I have a ViewPager and multiple tabs.
One of these tabs controls the settings, which affects every other tabs.
Everything updates itself perfectly fine when I change the settings, except for the pages that are kept in memory. In order to get these to update I have to select a tab far enough from it, then come back.
Is there a way to force these tabs to recreate themselves?
Thank you
According to this question on SO, you can reset the adapter which will reload all the pages:
viewPage.setAdapter( adapter );
The duplicate that that question is linked to also gives some helpful information, such as calling .notifyDataSetChanged() on your ViewPager adapter.
Related
I am using a view pager to show a list of images, it works fine but the main issue is that when I swipe between images, there is some kind of fading between images.
for example if I have 5 pictures and the first one is visible when i swipe the second one is visible directly.
if i decided to swipe faster, it shows white screen then the image appears "moving from first to third quickly - as example".
I think the fragment is being recycled - is there any way to avoid this ??
It's hard to tell with no details on your implementation, but just to answer your last question (I'm not sure if it will necessarily solve your problem) - if you are using a fragments in your ViewPager and are currently using a FragmentStatePagerAdapter, you can switch to a FragmentPagerAdapter, which will keep the fragments in memory (although it will of course use more memory, so you might not want to do it if you have a large number of fragments in your ViewPager). You can also specify how many offscreen pages for the ViewPager to keep using
mViewPager = (ViewPager)findViewById(R.id.pager);
mViewPager.setOffscreenPageLimit(2);
In the above case it would keep 2 pages on each side of the currently viewed page. Sorry, I would have confirmed the specific problem with you before posting this answer, but I don't have the status yet :(
I have an scrollable tabs + swipe activity with 3 different fragments on it. It works well but I don't want my fragments to be destroyed when I navigate between them. For example, when I create the activity, it's shown the first fragment but it's created the second one too. When I swipe to the second fragment, the third is created, so I can swipe to the third one and it will be created before I open it. When I return to the second one, my third fragment still stays created but when I return to the first one, the third fragment is deleted.
There would be any way to avoid this? I don't want my fragments to be deleted when I navigate between them.
If you use a ViewPager, it has a method called setOffscreenPageLimit(int limit). Try and see if setting that higher works
This answer should help you figure out what's going on. Pretty much you are most likely using a FragmentStatePagerAdapter, when you should be using a FragmentPagerAdapter. That keeps it from deleting fragments not in view.
If, for performance reasons, you need to have the fragments deleted when they aren't being used, there are other options. Either look at why the performance is that bad when you have only 3 tabs (It shouldn't be unless you are doing something wrong with a listview, or have a map open, etc.) or you can code the fragments to save their state when they are being destroyed (which should be happening anyways with a FragmentStatePagerAdapter).
If that doesn't help, we'll need more info on what you are doing exactly to help.
Offtopic: thank you for your time and sorry for my English.
The problem is the lag when swiping on ViewPager.
The configuration used is a TabHost with Tabs (and dummy content), ViewPager with four fragments and FragmentPagerAdapter to manage it.
All 4 fragments have a list, some with other widgets in the layout. The thing is 2 fragments, or the 2 list in those fragments are quite heavy. The list items are LinearLayout with ~10 weighted items inside binded with a CursorAdapter. I know here resides the big problem, but I have struggled my small head to get an approach to this "percentage width" list item without any luck.
But, after some logs, I have figured out that the 3 managed fragments are "invalidated" during every swipe. I mean "invalidated" because what I see is every list binding items many ( a lot of ) times. And because of the redrawing of the 3 list, including my 2 heavy lists, the lag occurs.
2 things more to point of my code: I'm using cursor loaders, that I'm sure are not the cause of recreation because loader callbacks aren't arise on swipe.
On FragmentPagerAdapter.onPageSelected I'm only updating the current tab.
Setting ViewPager.setOffScreenPageLimit(3) to keep 4 fragments alive do things worse. Even when I swipe from fragment 3 to 4, the list on first fragment is re-rendered, what I really don't want and don't understand.
My workaround is using the onPageSelected to set the visibility of current list view to Visible and the others hidden. With these approach the lag disappears (let's say 95%), but I can see, when I scroll the empty list view before is created.
I would like to ask, if I'm wrong at some point, maybe missing an important idea. If anyone has a possible solution, maybe avoiding those recreations (I don't know how) or, if other people is getting same, and there is nothing to do to solve it.
I will try to take I look to ViewPager source, but I've just opened the file woouu..
I will try to get a test project with this issue.
Thank you very much.
In my app I have the dropdown enabled in the ActionBar. The user has two elements to choose from. Depending on the choice I want a ViewPager to show different contents from different FragmentPagerAdapters. The user has to have the ability to switch all the time.
I've tried to set two different PagerAdapters in the listener with no luck. The Pager would just reload the previous fragments every time. Similar problems are described here and here. However in my approach I don't want to change the content of one adapter. I really just want to switch between two separate adapters.
This whole thing seems really confusing to me. Are there any known workaround for this or is there an alternative solution to my problem?
If it is possible for your application, I would suggest using FragmentStatePagerAdapter instead of FragmentPagerAdapter. Each adapter should be able to store a separate list of fragments, and should keep the saved state of your fragments when you switch to the other adapter.
I've tried to set two different PagerAdapters in the listener with no luck. The Pager would just reload the previous fragments every time.
I am assuming that you are using FragmentPagerAdapter or FragmentStatePagerAdapter. Both of those store their fragments by tag name in the FragmentManager, and therefore this switching approach will not work.
Are there any known workaround for this or is there an alternative solution to my problem?
One approach would be to fork FragmentPagerAdapter or FragmentStatePagerAdapter, replacing the makeFragmentName() method to use an alternative tag syntax, and use the revised adapter class for one of your two.
I'm a newbie Android developer and I'm trying to create an Android application with 2 tabs, using Activities for each tab. This is basically how it should work:
Tab A has 1 button
Tab B has 1 ListView
When the user clicks on the button in Tab A the application must put a value in the ListView in Tab B
My question is: how can I update the ListView in Tab B when I click on the button in Tab A? I know how to put values in a ListView when it's on the same tab where the button is located but my approach doesn't work when the ListView is in a different tab. I tried...
ListView myListInTabB = (ListView)findViewById(R.id.list_on_tabB);
but didn't work :-/
Any suggestion?
Thanks in advance.
Im not sure you actually need seperate activites for this, unless you are doing some specific work between your activities. Most tab solutions you see in Android solutions work simply by hiding the Views that are not related to the current shown tab. You will find the "visibility" property helpful for making this happen. Also, making sure all of your Views are in the same Activity lets you access their objects all the time, regardless of their visibility.
You don't do that. Just ensure the underlying Adapter has the latest data. Calling requery() on the Cursor does the trick, it automatically updates the ListView attached to it.
Edit: use notifyDataSetChanged() to let the list know that the data is stale.