Im saving the state of fragment on a View, it works in the way I expected, the problem is with the LiveData. When I navigate to other fragment and then come back to this fragment, I cant no longer observer for changes. This is the code of my OnCreateView():
#Override
public View onCreateView(#NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if(view == null){
view = inflater.inflate(R.layout.fragment, container, false);
initializeViews(view);
receivedProductViewModel.getProductMutableLiveData().observe(getViewLifecycleOwner(), new Observer<DispatchedProduct>() {
#Override
public void onChanged(DispatchedProduct dispatchedProduct) {
if(dispatchedProduct != null){
int index = dispatchedProducts.indexOf(dispatchedProduct);
dispatchedProductsAdapter.notifyItemChanged(index);
}
}
});
btnSearch.setOnClickListener(btnSearchListener());
btnRegister.setOnClickListener(btnRegisterListener());
initializeRV();
}
return view;
}
I'm initializing the VM in OnCreate():
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
receivedProductViewModel = new ViewModelProvider(getActivity()).get(ReceivedProductViewModel.class);
}
Move your observe outside of your if (view == null) block. You always need to create a new Observer for your View every time onCreateView is called - the previous getViewLifecycleOwner() was destroyed when the previous onDestroyView was called, which correctly stops your previous observe callback.
#Override
public View onCreateView(#NonNull LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if(view == null){
view = inflater.inflate(R.layout.fragment, container, false);
initializeViews(view);
btnSearch.setOnClickListener(btnSearchListener());
btnRegister.setOnClickListener(btnRegisterListener());
initializeRV();
}
receivedProductViewModel.getProductMutableLiveData().observe(
getViewLifecycleOwner(), new Observer<DispatchedProduct>() {
#Override
public void onChanged(DispatchedProduct dispatchedProduct) {
if(dispatchedProduct != null){
int index = dispatchedProducts.indexOf(dispatchedProduct);
dispatchedProductsAdapter.notifyItemChanged(index);
}
}
});
return view;
}
Related
I'm trying to understand the process of saving and restoring state using fragments. I've created sliding navigation menu using it.
In one of the fragments there is this code:
public class FifthFragment extends Fragment {
CheckBox cb;
View view;
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fifth_layout, container, false);
cb = (CheckBox) view.findViewById(R.id.checkBox);
return view;
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
if (savedInstanceState != null) {
// Restore save state
}
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// save state
}
}
For example I want to save the state of the CheckBox before user exits the fragment and restore it when the fragment is created again. How to achieve this?
EDIT:
According to raxellson's answer I've changed my fragment to this:
public class FifthFragment extends Fragment {
private static final String CHECK_BOX_STATE = "string";
CheckBox cb;
View view;
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fifth_layout, container, false);
cb = (CheckBox) view.findViewById(R.id.checkBox);
if (savedInstanceState == null) {
Log.i("statenull", "null");
}
if (savedInstanceState != null) {
// Restore last state for checked position.
boolean checked = savedInstanceState.getBoolean(CHECK_BOX_STATE, false);
cb.setChecked(checked);
}
return view;
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putBoolean(CHECK_BOX_STATE, cb.isChecked());
}
}
I got logged I/statenull: null so savedInstanceState was not saved. What am I doing wrong?
You want to save the value of your current checked state in onSaveInstanceState.
Something like this:
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putBoolean(CHECK_BOX_STATE, cb.getChecked());
}
and then when your view is created you want to get the value if it's present. And set your CheckBox state with it.
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fifth_layout, container, false);
cb = (CheckBox) view.findViewById(R.id.checkBox);
if (savedInstanceState != null) {
// Restore last state for checked position.
boolean checked = savedInstanceState.getBoolean(CHECK_BOX_STATE, false);
cb.setChecked(checked);
}
return view;
}
EDIT:
When you add the fragment, make sure to add it with a tag or id so that you can retrieve the same instance.
You could do a helper method to retrieve fragment and set the fragment.
private void setFragment(String tag, Fragment newFragment) {
FragmentManager fm = getSupportFragmentManager();
Fragment savedFragment = fm.getFragmentByTag(tag);
fm.replace(R.id.container, savedFragment != null ? savedFragment : newFragment, tag);
fm.commit();
}
so you your switch you can call the helper method instead.
switch (position) {
case 0:
setFragment("A", new FragmentA());
break;
....
}
Note: This is just an example not best practice since you are creating new fragments every time in your switch case now anyways. But it might point you in the right direction.
After see all the example. Here is the solution for save fragment state:
Two steps for this:
1.
String saveValue;
#Override
public void onCreate(#Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState == null) {
saveValue = "";
} else {
saveValue = savedInstanceState.getString("saveInstance");
}
}
#Override
public void onSaveInstanceState(Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
//save the values of fragment if destroy on second to back
if (!saveValue.isEmpty())
savedInstanceState.putString("saveInstance", saveValue);
}
In onSaveInstanceState you can save your values. And after destroy fragment you can receive your values through onCreate.
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.
I have an activity which receive data from other activity. This data has to be showed in a TextView in a fragment inflated in the activity. So, the code is:
public class DetailActivity extends Activity {
private int idEstablecimiento;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail);
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit(); //Here the fragment is added to the activity
}
Bundle extras = getIntent().getExtras();
if (extras != null) {
idEstablecimiento = extras.getInt("idEstablecimiento");
}
TextView textView = (TextView) this.findViewById(R.id.nombreView); //Declared in fragmentDetail, which has been already inflated at this point, but still null
textView.setText(this.idEstablecimiento);
}
//...
//Non related stuff...
//...
public static class PlaceholderFragment extends Fragment {
private int idEstablecimiento;
public PlaceholderFragment() {
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_detail,
container, false);
return rootView;
}
}
The problem is that the textView in the onCreate() method is null, why is this happening if the fragment has been already inflated? Shouldn't I be able to access to the IU elements once the fragment has been inflated in the onCreate() method? Or if not, what is the rigth way to do access to it?
You have to find the TextView in the Fragment.
public static class PlaceholderFragment extends Fragment {
private int idEstablecimiento;
public PlaceholderFragment() {
}
public PlaceholderFragment(int idEstablecimiento) {
this.idEstablecimiento = idEstablecimiento;
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_detail,
container, false);
TextView text = rootView.findViewById(R.id.nombreView);
text.setText(idEstablecimiento);
return rootView;
}
And then you can get the text and commit it.
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_detail);
Bundle extras = getIntent().getExtras();
if (extras != null) {
idEstablecimiento = extras.getInt("idEstablecimiento");
}
if (savedInstanceState == null) {
getFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment(idEstablecimiento)).commit();
}
}
Regards
Nils
If you want to get the View from a fragment layout you should use the view inside the oncreateView of the fragment and then get the textView inside the oncreate view..
example:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_detail,
container, false);
TextView textView = (TextView) rootView.this.findViewById(R.id.nombreView); //Declared in fragmentDetail, which has been already inflated at this point, but still null
textView.setText("I am here");
return rootView;
}
I have a list fragment on the left of another fragment and is essentially the standard click an item and update the right fragment pattern. When they click an item in the list fragment they are choosing the news article category and I need to keep whatever one is selected when they rotate the device. How do I do that? My current code doesn't work.
My code is as follows:
public class SideMenuFragment extends ListFragment {
ArrayList<SideItem> sideItems;
SideAdapter sideAdapter;
public SideMenuFragment() {
this.setRetainInstance(true);
}
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
return inflater.inflate(R.layout.list, null);
}
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
sideItems = new ArrayList<SideItem>();
...add bunch of items
sideAdapter = new SideAdapter(getActivity(), sideItems);
getListView().setVerticalScrollBarEnabled(false);
setListAdapter(sideAdapter);
if (savedInstanceState != null) {
sideAdapter.setSelectedItem(savedInstanceState.getInt("sidePosition"));
sideAdapter.notifyDataSetChanged();
}
}
#Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putInt("sidePosition", sideAdapter.getSelectedItem());
}
#Override
public void onListItemClick(ListView lv, View v, int position, long id) {
if (sideAdapter.getSelectedItem() != position) {
sideAdapter.setSelectedItem(position);
sideAdapter.notifyDataSetChanged();
}
switch (position) {
...switch the fragment depending on position.
}
}
// the meat of switching the above fragment
private void switchFragment(Fragment fragment, String title) {
if (getActivity() == null)
return;
if (getActivity() instanceof HomeActivity) {
HomeActivity a = (HomeActivity) getActivity();
a.switchContent(fragment, title);
}
}
}
First, add your Fragment in xml if the Activity layout.
In Activity onCreate
getFragmentManager().findFragmentById(R.id.youtfragmentid).setRetainInstance(true)
This means that the fragment will not be recreated on activity recreate.
Don't change your ListView in onActivityCreated - because it will be rebuilt every time orientation changes. If you set a new adapter - the states of children will be reseted.
Add checking for null or a boolean flag that the view already was created.
Next time onActivityCreated gets called, your list adapter should not change
if (sideAdapter == null) {
sideAdapter = new SideAdapter(getActivity(), sideItems);
getListView().setVerticalScrollBarEnabled(false);
setListAdapter(sideAdapter);
}
Also, don't create new view in onCreateView instead use previously created one.
private View v;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (v == null) {
v = inflater.inflate(R.layout.list, null);
} else {
// detatch from container and return the same view
((ViewGroup) getListView().getParent()).removeAllViews();
}
return v;
}
I'm having an issue with the ViewPager where my ListView is loosing it's scroll position.
The state of the ListView can easily be stored and restored using:
#Override
public View onCreateView (LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
View v = inflater.inflate(R.layout.frag_cool_things, container, false);
AdvListView listView = (AdvListView) v.findViewById(R.id.lv0);
listView.setOnItemClickListener( mOnListItemClicked );
if (null != savedInstanceState)
{
listView.onRestoreListViewInstanceState(savedInstanceState.getParcelable("list_state"));
}
mListView = listView;
return v;
}
#Override
public void onSaveInstanceState (Bundle outState)
{
super.onSaveInstanceState(outState);
outState.putParcelable("list_state", mListView.onSaveListViewInstanceState());
}
However the problem is that when fragments are being swiped onDestroyView() gets called but never calls onSaveInstanceState (Bundle outState).
Rotating the screen and such restores the ListView state just fine but swiping I can't figure out how to restore the list properly.
Update 12/17/11:
I actually found the correct way to save the content of the Fragments. You must use FragmentStatePagerAdapter. This adapter properly saves the state of the fragment! :)
OLD:
Well I found a way to do this.. Please share your input if you believe this is a huge no no! :P
Here is my FragmentBase class that fixed this issue:
public abstract class FragmentBase extends Fragment
{
private boolean mInstanceAlreadySaved;
private Bundle mSavedOutState;
#Override
public View onCreateView (LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState)
{
if (null == savedInstanceState && null != mSavedOutState) {
savedInstanceState = mSavedOutState;
}
mInstanceAlreadySaved = false;
return onCreateViewSafe(inflater, container, savedInstanceState);
}
#Override
public void onSaveInstanceState (Bundle outState)
{
super.onSaveInstanceState(outState);
mInstanceAlreadySaved = true;
}
#Override
public void onStop()
{
if (!mInstanceAlreadySaved)
{
mSavedOutState = new Bundle();
onSaveInstanceState( mSavedOutState );
}
super.onStop();
}
public abstract View onCreateViewSafe (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState);
}