My app has no XML. It is all made of Java code dynamically. In the app, when in portrait mode, only one screen is visible - a fragment which changes inside a FrameLayout inside a single activity. When rotating, the same single activity gets another FrameLayout (on the right) for displaying two halves of the screen.
The app itself has a user flow of fragments.
If a user rotate to landscape, the menu (ListFragment) is shown in the left half of the screen, and the right half of the screen is empty.
If a user selects one item from the ListFragment (on the left), the right FrameLayout shows another ListFragment or FormFragment (this depends of JSON response). If another list shows in the right FrameLayout, if a user selects one item from that list, now this ListFragment goes in left FrameLayout, and in the right is FormFragment etc.
So it is a "fine dance" of replacing the fragments inside left and right FrameLayouts which is then placed on the backstack. So if a user rotate the screen in some moment, I need a way to preserve that backstack, so the user can go back through a backstack when in landscape.
Also, if a user is in portrait mode, I also need a way to preserve that backstack when he rotates from landscape to portrait.
The problem:
How to retain (keep) the backstack of all the fragments, if a user rotates screen from portrait to landscape, and vice versa, so he can go back like it was no change at all.
Is it possible to achieve this in Android? I've tried with setRetainInstance() but I've also read that it is not the way if you want to work with backstack, and also I'm very new to all this, so if anyone can help me with this problem.
Thanks in advance!
You can use addToBackStack() method for adding fragment transaction to back stack. This means that the transaction will be remembered after it is committed, and will reverse its operation when later popped off the stack.
Code snippet :
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
fragmentTransaction.replace({your_Fragment_view});
fragmentTransaction.addToBackStack(null);
fragmentTransaction.commit();
Don't forget to do the addToBackStack(null) so your previous state will be added to the backstack allowing you to go back with the back button.
Reference link - https://developer.android.com/reference/android/app/FragmentTransaction.html#addToBackStack(java.lang.String)
Related
I have an app with a single activity showing a fragment to the user. On a click on a button, the activity shows another fragment but keeping the previous one in the backstack. I have now two problems:
On rotation (particularly in the second fragment), the data entered in the EditTexts is cleared
I want the backstack to be also restored with the text previously entered in the second fragment.
The problem is that when I save data to bundle using OnSaveInstanceState(...), I successfully get it again from OnViewCreated(...) but when I use editText.setText(str), the text is not shown.
At the moment, I think this is because the fragment is then destroyed and recreated by the parent Activity.
How can I do to make it work properly?
Thanks.
Make your fragments retainable:
setRetainInstance(true);
See the following guideline on orientation change state android orientation changes `
I have 2 fragments(Frag A, Frag B) which are shown in multi pane in landscape with different container id (R.id.containerA,R.id.containerB) respectively.
My screen flow for 1st fragment is FragA->FragA1->FragA2
My screen flow for 2nd fragment is FragB->FragB1
I am adding each fragment to backstack. So I have around 5 fragments in backstack.
Actual order of navigating is FragA->FragB->FragA1->FragB1->FragA2
Now when I press back button, I want FragB1 to be popped out first from backstack instead of FragA2. I know fragments are maintained in a stack but how to handle this particular multi pane scenario ?
Should I use reflection like mentioned in this post ?
Android Reorder Fragment Backstack
Any other alternatives ?
If you simply want to get FragB1 instead of FragA2, you can check by obtaining the name of the fragment and then go one step back if name of the fragment is FragA2. You can get the name using the following code:
FragmentManager.BackStackEntry backEntry=getFragmentManager().getBackStackEntryAt(getActivity().getFragmentManager().getBackStackEntryCount()-1);
String str=backEntry.getName();
I've implemented navigation in my Android app as one Activity and many Fragments.
When I open new child Fragment, I call this:
FragmentTransaction tx = getSupportFragmentManager().beginTransaction() .addToBackStack(null).replace(R.id.fragment_container, f)
.setBreadCrumbTitle(f.getClass().getSimpleName());
tx.commit()
This works quite well, as old fragment isn't destroyed, so when I go back in the back stack, the old fragment retains the scroll position and everything entered on it.
The problem is, in one Fragment I actually need to pause something when I add another fragment above it. I've thought that onPause() will be called, but it doesn't - I suppose that all other fragments live beneath the ones on top of them.
On the side note, I also think that my app gradually slows down as the user navigates deeper. Shouldn't I be replacing the fragment in the transaction instead, so only one is on the top?
in my Activity, I have a layout containing 3 FrameLayouts, one at the top, one at the left and one at the "center".
Now, I sometimes only want to display one or two of them. Atm I am doing it this way:
FrameLayout frame = (FrameLayout) findViewById(R.id.framelayout_menu_left);
frame.setVisibility(...);
frame = (FrameLayout) findViewById(R.id.framelayout_content);
frame.setVisibility(...);
frame = (FrameLayout) findViewById(R.id.framelayout_menu_top);
frame.setVisibility(...);
However this can get really ugly results, e.g. when I switch the "content" Fragment and hide the top and/or left FrameLayout. It all starts flickering as the "content" Fragment jumps to the top and/or left and only afterwards is replaced.
Also, I can obviously not navigate back to another setup, so is there any other way to do this?
Kind regards,
jellyfish
Edit:
Maybe a little drawing makes my question clearer...
A shows a Layout of 3 FrameLayouts containing 3 different Fragments. Each color represents one distinct Fragment.
Now what I want to do is to switch from A to D.
I am doing this by replacing the blue Fragment with the yellow Fragment via a FragmentTransaction.
However, this still keeps the other Frames visible, so I hide them via the code above.
Now, Frame.setVisibility() is called way before commit(), so in B and C the blue Fragment "jumps" to the left and the top and only afterwards (in D) is replaced with the yellow Fragment. This produces a nasty flickering.
As a workaround, I now hide all three FrameLayouts before the transaction and re-show the ones I need once the transaction has finished. But there still is the problem that I can't go back via the back button as this isn't a real transaction.
I would have two suggestions. Firstly, if you both add a fragment transition effect and do the visibility changes after the transaction, that would probably substantially reduce much of your flicker effect
ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
Secondly, I've simply given up on having the system manage the fragment stack for me -- it seems that this only works well with simple transactions. Override onBackPressed and do your own logic there.
--randy
I'm trying to add animation to my android app, and knew a lot about transition animation between activities, and about fragments. So I have MainActivity with some view (image), and SecondActivity which is empty itself, but contains fragments, which then needs to be used to display some detail information about this image. I've read about postponeentertransition() and it worked. But the problem is, that this fragment in second activity have links(or transitions) to the same kind of fragment.
Let's say in main activity I have set of images of cars, then I click one, second activity is starting and waiting for fragment loading, and then shows animation. And then, in this fragment I have "similar cars" recycler, and choose one of them, and wants, to show its details the same way, but with adding this fragment to the backstack (not replacing). So the problem is that transition name of the view in main activity and big image of fragment are the same (which is obvious), and transition name in fragment's recycler and big image of the next fragment have to be the same too(otherwise app doesn't know how to make the animation). On the other side, fragment (which was added) has to be the same class, but its different instance.
I just want to set up animation without crashing the existing architecture.:) If you have any solutions or advices how to make animation between different instances of one fragment, please help.)
Use setCustomAnimations on the Fragment transaction (see below). It doesn't matter if the instances are from the same class.
FragmentTransaction transaction = mActivity.getSupportFragmentManager().beginTransaction();
// To animate the fragment
// NOTE: Must be before replace/add otherwise it doesn't work
transaction
.setCustomAnimations(enter, exit, popEnter, popExit)
.replace(R.id.frame_container, fragment, null)
.commit();