Question

我最近将android sdk更新为api 22和android studio 1.1.0。之后我在RecyclerView上得到渲染问题。这是我得到的

  java.lang.NullPointerException
at android.support.v7.widget.RecyclerView.computeVerticalScrollRange(RecyclerView.java:1216)
at android.view.View.onDrawScrollBars(View.java:12943)
at android.view.View.draw(View.java:15237)
at android.support.v7.widget.RecyclerView.draw(RecyclerView.java:2440)
at android.view.View.draw(View.java:15140)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3405)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3405)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15138)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3405)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3405)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15234)
at android.view.View.draw(View.java:15140)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3405)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3405)
at android.support.v4.widget.DrawerLayout.drawChild(DrawerLayout.java:1086)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15138)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3405)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3405)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15138)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3405)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3405)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15234)
at android.view.View.draw(View.java:15140)
at android.view.ViewGroup.drawChild_Original(ViewGroup.java:3405)
at android.view.ViewGroup_Delegate.drawChild(ViewGroup_Delegate.java:53)
at android.view.ViewGroup.drawChild(ViewGroup.java:3405)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:3198)
at android.view.View.draw(View.java:15234)

我在xml预览/设计上遇到这个异常，所以我无法做到查看xml设计。

项目工作正常，没有任何例外。这是我的小部件

 <android.support.v7.widget.RecyclerView
            android:id="@+id/my_recycler_view"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="8"
            android:layout_gravity="center"
            android:gravity="center"
            android:scrollbars="vertical"
            android:fadeScrollbars="false"
            />

这是我的代码

    recyclerView= (RecyclerView) findViewById(R.id.my_recycler_view);
    layoutManager=new GridLayoutManager(this,2);
    recyclerView.setLayoutManager(layoutManager);
    recyclerView.setHasFixedSize(true);
    recyclerView.setItemAnimator(new DefaultItemAnimator());

如何解决这个问题？

Answer 1

当我从RecyclerView的xml文件中取出这一行时，我的问题解决了：

android:scrollbars="vertical"

我使用以下依赖项：

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    compile 'com.android.support:appcompat-v7:22.0.0'
    compile 'com.android.support:recyclerview-v7:22.0.0'
    compile 'com.android.support:cardview-v7:22.0.0'
}

编辑：评论员在此解决方案中指出了此问题的根源 - 为了解决问题，您可以确保在显示带有滚动条属性集的RecyclerView之前设置RecyclerView的LayoutManager。

Answer 2

您忘了设置LayoutManager： https://developer.android.com/reference/android/support/v7/widget/RecyclerView.html#setLayoutManager(android.support.v7.widget.RecyclerView.LayoutManager)

Answer 3

我遇到了同样的错误。 RecyclerView第1216行是：

return mLayout.canScrollVertically() ? mLayout.computeVerticalScrollRange(mState) : 0;

当时mLayout为空是问题，我不知道为什么它是null，但是看起来你必须在setContentView()或inflate()之后立即在RecyclerView上调用setLayoutManager（）。在我尝试访问RecyclerView并调用其setLayoutManager()之前，我的代码正在运行后台线程。一旦我改为以下，它就可以了

即。

this.setContentView(R.layout.schedule);
rv = (RecyclerView) this.findViewById(R.id.schedule_listview);
rv.setLayoutManager(new LinearLayoutManager(this));

我仍然不太明白为什么要这样做

Answer 4

您不需要删除任何行，只需在代码中添加以下行：

recyclerView.setLayoutManager(new LinearLayoutManager(recyclerView.getContext()));

这样，RecyclerView上的垂直滚动没有问题。

希望它有所帮助！

Answer 5

万一人们仍然想知道，您应该通过SDK Manager更新到API 22的最新SDK平台，并通过SDK Manager更新支持存储库，并在{{1}中更新到最新的回收站视图文件使用最新版本（22.0.0）

Answer 6

我刚删除了属性android：scrollbars =“vertical”，一切都会很好

渲染问题：Android Studio 1.1.0中android.support.v7.widget.RecyclerView的java.lang.NullPointerException

6 个答案: