我使用离子库从服务器接收数据。我有问题，我的代码多次发出获取请求，所以我的列表中有数据重复。我的适配器代码：
public class ArticleAdapter extends ArrayAdapter<Article> {
Future<List<Article>> loadingOfPrevious;
static class ArticleHolder {
ImageView articleImage;
TextView articleCaption;
}
@Override
public View getView(int position, View convertView, ViewGroup parent) {
ArticleHolder holder;
if (convertView == null) {
convertView = layoutInflater.inflate(R.layout.list_view_item, null);
holder = new ArticleHolder();
holder.articleImage = (ImageView) convertView.findViewById(R.id.articleImage);
holder.articleCaption = (TextView) convertView.findViewById(R.id.articleCaption);
convertView.setTag(holder);
} else {
holder = (ArticleHolder) convertView.getTag();
}
Article article = getItem(position);
holder.articleCaption.setText(article.getTitle());
Ion.with(holder.articleImage)
.placeholder(R.drawable.placeholder)
.error(R.drawable.default_article_image)
//.crossfade(true)
.load(article.getImageUrl());
// we're near the end of the list adapter, so load more items
if (position >= getCount() - 3) {
loadPrevious(getItem(getCount() - 1).getId());
}
return convertView;
}
private void loadPrevious(long id) {
// don't attempt to load more if a load is already in progress
if (loadingOfPrevious != null && !loadingOfPrevious.isDone() && !loadingOfPrevious.isCancelled()) {
return;
}
String url = "http://example.com/rest-api/"
url = url + "?id=" + id;
url = url + "&count=" + 30;
// This request loads a URL as JsonArray and invokes
// a callback on completion.
final String articleUrl = url;
loadingOfLatest = Ion.with(getContext())
.load(articleUrl)
.as(new TypeToken<List<Article>>() {
})
.setCallback(new FutureCallback<List<Article>>() {
@Override
public void onCompleted(Exception e, List<Article> result) {
// this is called back onto the ui thread, no Activity.runOnUiThread or Handler.post necessary.
if (e != null) {
Toast.makeText(getContext(), "Error.", Toast.LENGTH_LONG).show();
return;
}
// add the article
if (result != null) {
Collections.reverse(result);
for (int i = 0; i < result.size(); i++) {
add(result.get(i));
}
notifyDataSetChanged();
}
}
});
}
}
我认为问题出在这部分：
// we're near the end of the list adapter, so load more items
if (position >= getCount() - 3) {
loadPrevious(getItem(getCount() - 1).getId());
}