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我有一个navigation drawer包含2个项目。现在在我的第一个项目点击，我加载数据使用asynctask和加载的数据填充在相应片段的列表视图。现在当我切换到第二项时，我再次使用AsyncTask加载第二个片段的数据，并在listview中显示它。AsyncTask每次调用
现在问题就开始了。当我回到第一个片段时，我的 asyncTask再次被调用，并且数据再次从 服务器中获取，我想要阻止它并直接加载我的数据，如果它已经加载一次 。
请建议
P.S - 请询问代码，如果有人需要它。 USERPAYFRAGMENT
public class UserPay extends Fragment {
ProgressDialog prg;
Properties prop;
private PrefSingleton mMyPreferences;
private JSONParser jsonParser = new JSONParser();
ArrayList<HashMap<String, String>> RequestList;
HashMap<String, String> map;
UserAdapter req_adp;
ListView req;
private boolean flag;
@Override
public void onAttach(Activity activity) {
// TODO Auto-generated method stub
super.onAttach(activity);
Toast.makeText(getActivity(), "ATTACHED", 1000).show();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
Toast.makeText(getActivity(), "CREATE", 1000).show();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.user_pay, container, false);
initViews(rootView);
Toast.makeText(getActivity(), "ONCREATEVIEW", 1000).show();
return rootView;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Toast.makeText(getActivity(), "ONACTIVITYCREATED", 1000).show();
mMyPreferences = PrefSingleton.getInstance();
mMyPreferences.Initialize(getActivity());
RequestList = new ArrayList<HashMap<String, String>>();
Resources resources = this.getResources();
AssetManager assetManager = resources.getAssets();
try {
InputStream inputStream = assetManager.open("jsonURL.properties");
prop = new Properties();
prop.load(inputStream);
} catch (IOException e) {
System.err.println("Failed to open jsonURL property file");
e.printStackTrace();
}
req_adp = new UserAdapter(getActivity(), RequestList);
req.setAdapter(req_adp);
if (!flag) {
new GetRequests().execute();
} else {
}
}
@Override
public void onStart() {
// TODO Auto-generated method stub
super.onStart();
Toast.makeText(getActivity(), "ONSTART", 1000).show();
}
@Override
public void onResume() {
// TODO Auto-generated method stub
super.onResume();
Toast.makeText(getActivity(), "ONRESUME", 1000).show();
}
private void initViews(View v) {
req = (ListView) v.findViewById(R.id.req_list);
}
private class GetRequests extends AsyncTask<Void, Void, Integer> {
@Override
protected void onPreExecute() {
super.onPreExecute();
prg = new ProgressDialog(getActivity());
prg.setIndeterminate(true);
prg.setMessage("Fetching Pending Requests...");
prg.setCanceledOnTouchOutside(false);
prg.show();
}
@Override
protected Integer doInBackground(Void... params) {
List<NameValuePair> params1 = new ArrayList<NameValuePair>();
params1.add(new BasicNameValuePair("userID", mMyPreferences
.getPreference("LoginId")));
String error_code = null;
Log.e("URL ", "is" + prop.getProperty("GET_REQUESTS_URL"));
try {
// getting JSON string from URL
JSONObject json = jsonParser.makeHttpRequest(
Appconstant.GET_REQUESTS_URL, "POST", params1);
// Check your log cat for JSON response
Log.d("Inbox JSON: ", json.toString());
JSONObject jsonObj = json.getJSONObject("data");
error_code = jsonObj.getString("Error_Code");
RequestList.clear();
if ("1".equals(error_code)) {
JSONArray jArray = jsonObj.getJSONArray("result");
for (int i = 0; i < jArray.length(); i++) {
map = new HashMap<String, String>();
JSONObject jsonObj1 = jArray.getJSONObject(i);
String FBankId = jsonObj1
.getString("payment_from_bank_id");
String DestBankId = jsonObj1
.getString("payment_to_bank_id");
String FBank = jsonObj1.getString("fBank");
String TBank = jsonObj1.getString("tBank");
String reason = jsonObj1.getString("payment_reason");
String amt = jsonObj1.getString("amount");
String p_type = jsonObj1.getString("payment_type");
String status = jsonObj1.getString("status");
String r_date = jsonObj1
.getString("request_created_date");
map.put("FBankId", FBankId);
map.put("TBankId", DestBankId);
map.put("SourceBank", FBank);
map.put("DestBank", TBank);
map.put("ReqDate", r_date);
map.put("PayReason", reason);
map.put("Amt", amt);
map.put("PayType", p_type);
map.put("Status", status);
if (status.equals("pending")) {
if (p_type.equals("cheque")
|| p_type.equals("Net Banking")) {
RequestList.add(map);
}
}
}
}
} catch (JSONException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
return Integer.parseInt(error_code);
}
@Override
protected void onPostExecute(Integer result) {
super.onPostExecute(result);
if (prg.isShowing()) {
prg.cancel();
}
if (result == 2) {
Toast.makeText(getActivity(),
"No User Request Details Available.Please Try Again",
Toast.LENGTH_SHORT).show();
}
req_adp.notifyDataSetChanged();
flag = true;
}
}
@Override
public void onPause() {
// TODO Auto-generated method stub
super.onPause();
Toast.makeText(getActivity(), "ONPAUSE",1000).show();
}
@Override
public void onStop() {
// TODO Auto-generated method stub
super.onStop();
Toast.makeText(getActivity(), "ONSTOP", 1000).show();
}
@Override
public void onDestroyView() {
// TODO Auto-generated method stub
super.onDestroyView();
Toast.makeText(getActivity(), "ONDESTROYVIEW", 1000).show();
}
@Override
public void onDestroy() {
// TODO Auto-generated method stub
super.onDestroy();
Toast.makeText(getActivity(), "ONDESTROY", 1000).show();
}
@Override
public void onDetach() {
// TODO Auto-generated method stub
super.onDetach();
Toast.makeText(getActivity(), "ONDETACH", 1000).show();
}
}
分享您的代码 – 2014-11-03 06:46:12
我认为您应该提供代码（以避免downvotes）。 – turtle 2014-11-03 06:46:52
使用'FragmentTransaction'' add'而不是'replace'将第一个片段保留在后退栈中，当你回来时它不会再次加载数据。 – 2014-11-03 06:52:19