小编los*_*tie的帖子

所以我有一个listview从基于Room的SQLite数据库中提取数据.它看起来很好地读取数据,但是当页面加载时我会得到前10个条目(显示的大小),当我尝试向下滚动列表视图时,它会重新开始并开始获取条目在列表的开头再次.屏幕截图上的红色圆圈显示了列表的顶部和底部以及存在的重复.

public class NeighborhoodListAdapter
    extends ArrayAdapter<LivingCity> {

    private List<LivingCity> neighborhood;
    Context context;

    // View lookup cache
    private static class ViewHolder {
        TextView cityName;
    }

    public NeighborhoodListAdapter(List<LivingCity> neighborhood, Context context) {
        super(context, R.layout.object_main_citydetailsrow, neighborhood);
        this.context = context;
        this.neighborhood = neighborhood;
    }

    @NonNull
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        // Get the data item for this position
        LivingCity city = getItem(position);
        ViewHolder viewHolder; 

        if (convertView == null) {

            viewHolder = new ViewHolder();
            LayoutInflater inflater = LayoutInflater.from(getContext());
            convertView = …

有时我会看到类似somevariable.value?.add()问号的目的是什么？（抱歉，在发布时，我不知道这是Kotlin，我以为是Java）