recyclerview（二）添加头尾布局

最新推荐文章于 2020-06-22 21:30:26 发布

原创最新推荐文章于 2020-06-22 21:30:26 发布 · 906 阅读

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recyclerview有很强大的定制功能，但是刚接触的伙伴感觉肯定没有listview用着那么顺手。像listview的添加头布局（addHeadView），脚布局（footView）等api都是没有的，需要自己动手实现，今天实现一个为recyclerview添加脚布局进行上拉加载的逻辑。

虽然recyclerview没有添加头尾布局的api，但在recyclerview的adapter中有这样一个重写的方法getItemViewType(int position)，顾名思义，这个方法返回的是一个viewType，一个view的类型，而在我么的onCreateViewHolder(ViewGroup parent, int viewType)方法中，第二个参数恰好是viewType。其实getItemViewType（）返回的viewType就是onCreateViewHolder（）方法对应的viewType，这样一看瞬间明白了。

主要代码片段和注释：

    private static final int TYPE_ITEM =0;       //普通Item View
    private static final int TYPE_FOOTER = 1;    //底部FootView
    public static final int  PULLUP_LOAD_MORE=0;  //上拉加载
    public static final int  LOADING_MORE=1;      //正在加载中
    public static final int NO_MORE_DATA = 2;     //加载完成没有数据
    private int load_more_status=0;               //上拉加载状态默认0
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    //判断返回的ViewType是那种类型
        if (viewType == TYPE_ITEM) {
            ItemViewHolder ItemViewHolder = new ItemViewHolder (LayoutInflater.from(context).inflate(R.layout.memberadapter_item, parent, false));
            return ItemViewHolder ;
        }else if (viewType == TYPE_FOOTER){

            FootViewHolder  footViewHolder =  new FootViewHolder(LayoutInflater.from(context).inflate(R.layout.recycler_load_more_layout,parent,false));

            return footViewHolder ;

        }
        return null;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
    //根据返回的holder判断是普通条目还是脚布局，然后进行设置
        if (holder instanceof ItemViewHolder ){
            ((ItemViewHolder ) holder).tv_member_item.setText(list.get(position).getVipName());
        }else if (holder instanceof FootViewHolder){
            switch (load_more_status){
                case LOADING_MORE:
                    ((FootViewHolder) holder).foot_view_item_tv.setText("正在加载数据");
                    ((FootViewHolder) holder).pull_to_refresh_load_progress.setVisibility(View.VISIBLE);

                    break;
                case PULLUP_LOAD_MORE:
                    if (getItemCount()<20){
                        ((FootViewHolder) holder).foot_view_item_tv.setText("");
                        ((FootViewHolder) holder).pull_to_refresh_load_progress.setVisibility(View.INVISIBLE);
                    }else {
                        ((FootViewHolder) holder).foot_view_item_tv.setText("上拉加载更多");
                        ((FootViewHolder) holder).pull_to_refresh_load_progress.setVisibility(View.INVISIBLE);
                    }
                    break;
                case NO_MORE_DATA:
                    ((FootViewHolder) holder).foot_view_item_tv.setText("没有更多数据了");
                    ((FootViewHolder) holder).pull_to_refresh_load_progress.setVisibility(View.INVISIBLE);
                    break;
            }

        }

    }
//根据position的位置判断是普通条目还是脚布局
    @Override
    public int getItemViewType(int position) {
        if (position+1 == getItemCount()){
            return TYPE_FOOTER;
        }else {
            return TYPE_ITEM;
        }

    }

    @Override
    public int getItemCount() {
        return list.size()+1;    //因为在底部添加了脚布局，所以Count的数量要+1
    }

    public static class ItemViewHolder extends RecyclerView.ViewHolder { //普通条目的ViewHOlder
        TextView tv_member_item;
        public ItemViewHolder (View itemView) {
            super(itemView);
            tv_member_item = (TextView) itemView.findViewById(R.id.tv_member_item);

        }
    }
    //添加的脚布局的ViewHolder
    public static class FootViewHolder  extends RecyclerView.ViewHolder {
        TextView foot_view_item_tv;
        ProgressBar pull_to_refresh_load_progress;
        public FootViewHolder (View itemView) {
            super(itemView);
            foot_view_item_tv = (TextView) itemView.findViewById(R.id.foot_view_item_tv);
            pull_to_refresh_load_progress = (ProgressBar) itemView.findViewById(R.id.pull_to_refresh_load_progress);

        }
    }

    public void ChangeState(int statu){
        load_more_status=statu;
    }
}

在代码中使用，将recyclerview设置滚动监听

    private int lastVisibleItem;
    final LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
    rcMemberView.setLayoutManager(linearLayoutManager);
    adapter = new MemberRecyclerAdapter(this);


 rcMemberView.setOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(final RecyclerView recyclerView, final int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                //判断是否滑动到底部
                if (newState == recyclerView.SCROLL_STATE_IDLE && lastVisibleItem+1== adapter.getItemCount()){
                  //此处做加载数据操作，并调用adapter.changeMoreStatus（）时时改变底部局的状态     


                            });    

            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                lastVisibleItem = linearLayoutManager.findLastVisibleItemPosition();
            }
        });