Re-use fragments of ViewPager & FragmentPagerAdapter

Question

How to reuse the fragments inside view pager ??? I have view pager and inside that Having 3 fragments. I'm creating new instance of fragment to all time. So It's take more space in memory. In this 3 fragments having perform same functionality. While Im creating new instance every time. It's having more problems like. 1) It take times to keyboard open and close. 2) Scrollview take times to scroll. 3) Edit text take time to focus on and off.

https://prnt.sc/or86ec

Here screen that I have implemented viewpager with 3 fragment. In swipe it's look like same.

I have created Pager adapter:

public class ProposalDetailPagerAdapter : FragmentStatePagerAdapter, CardAdapter
{
    private static int NUM_ITEMS = 3;
    private float mBaseElevation;

    public ProposalDetailPagerAdapter(Android.Support.V4.App.FragmentManager fm, float baseElevation) : base(fm)
    {
        mBaseElevation = baseElevation;
    }

    public override int Count => NUM_ITEMS;

    public override int GetItemPosition(Java.Lang.Object @object)
    {

        if (@object is ProposalDetailFragment)
        {
           ProposalDetailFragment fragment = (ProposalDetailFragment)@object;
           if (fragment != null)
           {
               fragment.UpdateFragmentAfterCreate();
           }
        }

        return base.GetItemPosition(@object);
    }

    public int getCount()
    {
        return NUM_ITEMS;
    }

    public override Android.Support.V4.App.Fragment GetItem(int position)
    {
       switch (position)
        {
           case 0:
               return OpenFragment(0);
           case 1:
               return OpenFragment(1);
           case 2:
               return OpenFragment(2);
          default:
               return null;
      }
    }


    private Android.Support.V4.App.Fragment OpenFragment(int position)
    {

           ProposalDetailFragment createdFragment = new ProposalDetailFragment();

        Bundle bundle = new Bundle();
        bundle.PutInt("position", position);
        createdFragment.Arguments = bundle;
        return createdFragment;
    }


    public override Android.Support.V4.App.Fragment GetItem(int position)
    {

        switch (position)
        {
            case 0:
                return OpenFragment(0);
            case 1:
                return OpenFragment(1);
            case 2:
                return OpenFragment(2);
            default:
                return null;
        }

    }

}

In this adapter, created 3 fragments. But It's having lot's of memory problem. Because lot's of condition having in fragments. and created 3 instance of memory. So How to resolve this issue ???

Junior Jiang · Answer 1 · 2019-08-14T08:35:56.410

0

Here is a solution :

In ProposalDetailPagerAdapter , can override DestroyItem method.And comment out the method of calling the parent class to avoid repeated creation of the fragment.

As follow:

public class ProposalDetailPagerAdapter : FragmentStatePagerAdapter, CardAdapter
{
    ...

    public override void DestroyItem(ViewGroup container, int position, Java.Lang.Object @object)
    {
        //base.DestroyItem(container, position, @object);
        // Comment out the calling parent class
    }
    ...
}

edited Aug 14 '19 at 08:35

answered Aug 12 '19 at 09:48

Junior Jiang

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But It creates three instance of viewpager – Vanjara Sweta Aug 13 '19 at 07:03
@VanjaraSweta Yeah , if be added , will execute else method, this will not create new instance of fragment.Not understanding why creats three instance of viewpager. – Junior Jiang Aug 13 '19 at 07:09
It's create 3 instance of fragment because I have to show 3 views at a time. – Vanjara Sweta Aug 13 '19 at 09:50
@VanjaraSweta If want to re-use fragment , you need to only creare one instance of fragment. And three fragments can not be shown at the same time.When one appearing, fragment removes previous subcontent ,then adds new subcontent .Then you just need to use only one fragment to show three views. – Junior Jiang Aug 14 '19 at 01:15
how we can remove previous sub content while another showing?? – Vanjara Sweta Aug 14 '19 at 07:39
@VanjaraSweta Sorry,Maybe mistaking your shared screenshot. I think fragement re-used here seems to be impossible . – Junior Jiang Aug 14 '19 at 07:47
Not getting any proper solution. – Vanjara Sweta Aug 14 '19 at 07:49
@VanjaraSweta I have updated an solution in answer , you can have a try . – Junior Jiang Aug 14 '19 at 08:36
but it creates frgament one time when viewpager is initiated. – Vanjara Sweta Aug 14 '19 at 09:15
@VanjaraSweta Yeah, if want to re-use ,just need to create once . When scrolling ViewPaged it will not re-create Fragement, then improve the fluency of UI. – Junior Jiang Aug 14 '19 at 09:19
@VanjaraSweta Oh, it's strange. Here is a simular discussion about this topic with java code . Although can be a good reference. https://stackoverflow.com/questions/6976027/reusing-fragments-in-a-fragmentpageradapter – Junior Jiang Aug 14 '19 at 09:56
Yes,I have seen this post. And I applied all solution. – Vanjara Sweta Aug 14 '19 at 09:59
But I have to change many code so it's not possible.I have viewpager-> scrollview -> Recyclerview and others views – Vanjara Sweta Aug 14 '19 at 10:02
@VanjaraSweta Not sure .But you can have a try , I will leave office now.Later if find another solution found ,I will share with you :) – Junior Jiang Aug 14 '19 at 10:02

Re-use fragments of ViewPager & FragmentPagerAdapter

1 Answers1