I worked JSON. I have two classes (private class LoadDataToServer extends AsyncTask and class loadMoreListView extends AsyncTask) in the first grade, I parsing JSON and show item in the ListView and the second class, I'm trying to load multiple items. my problem is when I call the new loadMoreListView (). execute (); .. on listView.setOnScrollListener there is an error. my problem is adapter this is my code
private class loadMoreListView extends AsyncTask>> {
@Override
protected void onPreExecute() {
pd.show();
}
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
Void... params) {
jsonparser = new JSONParser();
URL = "http://bri.ge/api/getList.aspx?count=2&time=" + dateTime;
jsonarray = new JSONArray();
JSONObject jsonobject = jsonparser.getJSONfromURL(URL);
try {
jsonarray = jsonobject.getJSONArray("data");
for (int i = 0; i < jsonarray.length(); i++) {
jsonobject = jsonarray.getJSONObject(i);
HashMap<String, String> map = new HashMap<String, String>();
map.put("journal", jsonobject.getString(KEY_journal));
map.put("image", jsonobject.getString(KEY_image));
map.put("title", jsonobject.getString(KEY_title));
map.put("description",
jsonobject.getString(KEY_description));
map.put("JournalID", KEY_JournalID);
map.put("pubDate", jsonobject.getString(KEY_pubDate));
Content cont = new Content(jsonobject.getString("journal"),
jsonobject.getString("image"),
jsonobject.getString("title"),
jsonobject.getString("pubDate"),
jsonobject.getString("description"),
jsonobject.getInt("JournalID"));
contents.add(cont);
itemList.add(map);
}
// adapter.notifyDataSetChanged();
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
dateTime = itemList.get(itemList.size() - 1).get(KEY_pubDate);
return itemList;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
super.onPostExecute(result);
if (pd.isShowing()) {
pd.dismiss();
try {
// itemList.clear();
int currentPosition = list.getFirstVisiblePosition();
// Appending new data to menuItems ArrayList
adapter = new LazyAdapter(MainActivity.this, itemList);
adapter.notifyDataSetChanged();
list.setAdapter(adapter);
// list.add
// Setting new scroll position
list.setSelectionFromTop(currentPosition + 1, 0);
} catch (NullPointerException e) {
e.printStackTrace();
}
}
}
}
private class LoadDataToServer extends AsyncTask>> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pd.show();
}
@Override
protected ArrayList<HashMap<String, String>> doInBackground(
Void... params) {
jsonparser = new JSONParser();
@SuppressWarnings("static-access")
JSONObject jsonobject = jsonparser.getJSONfromURL(URL);
try {
jsonarray = jsonobject.getJSONArray("data");
for (int i = 0; i < jsonarray.length(); i++) {
jsonobject = jsonarray.getJSONObject(i);
HashMap<String, String> map = new HashMap<String, String>();
map.put("journal", jsonobject.getString(KEY_journal));
map.put("image", jsonobject.getString(KEY_image));
map.put("title", jsonobject.getString(KEY_title));
map.put("description",
jsonobject.getString(KEY_description));
map.put("JournalID", KEY_JournalID);
map.put("pubDate", jsonobject.getString(KEY_pubDate));
// contents = new ArrayList<Content>();
Content cont = new Content(jsonobject.getString("journal"),
jsonobject.getString("image"),
jsonobject.getString("title"),
jsonobject.getString("pubDate"),
jsonobject.getString("description"),
jsonobject.getInt("JournalID"));
contents.add(cont);
itemList.add(map);
}
} catch (JSONException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
dateTime = itemList.get(itemList.size() - 1).get(KEY_pubDate);
return itemList;
}
@Override
protected void onPostExecute(ArrayList<HashMap<String, String>> result) {
super.onPostExecute(result);
pd.dismiss();
// itemList.clear();
// Appending new data to menuItems ArrayList
adapter = new LazyAdapter(MainActivity.this, itemList);
adapter.notifyDataSetChanged();
list.setAdapter(adapter);
// list.add
// Setting new scroll position
}
}
list.setOnScrollListener(new OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
if (scrollState == 0) {
// new loadMoreListView().execute();
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
final int lastItem = firstVisibleItem + visibleItemCount;
if (lastItem == totalItemCount) {
new loadMoreListView().execute();
}
}
});
see i guess somewhere in your network call (Async task) your "itemList" get updated without notifying adapter. because you are adding item in "doInBackGround" which is on different thread.
I would suggest you to use these two library for making REST network call and json parsing . this is efficient in terms of memory and performance.
Android Asynchronous Http Client
these are open source . for any query ask me.
When you get new data then after setting data to adapter please call adapter.notifyDataSetChanged(); That will notify the list that the data in adapter is changed
hope this will help
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