【ListView】滚动且加载数据

public class ListBaseAdapter extends BaseAdapter {
    
    private Context context;
    private ArrayList<String> list;
    public int count = 30;
    
    public ListBaseAdapter (Context context, ArrayList<String> list ) {
        this.context = context;
        this.list = list;
         
    }
    @Override
    public int getCount() {
        return count;
    }
    @Override
    public Object getItem(int item) {
        return item;
    }
    @Override
    public long getItemId(int id) {
        return id;
    }
    @Override
    public View getView(int arg0, View view, ViewGroup arg2) {
        ViewHolder viewHolder;
        if (view == null) {
            viewHolder = new ViewHolder();
            view = View.inflate(context, R.layout.activity_main_item, null);
            viewHolder.tv = (TextView) view.findViewById(R.id.tv_01);
            view.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) view.getTag();  
        }
        viewHolder.tv.setText(list.get(arg0)+"");
        return view;
    }
    private class ViewHolder{
        TextView tv;
    }

}

public class MainActivity extends Activity {
    
    private ListView lv;
    private ArrayList<String> list;
    private int lastitem = 0;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) this.findViewById(R.id.listview01);
        
        loadData(); 
        
        final ListBaseAdapter listAdapter = new ListBaseAdapter(MainActivity.this, list);
        lv.setAdapter(listAdapter);
        lv.setOnScrollListener(new OnScrollListener() {
            @Override
            public void onScroll(AbsListView view, int firstVisibleItem,
                    int visibleItemCount, int totalItemCount) {
                lastitem = totalItemCount;
                //Log.i("QQQ", "lastitem.111.." + lastitem);
            }
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                //Log.i("QQQ", "lastitem.222.." + lastitem);
                if (lastitem != 100) {
                    if (lastitem == listAdapter.count
                            && scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
                        listAdapter.count += 10;
                        listAdapter.notifyDataSetChanged();
                    }
                } else {
                    Toast.makeText(getApplicationContext(), "啦啦啦啦", 1).show();
                }
            }
        });
    }
    
    private void loadData() {
        list = new ArrayList<String>();
        for (int i=0; i<100; i++) {
            list.add("张三"+i);
        }
        
    }


}