I have a FragmentStatePagerAdapter which is used as the ViewPagerAdapter for my ActionBar etc. I am trying to change a fragment and add the previous one to the backstack. It appears, however, that this is not possible.
If I look at the Code it seems as though the only way around this is to destroy the old Fragment then add the new one. This is not optimal for what I am trying to do (multipage form). What I really want to do is take the existing fragment and detach it, then add a new fragment and add it to the backstack.
I have tried this without the ViewPager and it works flawlessly. Short of rewriting my own FragmentStatePagerAdapter class that allows me to replace items in the Fragments List is there anything else I can do?
Related
There are already some open threads about this subject but mine is a little different and I can't seem to find out how to do it. This is my problem:
I'm creating a listview (recyclerview) inside a fragment which I put inside my Viewpager. This listview represent a timeline/agenda of the current day. Whenever the user swipe left or right, the exact same listview fragment needs to pop up with different data (data from the day before or after). Whenever you click on one of the items in the listview, the fragment is replaced by a detailed fragment.
This doesn't sounds so hard but here comes the tricky part:
All the examples I see on the internet show different Fragment classes inside the Viewpager which makes it possible to do a transaction from the listfragment to the detailed fragment, and all the examples that use multiple fragments of the same class don't do a transaction to a detailed fragment.
Whenever I'm trying to do the transaction to the detailed fragment, it looks like it can't find the proper fragment container (since there are 3 of the same now). I'm pretty sure of it since the new fragment does appear but the old fragment stays visibile underneath (when I don't use the viewpager it works fine).
If anyone could provide me with a simple example of a viewpager with multiple fragments of the same class that have a transaction to a detailed fragment you would save my day.
Regards
I am using a FragmentStatePagerAdapter in combination with a view pager, which is nested in a fragment on Android. Thus, I am using the ChildFragmentManager in combination with the FragmentStatePagerAdapter to create my fragments.
So far so good, but here is the problem:
If I open a different Activity without finishing the activity that hosts the fragment with the view pager and afterwards resume it, the fragment that was selected in the ViewPager is empty. If I switch the fragment in the ViewPager before I open the different Activity, this issue does not appear. After returning and seeing the empty Fragment in the ViewPager, I am still able to switch the next Fragments, but if I try to switch back to the empty Fragment, I get a NullPointerException. This issue does not occur if I switch between the Fragment hosting the ViewPager and a different Fragment or if I change orientations.
If I use the FragmentManager instead of the ChildFragmentManager, I do not have this issue when switching to a different Activity, but it will then occur if I switch between the hosting and a different fragment or if I change the orientation.
So here's what I already tried without any success:
* Use FragmentStatePagerAdapter adapter and FragmentPagerAdapter
* Use setRetainedInstance(true and false)
* Use getChildFragmentManager() and getFragmentManager()
* Override getItemPosition() return POSTION_NONE and use notifyDataChanged() in onResume()
The only thing that is currently doing the trick is recreating the PagerAdapter in onResume() and re-initializing the ViewPager, but I think that's really bad practice as everything needs to be recreated.
So is there somebody, who can explain to me how a correct implementation should look like, or why the fragments can become empty (they are not null, I checked that). I am searching for a more elegant solution rather than recreating everything each time I resume my activity.
Any help is really appreciated.
I am writing an android app that will have a number of different screens that I would like to swipe between, each screen will be a full page except for action bar header. On each screen there is the ability to open up another screen which will also be multiple screens that I would like swipeable. What is the best way to handle this. Do I have one fragment manager that holds all the screens and handle the onPageScrollStateChanged to only allow swipes between the current accessable screens or would I be best off nesting the fragments. I hope the above makes sense.
Thanks in advance
Sounds like you want to use a ViewPager to to swipe between views (Fragment extends View)
You could either:
In a single activity use a FragmentManager that switches between the parent and child Fragments, each with their own ViewPager and nested Fragments
Start a new activity to hold each ViewPager
Both are valid, if the Fragments need to communicate with each other or the Activity option one might suit the project needs better.
For the swiping between views you indeed need a ViewPager
For the nested fragments I would use a wrapper. I struggled a lot with fragments and found that this is the best way. A wrapper is very simple. This is just a fragment that holds other fragments. In the onCreate() of this fragment you get the childFragmentManager and add the fragment you originionally wanted to add. If you want to go to a new fragment you simply get the childFragmentManager again and replace the current item. This way you have nested fragment. You can add this to the backstack in order to get back navigation, but you need to override onBackPressed() inside your activity and call the method popBackStack() from the fragmentManager in order to get the first fragment back.
If you have any questions, comment below.
Im relatively new to android so im trying my hand at what i though would be an easy-ish app but I've ran into an issue to do with view/activity flow that i cant get an understanding on.
i have a fragmentActivity that uses a Viewpager to create tabs, each of those tabs is its own fragment class, thats all fine and working, but now i need to have one of the tabs display a list, when selected it takes you to another "view", my problem is how to create the first list and then how to handle tha clicking of an item in that list to take you to the new view so that the tabs stay in place and the back button doesn't exit the app.
currently ive swapped out the fragment with a list fragment that uses an arrayAdapter to build itself, this has worked as far as the list goes but i cant for the life of me figure out how to utelise its onclick() method to move on the the next screen, without as i said losing the tabs or having the back button simply exit.
so im not sure if A, the list fragment is the way to go, or B if it is how to move on to a new screen correctly
i can post code if needed but its a very general implementation of the classes mentioned so im not sure code will help
The callback you want to handle a click on an item in the list is onListItemClick.
As far as presenting a new screen, you can use a FragmentTransaction to replace your fragment with a new one, which gets a little hairy if you're doing this inside of a ViewPager. The code would look something like this:
FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.replace(R.id.some_containging_view, new SomeFragment())
.addToBackStack(null).commit();
Otherwise, you could simply launch a new Activity, which is simpler, but will mean that the tabs won't be present on the new screen unless you duplicate them there.
An elegant solution was finally found here, it uses a wrapper fragment around my list fragment so the pager is just concerned with the wrapper, meanwhile within the wrapper i can perform fragment transactions to my hearts desire, one small note the linked code uses getChildFragmentManager() that needs to be changed to regular fragmentmanager() from support.app for the backstack stuff to work.
I'm having a bit of trouble implementing a design based around multiple ViewPagers.
At a high level, I have a FragmentActivity with just a FrameLayout as it's content. I have 3 different Fragments that I want to display. All 3 are full screen and only 1 will be used at a time.
Fragment 1 is a basic fragment with some TextViews and ImageViews.
Fragment 2 has a ViewPager and a FragmentPagerAdapter that feeds it several simple fragments.
Fragment 3 has a ViewPager and a FragmentPagerAdapter that feeds it several simple fragments (that are different from Fragment 2)
In my FragmentActivity onCreate() I get the FragmentManager and begin a transaction to replace whatever is in my FrameLayout with a new instance of Fragment 2.
At this point everything is working as expected. My ViewPager in Fragment 2 works perfectly.
Now I have a menu option that replaces the Fragment 2 in my FrameLayout with a new instance of Fragment 3. This also works fine.
The problem arises when I try to put Fragment 2 back into the FrameLayout with another replace transaction. I see my PagerIndicater at the top, but my pages are blank.
I've tried just creating a new instance of my Fragment 2 and calling a replace transaction. I've also tried setting a tag on my Fragments when I call replace and adding a findFragmentByTag check before my replace instead of creating a new instance. Both gave me the same result of blank pages after my second replace.
For reference
My first design was simply a FragmentActivity with a ViewPager and a ViewIndicater. I only had Fragment 2 and Fragment 3 from my description above and a menu option to switch between them. To switch I had 2 different FragmentPagerAdapters defined and just called ViewPager.setAdapter to set the selected FragmentPagerAdapter. This was working perfectly, but now I need a new top level Fragment that isn't using ViewPager at all. This is why I decided to move my ViewPagers out into their own Fragments. My idea being that I would just swap in my fragments to a FrameLayout.
I don't have my code in front of me right now so I can't post any, but I'll add some code to my question tomorrow to help facilitate answers.
This question is a possible duplicate of Navigating back to FragmentPagerAdapter -> fragments are empty.
If your app can handle it (API 17), use getChildFragmentManager(). This problem seems to occur when using a Fragment to host your ViewPager and using FragmentPagerAdapter. Changing to FragmentStatePagerAdapter seemed to fix the problem as well, but I still think using getChildFragmentManager() is the smartest thing to do.
brockoli you can used not "good way". But for my it's worked.
You can use in view 2 layouts, where you bind fragments. First - for fragment with fragments. Second - for other fragments.
On replace fragment with fragments do not replace, but only change visibility first layout to gone and add new fragment to second layout. On back, remove fragment from second layout and set visibility for first layout to visible.