while using View pager, I face a strange problem.
In my project i have three fragment in a view pager, but while loading the second fragment by swiping from left to right , the OnCreate of third Fragment is automatically calling.in onCreate method i called an Api for getting some data.hence the Api is also called.Normal scenario is like that it only called while loading third fragment by swiping from left to right.
Thanks in Advance
View pager works same as listview.
It have same buffer of fragments to increase the UI experience.
so it creates fragments in advance and show to he user when asked.
so use http://developer.android.com/reference/android/support/v4/view/ViewPager.OnPageChangeListener.html
for your purpose.
Thanks
Related
So I have a fragment inside a viewpager which is contained inside a fragment which is getting initialize'd as shown in the debugger but doesn't have it's onCreate,onCreateView or any such methods being called. The activity containing has a bottom navigation view and contains 4 such fragments and this issue is only happening in 1 such fragment.
All these fragments and viewpagers and fragments inside them are created on the oncreate of the activity. If I move the logic to create the fragment to when a bottom tab is clicked, this issue gets solved on.
How is this possible ?
Only the currently active fragment and the two directly adjecant fragments are created when the viewpager is first shown. so the fragment for the first page, the fragment for the page shown if you "scroll to the left" and the fragment for the page shown when you "scroll to the right". the 4th fragment will be created when it is put in the next adjecant position.
so if you have fragments a,b,c,d in a viewpager like -a-[b]-c-d- where b is the first visible page, only a,b and c will be created at startup. when you scroll to c -a-b-[c]-d- onCreate for fragment d will be called.
You can control number of pages/fragments preloaded when you launch your activity by setting it's off Screen Page Limit on your view pager adapter. like this
mViewPager.setOffScreenPageLimit(limit)
If you set limit to 0 than only first fragment would be load.
https://spotandroid.com/2016/11/23/android-tricks-viewpager-and-offscreen-tabs/
https://techcodegeek.wordpress.com/2015/06/23/android-viewpager-and-performance-improvements/
Need more detail to know your issue.Issue which you are facing is not understood with information you have provided.
What i am doing is showing Fragment in view pager and has Gesture detector implemented on Whole view. When we touch the View i want to hide some layouts from current fragment and all other fragments in view pager.
But problem is this that view pager automatically generates next and previous view
and when i swipe to next view it does not hide those layouts but other Fragments other than its consecutive ones Layouts are Gone.
How do i refresh consecutive fragments of view pager from fragment itself.
Thanx in advance.
You should have an activity that control that ViewPager and detects what Fragments to display. That's the place to update the fragments.
Use the OnPageChangeListener listener and inform the fragment of the change.
If you want to do it from the Fragment itself, try onStart() or onResume()
Fragments can be notified of events, so they can take actions accordingly.
One way of doing this would be using a broadcast like in ViewPager Activity to notify a Fragment of a specific event
Other way is like #Antonio said, making it on the OnPageChangeListener (I suppose that would be a lot cleaner).
I am trying to implement swipe views with 2 tabs. For that, I am using view pager with 2 fragments. Now, the problem is that as soon as the main activity is opened (that contains those two tabs), onCreateView function is called for both the fragments. Please help me as how can I avoid calling of onCreateView of second fragment when one is in use.
Thanks,
Arpit
ViewPager retains the fragment to the left and to the right of the current view by default. This is to reduce a choppy user experience - that way you can begin swiping left or right and immediately see what is there without delay.
It is possible to disable (or increase the number of fragments to be retained) with setOffscreenPageLimit(0), but seriously consider if this is the right approach.
I am using ViewPager with 3 pages , each holding a listfragment. I place a footer for each listfragment's listview. Now, when I go to 3rd tab and then return to first, the footer is missing and the scroll listener also stops firing. I can get the scroll listener started again by binding the listener in onActivityCreated, but since list.addFooterView doesn't work after setListAdapter, I am not able to put in the footer view again into the listview.
Any help is much appreciated.
If you will only ever have 3 pages in your ViewPager, the easiest solution I can think of is to call viewPager.setOffscreenPageLimit(2). The first fragment will no longer move beyond the offscreen page limit when you visit the third fragment, so it will never be removed from the ViewPager.
I'm new in using view pager, I've done everything correctly, I conveted my activities into fragments and put them in FragmentPagerStateAdapter.
When testing it in the emulator, what I noticed is that the onCtreate to the onResume are called one fragment before the actual visibility on the view pager - it makes sense, the device wants to get ready for the next step, but the problem is that I have one fragment which calls a dialog every onStart so that actually happens on the wrong fragment.
What should be done?
You can use an OnPageChangeListener on your ViewPager to detect when you navigate to the right fragment.