Develop Reference

Can't Access to ExpandablelistView in fragment

MainActivity on startup add a fragment layout to Relativeview, then i send a data to fragment to add it to ExpandablelistView but my app shows me error that couldn't recognize ExpandablelistView.
MainActivity:
public class MainActivity extends AppCompatActivity implements FragmentAddCatergory.onClickButtonListener {
private FragmentManager manager;
private FragmentTransaction transactionShowList;
private FragmentTransaction transactionAddCatergory;
private FragmentAddCatergory addCatergory;
private FragmentShowCategory showCategory;
private boolean addcategory;
private TextView txtAddCategory;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
manager = getFragmentManager();
transactionShowList = manager.beginTransaction();
showCategory = new FragmentShowCategory();
addCatergory=new FragmentAddCatergory();
transactionShowList.add(R.id.Fragment_container, showCategory);
transactionShowList.commit();
addcategory=false;
txtAddCategory = (TextView) findViewById(R.id.txtaddcategory);
txtAddCategory.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
ChangeFragment();
}
});
}
public void ChangeFragment(){
transactionAddCatergory=manager.beginTransaction();
if (addcategory){
transactionAddCatergory.replace(R.id.Fragment_container,addCatergory);
txtAddCategory.setText("Do you want to see your List?Show me!");
addcategory=false;
}else{
transactionAddCatergory.replace(R.id.Fragment_container,showCategory);
txtAddCategory.setText("Do you want to add a Category?Create One");
addcategory=true;
}
transactionAddCatergory.commit();
}
#Override
public void ClickButton(String group, String child) {
FragmentShowCategory a=new FragmentShowCategory();
a.showExpand(this,group,child);
}}
in last above code i make object from first fragment and send a data and in below code is code of first fragment
public class FragmentShowCategory extends Fragment {
private View view;
#Nullable
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
super.onCreateView(inflater, container, savedInstanceState);
view = inflater.inflate(R.layout.activity_expandable_list_view, container, false);
return view;
}
public void showExpand(Context context, String g, String c) {
Toast.makeText(context, g + " is " + c, Toast.LENGTH_LONG).show();
HashMap<String, List<String>> carsDetails = DataProvider.getInfo(g, c);
List<String> carsBrands = new ArrayList<String>(carsDetails.keySet());
ItemClass adapter = new ItemClass(context, carsDetails, carsBrands);
ExpandableListView list = (ExpandableListView) view.findViewById(R.id.expandList);
list.setAdapter(adapter);
}}
but when i ran my app, i get error that i don't know why in line of:
ExpandableListView list = (ExpandableListView) view.findViewById(R.id.expandList);
i'd appreciate to help me.

Your fragment's view hierarchy is not inflated automatically just because you created an instance of your fragment, as you do in ClickButton. The onCreateView() method that has to be called first in order to inflate your views is part of the fragment's lifecycle. You should let Android instantiate your fragment, and acquire it's instance through the FragmentManager.
This tutorial explains basics about fragments very well.

PagerSlidingStrip is also loading another fragment

I have implemented Pager Sliding Strip and it is working totally fine.
I have 5 tabs each containing different fragment. When I click on 2nd tab to load respective fragment, it also load details of 3rd fragment, it showing the toast I coded in 3rd tab's fragment.
this is totally ruined the apps performance, How come I solve this problem I don't have any idea whats actually going on.
I am working on a really big project I cannot post the whole code.
Please Help me with this, I will post the respective code on demand.
Regards.
EDIT
Notification Fragment which is loading another fragment
ListView notification_listview;
ArrayList<FragmentNotificationDTO> arraylist;
NotificationAdapter adapter;
private static View notificationView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (notificationView != null) {
ViewGroup parent = (ViewGroup) notificationView.getParent();
if (parent != null)
parent.removeView(notificationView);
}
notificationView = inflater.inflate(R.layout.fragment_notification,
container, false);
initLayout(notificationView);
loadData();
return notificationView;
}
private void initLayout(View view) {
notification_listview = (ListView) view.findViewById(R.id.notification_listview);
arraylist = new ArrayList<FragmentNotificationDTO>();
adapter = new NotificationAdapter(mContext, arraylist);
notification_listview.setAdapter(adapter);
}
This is Food Fragment which is loaded also when we click on Notification Tab
private static View foodlistView;
RelativeLayout rl_foodshare, rl_foodrequested, rl_foodkitchen;
TextView tv_foodshare, tv_foodrequested, tv_foodkitchen;
ImageView img_foodshare, img_foodrequested, img_foodkitchen;
Fragment fr;
FragmentManager fm;
FragmentTransaction fragmentTransaction;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (foodlistView != null) {
ViewGroup parent = (ViewGroup) foodlistView.getParent();
if (parent != null)
parent.removeView(foodlistView);
}
foodlistView = inflater.inflate(R.layout.fragment_location_list,
container, false);
initLayout(foodlistView);
ChangeFragment(1);
return foodlistView;
}
MainActivity.java which contains the PagerSlidingStrip & View Pager
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ViewPager viewPager = (ViewPager) findViewById(R.id.viewpager);
viewPager.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()));
PagerSlidingTabStrip PGSTRIP = (PagerSlidingTabStrip) findViewById(R.id.tabs);
PGSTRIP.setViewPager(viewPager);
viewPager.setOffscreenPageLimit(0);
}

I solved my problem by overriding this method in each of my fragment and then calling the loading method when fragment's visibility is true to user.
#Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
// load data here
}else{
// fragment is no longer visible
}
}

Accessing Fragment's views after inflating

What I need to achieve
A screen displaying a ListView, which can be replaced by an error screen in case of problems (missing connection, server unavailable and the like).
I need to be able to switch (programmatically) back and forth between these two screens.
Requirements
The main screen must be a Fragment.
This is because my application is composed of several sections, each one accessible from the navigation drawer.
What I have done so far
The main fragment class is named AllQueuesFragment: its XML layout consists of a FrameLayout, which I use in combination with the FragmentManager to switch between ErrorFragment (containing the error message) and QueuesViewFragment (containing the ListView).
public class AllQueuesFragment extends Fragment
{
public AllQueuesFragment()
{
super();
}
#Override
public void onStart()
{
super.onStart();
// Show the right fragment based on connectivity status
checkConnection();
}
public void checkConnection()
{
final NetworkManager netManager = NetworkManager.getInstance(this.getActivity());
if (netManager.isConnected())
showQueues();
else
showNoConnection();
}
public void showNoConnection()
{
ErrorFragment fragNoConnection = new ErrorFragment();
displayFragment(fragNoConnection);
fragNoConnection.setTitle(R.string.text_no_connection);
fragNoConnection.setIcon(R.drawable.thatfeel);
fragNoConnection.setLoaderVisibility(false);
}
public void showQueues()
{
QueuesViewFragment fragQueuesView = new QueuesViewFragment();
displayFragment(fragQueuesView);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_allqueues, container, false);
return rootView;
}
// Displays a new fragment
public void displayFragment(Fragment fragment)
{
if (fragment != null)
{
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
}
}
}
The error screen is the following:
public class ErrorFragment extends Fragment
{
private TextView textTitle;
public ErrorFragment()
{
super();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
// Get the widgets
textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
return rootView;
}
// Set methods
public void setTitle(int id) { textTitle.setText(id); }
}
The problem
The setTitle() method gets called before the layout is ready, and as a result, a NullPointerException is thrown.
class AllQueuesFragment
{
....
public void displayFragment(Fragment fragment)
{
if (fragment != null)
{
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
}
}
public void showNoConnection()
{
ErrorFragment fragNoConnection = new ErrorFragment();
displayFragment(fragNoConnection);
// PROBLEM HERE: Before calling setTitle(), I must be sure that ErrorFragment's
// layout is inflated!
fragNoConnection.setTitle(R.string.text_no_connection);
}
....
}
class ErrorFragment
{
....
public void setTitle(String value) { textTitle.setText(value); }
....
}
I can't call setTitle() directly from ErrorFragment::onCreateView(), because I don't know beforehand which message I need to show.
How can I ensure that fragNoConnection has completed its layouting?
Is there a better way to achieve my goal?
Unsatisfying workaround
The only workaround I can think of is to use a buffer to defer the actual call:
class ErrorFragment
{
// This string will hold the title until the layout is inflated
private String titleBuffer;
private TextView textTitle = null;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
// Get the widgets
textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
// Do the actual set
setTitle(titleBuffer);
return rootView;
}
....
public void setTitle(String value)
{
titleBuffer = value;
// If the layout is not inflated, defer the actual set
if (textTitle != null)
textTitle.setText(titleBuffer);
}
....
}
but I don't like this solution very much (the code above is simplified; ErrorFragment has more properties).
Advices?
Thanks in advance

This is exactly the type of thing arguments are supposed to be used for:
public void showNoConnection() {
ErrorFragment fragNoConnection = new ErrorFragment();
Bundle args = new Bundle();
//you can also use putInt here if you'd rather pass a string resource id, along with anything else you can stick into a Bundle
args.putString("title", "some title");
fragNoConnection.setArguments(args);
displayFragment(fragNoConnection);
}
Then in ErrorFragment
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
TextView textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
//now retrieve the argument...
textTitle.setText(getArguments().getString("title"));
return rootView;
}
The Fragment will even remember it's arguments after an orientation change.
If you feel like being pedantic, you can create a static factory method within ErrorFragment that takes the title as an argument and then creates the Fragment and adds the argument, that way you can achieve proper encapsulation :)

You need to have a callback method in your ErrorFragment and when the view is inflated you then call the method in your callback interface in the onViewCreated and set the title.
sample:
in ErroFragment
public class ErroFragment extends Fragment
{
static interface ErrorDone{
public void doneInflating();
}
private TextView textTitle;
private ErrorDone ed;
public ErroFragment()
{
super();
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Inflate the view
View rootView = inflater.inflate(R.layout.fragment_error, container, false);
// Get the widgets
textTitle = (TextView)rootView.findViewById( R.id.fragment_error_text );
return rootView;
}
// Set methods
public void setTitle(int id) { textTitle.setText(id); }
public void setInterFace(ErrorDone er){ this.ed = er; }
}
Then you implement the interface in your AllQueuesFragment
public class AllQueuesFragment extends Fragment implements ErroFragment.ErrorDone
It will generate method doneInflating
and you need to set the interface:
public void showNoConnection()
{
ErrorFragment fragNoConnection = new ErrorFragment();
displayFragment(fragNoConnection);
fragNoConnection.setInterFace(this);
}
And in the generated method(doneInflating) of the AllQueuesFragment you then set the title in there:
public void doneInflating(){
fragNoConnection.setTitle(R.string.text_no_connection);
fragNoConnection.setIcon(R.drawable.thatfeel);
fragNoConnection.setLoaderVisibility(false);
}

If you want to be sure that the FragmentTransaction is commited and effective, you can use the executePendingTransactions method:
FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.frame_container, fragment).commit();
fragmentManager.executePendingTransactions();
But, the right way to do it is to send the title value to the Fragment when instantiating it. This is the default pattern when you create a Fragment from your IDE (eclipse or Android Studio)

Maintain fragment's view state

I have seen Link1 for this issue but could understand it right. I have a fragment that loads a list. When i click the list item it opens another activity. But i press back button it loads the list again. I want it to be at the same scroll position where it was before. In above mentioned link it specifies to use flag but i haven't got the point.
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_dashboard);
android.app.Fragment fragment = new MeFragment();
getFragmentManager().beginTransaction().replace(R.id.layout_FragmentsContainer, fragment).addToBackStack(null).commit();
}
}
public class MeFragment extends Fragment
{
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
return inflater.inflate(R.layout.fragment_me, container, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
meLV = (ListView) getView().findViewById(R.id.lv_Inbox);
loadingListProgress = (ProgressBar) getView().findViewById(R.id.progress_LoadingList);
meList = new ArrayList<Message>();
meAdapter = new MessagesListAdapter(getActivity(), meList);
//addFooter();
meLV.setAdapter(meAdapter);
meLV.setOnItemClickListener(this);
pageCount = 0;
loadmoreProgressDialog = new ProgressDialog(getActivity());
loadmoreProgressDialog.setTitle("Please wait ...");
loadmoreProgressDialog.setMessage("Loading more ...");
loadmoreProgressDialog.setCancelable(true);
loadUserMessages();
meLV.setOnScrollListener(new EndlessScrollListener() {
#Override
public void onLoadMore(int page, int totalItemsCount) {
// TODO Auto-generated method stub
//addFooter();
loadmoreProgressDialog.show();
loadUserMessages();
}
});
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position,
long id) {
// TODO Auto-generated method stub
Utils.showToast_msg(getActivity(), "MessageItemClicked");
ReferralDetailFragment fragment = new ReferralDetailFragment();
getFragmentManager().beginTransaction().replace(R.id.layout_FragmentsContainer, fragment).addToBackStack(null).commit();
}
}
public class ReferralDetailFragment extends Fragment implements OnClickListener {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.fragment_referraldetail,container, false);
linkToAcknowledge = (TextView) view.findViewById(R.id.lbl_Link_to_Acknowledge);
return view;
}
}

I implemented a simple solution for this in my app, basically when you press back to go to the fragment again, onCreateView() is called. Here in onCreateView() you have done all initialization, so we change
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
View view = inflater.inflate(R.layout.fragment_me, container, false);
/*
*Whatever you want to do
*
*/
return view;
}
to:
View view;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
if(view==null){
view = inflater.inflate(R.layout.fragment_me, container, false);
/*
*Whatever you want to do
*
*/
}
else{
((ViewGroup)view.getParent()).removeView(view);
}
return view;
}
Here, we move View view outside and make it a class variable. So if it is the first time the fragment is called, it is null and the initialization occurs, otherwise it goes to else black. Else block is required because onCreateView() adds whatever it returns as a child of the view's parent, so since view is already there, we remove it and onCreateView automatically adds it again.

According to our exchange in the comments, I completely deletde my answer and re-write a new one.
I copy/paste the code from one of my apps and removing the useless things and changing the names. Hope there is not too many typing mistakes, at that it is the minimum required to have it working.
When I pop back to FirstFragment from SecondFragment, the scroll position of FirstFragment is the same as when I clicked an item to load the SecondFragment.
Note that I don't extend FragmentActivity. I have an activity which loads the fragments.
Extend/modify to match your needs.
MainActivity :
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_layout);
}
}
FirstFragment Class :
public class FirstFragment extends Fragment implements OnItemClickListener {
private ListView mListView;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.first_fragment_layout, container, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mListView = (ListView) getView().findViewById(R.id.listview_first_fragment);
mListView.setAdapter(mAdapter); // depends on your adapter
mListView.setOnItemClickListener(this);
}
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
mListView.setItemChecked(position, true);
//in case you need, set the bundle here, for example pass the position
Bundle arguments = new Bundle();
arguments.putInt("position", position);
SecondFragment secondFragment = new SecondFragment();
secondFragment.setArguments(arguments);
getFragmentManager().beginTransaction().replace(R.id.fragment_container, secondFragment).addToBackStack(null).commit();
}
}
SecondFragment Class :
public class SecondFragment extends Fragment {
private Integer mPosition;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
return inflater.inflate(R.layout.second_fragment_layout, container, false);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Bundle arguments = getArguments();
if (arguments == null) {
mPosition= 0;
} else {
mPosition= arguments.getInt("Position");
}
}
}

What you are trying to achieve may be done with help of savedInstanceState. i also had this kind of problem which i resolved by using add() method instead of replace() in transition.
If you can change your method or already not using add() than give it a shot.
and if add() method didn't do the trick then check the implementation of savedInstanceState.
correctly save instance state.
How to save states of fragment views.

Listview fragment is getting recreated on pressing backbutton

I'm using loader in my ListView fragment, and it's getting recreated on pressing "back" button. Can you tell me how to handle this senario?
Here is my ListView fragment code. Here I have a boolean variable that I'm setting as true on clicking on list item. but once the back button is pressed onCreateView will get called so the backbutton will be false.
public class GTFragment extends SherlockFragment implements LoaderCallbacks<Cursor>{
ListView mTListview = null;
GoogleTasksAdapter mGTasksAdapter = null;
private SQLiteCursorLoader mTLoader=null;
private LoaderManager mTLoaderManager;
private String mSelectedListID = null;
private boolean mIsBackbuttonisPressed = false;
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.task_home_activity, container, false);
if(!mIsBackbuttonisPressed)
getLoaderManager().initLoader(0, null, this);
mTListview = (ListView) view.findViewById(R.id.id_task_list_home_activity);
mGTasksAdapter = new GoogleTasksAdapter(getActivity());
mTListview.setOnItemClickListener(new OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> listview,
View clickedview, int position, long arg3) {
// TODO Auto-generated method stub
GoogleTaskItem item = new GoogleTaskItem();
Cursor coursor = ((GoogleTasksAdapter)listview.getAdapter()).getCursor();
if(coursor.moveToPosition(position))
{
mIsBackbuttonisPressed = true;
GoogleTaskController.get_googletask_controllerObj()
.LaunchTaskPreviewActivity();
}
}
});
mTListview.setAdapter(mGTasksAdapter);
mIsBackbuttonisPressed = false;
return view;
}
My fragment activity class code
public class TLActivity extends SherlockFragmentActivity {
LeftSliderTaskListOptions mTaskOptionsFragment = null;
GoogleTasksFragment mTFragment = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setHomeButtonEnabled(true);
setContentView(R.layout.layout_gt_list);
// FragmentTransaction tfragment = this.getSupportFragmentManager().beginTransaction();
mTFragment = new GTasksFragment();
t.replace(R.id.id_tfragment, mTFragment);
t.commit();
}

instead of
t.replace(R.id.id_tfragment, mTFragment);
use
t.add(R.id.id_tfragment, mTFragment);
It worked for me

I don't think that the accepted answer is right because Fragment.onSaveInstanceState will not be called until the activity hosting it needs to save its state: The docs states:
There are many situations where a fragment may be mostly torn down
(such as when placed on the back stack with no UI showing), but its
state will not be saved until its owning activity actually needs to
save its state.
In other words: if you're using a Activity with multiple fragments for each screen (which is very common), the fragment state will not be saved when you move the next screen.
You also can't use Fragment.setRetainInstance because he's meant only to fragments that aren't on the back stack.
Most of the time, you don't have to think about this but sometimes it's important. Like when you have scrolled a list and want to "remember" the scroll location.
I took a long time to realize that the fragments put on the back stack are kind of saved and you can reuse the view that you already created instead of creating one every time the fragment calls onCreateView. My setup is something like this:
public abstract class BaseFragment extends Fragment {
private boolean mSaveView = false;
private SoftReference<View> mViewReference;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
if (mSaveView) {
if (mViewReference != null) {
final View savedView = mViewReference.get();
if (savedView != null) {
if (savedView.getParent() != null) {
((ViewGroup) savedView.getParent()).removeView(savedView);
return savedView;
}
}
}
}
final View view = inflater.inflate(getFragmentResource(), container, false);
mViewReference = new SoftReference<View>(view);
return view;
}
protected void setSaveView(boolean value) {
mSaveView = value;
}
}
public class MyFragment extends BaseFragment {
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
setSaveView(true);
final View view = super.onCreateView(inflater, container, savedInstanceState);
ListView placesList = (ListView) view.findViewById(R.id.places_list);
if (placesList.getAdapter() == null) { // this check is important so you don't restart your adapter
placesList.setAdapter(createAdapter());
}
}
}

You have multiple options to rectify this issue.
Override onSaveInstanceState like this:
#Override
public void onSaveInstanceState (Bundle outState) {
super.onSaveInstanceState(outState);
outState.putBoolean("mIsBackbuttonisPressed", mIsBackbuttonisPressed);
}
and then in your onCreateView you can get your variable back by:
if (savedInstanceState != null)
mIsBackbuttonisPressed = savedInstanceState.getBoolean("mIsBackbuttonisPressed", false);
You can set this.setRetainInstance(true); in your onCreate method of your fragment.
If you could post your Activity code with creates your fragment I can also tell you other options. (P.S I cannot write it as a comment so posting it in the answer.)