[转]ListView滚动到底部自动加载数据

转自：http://blog.csdn.net/shineflowers/article/details/41744241

在Android中有很多时候会选择用ListView加载数据，有的是分批加载，比如每次加载20条，100条就要加载5次，如果一次性加载100条，ListView加载就会变慢，如果是有图片的话，一是浪费流量，二是item中带图片会出现错位的问题l，ListView加载数据目前好多App的做法

1. 分批加载，滑动到底部自动更新

2. 滑动到底部，手动的点击加载更多

3. 下拉刷新 + 底部加载更多

今天实现ListView滑动到底部自动更新的效果。

原理：监听ListView的滑动事件,判断ListView是否滑动到底部,然后去加载数据。

public class MainActivity extends Activity {
    private ListView listview;
    private List<String> datas;
    private LayoutInflater inflater;
    private MyAdapter adapter;
    private List<String>  contents;
    private int count = 0;
    private View footView;
    private Handler handler = new Handler();
    int lastItem;
    private RelativeLayout loading;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();
        inflater = LayoutInflater.from(this);
        listview = (ListView) findViewById(R.id.listview);
        adapter = new MyAdapter();
        footView = inflater.inflate(R.layout.footer, null);
        loading = (RelativeLayout) footView.findViewById(R.id.loading);
        //listview的addFooterView()添加view到listview底部一定要加在listview.setAdapter(adapter);这代码前面
        listview.addFooterView(footView);
        listview.setAdapter(adapter);
        //添加listview滚动监听
        listview.setOnScrollListener(new OnScrollListener() {
            //AbsListView view 这个view对象就是listview
            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                if (scrollState == OnScrollListener.SCROLL_STATE_IDLE) {
                    if (view.getLastVisiblePosition() == view.getCount() - 1) {
                        loadData();
                    }
                }
            }
            @Override
            public void onScroll(AbsListView view, int firstVisibleItem,
                    int visibleItemCount, int totalItemCount) {
                   lastItem = firstVisibleItem + visibleItemCount - 1 ;
            }
        });
    }
    protected void loadData() {
        loading.setVisibility(View.VISIBLE);
        handler.postDelayed(new Runnable() {
            @Override
            public void run() {
                 load();
                 loading.setVisibility(View.GONE);
                 adapter.notifyDataSetChanged();
            }
        }, 5000);
    }
    protected void load() {
        int count=adapter.getCount()+1;
        for(int i=count;i<count+20;i++){
             contents.add("加载数据:::"+i);
        }
    }
    private void initData() {
        contents = new ArrayList<String>();
        for(int i=1;i<20;i++){
            contents.add("加载数据:::"+i);
        }
    }
    
    class MyAdapter extends BaseAdapter{
        @Override
        public int getCount() {
            return contents.size();
        }
        @Override
        public Object getItem(int position) {
            return contents.get(position);
        }

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

        @Override
        public View getView(int position, View convertView, ViewGroup parent) {
            ViewHolder holder;
            if(convertView==null){
                convertView = inflater.inflate(R.layout.item, parent, false);
                holder = new ViewHolder();
                holder.tvContent = (TextView) convertView.findViewById(R.id.tvContent);
                convertView.setTag(holder);
            }else{
                holder = (ViewHolder) convertView.getTag();
            }
            holder.tvContent.setText(contents.get(position));
            return convertView;
        }
        class ViewHolder{
            TextView tvContent;
        }
    }
}