I am trying to access the parent viewpager from inside a fragment, but i have no idea how to do that.
I need to switch the currentItem on the ViewPager after a onClick event inside the fragment.
Any ideas?
EDIT:
I want access to the parent view(ViewPager View) so that i can change the currentItem which is visible, from inside one of my fragments.
From fragment, call getActivity() which will gives you the activity in which the fragment is hosted. Then call findViewById(ViewPagerId) to get the ViewPager.
ViewPager vp=(ViewPager) getActivity().findViewById(ViewPagerId);
Edit: I must add, even though Eldhose answer's works, I would defend my approach. Because the less the fragment knows about the Activity containing it, the better. By doing this, you can get the parent view without depending on IDs, and you can still get information from it even if it isn't a ViewPager.
You can get the in the Fragment's onCreateView method.
The container param is the parent View, in that case, a ViewPager.
In Java:
#Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
ViewPager pager = (ViewPager) container;
//.... Rest of your method
}
Kotlin Version:
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup,
savedInstanceState: Bundle) {
val pager = container as ViewPager
//.... Rest of your method
}
The methods onCreateView and onViewCreated and onAttach are called too early.
The view is definitely attached to its parent view in the fragment's onResume method. This is a good place to then use getView().getParent()
Another way that helped me :
List<Fragment> fragment = getActivity().getSupportFragmentManager().getFragments();
for (Fragment f:fragment) {
if (f instanceof CreatCheckInFragment){
((ParentFragment) f).viewPager.arrowScroll(View.FOCUS_LEFT);
}
}
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 could use onCreateView() to get a reference to a a child view in a fragment, and then write a getter method inside the same fragment for this view, which would be called by the Activity to get a reference to the view. Like:
#Override
public View onCreateView(LayoutInflater layoutInflater, ViewGroup container, Bundle savedInstanceState) {
LinearLayout rootLinearLayout = (LinearLayout) layoutInflater.inflate(R.layout.my_fragment, container, false);
javaCameraView = (JavaCameraView) rootLinearLayout.findViewById(R.id.myFragment_javaCameraView);//***********
return rootLinearLayout;
}
JavaCameraView getCameraView() {
return javaCameraView;
}
But the problem is that I need the child view inside the Activity's onCreate(), and I think onCreateView() of fragment is called AFTER the onCreate() of Activity returns. Reference
So is there a way to get a reference to a fragment's view, inside the onCreate() of the Activity?
You are doing it wrong. You should not be exposing a fragment's UI elements to the hosting activity. A fragment should encapsulate it's views and functionality. If you are really only using the fragment as a UI component, create a custom View and use that in the activity.
To answer your question, no, you can't get a reference to the fragment's view in the activity's onCreate(). The reason is that the fragment's view doesn't exist until the fragment has gone through it's lifecycle. There's no guarantee when that's going to happen, which is why it's bad to be coding based on such assumptions.
If the fragment needs to communicate events back to the activity, have your activity implement a listener interface, and have the fragment call that interface when appropriate.
So in your case, you could do something like this in the fragment's onCreateView(),
if (getActivity() instanceof Listener) {
((Listener)getActivity()).onViewCreated(fragmentViews);
}
But again, that's doing it wrong.
To call onCreateView() manually should work, though this is not a good way to do it.
private JavaCameraView javaCameraView;
#Override
public View onCreateView(LayoutInflater layoutInflater, ViewGroup container, Bundle savedInstanceState) {
LinearLayout rootLinearLayout = (LinearLayout) layoutInflater.inflate(R.layout.my_fragment, container, false);
javaCameraView = (JavaCameraView) rootLinearLayout.findViewById(R.id.myFragment_javaCameraView);
return rootLinearLayout;
}
JavaCameraView getCameraView(LayoutInflater layoutInflater) {
if (javaCameraView == null) {
onCreateView(layoutInflater, null, null);
}
return javaCameraView;
}
You can then use yourFragment.getCameraView(getLayoutInflater()) in your onCreate().
I want to access a parent Fragment views in a child fragment which is attached with a View Pager. Means Parent Fragment contains a View Pager and View Pager then have a Fragment, and I want to use Parent Fragment Views in current Fragment of Pager.
Parent Fragment---->(Contains)View Pager------>(Contains)Child Fragment. Child Fragment wants to use Parent Fragment multiple views. Please suggest any solution regarding the same.
Thanks in advance.
in your child fragment use:
ParentFragment frag = ((ParentFragment)this.getParentFragment());
and in your parent fragment you can store the references of your required views and use getter setter to access them, another solution is creating a listener interface. follow below link to find out how to implement:
http://developer.android.com/training/basics/fragments/communicating.html
Inside Parent Fragment
ViewPagerAdapter adapter = new ViewPagerAdapter(getChildFragmentManager())
make sure it is getChildFragmentManager()
and inside the child fragment, to access anything from parent fragment
((ParentFragment)this.getParentFragment()).any_thing_inside_parent_fragment;
You can use the below code.
FloatingActionButton fab = getParentFragment().getView().findViewById(R.id.menu_item);
I was trying to get a sibling Fragment using the parent so I tried to use getParentFragment() from the child Fragment and it was always returning null. So instead I just got the fragment from the viewpagerAdapter here's what I did to access a sibling Fragment:
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
mViewPager = (ViewPager) container;
BasePagerAdapter bpa = (BasePagerAdapter) mViewPager.getAdapter();
MySiblingFragment f = (MySiblingFragment) bpa.getItem(1); //I know the position of the fragment so I hardcoded it
}
hopes this will help someone.
I get the variable and view from activity using this
YourActivity activity = (YourActivity) getActivity();
activity.mVar = 1;
activity.textView.setText("Number "+activity.mVar);
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.
I have a fragment added using
transaction.add(R.id.content, fragment, null);
and I need to start new fragment from this one. But to do this I need to know first fragment's container view id (R.id.content in my case). How can I get this?
I can just use this id directly but I suppose fragment shouldn't know such kind of details about parent activity. For example it will be impossible to use this fragment in another activity in this case.
May be "starting" fragment from another one is a bad practice and all fragment handling logic should be handled by activity itself? But creating nice sequences of fragments starting each other seems quite useful (for example detalView->moreDetailView->evenMoreDetailView).
You can access the container's id by calling
((ViewGroup)getView().getParent()).getId();
I don't know if I exactly understand your question, but you get the Container in onCreateView. I suppose you could stash it in a local variable.
public View onCreateView(LayoutInflater inflater,
ViewGroup container,
Bundle savedInstanceState) {
mContainer = container;
...
}
I think there's a more standard way of accessing the view rather than using
((ViewGroup) getView().getParent()).getId()
I will assume that you're working with a MainActivity that presents a list fragment, which can then present another list fragment upon clicking an item, and so on. I'm assuming that you've chosen to replace the main view of MainActivity with the contents of the list fragments you present.
Because each list fragment is being hosted in the MainActivity, you can always access the view of the MainActivity.
// Inside of onListItemClick...
FragmentManager fm = getFragmentManager();
Fragment fragment = new MyOtherListFragment();
FrameLayout contentView = (FrameLayout) getActivity().findViewById(R.id.content_view);
fm.beginTransaction()
.replace(contentView.getId(), fragment)
.addToBackStack(null)
.commit();
The above example assumes you have an XML layout resource that you set in the MainActivity, call the XML resource R.layout.activity_main, where there is a FrameLayout with the id R.id.content_view. This is the approach I took. The example I present here is a simpler version from the one that I actually wrote in my app.
Incidentally, my version of IntelliJ (version 1.0.1) warns me that
((ViewGroup) getView().getParent)
may throw a NullPointerException.
Assuming you have Fragment instance mCurrentFragment in Activity class.
You can get Fragment's container View via
int id = mCurrentFragment.getView().getParent().getId();
ViewGroup vg = (ViewGroup) findViewById(id); // Fragment's container View
The Kotlin version
val container = view?.parent as? ViewGroup ?: return
It can be added to a "hand-dandy" extension:
fun Fragment.container(): ViewGroup? {
return view?.parent as? ViewGroup
}
Then get the id
container.id
container().id
Add the new class
import androidx.navigation.NavController
class Navigator {
companion object {
var fragment1_id: Int = 0
var fragment2_id: Int = 0
var navController : NavController? = null
fun goFragment1()
{
navController?.navigate(fragment1_id)
}
fun goFragment2()
{
navController?.navigate(fragment2_id)
}
}
}
In main activity:
override fun onCreateView(
inflater: LayoutInflater,
container: ViewGroup?,
savedInstanceState: Bundle?
): View {
...
val navController = findNavController(R.id.nav_host_fragment_content_main)
Navigator.navController = navController
Navigator.fragment1_id = R.id.nav_fragment1
Navigator.fragment2_id = R.id.nav_fragment2
<navigation xmlns:android...
<fragment
android:id="#+id/nav_fragment1"
...
<fragment
android:id="#+id/nav_fragment2"
Click Listener in any fragment:
fun onClickButton(view: View)
{
Navigator.goFragment1()
}