Question

我正在尝试在DialogFragment内部填充RecyclerView，这是在片段内部。我按照指南正常制作了RecyclerView适配器。

但我收到此错误java.lang.NullPointerException: Attempt to invoke virtual method 'voidandroid.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference

在线

recyclerView.setLayoutManager（经理）;

这里是完整的代码

public class AlertFragment extends DialogFragment {
RecyclerView recyclerView;
RecyclerView.Adapter adapter2;
RecyclerView.LayoutManager manager;

ArrayList<String> goalname = new ArrayList<String>();
 ArrayList<String> goalcategory = new ArrayList<String>();

@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_alert, container, false);
    goalname.add("Running");
    goalcategory.add("Physical");
    goalname.add("Yoga");
    goalcategory.add("Physical");
    goalname.add("Gym");
    goalcategory.add("Physical");
    goalname.add("Meditation");
    goalcategory.add("Mental");
    goalname.add("Puzzle Solving");
    goalcategory.add("Habits");
    manager = new LinearLayoutManager(getActivity());
    recyclerView = (RecyclerView) getActivity().findViewById(R.id.bookhistory);
    recyclerView.setLayoutManager(manager);


    adapter2 = new GoalListAdapter(goalname, goalcategory,getActivity());
    recyclerView.setAdapter(adapter2);
    adapter2.notifyDataSetChanged();
    return v;
}}

Answer 1

显然它会崩溃，因为它没有找到回收站视图实例。

只需替换此行：

  recyclerView = (RecyclerView) getActivity().findViewById(R.id.bookhistory);

。通过

recyclerView = (RecyclerView) v.findViewById(R.id.bookhistory);

现在它适合你。

Answer 2

你的问题在于这一行：

    recyclerView = (RecyclerView) getActivity().findViewById(R.id.bookhistory);

您真的希望从您在此行中的片段中充气的视图中获取RecyclerView

    View v = inflater.inflate(R.layout.fragment_alert, container, false);

所以要解决这个问题，请将我提到的第一行代码更改为

    recyclerView = (RecyclerView) v.findViewById(R.id.bookhistory);

这假设DialogFragment包含bookhistory

Fragment里面的DialogFragment内的RecyclerView

2 个答案: