ListView在滚动底部加载更多 [英] ListView load more on scroll bottom
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问题描述
在MainActivity中，我创建了DownloadTask，该模型填充了模型类，然后通过CustomListAdapter类填充了listview，但是我创建了识别滚动结束的函数，并且希望将更多项目加载到listview中.我正在阅读和查看Internet上的代码，但由于它与众不同，因此无法解决该问题. MainActivity类
In MainActivity I create the DownloadTask which populate model class then listview via CustomListAdapter class but I created the function to recognize end of scroll and I want to load more items to the listview. I was reading and looking at code on internet but I can't figure it out to solve this because its a kind different. The MainActivity class
public void updateList() {
adap = new CustomListAdapter(this, feedList, null);
feedListView.setAdapter(adap);
feedListView.setOnScrollListener(new OnScrollListener() {
public void onScrollStateChanged(AbsListView view,
int scrollState) { // TODO Auto-generated method stub
int threshold = 1;
int count = feedListView.getCount();
if (scrollState == SCROLL_STATE_IDLE) {
if (feedListView.getLastVisiblePosition() >= count
- threshold) {
mHandler = new Handler();
mIsLoading = true;
Toast.makeText(getApplicationContext(), "END", Toast.LENGTH_LONG).show();
}
}
}
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
}
});
}
public class DownloadFilesTask extends AsyncTask<String, Integer, Void> {
@Override
protected void onProgressUpdate(Integer... values) {
}
@Override
protected void onPostExecute(Void result) {
if (null != feedList) {
updateList();
}
if (progressbar.isShown()) {
progressbar.setVisibility(View.INVISIBLE);
}
}
@Override
protected Void doInBackground(String... params) {
String url = params[0];
// getting JSON string from URL
JSONObject json = getJSONFromUrl(url);
//parsing json data
parseJson(json);
return null;
}}
public JSONObject getJSONFromUrl(String url) {
InputStream is = null;
JSONObject jObj = null;
String json = null;
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
public void parseJson(JSONObject json) {
try {
// parsing json object
if (json.getString("status").equalsIgnoreCase("ok")) {
JSONArray posts = json.getJSONArray("posts");
feedList = new ArrayList<FeedItem>();
for (int i = 0; i < posts.length(); i++) {
JSONObject post = (JSONObject) posts.getJSONObject(i);
FeedItem item = new FeedItem();
/////.....
feedList.add(item);
}
}
} catch (JSONException e) {
e.printStackTrace();
}
}
CustomListAdapter
CustomListAdapter
public class CustomListAdapter extends BaseAdapter
{
private int mCount = 25;
private ArrayList<FeedItem> listData;
private LayoutInflater layoutInflater;
private Context mContext;
private ArrayList<String> data;
protected ListView feedListView;
public CustomListAdapter( Context context, ArrayList<FeedItem> listData)
{
this.listData = listData;
layoutInflater = (LayoutInflater) context
.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
mContext = context;
}
public void addMoreItems(int count) {
mCount += count;
notifyDataSetChanged();
}
@Override
public int getCount()
{
return mCount;
}
@Override
public Object getItem(int position)
{
return position;
}
@Override
public long getItemId(int position)
{
return position;
}
public View getView( int position, View convertView, ViewGroup parent)
{
final ViewHolder holder;
View row=convertView;
if ((row == null) || (row.getTag()==null)) {
convertView = layoutInflater.inflate(R.layout.list_row_layout, null);
holder = new ViewHolder();
////
convertView.setTag(holder);
}
else
{
holder = (ViewHolder) convertView.getTag();
}
final FeedItem newsItem = (FeedItem) listData.get(position);
/////
return convertView;
}
static class ViewHolder
{
////
}
}
当我到达底部时，就创建了吐司.
When I reach the bottom the toast is created.
推荐答案
@Override
public void onScrollStateChanged(int scrollState) {
// TODO Auto-generated method stub
if(scrollState==RecyclerView.SCROLL_STATE_IDLE){
visibleItemCount = mLayoutManager.getChildCount();
totalItemCount = mLayoutManager.getItemCount();
firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition();
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
}
}
if (!loading && (totalItemCount - visibleThreshold) <= (firstVisibleItem + visibleItemCount)) {
Log.v("scroll","Last Item Wow !");
if(footerView.getVisibility()!=View.VISIBLE){
footerView.setVisibility(View.VISIBLE);
}
refreshExpListViewData();
}
}
}
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