设置背景颜色时回收站视图不显示视图

Question

您好，我是 Android Studio 的新手，我正在尝试制作一个包含卡片视图列表的简单回收器视图。代码运行得很好，当我运行它时每个视图都渲染得很好，但后来我决定向回收器视图添加背景颜色，而不是一切都出错了。我唯一改变的是设置回收站视图的背景颜色。顺便说一句，我的回收站视图存在于片段中。

这是我设置背景颜色之前的样子：

recycler视图修改前的xml文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:listitem="@layout/recycler_view_item" />

</android.support.constraint.ConstraintLayout>

这是现在的样子，我所做的只是设置回收站视图的背景颜色：

这是新的 xml 文件：

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <android.support.v7.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@android:color/holo_green_dark"
        tools:listitem="@layout/recycler_view_item" />

</android.support.constraint.ConstraintLayout>

我的猜测是背景颜色以某种方式覆盖了我的视图？ 顺便说一句，我确实注意到 logcat 中发生了错误：

2018-12-21 22:02:05.515 20644-20644/com.steven97102gmail.todoassistant E/RecyclerView: No adapter attached; skipping layout

但是，即使我没有设置背景，也会出现该错误，并且工作正常。

这是我的 frament 课程：

public class RecycleFragment extends Fragment {
    private RecyclerView recyclerView;
    private RecyclerView.Adapter viewAdapter;
    private RecyclerView.LayoutManager viewLayouManager;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.recyler_view, container, false);
    }

    @Override
    public void onActivityCreated(@Nullable Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        // get and configure the recycle view
        recyclerView = (RecyclerView) getActivity().findViewById(R.id.recycler_view);
        recyclerView.setHasFixedSize(true);
        // layout manager for recyler view
        viewLayouManager = new LinearLayoutManager(getActivity());
        recyclerView.setLayoutManager(viewLayouManager);
        // creates the initial cards
        ArrayList<CardItem> card_lists = new ArrayList<>();
        for (int i = 0;i<=10;i++){
            CardItem card = new CardItem("TODO"+i,"12/" + i);
            card_lists.add(card);
        }
        // adapter for recycler view, initialize the recycler view
        viewAdapter = new RecyclerAdapter(card_lists);
        recyclerView.setAdapter(viewAdapter);
        // test add a new item
        card_lists.add(0,new CardItem("Test Insert","12/16"));
        viewAdapter.notifyItemInserted(0);
    }
}

这是我的回收站视图适配器类：

public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.RecyclerViewHolder> {
   private ArrayList<CardItem> card_item_list;

   // view holder is created from the recycler_card_item template
   public static class RecyclerViewHolder extends RecyclerView.ViewHolder {
       public TextView title_tv, date_tv;
       public RecyclerViewHolder(LinearLayout layout) {
            super(layout);
            title_tv = layout.findViewById(R.id.card_item_title);
            date_tv = layout.findViewById(R.id.card_item_date);
       }
   }

   // take in a list of card items to initialize with
   public RecyclerAdapter(ArrayList<CardItem> card_list) {
        card_item_list = card_list;
   }

    @NonNull
    @Override
    // inflate and creates a viewholder objects, which is from the recycler care item template;
    public RecyclerAdapter.RecyclerViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
       // create a new card item
        LinearLayout cardLayout = (LinearLayout) LayoutInflater.from(viewGroup.getContext())
                    .inflate(R.layout.recycler_card_item, viewGroup, false);
        RecyclerViewHolder vh = new RecyclerViewHolder(cardLayout);
        return vh;
    }

    @Override
    // bind the CardItem class with the viewholder to complete the card
    public void onBindViewHolder(@NonNull RecyclerViewHolder holder, int position) {
       CardItem target_card = card_item_list.get(position);
       holder.title_tv.setText(target_card.title);
       holder.date_tv.setText(target_card.date);
    }

    @Override
    public int getItemCount() {
        return card_item_list.size();
    }
}

Answer 1

在您的代码中，您尝试在 Activity 级别检索 recyclerview：

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

但是 recyclerview 在你的片段中。奇怪的是您没有任何其他错误，我预计该应用程序会崩溃。无论如何，应该这样解决：像这样改变你的onCreateView

@Nullable
@Override
public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View root = inflater.inflate(R.layout.recyler_view, container, false);
    recyclerView = root.findViewById(R.id.recycler_view);
    return root;
} 

上一行，即从活动中检索recyclerview的那一行，不再需要了。