ListView分类列表条目滑到中间

MainActivity

public class MainActivity extends AppCompatActivity {

    private ListView mListView;
    private List<String> list;
    private ListViewAdapter adapter;

    //当前所显示的条目
    private int visibleCount = 0;
    //当前所显示条目数一半，也就是所显示的中间位置占几个条目
    private int middleCount = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        mListView = (ListView) findViewById(R.id.listView);
        //添加数据
        initData();

        adapter = new ListViewAdapter(list, this);

        mListView.setAdapter(adapter);

        mListView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {

                //改变背景
                adapter.changeSelectBackground(position);


                if (visibleCount == 0) {
                    // 得到当前显示条目
                    visibleCount = parent.getChildCount();

                    if (visibleCount != list.size()) {

                        middleCount = visibleCount / 2;

                    }
                }

                //如果点击条目高于 此列表的正中 则 列表整体上移
                if (position <= (parent.getFirstVisiblePosition() + middleCount)) {

                    mListView.smoothScrollToPosition(position + 1 - middleCount);

                }
                //如果点击条目低于 此列表的正中 则 列表整体下移
                else {

                    mListView.smoothScrollToPosition(position - 1 + middleCount);
                }


            }
        });
    }

    private void initData() {

        list = new ArrayList<>();

        for (int i = 0; i < 20; i++) {

            list.add("商品" + i);
        }
    }

}

Adapter

public class ListViewAdapter extends BaseAdapter {

    private List<String> list;
    private Context context;

    private int selectId;

    public ListViewAdapter(List<String> list, Context context) {
        this.list = list;
        this.context = context;
    }

    //改变背景方法
    public void changeSelectBackground(int pos){

        this.selectId = pos;

        notifyDataSetChanged();
    }


    @Override
    public int getCount() {
        return list.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 parent) {


        convertView = View.inflate(context, R.layout.item, null);

        TextView t = (TextView) convertView.findViewById(R.id.ttt);

        t.setText(list.get(position));

        /**
         * 如果点击的是此条目 则改变背景
         */
        if(position == selectId){
            t.setTextColor(Color.parseColor("#FFE13F5A"));
            convertView.setBackgroundColor(Color.parseColor("#d9d8dd"));
        }else {
            t.setTextColor(Color.parseColor("#000000"));
            convertView.setBackgroundColor(Color.parseColor("#ffffff"));
        }

        return convertView;
    }
}