listview滚动到底部自动加载数据

在android中listvieww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加载就变的慢,如果是有图片的话,一时浪费流量,二是item中带图片会出现错位的问题,listview加载数据目前好多app做法

一：分批加载 滑动到底部自动更新

二：滑动到底部 手动的点击加载更多

三：下拉刷新+底部加载更多

今天就讲下listview滑动到底部自动更新

分析：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

代码如下：

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;
		}
	}
}