RecycleView Adapter 方法与作用及执行时机

最新推荐文章于 2023-07-21 11:50:21 发布

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本文详细解析了RecyclerView.Adapter中的关键方法：onCreateViewHolder、onBindViewHolder和getItemCount。onCreateViewHolder用于创建列表项视图，缓存复用；onBindViewHolder负责绑定数据到视图，每次组件重新显示时执行；getItemCount确定列表项数量。文章通过实例展示了这些方法的执行时机，包括预加载机制，帮助读者深入理解列表滚动时的数据绑定过程。

方法与作用

创建一个adapter后需要重写三个方法

onCreateViewHolder
该方法用于创建列表项组件使用该方法所创建的组件会自动被缓存
onBindViewHolder
该方法负责为列表项组件绑定数据每次组件重新显示出来时都会重新执行该方法
getItemCount
该方法的返回值决定包含多少个列表项

public class FeedAdapter extends RecyclerView.Adapter<BaseHolder> {

    private Context mContext;

    private ArrayList<FeedVideoDate> feedList;
    private ArrayList<FeedImageDate> feedImageList;

    private RecyclerView feedRecycleView;
//    private OnItemClickListener listener;

    private FeedRecommendAdapter feedRecommendAdapter;

    private FeedVideoHolder feedVideoHolder;

    private FeedImageHolder feedImageHolder;

    public FeedAdapter(ArrayList<FeedVideoDate> feedList, ArrayList<FeedImageDate> feedImageList, Context context) {
        this.feedImageList = feedImageList;
        this.feedList = feedList;
        this.mContext = context;
    }

    @Override
    public int getItemViewType(int position) {
        Log.i("AAAAAAAgetItemViewType","获取item类型+++++++");
        return feedList.get(position).getViewType();

    }

    @Override
    public BaseHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        Log.i("AAAAACreateViewHolder","创建onCreateViewHolder+++++++");
        switch (viewType) {
            case FeedVideoDate.VIEW_TYPE_IMAGE:
                return new FeedImageHolder(LayoutInflater.from(mContext).inflate(R.layout
                        .feed_item_image, parent, false));
            case FeedVideoDate.VIEW_TYPE_VIDEO:
                return new FeedVideoHolder(LayoutInflater.from(mContext).inflate(R.layout
                        .feed_item_video, parent, false));
            default:
                return new FeedBlankHolder(LayoutInflater.from(mContext).inflate(R.layout
                        .feed_item_blank, parent, false));

        }
    }

    @Override
    public void onBindViewHolder(BaseHolder holder, int position) {
        Log.i("AAAAAonBindViewHolder","onBindViewHolder+++++++");

        if (feedList.get(position).getViewType() == FeedVideoDate.VIEW_TYPE_IMAGE) {
            holder.bindData(feedImageList.get(position));
        } else {
            holder.bindData(feedList.get(position));
        }
    }


    @Override
    public int getItemCount() {
        Log.i("AAAAAgetItemCount","获取item数量+++++++");
         if (feedList != null) {
            return feedList.size();
        } else {
            return 0;
        }
    }
}