Android头部悬浮ListView第二种实现方式

上篇博客，根据几位大神的博客总结出了一篇ListView悬浮，快速索引。效果非常不错，而且易于扩展，可在实际项目中并不是很通用，因为总需要实现SectionIndexer接口，比较复杂而且不是所有的分且头部都是由A-Z 这种分组，也可能是以任意条件的分组，比如时间。这种情况下上一篇的方法就不能用了。本篇则是基于上一篇的代码修改，使的ListView不再去实现SectionIndexer.修改OnScrollListener中的监听，使得可悬浮ListView能够基本通用。
效果与上篇完全一样。

代码如下：
1.adapter代码

/** * @description 通用Adapter* @author rzq* @date 2015*/public class SortAdapter extends BaseAdapter{    private List<SortModel> list = null;    private Context mContext;    private SortModel country;    private ViewHolder holder1, holder2;    public SortAdapter(Context mContext, List<SortModel> list)    {        this.mContext = mContext;        this.list = list;    }    @Override    public int getCount()    {        return list.size();    }    @Override    public Object getItem(int position)    {        return list.get(position);    }    @Override    public long getItemId(int position)    {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent)    {        country = (SortModel) list.get(position);        int type = getItemViewType(position);        if (convertView == null)        {            switch (type)            {            case 0:                holder1 = new ViewHolder();                convertView = LayoutInflater.from(mContext).inflate(R.layout.item_group, parent, false);                holder1.tvTitle = (TextView) convertView.findViewById(R.id.catalog);                convertView.setTag(holder1);                break;            case 1:                holder2 = new ViewHolder();                convertView = LayoutInflater.from(mContext).inflate(R.layout.item, parent, false);                holder2.tvTitle = (TextView) convertView.findViewById(R.id.title);                convertView.setTag(holder2);                break;            }        }        else        {            switch (type)            {            case 0:                holder1 = (ViewHolder) convertView.getTag();                break;            case 1:                holder2 = (ViewHolder) convertView.getTag();                break;            }        }        switch (type)        {        case 0:            holder1.tvTitle.setText(country.getSortLetters());            break;        case 1:            holder2.tvTitle.setText(country.getName());            break;        }        return convertView;    }    @Override    public int getItemViewType(int position)    {        country = (SortModel) getItem(position);        if (country.isGroup())        {            return 0;        }        else        {            return 1;        }    }    @Override    public int getViewTypeCount()    {        return 2;    }    final static class ViewHolder    {        TextView tvTitle;    }}

上述代码是一个最普通的多布局Adapter写法，无需实现SectionIndex.

2.Activity代码：

public class MainActivity extends Activity{    private ListView sortListView;    private SortAdapter adapter;    private CharacterParser characterParser;    private List<SortModel> SourceDateList;    private PinyinComparator pinyinComparator;    private LinearLayout titleLayout;    private TextView title;    @Override    protected void onCreate(Bundle savedInstanceState)    {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initViews();    }    private void initViews()    {        titleLayout = (LinearLayout) findViewById(R.id.title_layout);        title = (TextView) findViewById(R.id.title);        characterParser = CharacterParser.getInstance();        pinyinComparator = new PinyinComparator();        sortListView = (ListView) findViewById(R.id.country_lvcountry);        SourceDateList = filledData(getResources().getStringArray(R.array.date));        Collections.sort(SourceDateList, pinyinComparator);        adapter = new SortAdapter(this, SourceDateList);        sortListView.setAdapter(adapter);        sortListView.setOnScrollListener(new OnScrollListener()        {            @Override            public void onScrollStateChanged(AbsListView view, int scrollState)            {            }            /**             * AbsListView滑动时执行              */            @Override            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)            {                /**                 * 取出列表相临两项                 */                SortModel modelFirst = (SortModel) adapter.getItem(firstVisibleItem);                SortModel modelSecond = (SortModel) adapter.getItem(firstVisibleItem + 1);                if (firstVisibleItem != lastFirstVisibleItem)                {                    MarginLayoutParams params = (MarginLayoutParams) titleLayout.getLayoutParams();                    params.topMargin = 0;                    titleLayout.setLayoutParams(params);                    if (modelFirst.getSortLetters() != null)                    {                        title.setText(modelFirst.getSortLetters());                    }                }                /**                 * 相临两组Data状态不同，且第一组数据的状态为普              通数据,第二组数据为Group,则符合悬浮的条件，开始进行判断部悬浮计算                 */                if (modelFirst.isGroup() == false && modelSecond.isGroup() == true)                {                    View childView = view.getChildAt(1);                    if (childView != null)                    {                        int titleHeight = titleLayout.getHeight();                        int top = childView.getTop();                        MarginLayoutParams params = (MarginLayoutParams) titleLayout.getLayoutParams();                        if (top <= titleHeight)                        {                            float pushedDistance = -(titleHeight - top);                            params.topMargin = (int) pushedDistance;                            titleLayout.setLayoutParams(params);                        }                    }                }                lastFirstVisibleItem = firstVisibleItem;            }        });    }    private int lastFirstVisibleItem = -1;    private List<SortModel> filledData(String[] date)    {        List<SortModel> mSortList = new ArrayList<SortModel>();        for (int i = 0; i < date.length; i++)        {            SortModel sortModel = new SortModel();            sortModel.setName(date[i]);            /**             * 添加了Group数据，[A-Z]             */            if (date[i].matches("[A-Z]"))            {                sortModel.setSortLetters(date[i]);                sortModel.setGroup(true);            }            else            {                String pinyin = characterParser.getSelling(date[i]);                String sortString = pinyin.substring(0, 1).toUpperCase();                if (sortString.matches("[A-Z]"))                {                    sortModel.setSortLetters(sortString.toUpperCase());                }                else                {                    sortModel.setSortLetters("#");                }                sortModel.setGroup(false);            }            mSortList.add(sortModel);        }        return mSortList;    }}

  通过上述代码可以看出，通过这訲方式实现的效果更加的通用，也是在研究了多位大神的博客后，自己有了改进的想法，编码实现了自己的想法。使用这訲不重写ListView的方式，我们还可以结合PullToRefresh做上下拉刷新，而如果你重定义ListView则很难再与其它开源库相结合。这是使用这一方式最大的优势。

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