我需要帮助才能使我的 Gridview OnscrollListener 正常工作。我的结果没有按预期运行。它只是加载我所有的 gridview 项目，然后当我将 gridview 滚动到底部时，它会显示一个进度对话框并刷新。
我承认我不理解 OnScrollListener() 中的逻辑。我指的是这里给出的这个例子Endless Scrolling ListView in Android。希望有人可以为我编辑代码？
我想限制每个滚动 20 个图像，直到它完成从我的 xml 加载我的所有图像。我正在从 xml 解析 url，然后将其加载到我的 Gridview 中。
GridViewActivity.class
public class GridViewActivity extends Activity {
static final String URL = "http://api.androidhive.info/music/music.xml";
private ProgressDialog pDialog;
ArrayList<HashMap<String, String>> songsList;
static final String KEY_SONG = "song";
static final String KEY_ID = "id";
static final String KEY_CAT_ARTIST = "artistcat";
static final String KEY_THUMB_URL = "thumb_url";
static final String KEY_BIG_URL = "big_url";
static final String KEY_CAT_URL = "cat_url";
GridView grid;
GridViewActivityLazyAdapter adapter;
String cat_url;
String artist_url;
private int visibleThreshold = 5;
private int currentPage = 0;
private int previousTotal = 0;
private boolean loading = true;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.gridview_main);
new loadGridView().execute();
grid = (GridView) findViewById(R.id.grid_view);
grid.setOnScrollListener(new OnScrollListener() {
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
// TODO Auto-generated method stub
if (loading) {
if (totalItemCount > previousTotal) {
loading = false;
previousTotal = totalItemCount;
currentPage++;
}
}
if (!loading && (totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold)) {
// I load the next page of gigs using a background task,
// but you can call any function here.
new loadGridView().execute(currentPage + 20);
loading = true;
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
});
}
public class loadGridView extends AsyncTask<Integer, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(GridViewActivity.this);
pDialog.setTitle("Connect to Server");
pDialog.setIndeterminate(false);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected String doInBackground(Integer... args) {
// updating UI from Background Thread
Intent in = getIntent();
songsList = new ArrayList<HashMap<String, String>>();
cat_url = in.getStringExtra(KEY_CAT_URL);
artist_url = in.getStringExtra(KEY_CAT_ARTIST);
XMLParser parser = new XMLParser();
String xml = parser.getXmlFromUrl(URL); // getting XML from URL
Document doc = parser.getDomElement(xml); // getting DOM element
NodeList nl = doc.getElementsByTagName(KEY_SONG);
// looping through all song nodes <song>
int page = args[0];
int limit = 20; // items per page
int istart = page * limit; // what item to start on (onCreate() calls it with 0 and 0 * 20 = 0)
int iend = istart + limit; // how far to go
for (int i = istart; (i < nl.getLength()) && (i < iend); i++) {
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
Element e = (Element) nl.item(i);
// adding each child node to HashMap key => value
map.put(KEY_ID, parser.getValue(e, KEY_ID));
map.put(KEY_THUMB_URL, parser.getValue(e, KEY_THUMB_URL));
map.put(KEY_BIG_URL, parser.getValue(e, KEY_BIG_URL));
// adding HashList to ArrayList
songsList.add(map);
}
return null;
}
@Override
protected void onPostExecute(String args) {
adapter=new GridViewActivityLazyAdapter(GridViewActivity.this, songsList);
grid.setAdapter(adapter);
pDialog.dismiss();
}
}