我是新手Android编程。我有Listview在Listview上显示，现在，我希望Listview在列表结束时加载更多项目。但数据没有附加。我需要帮助！
我的代码：
public class InfoTeacherFragment extends Fragment {
private String URL = "http://scv.udn.vn/dhdn/trdhsp/page/";
ProgressDialog pDialog;
Context mContext;
Vector<ArrayList<String>> data;
ArrayList<String> Name;
ArrayList<String> School;
ArrayList<String> Link;
ArrayList<String> Icon;
ListView lvItem;
DisplayImageOptions options;
ImageLoader imageloader;
View mFooterView;
InfoTeacher adapter;
ProgressBar loading;
int CurrentPage = 1;
int visibleThreshold = 3;
int startPage = 1;
boolean loadingMore = false;
public InfoTeacherFragment() {
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
options = new DisplayImageOptions.Builder()
.showImageOnLoading(R.drawable.ic_mission)
.showImageForEmptyUri(R.drawable.ic_empty)
.showImageOnFail(R.drawable.ic_error).cacheInMemory(true)
.cacheOnDisk(true).considerExifParams(true)
.bitmapConfig(Bitmap.Config.RGB_565).build();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.teacherinfo_layout,
container, false);
mContext = container.getContext();
lvItem = (ListView) rootView.findViewById(R.id.lvTeacher);
lvItem.setOnScrollListener(new EndlessScrollListener() {
@Override
public void onLoadMore(int page, int totalItemsCount) {
CurrentPage++;
customLoadMoreDataFromApi(CurrentPage);
Toast.makeText(mContext, "EndlessScrollListener",
Toast.LENGTH_SHORT).show();
}
});
imageloader = ImageLoader.getInstance();
imageloader.init(ImageLoaderConfiguration.createDefault(mContext));
if (Utils.isOnline(mContext) == true
&& Utils.KEY_CHECK_SUCCESS.equals("SUCCESS")) {
new LoadData().execute(URL + startPage);
lvItem.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapter, View view,
int position, long id) {
Intent intent = new Intent(mContext, NewsItemView.class);
if (Link != null) {
intent.putExtra("URL", Link.get(position));
startActivity(intent);
}
}
});
} else if (Utils.isOnline(mContext) == true
&& Utils.KEY_CHECK_SUCCESS.equals("FAIL")) {
Utils.MyToast(Utils.KEYWORK_ERROR[0], R.drawable.warning_icon,
mContext, false);
}
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
@Override
public void onDestroy() {
super.onDestroy();
AnimateFirstDisplayListener.displayedImages.clear();
}
class LoadData extends AsyncTask<String, Void, String> {
@Override
protected void onPreExecute() {
pDialog = ProgressDialog.show(mContext, "", Utils.KEYWORK_ERROR[2]);
data = new Vector<ArrayList<String>>();
Name = new ArrayList<String>();
School = new ArrayList<String>();
Link = new ArrayList<String>();
Icon = new ArrayList<String>();
super.onPreExecute();
}
@Override
protected String doInBackground(String... URL) {
data = Utils.getInformationTeacher(URL[0]);
if (!(data.isEmpty())) {
return Utils.KEY_CHECK_SUCCESS;
} else {
return Utils.KEY_CHECK_FAIL;
}
}
@Override
protected void onPostExecute(String result) {
if (result.equals(Utils.KEY_CHECK_SUCCESS)) {
pDialog.dismiss();
Name = data.get(0);
School = data.get(1);
Icon = data.get(2);
Link = data.get(3);
adapter = new InfoTeacher(mContext, Name, School, Icon);
lvItem.setAdapter(adapter);
} else if (result.equals(Utils.KEY_CHECK_FAIL)) {
pDialog.dismiss();
Utils.MyToast(Utils.KEYWORK_ERROR[0], R.drawable.warning_icon,
mContext, false);
}
super.onPostExecute(result);
}
}
class InfoTeacher extends BaseAdapter {
private ArrayList<String> Icon = new ArrayList<String>();
private ArrayList<String> Name = new ArrayList<String>();
private ArrayList<String> School = new ArrayList<String>();
private LayoutInflater inflater;
ImageLoadingListener animateFirstListener = new AnimateFirstDisplayListener();
public InfoTeacher(Context context, ArrayList<String> Name,
ArrayList<String> School, ArrayList<String> Icon) {
this.Name = Name;
this.Icon = Icon;
this.School = School;
Collections.reverse(Name);
Collections.reverse(School);
Collections.reverse(Icon);
inflater = LayoutInflater.from(getActivity());
}
@Override
public int getCount() {
return Name.size();
}
@Override
public Object getItem(int position) {
return position;
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(int position, View view, ViewGroup arg2) {
View rowView = view;
ViewHolder holder;
if (rowView == null) {
holder = new ViewHolder();
rowView = inflater
.inflate(R.layout.teacher_layout, arg2, false);
holder.Name = (TextView) rowView
.findViewById(R.id.tv_NameTeacher);
holder.School = (TextView) rowView.findViewById(R.id.tv_School);
holder.ic_naviga = (ImageView) rowView
.findViewById(R.id.ivNaviga);
holder.icon = (ImageView) rowView
.findViewById(R.id.iv_IconTeacher);
rowView.setTag(holder);
} else
holder = (ViewHolder) view.getTag();
final String mIcon = Icon.get(position);
holder.Name.setText(Name.get(position).toString());
holder.School.setText(School.get(position).toString());
ImageLoader.getInstance().displayImage(mIcon, holder.icon, options,
animateFirstListener);
return rowView;
}
}
static class ViewHolder {
ImageView icon;
TextView Name;
TextView School;
ImageView ic_naviga;
}
private static class AnimateFirstDisplayListener extends
SimpleImageLoadingListener {
static final List<String> displayedImages = Collections
.synchronizedList(new LinkedList<String>());
@Override
public void onLoadingComplete(String imageUri, View view,
Bitmap loadedImage) {
if (loadedImage != null) {
ImageView imageView = (ImageView) view;
boolean firstDisplay = !displayedImages.contains(imageUri);
if (firstDisplay) {
FadeInBitmapDisplayer.animate(imageView, 500);
displayedImages.add(imageUri);
}
}
}
}
public void customLoadMoreDataFromApi(int page) {
new LoadData().execute(URL + page);
adapter.notifyDataSetChanged();
// This method probably sends out a network request and appends new data
// items to your adapter.
// Use the offset value and add it as a parameter to your API request to
// retrieve paginated data.
// Deserialize API response and then construct new objects to append to
// the adapter
}
class LoadMoreItemsList extends
AsyncTask<Void, Void, Vector<ArrayList<String>>> {
private LoadMoreItemsList() {
loadingMore = true;
mFooterView = LayoutInflater.from(mContext).inflate(
R.layout.loading_view, null);
}
@Override
protected void onPreExecute() {
lvItem.addFooterView(mFooterView);
lvItem.setAdapter(adapter);
super.onPreExecute();
}
@Override
protected Vector<ArrayList<String>> doInBackground(Void... params) {
return null;
}
@Override
protected void onPostExecute(Vector<ArrayList<String>> result) {
super.onPostExecute(result);
}
}
}
功能Utils.Utils.getInformationTeacher(URL[0])：
public static Vector<ArrayList<String>> getInformationTeacher(String url) {
Vector<ArrayList<String>> data = new Vector<ArrayList<String>>();
ArrayList<String> Name = new ArrayList<String>();
ArrayList<String> School = new ArrayList<String>();
ArrayList<String> Link = new ArrayList<String>();
ArrayList<String> Icon = new ArrayList<String>();
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
.permitAll().build();
StrictMode.setThreadPolicy(policy);
try {
Document doc = Jsoup.connect(url).timeout(10 * 300).get();
Charset.forName("UTF-8");
doc.outputSettings().escapeMode(EscapeMode.xhtml);
Elements eles = doc.select("div#Thu tbody a.linkheader");
Elements elesIcon = doc.select("div#Thu img[src]");
int i = 0;
for (Element element : eles) {
i++;
String fillinfo = element.ownText();
String link = element.attr("href");
if (i % 2 == 0) {
School.add(fillinfo);
} else {
Name.add(fillinfo);
Link.add(link);
}
}
for (Element icon : elesIcon) {
String hrefIcon = icon.attr("src");
Icon.add(hrefIcon);
}
data.add(Name);
data.add(School);
data.add(Icon);
data.add(Link);
} catch (IOException e) {
return data;
}
}
return data;
}
最后：摘要EndlessScrollListener
package android.readnews.support;
import android.util.Log;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
public abstract class EndlessScrollListener implements OnScrollListener {
// The minimum amount of items to have below your current scroll position
// before loading more.
private int visibleThreshold = 5;
// The current offset index of data you have loaded
private int currentPage = 0;
// The total number of items in the dataset after the last load
private int previousTotalItemCount = 0;
// True if we are still waiting for the last set of data to load.
private boolean loading = true;
// Sets the starting page index
private int startingPageIndex = 0;
public EndlessScrollListener() {
}
public EndlessScrollListener(int visibleThreshold) {
this.visibleThreshold = visibleThreshold;
}
public EndlessScrollListener(int visibleThreshold, int startPage) {
this.visibleThreshold = visibleThreshold;
this.startingPageIndex = startPage;
this.currentPage = startPage;
}
// This happens many times a second during a scroll, so be wary of the code
// you place here.
// We are given a few useful parameters to help us work out if we need to
// load some more data,
// but first we check if we are waiting for the previous load to finish.
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// If the total item count is zero and the previous isn't, assume the
// list is invalidated and should be reset back to initial state
if (totalItemCount < previousTotalItemCount) {
Log.i("abc", "ABC + totalItemCount < previousTotalItemCount");
this.currentPage = this.startingPageIndex;
this.previousTotalItemCount = totalItemCount;
if (totalItemCount == 0) {
this.loading = true;
}
}
// If it’s still loading, we check to see if the dataset count has
// changed, if so we conclude it has finished loading and update the
// current page
// number and total item count.
if (loading && (totalItemCount > previousTotalItemCount)) {
Log.i("abc", "ABC + totalItemCount > previousTotalItemCount");
loading = false;
previousTotalItemCount = totalItemCount;
currentPage++;
}
// If it isn’t currently loading, we check to see if we have breached
// the visibleThreshold and need to reload more data.
// If we do need to reload some more data, we execute onLoadMore to
// fetch the data.
if (!loading
&& (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
Log.i("abc", "ABC + !loading");
onLoadMore(currentPage + 1, totalItemCount);
loading = true;
}
}
// Defines the process for actually loading more data based on page
public abstract void onLoadMore(int page, int totalItemsCount);
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// Don't take any action on changed
}
}
答案 0 :(得分：1)
在LoadData AsyncTask中，在onPostExecute中，您始终使用收到的新数据重新创建适配器，因此它不会附加现有数据。
您需要做的是向InfoTeacher适配器添加一个方法，以便将新项目附加到现有数据，然后如果适配器已经存在，则从onPostExecute调用该方法（适配器！= null）。