getView 經典寫法

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        final ViewHolder holder;
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.atom_alexhome_new_customer_module_a_grid_item, parent, false);
            holder = new ViewHolder();
 


            holder.tvTitle = (TextView) convertView.findViewById(R.id.tv_title);
            holder.tvSubTitle = (TextView) convertView.findViewById(R.id.tv_subtitle);
            holder.img = (SimpleDraweeView) convertView.findViewById(R.id.image);
            holder.tvFetchNow = (TextView) convertView.findViewById
 
(R.id.tv_fetch_now);
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }
        ModuleAItem bean = list.get(position);
        holder.tvTitle.setText(bean.title);
        holder.tvTitle.setTextColor(Color.parseColor(bean.titleColor
 
));
        holder.tvSubTitle.setText(bean.subtitle);
        holder.tvSubTitle.setTextColor(Color.parseColor(bean.subtitleColor));
        return convertView；

可以看出有一個對convertView的判空操作，如果不為null,就複用。那麼我們要知道為啥有時候他不是null

深入listview原始碼

在閱讀之後，我再自己看了下程式碼，整理了一張圖片。