrepared;//fragment中view创建是否完成。

    private int AD_NUM = 4;//广告页面数

    private int SCROLL_FACTOR = 7;//广告viewpager页面，切换的速度因子。

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_cartoon_page, null);
        //do init
        autoScrollViewPager = (AutoScrollViewPager) view.findViewById(R.id.advertise_viewpager);
        Log.e("autoScrollViewPager", "findViewById-------------");
        latestRecyclerView = (RecyclerView) view.findViewById(R.id.latest_recycler_view);
        layoutManager = new GridLayoutManager(getActivity(),3);
        latestCartoonAdapter = new LatestCartoonAdapter();
        latestRecyclerView.setHasFixedSize(true);
       //i have set the layout manager , and debug layoutmanager is not null 
        latestRecyclerView.setLayoutManager(layoutManager);
        latestRecyclerView.setAdapter(latestCartoonAdapter);


        waveLineLayout = (LinearLayout) view.findViewById(R.id.waveline_layout);
        initWaveLine();

        for (int i = 0; i < AD_NUM; i++) {
            AdvertiseFragment advertiseFragment = new AdvertiseFragment();
            advertiseList.add(advertiseFragment);
        }
        ADFragmentAdapter adFragmentAdapter = new ADFragmentAdapter(getActivity().getSupportFragmentManager(), advertiseList);
        configViewpager(adFragmentAdapter);

        //init finish
        isPrepared = true;

        //lazyload
        lazyLoad();

        return view;
      }

here is the xml layout code , there are two recyclerview in the layout

<?xml version="1.0" encoding="utf-8"?>
<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <com.mstation.firstblood.customer.AutoScrollViewPager
            android:id="@+id/advertise_viewpager"
            android:layout_width="match_parent"
            android:layout_height="200dp" />


        <LinearLayout
            android:id="@+id/classify_layout"
            android:layout_width="match_parent"
            android:layout_height="45dp"
            android:layout_below="@id/advertise_viewpager"
            android:background="@color/themeColor"
            android:orientation="horizontal">

            <TextView
                style="@style/CartoonPage_Classify_text"
                android:background="@drawable/round_text_bg_white"
                android:text="分类" />

            <TextView
                style="@style/CartoonPage_Classify_text"
                android:background="@drawable/round_text_bg_white"
                android:text="排行" />

            <TextView
                style="@style/CartoonPage_Classify_text"
                android:background="@drawable/round_text_bg_white"
                android:text="专题" />

            <TextView
                style="@style/CartoonPage_Classify_text"
                android:background="@drawable/round_text_bg_white"
                android:text="安利" />
        </LinearLayout>

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="@dimen/round_pointer_size_half"
            android:layout_below="@id/classify_layout"
            android:background="@color/themeColor"
            android:orientation="vertical" />

        <LinearLayout
            android:id="@+id/waveline_layout"
            android:layout_width="match_parent"
            android:layout_height="@dimen/round_pointer_size"
            android:layout_below="@id/classify_layout"
            android:orientation="horizontal" />

        <LinearLayout
            android:id="@+id/latest_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/waveline_layout"
            android:layout_marginTop="20dp"
            android:orientation="vertical"
            android:paddingLeft="10dp"
            android:paddingRight="10dp">

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="20dp">

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:text="最近更新"
                    android:textColor="@color/themeColor"
                    android:textSize="15sp" />

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:layout_alignParentRight="true"
                    android:text="更多"
                    android:textColor="@color/gray"
                    android:textSize="15sp" />
            </RelativeLayout>

            <android.support.v7.widget.RecyclerView
                android:id="@+id/latest_recycler_view"
                android:scrollbars="vertical"
                android:layout_width="match_parent"
                android:layout_height="200dp"/>

        </LinearLayout>

        <LinearLayout
            android:id="@+id/recommend_layout"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_below="@id/latest_layout"
            android:layout_marginTop="20dp"
            android:orientation="vertical"
            android:paddingLeft="10dp"
            android:paddingRight="10dp">

            <RelativeLayout
                android:layout_width="match_parent"
                android:layout_height="20dp">

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:text="每日推荐"
                    android:textColor="@color/themeColor"
                    android:textSize="15sp" />

                <TextView
                    android:layout_width="wrap_content"
                    android:layout_height="match_parent"
                    android:layout_alignParentRight="true"
                    android:text="更多"
                    android:textColor="@color/gray"
                    android:textSize="15sp" />
            </RelativeLayout>

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

        </LinearLayout>

    </RelativeLayout>
</ScrollView>

and the layout picture the selected part is the first recyclerview

Answer 1

i got it finally, i have two RecycleView in my layout. but when i test the project, i only initial one of them .

so , the conclusion, when more than one RecycleView appear in the layout you should initial all of them in java code. except you set the visible attribute is gone.