Android应用程序中的数据绑定和RecyclerView

Question

我想知道如何使Databinding和RecyclerView协同工作。 我有一个如下定义的适配器类：

public class RestaurantRecyclerViewAdapter extends RecyclerView.Adapter<RestaurantRecyclerViewAdapter.BindingHolder> {

    private RestaurantsListViewModel mDataContext;

    public RestaurantRecyclerViewAdapter(RestaurantsListViewModel vm) {
        mDataContext = vm;
    }


    @Override
    public BindingHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.fragment_restaurant_list_item, parent, false);
        BindingHolder holder = new BindingHolder(v);

        return holder;
    }

    @Override
    public void onBindViewHolder(final BindingHolder holder, int position) {
        final RestaurantListItemViewModel restaurant = mDataContext.getRestaurant(position);

        holder.getBinding().setVariable(BR.restaurant, restaurant);
        holder.getBinding().executePendingBindings();
    }

    @Override
    public int getItemCount() {
        return mDataContext.getRestaurantsCount();
    }

    public class BindingHolder extends RecyclerView.ViewHolder {

        private ViewDataBinding binding;

        public BindingHolder(View rowView) {
            super(rowView);
            binding = DataBindingUtil.bind(rowView);
        }

        public ViewDataBinding getBinding() {
            return binding;
        }

    }

}

如果RestaurantListViewModel得到了一些新的餐馆更新我想要RecyclerView重新呈现这些新对象。 我怎么能做到这一点？

编辑：

@Vladimirs方法似乎很明智，但是我在实现onBindViewHolder方法时遇到了麻烦：

public void onBindViewHolder(final RecyclerView.ViewHolder holder, int position) {
    final RestaurantListItemViewModel restaurant = restaurants.get(position);

    holder.getBinding().setVariable(BR.restaurant, restaurant);
    holder.getBinding().executePendingBindings();
}

现在没有getBinding方法。

Answer 1

您可以先创建适配器

public class RecyclerViewAdapters {

    @BindingAdapter("items")
    public static void setItems(RecyclerView view, List<Object> items) {
        RecyclerView.Adapter<?> adapter = view.getAdapter();
        if (adapter instanceof RestaurantRecyclerViewAdapter) {
            // tell RestaurantRecyclerViewAdapter to set new list of items
        } else {
            throw new IllegalArgumentException("RecyclerView.Adapter is not RestaurantRecyclerViewAdapter");
        }
    }
}

然后在视图模型中

public final ObservableList<Object> items = new ObservableArrayList<>();

最后是在xml布局中

<android.support.v7.widget.RecyclerView
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:items="@{viewModel.items}"
    app:layoutManager="LinearLayoutManager"/>

这是一个非常简单的方法，不考虑项目的部分更改，你可以看看ObservableList和OnListChangedCallback

UPD作为对OnListChangedCallback的跟进，我认为可能是这样的事情可以用适配器来实现对列表的确切更改做出反应。

public class ObservableListAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    ObservableList<Object> list;

    ObservableList.OnListChangedCallback<ObservableList<Object>> callback = new ObservableList.OnListChangedCallback<ObservableList<Object>>() {
        @Override
        public void onChanged(ObservableList<Object> sender) {
            notifyDataSetChanged();
        }

        @Override
        public void onItemRangeChanged(ObservableList<Object> sender, int positionStart, int itemCount) {
            notifyItemRangeChanged(positionStart, itemCount);
        }

        @Override
        public void onItemRangeInserted(ObservableList<Object> sender, int positionStart, int itemCount) {
            notifyItemRangeInserted(positionStart, itemCount);
        }

        @Override
        public void onItemRangeMoved(ObservableList<Object> sender, int fromPosition, int toPosition, int itemCount) {
            notifyItemRangeRemoved(fromPosition, itemCount);
            notifyItemRangeInserted(toPosition, itemCount);
        }

        @Override
        public void onItemRangeRemoved(ObservableList<Object> sender, int positionStart, int itemCount) {
            notifyItemRangeRemoved(positionStart, itemCount);
        }
    };

    public ObservableListAdapter(@NonNull ObservableList<Object> list) {
        this.list = list;
        this.list.addOnListChangedCallback(callback);
    }

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

    @Override
    public long getItemId(int position) {
        return position;
    }
}