android - RecyclerView onCreateViewHolder 返回类型与多个自定义 ViewHolder 不兼容

Question

我正在尝试在 RecyclerView 中使用多个 ViewHolder，以便在运行时交换这些 View 。我创建了两个扩展 RecyclerView.ViewHolder 的类:

MenuItemViewHolder

public class MenuItemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    public TextView menuItemText;
    public ImageView menuItemPhoto;
    public RecyclerViewAdapter rva;

    public MenuItemViewHolder(View itemView) {
         super(itemView);
         itemView.setOnClickListener(this);

         rva = caller;
         menuItemText = (TextView) itemView.findViewById(R.id.grid_text);
         menuItemPhoto = (ImageView) itemView.findViewById(R.id.grid_image);
    }

    @Override
    public void onClick(View view) {
          Toast.makeText(view.getContext(), "Clicked Position = " + getPosition(), Toast.LENGTH_SHORT).show();

    }

}

SelectedItemViewHolder

public class SelectedItemViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {

    public TextView menuItemText;
    public ImageView menuItemPhoto;
    public RecyclerViewAdapter rva;

    public SelectedItemViewHolder(View itemView) {
        super(itemView);
        itemView.setOnClickListener(this);

         menuItemText = (TextView) itemView.findViewById(R.id.grid_text_full);
         menuItemPhoto = (ImageView) itemView.findViewById(R.id.grid_image_full);
    }

    @Override
    public void onClick(View view) {
          Toast.makeText(view.getContext(), "Clicked Position = " + getPosition(), Toast.LENGTH_SHORT).show();
    }
}

它们在我的 RecyclerViewAdapter 类的 onCreateViewHolder 函数中被调用:

RecyclerViewAdapter onCreateViewHolder

// Create new views (invoked by the layout manager)

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        switch (viewType) {

            case 0:
                View gridItemLayout = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.grid_single, parent, false);
                // set the view's size, margins, paddings and layout parameters
                MenuItemViewHolder vh = new MenuItemViewHolder(gridItemLayout);

            case 2:
                View selectedItemLayout = LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.grid_single_full, parent, false);
                // set the view's size, margins, paddings and layout parameters
                SelectedItemViewHolder sivh = new SelectedItemViewHolder(selectedItemLayout);
                return sivh;
          }
    }

当我尝试运行代码时，我收到此错误:

Error:(48, 36) error: onCreateViewHolder(ViewGroup,int) in RecyclerViewAdapter cannot override onCreateViewHolder(ViewGroup,int) in Adapter return type ViewHolder is not compatible with MenuItemViewHolder where VH is a type-variable: VH extends ViewHolder declared in class Adapter

所以，问题似乎是 onCreateViewHolder 不接受我的自定义类是从 RecyclerView.ViewHolder 继承的。我正在使用 Android Studio，所以问题可能就在那里。我很困惑，因为我认为 Java 继承可以毫无问题地处理这个问题。有人可以提出解决方案吗？

编辑:当我将 onCreateViewHolder 的返回类型更改为只有一个 VH 的 MenuItemViewHolder 时，一切正常。但是，当我有多个可以随时交换的 VH 类时，这不起作用。

Answer 1

RecyclerView.Adapter 是一个参数化类，它采用单个 ViewHolder 类型。您的定义可能如下所示:

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerViewAdapter.MenuItemViewHolder>

应该是:

public class RecyclerViewAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>

不要忘记对 onBindViewHolder 也有正确的定义。您还需要覆盖 getItemViewType。