RecyclerView一个奇怪的npe异常

java.lang.NullPointerException
at android.support.v7.widget.RecyclerView.computeVerticalScrollOffset(RecyclerView.java:1613)
at android.view.View.canScrollVertically(View.java:12016)
at android.support.v4.view.ViewCompatICS.canScrollVertically(ViewCompatICS.java:35)
at android.support.v4.view.ViewCompat$ICSViewCompatImpl.canScrollVertically(ViewCompat.java:1253)
at android.support.v4.view.ViewCompat.canScrollVertically(ViewCompat.java:1695)
at com.leo.enjoytime.view.SwipyRefreshLayout.canChildScrollUp(SwipyRefreshLayout.java:644)
at com.leo.enjoytime.view.SwipyRefreshLayout.onInterceptTouchEvent(SwipyRefreshLayout.java:744)

原因是：

recyclerview is showing but no layout manager is set

解决办法：

you can just ensure that the layoutmanager for the recyclerview is set before you display the recyclerview with the scrollbars property set.

在recycleView被初始化之后需要setlayoutManager

recyclerView = (RecyclerView) rootView.findViewById(R.id.recycle);

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

参考：

http://stackoverflow.com/questions/29005644/rendering-problems-java-lang-nullpointerexception-at-android-support-v7-widget?s=1|3.6524

http://stackoverflow.com/questions/26737113/java-lang-nullpointerexception-at-android-support-v7-widget-recyclerview-onmeasu