I have a RecyclerView in a Fragment and initially is hidden. When user clicks a button, I set visibility to true for the RecyclerView and I display some data I have on an ArrayList.
The problem starts when I move another fragment on top (I add the previous fragment with the RecyclerView in the backStack) : if I click back from the new fragment the previous fragment (the one with the RecyclerView ) is visible and in onCreateView() I log the values of the dataSet I'm using for the recyclerView and everything is there, but the recyclerView is empty ( only footer item is presented ).
If we call RvFragment the Fragment with the RecyclerView and NextFragment the fragment that comes to the backstack and then leaves the schema is :
(back pressed)
RvFragment ----------> NextFragment ------------> RvFragment
and here's the code from onCreateView() :
#Nullable
#Override
public View onCreateView(final LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_photo_comments, container, false);
ButterKnife.bind(this, view);
Timber.i("onCreateView data.size == %d", commentArrayList.size());
setToolbarTitle();
Picasso.with(getActivity())
.load(photo)
.placeholder(R.drawable.ic_timeline_image_placeholder)
.centerCrop()
.fit()
.into(ivPhoto);
if (hasCommentsVisible) {
Timber.i("comments are visible!! and dataSize == %d", commentArrayList.size());
llFlagsCommentsContainer.setVisibility(View.GONE);
rvCommentsList.setVisibility(View.VISIBLE);
}
tvComments.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
hasCommentsVisible = true;
llFlagsCommentsContainer.setVisibility(View.GONE);
rvCommentsList.setVisibility(View.VISIBLE);
}
});
initRecyclerView();
return view;
}
You can see with the log statements in the code above I can confirm the data exist. Thanks!
I'm not sure I understand how you set up your fragment stack but just to be sure : onCreateView won't be called again when you press the back button if the fragment is still on the stack.
https://developer.android.com/training/basics/fragments/fragment-ui.html#Replace
transaction.replace(R.id.fragment_container, newFragment);
transaction.addToBackStack(null);
Only onStart() will.
If you want onCreateView to be called again then you need to use the
FragmentTransaction.replace(NextFragment)
without the addToBackStack() but it means the whole fragment will be recreated from scratch. Probably not what you want, especially if you are getting your data from a webservice.
Alternatively, to fully recreate your fragment every time you come back to it, you can simply remove it entirely :
FragmentTransaction.remove(RvFragment)
and then push your next fragment
Related
The main page of my application has a FrameLayout.
I'm instantiating two fragments when the activity starts, and I'm trying to use a menu button to swap between the fragment.
scanHistoryFrag = new HistoryFragment();
scanFrag = new ScanFragment();
I never replace these objects - I use the same ones throughout the lifecycle of the application. However, when I swap them in my FrameLayout...
private void ChangeFragment(Android.Support.V4.App.Fragment fragment)
{
Android.Support.V4.App.FragmentTransaction ft = SupportFragmentManager.BeginTransaction();
ft.Replace(Resource.Id.fragmentContainer, fragment);
ft.Commit();
}
OnCreate and OnCreateView are called on the Fragment again... which means any adjustments I made post creation on that fragment are overwritten with initial values again. I can't seem to find any explanation for why this is happening or how I might avoid it.
The ChangeFragment method is being called by OnOptionsItemSelected, as I'm using a menu button to toggle them.
I never replace these objects - I use the same ones throughout the lifecycle of the application.
Initialization of a subclass of Fragment just create a instance of this class object, the constructor of this class will be called, but it will not go through the lifecycle of Fragment unless this Fragment is added, for more information, you can refer to Fragments. To understand it easier, I personal think the instance saves the data state of this Fragment class, but the events of lifecycle handle the view state of this Fragment.
which means any adjustments I made post creation on that fragment are overwritten with initial values again.
Yes, you're right. To avoid overwritting with initial values again, we can cache the fragment's view in OnCreateView for example like this:
private View rootView;
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
// Use this to return your custom view for this Fragment
// return inflater.Inflate(Resource.Layout.YourFragment, container, false);
if (rootView == null)
{
//first time creating this fragment view
rootView = inflater.Inflate(Resource.Layout.fragmentlayout1, container, false);
//Initialization
//TODO:
}
else
{
//not first time creating this fragment view
ViewGroup parent = (ViewGroup)rootView.Parent;
if (parent != null)
{
parent.RemoveView(rootView);
}
}
return rootView;
}
I have five fragments a user can switch between. One of these fragments loads a list of users from the server to populate the UI list on the fragment. I need the list information to persist if a user swipes to a different fragment and then swipes back to the original. I do not want the fragment to reload the users every time a user leaves the fragment and goes back.
I am looking at setRetainInsance(true) and was wondering if this is possible solution? What would be the best way for the fragment to retain the information without being created from scratch each time.
I am using this to switch between fragements -getSupportFragmentManager().beginTransaction().replace(R.id.searchLayout, ratingFragment).commit();
A Fragment is Just like any other object.
on Fragment transaction , the Fragment does not call OnCreate() method instead it starts from onCreateView , therefore , load your users and save it an instance variable and assign it in onCreate()
Example
class MyFragment extends Fragment{
List<users> userList;
void onCreate(){
userList = getUserList();}
//the list is loaded during Oncreate();
now imagine you have replaced the Fragment
now According to Andorid Framework , onCreate() is not Called again
instead onCreateView() is called
void onCreateView(){
//you can check whether instance Variable is initialised or not
if(userList != null) {
listview.setAdapter(new Myadapter(this,userList);
Replace the fragment by adding it to backstack.
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.addToBackStack(tag);
fragmentTransaction.replace(container, fragment, tag);
fragmentTransaction.commit();
Also create object of View and return it if it's not null.
private void View view ;
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
if (view != null)
return view;
view = inflater.inflate(R.layout.fragment_browse_recipe, container, false);
//initialize layout views
return view;
}
I am using Fragments and Activity extended by AppCompatActivity in an application.
Working:
I have two fragments "Dashboard" and "Order". I am replacing fragment after clicking "Order Button" from Dashboard Fragment, and coming back to "Dashboard Fragment" after pressing back button.
Problem
I have called an API on onCreateView() of Dashboard Fragment. When I press back from Order Fragment then I come to "Dashboard Fragment" the it recall the API. I don't want to recall the API if I come to the fragment by back press.
Thanks in advance.
Code to replace dashboard fragment with order fragment
// Click event of Order
#OnClick(R.id.ll_order)
void openOrder() {
if (isOrderNotClicked) {
OrderFragment fragment = new OrderFragment();
this.getFragmentManager().beginTransaction().replace(R.id.flContent, fragment, "Order").addToBackStack(null).commit();
isOrderNotClicked = !isOrderNotClicked;
}
}
I did had same problem so i solved by `View view;
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (view == null) {
//inflate layout and codes
}
return view;
}` but i dont know it is the best solution
I have a view that shows a List of Properties, at the bottom of the screen there's a button that opens a fragment containing a MapView.
#Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.find_property_btn_map:
PropertyMapFragment fragment = PropertyMapFragment.newInstance(false, null);
getActivity().getSupportFragmentManager().beginTransaction()
.addToBackStack(null)
.replace(((ViewGroup) getView().getParent()).getId(), fragment, PropertyMapFragment.class.getSimpleName())
.commit();
break;
}
}
The onCreateView method for my Properties fragments is as follows
#Override
public View onCreateView(LayoutInflater inflater, #Nullable ViewGroup container, #Nullable Bundle savedInstanceState) {
mRootView = inflater.inflate(R.layout.fragment_properties_list, container, false);
getmBtnMap().setOnClickListener(this);
getmBtnSaveSearch().setOnClickListener(this);
getmBtnSort().setOnClickListener(this);
getmListView().setAdapter(getPropertyAdapter());
getmListView().setOnItemClickListener(this);
getmListView().setOnScrollListener(this);
getmListView().setScrollingCacheEnabled(false);
searchProperties();
return mRootView;
}
searchProperties(); takes care of calling a Web Service and filling the ArrayAdapter.
The thing is that, when I open the MapFragment and then press the back button, my Property fragment is blank and the buttons do not respond to onClick events.
I tried debugging and saw that onCreateView() is being called when coming back to Property fragment, but the buttons are no longer working and the listview is nowhere to be seen.
What am I doing wrong?
If you are trying to launch that web view from a fragment, then try to use add fragment instead of replace.
For example :
getActivity().getSupportFragmentManager().beginTransaction()
.addToBackStack(null)
.replace(YOUR_CONTAINER_ID, fragment, PropertyMapFragment.class.getSimpleName())
.commit();
The code above is replace that fragment container with the new one and not adding that fragment on top of that. So when you do a replace fragment with that ID, it just replaces that view with new one.
Now,
Same code but with add:
getActivity().getSupportFragmentManager().beginTransaction()
.addToBackStack(null)
.add(YOUR_CONTAINER_ID, fragment, PropertyMapFragment.class.getSimpleName())
.commit();
Now, that web view fragment that you have will be added to the view/fragment and now when you press back from that web view, you previous fragment will be visible.
Just make sure that that the ID you are replacing is the same as the one in which you have all the other properties.
Maybe i misinterpreted the question so please correct me in that context.
Hope this helps.
addToBackStack() <--dont include this for your first fragment.-->
if(getSupportFragmentManager().getBackStackEntryCount() !=1){
fragmentTransaction.addToBackStack(null);
}
I have an app with hierarchy like this:
FragmentTabHost (Main Activity)
- Fragment (tab 1 content - splitter view)
- Fragment (lhs, list)
- Framment (rhs, content view)
- Fragment (tab 2 content)
- Fragment (tab 2 content)
All fragment views are being inflated from resources.
When the app starts everything appears and looks fine. When I switch from the first tab to another tab and back again I get inflate exceptions trying to recreate tab 1's views.
Digging a little deeper, this is what's happening:
On the first load, inflating the splitter view causes its two child fragments to be added to the fragment manager.
On switching away from the first tab, it's view is destroyed but it's child fragments are left in the fragment manager
On switching back to the first tab, the view is re-inflated and since the old child fragments are still in the fragment manager an exception is thrown when the new child fragments are instantiated (by inflation)
I've worked around this by removing the child fragments from the fragment manager (I'm using Mono) and now I can switch tabs without the exception.
public override void OnDestroyView()
{
var ft = FragmentManager.BeginTransaction();
ft.Remove(FragmentManager.FindFragmentById(Resource.Id.ListFragment));
ft.Remove(FragmentManager.FindFragmentById(Resource.Id.ContentFragment));
ft.Commit();
base.OnDestroyView();
}
So I have a few questions:
Is the above the correct way to do this?
If not, how should I be doing it?
Either way, how does saving instance state tie into all of this so that I don't lose view state when switching tabs?
I'm not sure how to do this in Mono, but to add child fragments to another fragment, you can't use the FragmentManager of the Activity. Instead, you have to use the ChildFragmentManager of the hosting Fragment:
http://developer.android.com/reference/android/app/Fragment.html#getChildFragmentManager()
http://developer.android.com/reference/android/support/v4/app/Fragment.html#getChildFragmentManager()
The main FragmentManager of the Activity handles your tabs.
The ChildFragmentManager of tab1 handles the split views.
OK, I finally figured this out:
As suggested above, first I changed the fragment creation to be done programatically and had them added to the child fragment manager, like so:
public override View OnCreateView(LayoutInflater inflater, ViewGroup viewGroup, Bundle savedInstance)
{
var view = inflater.Inflate(Resource.Layout.MyView, viewGroup, false);
// Add fragments to the child fragment manager
// DONT DO THIS, SEE BELOW
var tx = ChildFragmentManager.BeginTransaction();
tx.Add(Resource.Id.lhs_fragment_frame, new LhsFragment());
tx.Add(Resource.Id.rhs_fragment_frame, new RhsFragment());
tx.Commit();
return view;
}
As expected, each time I switch tabs, an extra instance of Lhs/RhsFragment would be created, but I noticed that the old Lhs/RhsFragment's OnCreateView would also get called. So after each tab switch, there would be one more call to OnCreateView. Switch tabs 10 times = 11 calls to OnCreateView. This is obviously wrong.
Looking at the source code for FragmentTabHost, I can see that it simply detaches and re-attaches the tab's content fragment when switching tabs. It seems the parent Fragment's ChildFragmentManager is keeping the child fragments around and automatically recreating their views when the parent fragment is re-attached.
So, I moved the creation of fragments to OnCreate, and only if we're not loading from saved state:
public override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
if (savedInstanceState == null)
{
var tx = ChildFragmentManager.BeginTransaction();
tx.Add(Resource.Id.lhs_fragment_frame, new LhsFragment());
tx.Add(Resource.Id.rhs_fragment_frame, new RhsFragment());
tx.Commit();
}
}
public override View OnCreateView(LayoutInflater inflater, ViewGroup viewGroup, Bundle savedInstance)
{
// Don't instatiate child fragments here
return inflater.Inflate(Resource.Layout.MyView, viewGroup, false);
}
This fixed the creation of the additional views and switching tab's basically worked now.
The next question was saving and restoring view state. In the child fragments I need to save and restore the currently selected item. Originally I had something like this (this is the child fragment's OnCreateView)
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstance)
{
var view = inflater.Inflate(Resource.Layout.CentresList, container, false);
// ... other code ommitted ...
// DONT DO THIS, SEE BELOW
if (savedInstance != null)
{
// Restore selection
_selection = savedInstance.GetString(KEY_SELECTION);
}
else
{
// Select first item
_selection =_items[0];
}
return view;
}
The problem with this is that the tab host doesn't call OnSaveInstanceState when switching tabs. Rather the child fragment is kept alive and it's _selection variable can be just left alone.
So I moved the code to manage selection to OnCreate:
public override void OnCreate(Bundle savedInstance)
{
base.OnCreate(savedInstance);
if (savedInstance != null)
{
// Restore Selection
_selection = savedInstance.GetString(BK_SELECTION);
}
else
{
// Select first item
_selection = _items[0];
}
}
public override View OnCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstance)
{
// Don't restore/init _selection here
return inflater.Inflate(Resource.Layout.CentresList, container, false);
}
Now it all seems to be working perfectly, both when switching tabs and changing orientation.