我有一个listview，可以从parse.com检索数据。我添加了一个onscroll监听器，首先加载20个项目，当用户滚动到结束时（即20），显示一个加载页脚，接下来显示20个项目，直到列表结束 但我面临以下问题 1}不显示加载页脚 2}当滚动到达我的情况50列表的末尾时，仍然执行onscroll 3}当滚动回到顶部时，滚动不顺畅，它就像一次又一次地卡在同一个列表项
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我的代码
public class InterActivity extends Activity implements OnItemClickListener, OnItemLongClickListener
{
ListView listview;
List<ParseObject> ob;
ProgressDialog mProgressDialog;
FinalAdapter adapter;
List<CodeList> codelist = null;
SharedPreference shrdPreference;
boolean loadingMore = false;
private int limit = 20;
View footerView;
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.inter_layout);
shrdPreference = new SharedPreference();
footerView = ((LayoutInflater) getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE)).inflate(R.layout.loadmore, null, false);
//Execute RemoteDataTask AsyncTask
new RemoteDataTask().execute();
}
private class RemoteDataTask extends AsyncTask<Void, Void, Void> {
@Override
protected void onPreExecute() {
super.onPreExecute();
// Create a progressdialog
mProgressDialog = new ProgressDialog(InterActivity.this);
// Set progressdialog title
mProgressDialog.setTitle("Loading");
// Set progressdialog message
mProgressDialog.setMessage("Please wait loading ...");
mProgressDialog.setIndeterminate(false);
mProgressDialog.setCancelable(false);
// Show progressdialog
mProgressDialog.show();
}
@Override
protected Void doInBackground(Void... params) {
// Create the array
codelist = new ArrayList<CodeList>();
try {
// Locate the class table named "Country" in Parse.com
ParseQuery<ParseObject> query = new ParseQuery<ParseObject>(
"InterActivity");
// Locate the column named "ranknum" in Parse.com and order list
// by ascending
query.orderByAscending("_created_at");
query.setLimit(limit);
ob = query.find();
for (ParseObject inter : ob) {
CodeList map = new CodeList();
map.setIntroduction((String) inter.get("intro"));
map.setFinalCodeText((String) inter.get("codetext"));
codelist.add(map);
}
} catch (ParseException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
// Locate the listview in listview_main.xml
listview = (ListView) findViewById(R.id.inter_layoutListView);
// Pass the results into ListViewAdapter.java
adapter = new FinalAdapter(InterActivity.this,
codelist);
AlphaInAnimationAdapter animationAdapter = new AlphaInAnimationAdapter(adapter);
animationAdapter.setAbsListView(listview);
// Binds the Adapter to the ListView
listview.setAdapter(adapter);
listview.setOnItemClickListener(InterActivity.this);
listview.setOnItemLongClickListener(InterActivity.this);
// Close the progressdialog
mProgressDialog.dismiss();
listview.setOnScrollListener(new OnScrollListener() {
public void onScrollStateChanged(AbsListView view,
int scrollState) { // TODO Auto-generated method stub
int threshold = 1;
int count = listview.getCount();
if (scrollState == SCROLL_STATE_IDLE) {
if (listview.getLastVisiblePosition() >= count
- threshold) {
// Execute LoadMoreDataTask AsyncTask
new LoadMoreDataTask(InterActivity.this).execute();
}
}
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub
}
});
}
}
private class LoadMoreDataTask extends AsyncTask<Void, Void, Void> {
private Activity activity;
private View footer;
private LoadMoreDataTask(Activity activity) {
this.activity = activity;
loadingMore = true;
footer = activity.getLayoutInflater().inflate(R.layout.loadmore, null);
}
@Override
protected void onPreExecute() {
listview.addFooterView(footer);
super.onPreExecute();
}
@Override
protected Void doInBackground(Void... params) {
codelist = new ArrayList<CodeList>();
try {
// Locate the class table named "Country" in Parse.com
ParseQuery<ParseObject> query = new ParseQuery<ParseObject>(
"InterActivity");
// Locate the column named "ranknum" in Parse.com and order list
// by ascending
query.orderByAscending("_created_at");
query.setLimit(limit += 20);
ob = query.find();
for (ParseObject inter : ob) {
map.setIntroduction((String) inter.get("intro"));
map.setFinalCodeText((String) inter.get("codetext"));
codelist.add(map);
}
} catch (ParseException e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(Void result) {
if (footer != null) {
listview.removeFooterView(footer);
}
// Locate listview last item
int position = listview.getLastVisiblePosition();
// Pass the results into ListViewAdapter.java
adapter = new FinalAdapter(InterActivity.this, codelist);
// Binds the Adapter to the ListView
listview.setAdapter(adapter);
// Show the latest retrived results on the top
listview.setSelectionFromTop(position, 0);
}
}