Question

我想使用recyclerview，但是出现了空指针。

所以我搜索了这个问题，他们说我必须像下面那样设置LinearLayoutManager，我做到了：

setLayoutManager(new LinearLayoutManager(context))

但是，它不起作用。

我的错误日志是：

   java.lang.NullPointerException
        at android.support.v7.widget.RecyclerView.onMeasure(RecyclerView.java:1694)
        at android.view.View.measure(View.java:16628)
        at android.widget.LinearLayout.measureVertical(LinearLayout.java:847)
        at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
        at android.view.View.measure(View.java:16628)
        at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:883)
        at android.view.View.measure(View.java:16628)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:16628)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
        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:16628)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at android.view.View.measure(View.java:16628)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
        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:16628)
        at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
        at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
        at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2298)
        at android.view.View.measure(View.java:16628)
        at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
        at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
        at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
        at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
        at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5610)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
        at android.view.Choreographer.doCallbacks(Choreographer.java:574)
        at android.view.Choreographer.doFrame(Choreographer.java:544)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
        at android.os.Handler.handleCallback(Handler.java:733)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:212)
        at android.app.ActivityThread.main(ActivityThread.java:5137)
        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:902)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:718)
        at dalvik.system.NativeStart.main(Native Method)

我的代码：

GridLayoutManager gridLayoutManager = new GridLayoutManager(IndexActivity.this , 2 );
        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(gridLayoutManager);
        recyclerView.setAdapter(mAdapter);

xml：

<android.support.v7.widget.RecyclerView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:horizontalSpacing="@dimen/index_gridview_horizontal_spacing"
            android:verticalSpacing="@dimen/index_gridview_vertical_spacing"
            android:numColumns="2"
            android:id="@+id/recyclerView" />

通过更改gradle解决了这个问题。

我的参考资料如下：beecanvas.com/yjcSh8Tp

Answer 1

试试这样：

RecyclerView recyclerView = (RecyclerView) findViewById(
    R.id.recycler_view);
recyclerView.setHasFixedSize(true);
recyclerView.setLayoutManager(new GridLayoutManager(this, 2));
recyclerView.setAdapter(new NumberedAdapter(30));

这里我使用的跨度数为2，你将有30个元素，你可以根据需要进行修改。希望这会对你有所帮助。

Answer 2

我猜你使用了错误的GridLayoutManager。请确保您拥有import android.support.v7.widget.GridLayoutManager，然后：

//for Activity
recyclerView.setLayoutManager(new GridLayoutManager(this, 2));

or //for Fragment
recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 2));

应该没问题。

[<强>更新] 您只能为LayoutManager，RecyclerView或LinearLayoutManager或GridLayoutManager设置一个StaggeredGridLayoutManager，而不是两者。对于您的情况，只需设置GridLayoutManager。

希望这有帮助！

android RecyclerView onMeasure nullpointer

2 个答案: