当片段中的一个活动启动时，它会成功请求POST方法（使用AsyncTask）并填充Arraylist。
在我转移到片段中的其他活动并回归之后，以前填充的内容似乎已经消失，但是当我单击后退按钮时，突然它再次填充（我不确定它是否正在填充或只是隐藏数据显示起来）。但是，如果我做同样的工作（转换到其他活动并回来），那么以前填充的东西就会消失，永远不会回来。
我假设当我回来时它是从代码的第一行开始，那么它应该已经填充但我认为它没有。但我真的希望通过设置总是可见的填充数据为用户创建一个更简单的界面。
下面是我的“那个”活动的代码，还包括片段控制器的代码。
public class VideoCallFragment extends Fragment implements LifeCycleListener{
private LinearLayout parentFragment;
private ViewGroup.LayoutParams selfLayoutParams;
private ArrayList<String> prgmNameList = new ArrayList<String>();
private ArrayList<String> caseList = new ArrayList<String>();
private ArrayList<String> dateList = new ArrayList<String>();
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_video_call, container, false);
parentFragment = (LinearLayout) rootView.findViewById(R.id.ll_video_call);
SharedPreferences settings = PreferenceManager
.getDefaultSharedPreferences(getContext());
String auth_token_string = settings.getString("token", ""/*default value*/);
new soonClass().execute(auth_token_string);
final ListView lv=(ListView) rootView.findViewById(R.id.listView_classroom);
lv.setAdapter(new CustomAdapter(getActivity(), prgmNameList, dateList, caseList));
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
String classroom = ((TextView) view.findViewById(R.id.lesson)).getText().toString();
lv.setVisibility(View.GONE);
Toast.makeText(getActivity(),classroom,Toast.LENGTH_SHORT).show();
classroom_enter(classroom);
}
}
);
return rootView;
}
class soonClass extends AsyncTask<String, String, String> {
private Exception exception;
protected void onPreExecute() {
}
protected String doInBackground(String... args) {
String auth_token_string = args[0];
try {
URL url = new URL("myurl");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
String urlParameters = "token=" + auth_token_string ;
connection.setRequestMethod("POST");
connection.setDoOutput(true);
DataOutputStream dStream = new DataOutputStream(connection.getOutputStream());
dStream.writeBytes(urlParameters);
dStream.flush();
dStream.close();
InputStream in = connection.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(in,"iso-8859-1"),8);
StringBuffer buffer = new StringBuffer();
String line = "";
while ((line = reader.readLine()) != null) {
buffer.append(line).append("\n");
}
reader.close();
connection.disconnect();
JSONObject jsonObj = null;
jsonObj = new JSONObject(buffer.toString().trim());
JSONArray classes = null;
classes = jsonObj.getJSONArray("lessons");
// looping through All Contacts
for (int i = 0; i < classes.length(); i++) {
JSONObject c = classes.getJSONObject(i);
prgmNameList.add("lesson_" + c.getString("id"));
caseList.add(c.getString("course"));
dateList.add(c.getString("date"));
}
return "done";
}
catch(Exception e) {
Log.e("ERROR", e.getMessage(), e);
return null;
}
}
protected void onPostExecute(String response) {
Toast.makeText(getActivity(), "된다", Toast.LENGTH_SHORT).show();
if(response == null) {
response = "THERE WAS AN ERROR";
}
//progressBar.setVisibility(View.GONE);
Log.i("INFO", response);
//responseView.setText(response);
}
}
public void classroom_enter(String room_name) {
somefunction();
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Allow volume to be controlled using volume keys
getActivity().setVolumeControlStream(AudioManager.STREAM_VOICE_CALL);
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
((MainActivity2) activity).onSectionAttached(
getArguments().getInt(ARG_SECTION_NUMBER));
}
@Override
public void onDetach() {
super.onDetach();
}
}
public class MainActivity2 extends ActionBarActivity
implements NavigationDrawerFragment.NavigationDrawerCallbacks {
private static final int CASE_SECTION_EDIT_PROFILE = 1;
private static final int CASE_SECTION_VIDEO_CALL = 2;
private static final int CASE_SECTION_PAST_CLASS = 3;
private static final int CASE_SECTION_SCHEDULE_CLASS = 4;
private static final int CASE_FRAGMENT_EDIT_PROFILE = 0;
private static final int CASE_FRAGMENT_VIDEO_CALL = 1;
private static final int CASE_FRAGMENT_PAST_CLASS = 2;
private static final int CASE_FRAGMENT_SCHEDULE_CLASS = 3;
private static final String TAG = MainActivity2.class.getName();
private NavigationDrawerFragment mNavigationDrawerFragment;
private CharSequence mTitle;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.mainactivity2);
mNavigationDrawerFragment = (NavigationDrawerFragment)
getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);
mTitle = getTitle();
mNavigationDrawerFragment.setUp(
R.id.navigation_drawer,
(DrawerLayout) findViewById(R.id.drawer_layout));
}
@Override
public void onNavigationDrawerItemSelected(int position) {
// update the main content by replacing fragments
FragmentManager fragmentManager = getSupportFragmentManager();
Fragment fragmentToLaunch = getFragmentToLaunch(position);
fragmentManager.beginTransaction()
.replace(R.id.container, fragmentToLaunch)
.commit();
}
public void onSectionAttached(int number) {
switch (number) {
case CASE_SECTION_EDIT_PROFILE:
mTitle = getString(R.string.title_section1);
break;
case CASE_SECTION_VIDEO_CALL:
mTitle = getString(R.string.title_section2);
break;
case CASE_SECTION_PAST_CLASS:
mTitle = getString(R.string.title_section3);
break;
case CASE_SECTION_SCHEDULE_CLASS:
mTitle = getString(R.string.title_section4);
break;
default:
break;
}
}
public void restoreActionBar() {
ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD);
actionBar.setDisplayShowTitleEnabled(true);
actionBar.setTitle(mTitle);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
if (!mNavigationDrawerFragment.isDrawerOpen()) {
// Only show items in the action bar relevant to this screen
// if the drawer is not showing. Otherwise, let the drawer
// decide what to show in the action bar.
getMenuInflater().inflate(R.menu.main, menu);
restoreActionBar();
return true;
}
return super.onCreateOptionsMenu(menu);
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
return super.onOptionsItemSelected(item);
}
public Fragment getFragmentToLaunch(int position) {
Fragment fragmentToLaunch = null;
switch (position) {
case CASE_FRAGMENT_EDIT_PROFILE:
fragmentToLaunch = new EditProfileFragment(); // <!-- this is a class.
break;
case CASE_FRAGMENT_VIDEO_CALL:
fragmentToLaunch = new VideoCallFragment();
break;
case CASE_FRAGMENT_PAST_CLASS:
fragmentToLaunch = new ChatFragment();
break;
case CASE_FRAGMENT_SCHEDULE_CLASS:
fragmentToLaunch = new FileTransferFragment();
break;
default:
break;
}
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, position + 1);
fragmentToLaunch.setArguments(args);
return fragmentToLaunch;
}
}
请给我任何关于如何解决这个问题的意见！ （：
答案 0 :(得分：1)
在片段中调用Asynctask（VideoCallFragment） onResume（）方法
@Override
public void onResume() {
super.onResume();
new soonClass().execute(auth_token_string);
}