LayoutManager - 将RecyclerView设置为ListVIew标题时出现空指针异常

Question

我有一个水平的RecyclerView，我将其添加为Listview的标题。但是一旦我开启我的活动，它就会崩溃。

这是我在做什么在我的活动：

headerView = getLayoutInflater().inflate(R.layout.header_layout, null); 
CustomViewHolder holder = new CustomViewHolder(headerView, this); 
holder.inflateView(); 
listView.addHeaderView(headerView); 

我的观点持有者构造函数中：

public CustomViewHolder(View itemView, Activity activity) { 
     this.mActivity = activity; 
     mainView = itemView; 
     recyclerView = (RecyclerView) itemView.findViewById(R.id.recyclerView); 

     LinearLayoutManager layoutManager = new LinearLayoutManager(mActivity); 
     layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL); 
     layoutManager.canScrollHorizontally(); 
     recyclerView.setLayoutManager(layoutManager); 
    } 

而且在我的观点持有者充气方法：

adapter = new CustomHorizontalAdapter(mActivity, list); 
recyclerView.setAdapter(adapter); 

这是我的观点XML：

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

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

</LinearLayout> 

但只要我打开我的活动，它与以下日志崩溃 -

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:17565) 
                    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5537) 
                    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:17565) 
                    at android.widget.ListView.setupChild(ListView.java:1944) 
                    at android.widget.ListView.makeAndAddView(ListView.java:1867) 
                    at android.widget.ListView.fillDown(ListView.java:698) 
                    at android.widget.ListView.fillFromTop(ListView.java:759) 
                    at android.widget.ListView.layoutChildren(ListView.java:1659) 
                    at android.widget.AbsListView.onLayout(AbsListView.java:2151) 
                    at android.view.View.layout(View.java:15689) 
                    at android.view.ViewGroup.layout(ViewGroup.java:5040) 
                    at android.support.v4.widget.SwipeRefreshLayout.onLayout(SwipeRefreshLayout.java:581) 

有人可以帮我明白这是为什么崩溃？我将布局管理器设置为回收站视图。有没有其他的方式来添加一个水平滚动视图作为头到一个列表视图？这不可能吗？

Answer 1

你可以试试Recyclerview的布局管理器。

RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext()); 
    recyclerView.setLayoutManager(mLayoutManager);