Android之ListView的getItemViewType和getViewTypeCount

public class ListAdapter extends BaseAdapter {

    /**
     * Item类型,int值.必须从0开始依次递增.
     * */
    private static final int TYPE_TITLE = 0;
    private static final int TYPE_CONTENT = 1;

    /**
     * Item Type 的数量
     * */
    private static final int TYPE_ITEM_COUNT = 2;

    /**
     * 数据
     * */
    private List<Company> mData = new ArrayList<>();
    private Context context;



    public ListAdapter(Context context,List<Company>mData){
        this.context = context;
        this.mData = mData;
    }


    @Override
    public int getCount() {
        return mData.size();
    }

    @Override
    public Object getItem(int position) {
        return mData.get(position);
    }

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

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

        /**
         * 不同类型的ViewHolder
         * */
        TitleViewHolder titleViewHolder = null;
        CompanyViewHolder contentViewHolder = null;
        /**
         * 对类型进行判断,分别inflate不同的布局.
         * */
        switch (getItemViewType(position)){
            case TYPE_TITLE:
                titleViewHolder = new TitleViewHolder();
                if(convertView == null){
                    convertView = View.inflate(context, R.layout.view_holder_company_index,null);
                    titleViewHolder.title = (TextView) convertView.findViewById(R.id.tv_title);
                    //setTag()
                    convertView.setTag(titleViewHolder);
                }else{
                    //getTag();
                    titleViewHolder = (TitleViewHolder) convertView.getTag();
                }
                titleViewHolder.title.setText(mData.get(position).getName());
                break;
            case TYPE_CONTENT:
                contentViewHolder = new CompanyViewHolder();
                if(convertView == null){
                    convertView = View.inflate(context,R.layout.view_holder_company,null);
                    contentViewHolder.content = (TextView) convertView.findViewById(R.id.tv_content);
                    convertView.setTag(contentViewHolder);
                }else{
                    contentViewHolder = (CompanyViewHolder) convertView.getTag();
                }
                contentViewHolder.content.setText(mData.get(position).getCode());
                break;
        }
        return convertView;
    }

    /**
     * 根据position获取Item的类型
     * */
    @Override
    public int getItemViewType(int position) {
        if(TextUtils.isEmpty(mData.get(position).getCode())){
            return TYPE_TITLE;
        }else{
            return TYPE_CONTENT;
        }
    }

    /**
     * 返回Item Type的总数量
     * */
    @Override
    public int getViewTypeCount() {
        return TYPE_ITEM_COUNT;
    }

    static class TitleViewHolder{
        TextView title;
    }

    static class CompanyViewHolder{
        TextView content;
    }
}

/**
 *ListView在针对不同Item复用时会调用这个方法
 *为每一种不同的Item设置一个RecycleBin,用于复用.
 */
public void setViewTypeCount(int viewTypeCount) {
   
    if (viewTypeCount < 1) {
        throw new IllegalArgumentException("Can‘t have a viewTypeCount < 1");
    }
    // noinspection unchecked  
    /**
     * 根据viewTypeCount的数量设置一个ArrayList.
     * 同时为每一个Item再设置一个ArrayList,用来存储ScrapView.
     * 相当于一个二维数组来维护每一个Item的ScrapView数组.
     * 这里也就相当于为不同的Item设置单独的RecycleBin.
     */
    ArrayList<View>[] scrapViews = new ArrayList[viewTypeCount];
    for (int i = 0; i < viewTypeCount; i++) {
       scrapViews[i] = new ArrayList<View>();
    }
    //保存ViewTypeCount,也就 = 2
    mViewTypeCount = viewTypeCount;
    //当前的Scrap是第一个Item的ScrapView数组.
    mCurrentScrap = scrapViews[0];
    //mScrapViews就保存了一个二维数组维护的RecycleBin.
    mScrapViews = scrapViews;
}

  void addScrapView(View scrap) {  
        AbsListView.LayoutParams lp = (AbsListView.LayoutParams) scrap.getLayoutParams();  
        if (lp == null) {  
            return;  
        }  
        // Don‘t put header or footer views or views that should be ignored  
        // into the scrap heap  
        int viewType = lp.viewType;  
        if (!shouldRecycleViewType(viewType)) {  
            if (viewType != ITEM_VIEW_TYPE_HEADER_OR_FOOTER) {  
                removeDetachedView(scrap, false);  
            }  
            return;  
        }  
        /**
         *核心代码就是这块,由于我们mViewTypeCount != 1 的,因此if条件不成立.
         *因此会执行else代码.
         */
        if (mViewTypeCount == 1) {  
            dispatchFinishTemporaryDetach(scrap);  
            mCurrentScrap.add(scrap);  
        } else {  
            dispatchFinishTemporaryDetach(scrap);  
            mScrapViews[viewType].add(scrap);  
        }  
  
        if (mRecyclerListener != null) {  
            mRecyclerListener.onMovedToScrapHeap(scrap);  
        }  
    }