我制作图库并尝试在滚动期间下载新图像，但不调用onScroll（）！当我启动片段时，onScroll（）被调用一次，但是当我滚动listView时，onScroll不起作用
public class FotoActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_filter);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new FotoFragment())
.commit();
}
}
public static class FotoFragment extends AbsListViewBaseFragment implements AbsListView.OnScrollListener {
private static final String CLIENT_ID = "7f38ead5152e46f1a42284c2d84b0862";
private static final String API_REQUEST = "cat";
private static final String API_URL = "https://api.instagram.com/v1";
static String downloadJsonUrl = API_URL + "/tags/" + API_REQUEST + "/media/recent?client_id=" + CLIENT_ID;
private ImageAdapter picAdapter;
ArrayList<String> picUrls = new ArrayList<String>();
GetImages getInstagramImages;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
picAdapter = new ImageAdapter();
getInstagramImages = new GetImages();
getInstagramImages.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fr_image_grid, container, false);
listView = (GridView) rootView.findViewById(R.id.grid);
((GridView) listView).setAdapter(picAdapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
}
});
listView.setOnScrollListener(this);
return rootView;
}
@Override
public void onScrollStateChanged(AbsListView absListView, int i) {
}
@Override
public void onScroll(AbsListView absListView, int firstVisible, int visibleCount, int totalCount) {
boolean loadMore = firstVisible + visibleCount >= totalCount;
if (loadMore == true && getInstagramImages.getStatus() == AsyncTask.Status.FINISHED) {
getInstagramImages = new GetImages();
getInstagramImages.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
}
}
protected class GetImages extends AsyncTask<Void, Void, ArrayList> {
@Override
protected ArrayList doInBackground(Void... voids) {
try {
picUrls = parseJson();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return picUrls;
}
@Override
protected void onPostExecute(ArrayList result) {
super.onPostExecute(result);
picAdapter.notifyDataSetChanged();
}
}
private InputStream downloadJSON(String stringUrl) throws IOException {
URL url = new URL(stringUrl);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setDoInput(true);
connection.connect();
return connection.getInputStream();
}
private ArrayList parseJson() throws IOException, JSONException {
InputStream inputStream = downloadJSON(downloadJsonUrl);
JSONObject jsonObject = (JSONObject) new JSONTokener(responseJSON).nextValue();
JSONArray jsonArray = jsonObject.getJSONArray("data");
for(int i = 0; i < jsonArray.length(); i ++){
JSONObject imageJsonObject = jsonArray.getJSONObject(i).getJSONObject("images").getJSONObject("standard_resolution");
picUrls.add(imageJsonObject.getString("url"));
}
downloadJsonUrl = jsonObject.getJSONObject("pagination").getString("next_url");
return picUrls;
}
}