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我知道有很多關於計算器這個問題的例子，但我不知道如何實現我的代碼中的任何人。追加更多的項目listfragment上滾動結束
我想要做的就是從json url（第15個元素）加載數據，並將它們追加到listfragment中，當用戶向下滾動到列表的末尾時，再追加15個元素（列表上共有30個元素）等..
我現在可以正確讀取前15個元素，但是當我嘗試添加更多項目，當用戶到達滾動的結束，我不知道該怎麼辦......這裏是我的代碼：
在MainActivity我有以下的類延伸listfragment：
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;
}
}
更具體地，當用戶到達滾動下面的代碼將觸發的其中裝載多個端來自json url的數據：
@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);
}
}
那麼會的getJSON光潔度提取和解析數據後調用以下方法：
@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 {
}
}
所以如果當前頁不等於一個，我想附加更多的數據。如何實現這一目標？