我想做一些事情。我希望在ListView
中实现延迟加载。我的ListView
包含超过10,000条仅为TextView
的数据,所以当我启动列表活动时,我不能一次性加载所有数据,这不太有效率。因此,我只能在列表中加载前20或30个项目。当我滚动到ListView
的某一行时,再去加载相应的数据。当我到达ListView
的索引的最后一个时,我会将进度条放置在那里,并提示新数据已加载,此时会加载新的数据并将其与上一个索引相加。怎么做呢?
我想做一些事情。我希望在ListView
中实现延迟加载。我的ListView
包含超过10,000条仅为TextView
的数据,所以当我启动列表活动时,我不能一次性加载所有数据,这不太有效率。因此,我只能在列表中加载前20或30个项目。当我滚动到ListView
的某一行时,再去加载相应的数据。当我到达ListView
的索引的最后一个时,我会将进度条放置在那里,并提示新数据已加载,此时会加载新的数据并将其与上一个索引相加。怎么做呢?
public abstract class LazyLoader implements AbsListView.OnScrollListener {
private static final int DEFAULT_THRESHOLD = 10 ;
private boolean loading = true ;
private int previousTotal = 0 ;
private int threshold = DEFAULT_THRESHOLD ;
public LazyLoader() {}
public LazyLoader(int threshold) {
this.threshold = threshold;
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if(loading) {
if(totalItemCount > previousTotal) {
// the loading has finished
loading = false ;
previousTotal = totalItemCount ;
}
}
// check if the List needs more data
if(!loading && ((firstVisibleItem + visibleItemCount ) >= (totalItemCount - threshold))) {
loading = true ;
// List needs more data. Go fetch !!
loadMore(view, firstVisibleItem,
visibleItemCount, totalItemCount);
}
}
// Called when the user is nearing the end of the ListView
// and the ListView is ready to add more items.
public abstract void loadMore(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount);
}
活动:
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main_layout);
ListView listView = (ListView) findViewById(R.id.listView);
listView.setOnScrollListener(new LazyLoader() {
@Override
public void loadMore(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
// Fetch your data here !!!
}
});
}
}
让您的列表滚动更快:
getView
方法中使用的条件数量。//放在调用函数中:
@Override
public View onCreateView(android.view.LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
ScrollListener scrollListener = new ScrollListener();
listView.setOnScrollListener(scrollListener);
}
还有内部类:
class ScrollListener implements OnScrollListener
{
@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount)
{
int size = searchedPeople.size();
if(isScrolled && totalItemCount != 0 && size < totalPeoples)
{
if(firstVisibleItem + visibleItemCount >= totalItemCount)
{
yourfunction(size, size + limit); // call service in your functioin
isScrolled = false;
}
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState)
{
}
}