在滚动结束时将更多项目附加到 listfragment
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【中文标题】在滚动结束时将更多项目附加到 listfragment【英文标题】：append more items to listfragment on scroll end 【发布时间】：2014-03-14 20:54:40 【问题描述】：我知道在 *** 上有很多关于这个问题的例子，但我不知道如何在我的代码中实现它们中的任何一个。
我想要做的是从 json url 加载数据（前 15 个元素），并将它们附加到 listfragment 并且当用户向下滚动到列表末尾时附加另外 15 个元素（列表中总共 30 个元素）等等..
现在我可以正确获取前 15 个元素，但是当我尝试在用户到达滚动末尾时添加更多项目时，我不知道该怎么做......这是我的代码：
在 MainActivity 我有以下扩展 listfragment 的类：
public static class NewsFragment extends ListFragment implements ILoadDataListener, OnScrollListener
private ListView listView;
private NewsAdapter newsAdapter;
private int currentPage=1;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceStatee)
View rootView = inflater.inflate(R.layout.fragment_news, container, false);
listView = (ListView) rootView.findViewById(android.R.id.list);
return rootView;
@Override
public void onActivityCreated(Bundle savedInstanceState)
super.onActivityCreated(savedInstanceState);
getListView().setOnScrollListener( this);
// URL to the JSON data
String strUrl = "http://opetmar.hostzi.com/test.php";
// Creating a new non-ui thread task to download json data
ProgressDialog progress = new ProgressDialog(getActivity());
progress.setMessage("loading ...");
GetJSON downloadTask = new GetJSON(this , progress , "news");
// Starting the download process
downloadTask.execute(strUrl);
@Override
public void onComplete(String[] titles , String[] images , String[] ids , String[] snippets , String[] data)
if ( currentPage == 1 )
newsAdapter = new NewsAdapter( getActivity() , titles , images , ids , snippets , data );
listView.setAdapter(newsAdapter);
else
@Override
public void onListItemClick(ListView l, View v, int position, long id)
super.onListItemClick(l, v, position, id);
DataHolder holder;
holder = (DataHolder) v.getTag();
Intent myIntent = new Intent(getActivity(), NewsOpen.class);
myIntent.putExtra("image", holder.image);
myIntent.putExtra("data", holder.data);
startActivity(myIntent);
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount)
@Override
public void onScrollStateChanged(AbsListView listView, int scrollState)
if (scrollState == SCROLL_STATE_IDLE)
if (listView.getLastVisiblePosition() >= listView.getCount() - 1 )
currentPage++;
String strUrl = "http://opetmar.hostzi.com/test.php?page="+currentPage;
ProgressDialog progress = new ProgressDialog(getActivity());
progress.setMessage("loading ...");
GetJSON downloadTask = new GetJSON(this , progress , "news");
// Starting the download process
downloadTask.execute(strUrl);
NewsAdapter.java
public class NewsAdapter extends ArrayAdapter<String>
private final Context context;
private final String[] titles;
private final String[] images;
private final String[] ids;
private final String[] snippets;
private final String[] data;
public NewsAdapter(Context context, String[] titles, String[] images , String[] ids , String[] snippets , String[] data)
super(context, R.layout.drawer_list_item, titles);
this.context = context;
this.titles = titles;
this.images = images;
this.ids = ids;
this.snippets = snippets;
this.data = data;
@Override
public View getView(int position, View convertView, ViewGroup parent)
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View rowView = inflater.inflate(R.layout.news_list_item, parent, false);
TextView title = (TextView) rowView.findViewById(R.id.news_title);
TextView snippet = (TextView) rowView.findViewById(R.id.news_snippet);
ImageView imageView = (ImageView) rowView.findViewById(R.id.news_thumble);
title.setText(titles[position]);
snippet.setText(snippets[position]);
DataHolder holder = new DataHolder();
holder.data=data[position];
holder.image=images[position];
rowView.setTag(holder);
new DownloadImageTask(imageView).execute(images[position]);
return rowView;
public class DataHolder
String image;
String data;
GetJSON.java
/** AsyncTask to download json data */
public class GetJSON extends AsyncTask<String, Integer, String>
String data = null;
private ListView listView;
private NewsAdapter newsAdapter;
private ILoadDataListener mListener;
private ProgressDialog progress;
private String type;
public GetJSON(ILoadDataListener listener , ProgressDialog progress , String type)
this.mListener = listener;
this.progress = progress;
this.type = type;
public void onPreExecute()
progress.show();
@Override
protected String doInBackground(String... url)
try
data = downloadUrl(url[0]);
catch(Exception e)
Log.d("Background Task",e.toString());
return data;
@Override
protected void onPostExecute(String result)
if (result != null)
if (this.type == "news")
try
JSONObject jObject;
jObject = new JSONObject(result);
JSONArray jCountries = jObject.optJSONArray("news");
ArrayList<String> stringArrayList = new ArrayList<String>();
ArrayList<String> stringArrayList2 = new ArrayList<String>();
ArrayList<String> stringArrayList3 = new ArrayList<String>();
ArrayList<String> stringArrayList4 = new ArrayList<String>();
ArrayList<String> stringArrayList5 = new ArrayList<String>();
for (int i=0; i < jCountries.length(); i++)
try
JSONObject oneObject = jCountries.getJSONObject(i);
// Pulling items from the array
stringArrayList.add(oneObject.getString("title"));
stringArrayList2.add( oneObject.getString("image"));
stringArrayList3.add( oneObject.getString("id"));
stringArrayList4.add( oneObject.getString("snippet"));
stringArrayList5.add( oneObject.getString("data"));
catch (JSONException e)
// Oops
String [] stringArray = stringArrayList.toArray(new String[stringArrayList.size()]);
String [] stringArray2 = stringArrayList2.toArray(new String[stringArrayList2.size()]);
String [] stringArray3 = stringArrayList3.toArray(new String[stringArrayList3.size()]);
String [] stringArray4 = stringArrayList4.toArray(new String[stringArrayList4.size()]);
String [] stringArray5 = stringArrayList5.toArray(new String[stringArrayList5.size()]);
progress.dismiss();
if (mListener != null)
mListener.onComplete(stringArray , stringArray2 , stringArray3 , stringArray4 , stringArray5);
catch (JSONException e)
e.printStackTrace();
else
Log.e("ServiceHandler", "Couldn't get any data from the url");
/** A method to download json data from url */
private String downloadUrl(String strUrl) throws IOException
String data = "";
InputStream iStream = null;
try
URL url = new URL(strUrl);
// Creating an http connection to communicate with url
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
// Connecting to url
urlConnection.connect();
// Reading data from url
iStream = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(iStream));
StringBuffer sb = new StringBuffer();
String line = "";
while( ( line = br.readLine()) != null)
sb.append(line);
data = sb.toString();
br.close();
catch(Exception e)
Log.d("Exception while downloading url", e.toString());
finally
iStream.close();
return data;
更具体地说，当用户到达滚动结束时，将触发以下代码，从 json url 加载更多数据：
@Override
public void onScrollStateChanged(AbsListView listView, int scrollState)
if (scrollState == SCROLL_STATE_IDLE)
if (listView.getLastVisiblePosition() >= listView.getCount() - 1 )
currentPage++;
String strUrl = "http://opetmar.hostzi.com/test.php?page="+currentPage;
ProgressDialog progress = new ProgressDialog(getActivity());
progress.setMessage("loading ...");
GetJSON downloadTask = new GetJSON(this , progress , "news");
// Starting the download process
downloadTask.execute(strUrl);
那么GetJSON会在完成获取和解析数据后调用如下方法：
@Override
public void onComplete(String[] titles , String[] images , String[] ids , String[] snippets , String[] data)
if ( currentPage == 1 )
newsAdapter = new NewsAdapter( getActivity() , titles , images , ids , snippets , data );
listView.setAdapter(newsAdapter);
else
所以如果 currentpage 不等于一，我想追加更多数据。如何做到这一点？
【问题讨论】：
【参考方案1】：我不确定 ListView 是否可以，但使用 Gallery 你可以覆盖
public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY);
并使用它来定义项目滚动到末尾时的事件。我这样做是为了在图库中组织无限的日历 ietms 列表。
问候，
亚历克斯。
【讨论】：
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