android - Android 应用程序中的数据绑定(bind)和 RecyclerView

Question

我想知道如何使 Databinding 和 RecyclerView 协同工作。我有一个定义如下的适配器类:

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 更新了一些新餐厅，我希望 RecyclerView 重新呈现这些新对象。我怎样才能做到这一点？

编辑:

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

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 View 模型中

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

最后是xml布局

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

很简单的方法，不考虑项目的部分变化，你可以多看看ObservableList和 OnListChangedCallback

UPD作为 OnListChangedCallback 的后续，我认为可能可以使用适配器来实现类似的东西，以对列表的确切更改使用react。

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;
    }
}