我从URL解析了JSON数据，并显示了前十个Feed。当我滚动到列表视图中的第9个数据时，调用AsynTask并且无限加载所有其他数据，但是我需要通过递增下一页索引来加载JSON中的下十个数据。
当我滚动到页面末尾时，如何仅从JSON加载下十个数据？
以下是我的代码的MainActivity：
public class MainActivity extends Activity {
private static final String TAG = MainActivity.class.getSimpleName();
private ListView listView;
ProgressDialog pDialog;
private FeedListAdapter listAdapter;
private List<FeedItem> feedItems;
public String URL_FEED = "http://saverken.com/saverken/featuredpost/getPost?logged_in_user_id=6&start_index=0";
private int PAGE_NUM = 0;
public static JSONArray feedArray;
boolean stillAvaialble=true;
@SuppressLint("NewApi")
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.list);
feedItems = new ArrayList<FeedItem>();
listAdapter = new FeedListAdapter(this, feedItems);
listView.setAdapter(listAdapter);
// These two lines not needed,
// just to get the look of facebook (changing background color & hiding the icon)
getActionBar().setBackgroundDrawable(new ColorDrawable(Color.parseColor("#3b5998")));
getActionBar().setIcon(
new ColorDrawable(getResources().getColor(android.R.color.transparent)));
// We first check for cached request
Cache cache = AppController.getInstance().getRequestQueue().getCache();
Entry entry = cache.get(URL_FEED);
if (entry != null) {
// fetch the data from cache
try {
String data = new String(entry.data, "UTF-8");
try {
parseJsonFeed(new JSONObject(data));
} catch (JSONException e) {
e.printStackTrace();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
} else {
// making fresh volley request and getting json
JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
URL_FEED, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
VolleyLog.d(TAG, "Response: " + response.toString());
Log.v("response", ""+response);
if (response != null) {
parseJsonFeed(response);
stillAvaialble=true;
PAGE_NUM += 1;
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
stillAvaialble=false;
}
});
// Adding request to volley request queue
AppController.getInstance().addToRequestQueue(jsonReq);
}
listView.setOnScrollListener(new OnScrollListener() {
@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// TODO Auto-generated method stub
}
@Override
public void onScroll(AbsListView view, int firstVisibleItem,
int visibleItemCount, int totalItemCount) {
Log.d(TAG,"onScroll !!!!!");
int lastInScreen = firstVisibleItem + visibleItemCount;
// TODO Auto-generated method stub
if (PAGE_NUM != 0 && listView.getLastVisiblePosition() == totalItemCount - 1
&& stillAvaialble && (lastInScreen == totalItemCount) ) {
new AsynThread().execute();
}
}
});
}
这是AsynTask：
public class AsynThread extends AsyncTask<Void, Void, Void>{
protected void onPreExecute() {
// Showing progress dialog before sending http request
pDialog = new ProgressDialog(
MainActivity.this);
pDialog.setMessage("Please wait..");
pDialog.setIndeterminate(true);
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected Void doInBackground(Void... arg0) {
runOnUiThread(new Runnable() {
public void run() {
URL_FEED = "http://saverken.com/saverken/featuredpost/getPost?logged_in_user_id=6&start_index=" + PAGE_NUM;
Cache cache = AppController.getInstance().getRequestQueue().getCache();
Entry entry = cache.get(URL_FEED);
if (entry != null) {
// fetch the data from cache
try {
String data = new String(entry.data, "UTF-8");
try {
parseJsonFeed(new JSONObject(data));
} catch (JSONException e) {
e.printStackTrace();
}
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
} else {
// making fresh volley request and getting json
JsonObjectRequest jsonReq = new JsonObjectRequest(Method.GET,
URL_FEED, null, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
VolleyLog.d(TAG, "Response: " + response.toString());
Log.v("response", ""+response);
if (response != null) {
stillAvaialble=true;
PAGE_NUM +=1;
parseJsonFeed(response);
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
stillAvaialble=false;
PAGE_NUM=0;
}
});
// Adding request to volley request queue
AppController.getInstance().addToRequestQueue(jsonReq);
}
}
});
return null;
}
}
解析json响应并将数据传递给提要视图列表适配器
private void parseJsonFeed(JSONObject response) {
try {
feedArray = response.getJSONArray("post_details");
Log.v("jsonarray", ""+feedArray.length());
for (int i = 0; i < feedArray.length(); i++) {
JSONObject feedObj = (JSONObject) feedArray.get(i);
FeedItem item = new FeedItem();
item.setPost_id(feedObj.getInt("post_id"));
item.setName(feedObj.getString("firstname"));
item.setCity(feedObj.getString("city"));
item.setState(feedObj.getString("state"));
item.setInterest(feedObj.getString("interest"));
item.setSpecialty(feedObj.getString("specialty"));
item.setEmail(feedObj.getString("email"));
item.setSubject(feedObj.getString("subject"));
// Image might be null sometimes
String image = feedObj.isNull("video") ? null : feedObj
.getString("video");
item.setImage("http://saverken.com/saverken/"+image);
item.setStatus(feedObj.getString("posts"));
String profilePic = feedObj.isNull("personal_photo") ? null : feedObj
.getString("personal_photo");
item.setProfilePic("http://saverken.com/saverken/"+profilePic);
item.setTimeStamp(feedObj.getString("date"));
// url might be null sometimes
String feedUrl = feedObj.isNull("url") ? null : feedObj
.getString("url");
item.setUrl(feedUrl);
feedItems.add(item);
}
// notify data changes to list adapater
listAdapter.notifyDataSetChanged();
} catch (JSONException e) {
e.printStackTrace();
}
参考：http://www.androidhive.info/2014/06/android-facebook-like-custom-listview-feed-using-volley