ListView 的 Adapter 适配器模板

Adapter优化.png

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ListView中的Adapter优化的通用模板。

如果发现对ListView优化工作做完后，还会卡顿，可以检查notifyDataSetChanged()方法是否运用合理，频繁的调用此方法也会引发卡顿。

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1.构造函数的通用化

构造函数中的List不指定数据类型

public TemplateAdapter(Context context, List data) {
    this.mContext = context;
    this.mData = data;
}

2.创建 ViewHolder

// 使用ViewHolder
...
private static class ViewHolder {
    private TextView tvTitle, tvContent;
    private ImageView ivIcon;
}
...

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3.非空判断

@Override
public int getCount() {
    return null == mArrayList ? 0 : mArrayList.size();
}

4.getView中操作

getView中inflate的两种方式：

// 方式一 推荐使用方式一，简介
convertView = View.inflate(mContext, R.layout.item_ad, null);
// 方式二
convertView = mInflater.inflate(R.layout.item_layout, parent, false);

Override
public View getView(int position, View convertView, ViewGroup parent) {
    final ViewHolder viewHolder;
    //判断是否有缓存
    if (convertView == null || convertView.getTag == null) {
        //通过LayoutInflate实例化布局
        viewHolder = new ViewHolder();
        //convertView = mInflater.inflate(R.layout.item_layout, parent, false);
        convertView = View.inflate(mContext, R.layout.item_ad, null);
        viewHolder.ivIcon = (ImageView) convertView.findViewById(R.id.iv_icon);
        viewHolder.tvTitle = (TextView) convertView.findViewById(R.id.tv_title);
        viewHolder.tvContent = (TextView) convertView.findViewById(R.id.tv_content);
        convertView.setTag(viewHolder);
      } else {
        //通过tag找到缓存的布局
        viewHolder = (ViewHolder) convertView.getTag();
      }

      // 数据渲染
      NewsBean newsBean = newsBeanList.get(position);
      
      // 所有的字段必须做非空判断
      String urlString = null == newsBean.newsIconUrl ? "" : newsBean.newsIconUrl;
      viewHolder.ivIcon.setTag(urlString); // 将ImageView与url绑定
      //普通异步加载
     // mImageLoader.showImageByThread(viewHolder.ivIcon,urlString);
      mImageLoader.showImageByAsyncTask(viewHolder.ivIcon,urlString);
      viewHolder.tvTitle.setText(newsBean.newsTitle);
      viewHolder.tvContent.setText(newsBean.newsContent);
      return convertView;
  }

5.完整的Adapter模板

public class TemplateAdapter extends BaseAdapter {

    private Context mContext;
    // 加上<Object>防止警告
    private List<Object> mDatas;

    // 构造函数通用化，对List参数不要指定数据类型
    public TemplateAdapter(Context context, List<Object> datas) {
        this.mContext = context;
        this.mDatas = datas;
    }

    // 预防空指针处理
    @Override
    public int getCount() {
        return null == mDatas ? 0 : mDatas.size();
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup viewGroup) {
        // 一、初始化布局
        final ViewHolder viewHolder;
        //判断是否有缓存
        if (convertView == null || convertView.getTag() == null) {
            viewHolder = new ViewHolder();
            // 方式一 推荐使用
            convertView = View.inflate(mContext, R.layout.adapter_content, null);
            // 方式二
            //convertView = mInflater.inflate(R.layout.item_layout, parent, false);
            viewHolder.tvTitle = (TextView) convertView.findViewById(R.id.title);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }

        // 二、渲染数据
        CommentEntity.Data data = (CommentEntity.Data) mDatas.get(position);
        // 所有去除的数据做非空判断
        String title = null == data.userNick ? "" : data.userNick;
        viewHolder.tvTitle.setText(title);

        return convertView;
    }

    private static class ViewHolder {
        TextView tvTitle;
    }
}