经过SO和Google的大量搜索和试用后，我再次回到列表视图中无法滚动:( ...当我滚动到列表视图的末尾时，它应该在listview中加载更多项目，如分页。以下是我的代码任何人都可以帮助解决这个问题吗？答案将非常感谢。
public class MainActivity extends ListActivity implements OnScrollListener{
//implement onScrollListener for scrolling {
ArrayList<HashMap<String, String>> songsList;
ListView list;
LazyAdapter adapter;
JSONArray posts;
/*
* some private variables to implement endless scrolling
*/
private int visibleThreshold = 3;
private int previousTotal = 0;
private boolean loading = true;
// All static variables
static final String URL = "siteurl";
static final String KEY_POSTS = "posts";
static final String KEY_ID = "id";
static final String KEY_TITLE = "title";
static final String KEY_DATE = "date";
static final String KEY_CONTENT = "content";
static final String KEY_AUTHOR = "author";
static final String KEY_NAME = "name";
static final String KEY_ATTACHMENTS = "attachments";
static final String KEY_SLUG = "slug";
static final String KEY_THUMB_URL = "thumbnail";
static final String KEY_IMAGES = "images";
static final String KEY_URL = "url";
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
if(loading){
//if trying to loading
if(totalItemCount > previousTotal){
loading = false;
previousTotal = totalItemCount;
}
}
if(!loading && ((totalItemCount - visibleItemCount) <= (firstVisibleItem + visibleThreshold))){
new LoadMoreEntries().execute();
loading = true;
}
}
@Override
protected Dialog onCreateDialog(int id) {
// TODO Auto-generated method stub
Dialog loadingDialog = ProgressDialog.show(MainActivity.this, "", "Loading.Please wait...",false);
return loadingDialog;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(URL);
try {
posts = json.getJSONArray(KEY_POSTS);
// looping through all song nodes <song>
for(int i = 0; i < posts.length(); i++){
JSONObject c = posts.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(KEY_ID);
String title = c.getString(KEY_TITLE);
String date = c.getString(KEY_DATE);
String content = c.getString(KEY_CONTENT);
// to remove all <P> </p> and <br /> and replace with ""
content = content.replace("<br />", "");
content = content.replace("<p>", "");
content = content.replace("</p>", "");
//authornumber is agin JSON Object
JSONObject author = c.getJSONObject(KEY_AUTHOR);
String name = author.getString(KEY_NAME);
String url = null;
String slug = null;
try {
JSONArray atta = c.getJSONArray("attachments");
for(int j = 0; j < atta.length(); j++){
JSONObject d = atta.getJSONObject(j);
slug = d.getString(KEY_SLUG);
JSONObject images = d.getJSONObject(KEY_IMAGES);
JSONObject thumbnail = images.getJSONObject(KEY_THUMB_URL);
url = thumbnail.getString(KEY_URL);
}
} catch (Exception e) {
e.printStackTrace();
}
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(KEY_ID, id);
map.put(KEY_TITLE, title);
map.put(KEY_DATE, date);
map.put(KEY_NAME, name);
map.put(KEY_CONTENT, content);
map.put(KEY_SLUG, slug);
map.put(KEY_URL, url);
// adding HashList to ArrayList
songsList.add(map);
}
}catch (JSONException e) {
e.printStackTrace();
}
final ListView list=(ListView)findViewById(android.R.id.list);
// Getting adapter by passing json data ArrayList
adapter=new LazyAdapter(this, songsList);
list.setAdapter(adapter);
// Launching new screen on Selecting Single ListItem
list.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
// getting values from selected ListItem
String title = ((TextView) view.findViewById(R.id.title)).getText().toString();
String date = ((TextView) view.findViewById(R.id.date)).getText().toString();
String name = ((TextView) view.findViewById(R.id.name)).getText().toString();
String content = ((TextView) view.findViewById(R.id.content)).getText().toString();
// Starting new intent
Intent in = new Intent(getApplicationContext(),SampleDesp.class);
in.putExtra(KEY_TITLE, title);
in.putExtra(KEY_DATE, date);
in.putExtra(KEY_NAME, name);
in.putExtra(KEY_CONTENT, content);
startActivity(in);
}
});
}
class LoadMoreEntries extends AsyncTask<String, Void, String>{
@Override
protected void onPreExecute() {
// show your dialog
super.onPreExecute();
showDialog(1);
}
protected String doInBackground(ArrayList... params) {
// do your request here
ArrayList<HashMap<String, String>> songsList = new ArrayList<HashMap<String, String>>();
// Creating JSON Parser instance
JSONParser jParser = new JSONParser();
// getting JSON string from URL
JSONObject json = jParser.getJSONFromUrl(URL);
try {
posts = json.getJSONArray(KEY_POSTS);
// looping through all song nodes <song>
for(int i = 0; i < posts.length(); i++){
JSONObject c = posts.getJSONObject(i);
// Storing each json item in variable
String id = c.getString(KEY_ID);
String title = c.getString(KEY_TITLE);
String date = c.getString(KEY_DATE);
String content = c.getString(KEY_CONTENT);
// to remove all <P> </p> and <br /> and replace with ""
content = content.replace("<br />", "");
content = content.replace("<p>", "");
content = content.replace("</p>", "");
//authornumber is agin JSON Object
JSONObject author = c.getJSONObject(KEY_AUTHOR);
String name = author.getString(KEY_NAME);
String url = null;
String slug = null;
try {
JSONArray atta = c.getJSONArray("attachments");
for(int j = 0; j < atta.length(); j++){
JSONObject d = atta.getJSONObject(j);
slug = d.getString(KEY_SLUG);
JSONObject images = d.getJSONObject(KEY_IMAGES);
JSONObject thumbnail = images.getJSONObject(KEY_THUMB_URL);
url = thumbnail.getString(KEY_URL);
}
} catch (Exception e) {
e.printStackTrace();
}
// creating new HashMap
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(KEY_ID, id);
map.put(KEY_TITLE, title);
map.put(KEY_DATE, date);
map.put(KEY_NAME, name);
map.put(KEY_CONTENT, content);
map.put(KEY_SLUG, slug);
map.put(KEY_URL, url);
// adding HashList to ArrayList
songsList.add(map);
}
}catch (JSONException e) {
e.printStackTrace();
}
return null;
}
protected void onPostExecute(String result) {
// close the dialog and notify adapter for data
super.onPostExecute(result);
Dialog loadingDialog = null;
loadingDialog.dismiss();
adapter.notifyDataSetChanged();
//dismiss the progress dialog
}
@Override
protected String doInBackground(String... params) {
// TODO Auto-generated method stub
return null;
}
}
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
}