Question

嗨，我是Android Studio的新手，我正在尝试制作一个简单的回收站视图，其中包含卡片视图列表。代码运行得很好，当我运行它时，每个视图都可以正常显示，但是后来我决定将背景色添加到回收器视图中，而不是一切都出错了。我唯一更改的是设置回收者视图的背景颜色。顺便说一下，我的回收者视图生活在一个碎片中。

这是设置背景颜色之前的样子：

更改之前的回收者视图的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线？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，也会发生该错误，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“回收者视图”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“活动”级别检索recyclerview：

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

但是recyclerview在您的片段中。奇怪的是您没有其他错误，我期望该应用程序崩溃。无论如何，应该以这种方式解决：像这样更改您的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;
}

不再需要上一行，即从活动中检索recyclerview的那一行。

设置背景颜色后，回收站视图不显示视图

1 个答案: