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，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。

[java] view
plaincopyprint?

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;

}

}

}