BaseAdapter的getView()与ViewHolder的两种写法-更深刻理解ViewHolder

最新推荐文章于 2021-05-28 01:58:56 发布

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#android #ViewHolder

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本文介绍了一种优化Android ListView的方法，通过使用BaseAdapter实现ListView的数据绑定，并对比了两种ViewHolder的实现方式，一种是直接在getView中完成视图初始化和数据绑定，另一种则是将这些操作抽取到ViewHolder中，提高了代码的复用性和开发效率。

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普通android基础书上都会写这种：

private class HomeAdapter extends BaseAdapter{

        ......

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            View view;
            ViewHolder holder;
            if(convertView==null){
                view=View.inflate(UiUtils.getContext(), R.layout.item_app, null);
                holder=new ViewHolder();

                holder.item_icon=(ImageView) view.findViewById(R.id.item_icon);
                holder.item_title=(TextView) view.findViewById(R.id.item_title);
                holder.item_size=(TextView) view.findViewById(R.id.item_size);
                holder.item_bottom=(TextView) view.findViewById(R.id.item_bottom);
                holder.item_rating=(RatingBar) view.findViewById(R.id.item_rating);
                view.setTag(holder);
            }else{
                view=convertView;
                holder=(ViewHolder) view.getTag();
            }

            AppInfo appInfo=datas.get(position);
            holder.item_title.setText(appInfo.getName());// 设置应用程序的名字
            String size=Formatter.formatFileSize(UiUtils.getContext(), appInfo.getSize());
            holder.item_size.setText(size);
            holder.item_bottom.setText(appInfo.getDes());
            float stars = appInfo.getStars();
            holder.item_rating.setRating(stars); // 设置ratingBar的值
            String iconUrl = appInfo.getIconUrl();  //http://127.0.0.1:8090/image?name=app/com.youyuan.yyhl/icon.jpg

            // 显示图片的控件
            bitmapUtils.display(holder.item_icon, HttpHelper.URL+"image?name="+iconUrl);
            return view;
        }

        ......
    }

    static class ViewHolder{
        ImageView item_icon;
        TextView item_title,item_size,item_bottom;
        RatingBar item_rating;
    }

这里给出第二种写法【方便抽取DefaultAdapter和BaseViewHolder进行快速开发】

private class HomeAdapter extends BaseAdapter{

        ......

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            ViewHolder holder;
            if(convertView==null){

                holder=new ViewHolder();

            }else{
                holder=(ViewHolder) convertView.getTag();
            }

            AppInfo appInfo=datas.get(position);
            holder.setData(appInfo);

            return holder.getContentView();
        }

        ......

    }
    static class ViewHolder{
        ImageView item_icon;
        TextView item_title,item_size,item_bottom;
        RatingBar item_rating;

        View contentView;
        AppInfo appInfo;

        public ViewHolder(AppInfo appInfo){
            contentView = initView();
            contentView.setTag(this);
        }

        public void setData(AppInfo appInfo){
            this.appInfo = appInfo;
            refreshView(appInfo);
        }
        public View getContentView(){
            return contentView;
        }
    }

public View initView(){
    View view;
    view = View.inflate(UiUtils.getContext(), R.layout.item_app, null);

    this.item_icon=(ImageView) view.findViewById(R.id.item_icon);
                this.item_title=(TextView) view.findViewById(R.id.item_title);
                this.item_size=(TextView) view.findViewById(R.id.item_size);
                this.item_bottom=(TextView) view.findViewById(R.id.item_bottom);
                this.item_rating=(RatingBar) view.findViewById(R.id.item_rating);

    return view;
}
public void refreshView(AppInfo appInfo){
    this.item_title.setText(appInfo.getName());// 设置应用程序的名字
            String size=Formatter.formatFileSize(UiUtils.getContext(), appInfo.getSize());
            this.item_size.setText(size);
            this.item_bottom.setText(appInfo.getDes());
            float stars = appInfo.getStars();
            this.item_rating.setRating(stars); // 设置ratingBar的值
            String iconUrl = appInfo.getIconUrl();  //http://127.0.0.1:8090/image?name=app/com.youyuan.yyhl/icon.jpg

            // 显示图片的控件
            bitmapUtils.display(this.item_icon, HttpHelper.URL+"image?name="+iconUrl);
}