ListView滚动到底部自动加载数据

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++) {  //每次加载20条数据                   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;                }            }        }