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  • 吴裕雄--天生自然ANDROID开发学习:2.4.6 BaseAdapter优化

    1.复用ConvertView:
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        convertView = LayoutInflater.from(mContext).inflate(R.layout.item_list_animal,parent,false);
        ImageView img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
        TextView txt_aName = (TextView) convertView.findViewById(R.id.txt_aName);
        TextView txt_aSpeak = (TextView) convertView.findViewById(R.id.txt_aSpeak);
    
        img_icon.setBackgroundResource(mData.get(position).getaIcon());
        txt_aName.setText(mData.get(position).getaName());
        txt_aSpeak.setText(mData.get(position).getaSpeak());
        return convertView;
    }
    inflate()每次都要加载一次xml,其实这个convertView是系统提供给我们的可供服用的View 的缓存对象,那就坐下判断咯,修改下,优化后的代码:
    
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
    
        if(convertView == null){
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_list_animal,parent,false);
        }
    
        ImageView img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
        TextView txt_aName = (TextView) convertView.findViewById(R.id.txt_aName);
        TextView txt_aSpeak = (TextView) convertView.findViewById(R.id.txt_aSpeak);
    
        img_icon.setBackgroundResource(mData.get(position).getaIcon());
        txt_aName.setText(mData.get(position).getaName());
        txt_aSpeak.setText(mData.get(position).getaSpeak());
        return convertView;
    }
    
    2.ViewHolder重用组件
    getView()会被调用多次,那么findViewById不一样得调用多次,而我们的ListView的Item 一般都是一样的布局,我们可以对这里在优化下,我们可以自己定义一个ViewHolder类来对这一部分 进行性能优化!修改后的代码如下:
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder = null;
        if(convertView == null){
            convertView = LayoutInflater.from(mContext).inflate(R.layout.item_list_animal,parent,false);
            holder = new ViewHolder();
            holder.img_icon = (ImageView) convertView.findViewById(R.id.img_icon);
            holder.txt_aName = (TextView) convertView.findViewById(R.id.txt_aName);
            holder.txt_aSpeak = (TextView) convertView.findViewById(R.id.txt_aSpeak);
            convertView.setTag(holder);   //将Holder存储到convertView中
        }else{
            holder = (ViewHolder) convertView.getTag();
        }
        holder.img_icon.setBackgroundResource(mData.get(position).getaIcon());
        holder.txt_aName.setText(mData.get(position).getaName());
        holder.txt_aSpeak.setText(mData.get(position).getaSpeak());
        return convertView;
    }
    
    static class ViewHolder{
        ImageView img_icon;
        TextView txt_aName;
        TextView txt_aSpeak;
    }
    
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  • 原文地址:https://www.cnblogs.com/tszr/p/13581734.html
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