CODEWITHSUNDEEP
androidandroid-viewpager
rcperso
rcperso

Reputation: 500

Android ViewPager preloading too much fragments

A ViewPager preloads fragments.

But with a pageWidth=0.5 (2 fragments per screen), I think it loads too much views before the current position...

fff I have pageLimit=1 and pageWidth=0.5.
It should be ok to preload LEFT1 and LEFT2, but why LEFT3 ?
LEFT3 is not on the next left screen...

I tried to understand ViewPager.java from support v4:
https://android.googlesource.com/platform/frameworks/support/+/support-library-27.1.1/core-ui/src/main/java/android/support/v4/view/ViewPager.java#1155

line 1155, it says

// Fill 3x the available width or up to the number of offscreen
// pages requested to either side, whichever is larger. But for multiple fragments per screen, it loads more before than current and after the current position.

With the Google sample project https://github.com/googlesamples/android-SlidingTabsBasic/
adding

protected void onCreate(Bundle savedInstanceState) {
   [...]
   mViewPager.setCurrentItem(25);

@Override
public float getPageWidth(int position) {
     // 2 fragments per screen
     return .5f;
}
@Override
public int getCount() {
    // 50 fragments
    return 50;
}
public Fragment getItem(int position) {
    [...]
    Log.d("debugpageviewer", "position="+position);
}

And it loads 7 fragments (3 before current position). The smaller the pageWidth, the more fragments are loaded before.

So, is this a bug or did I miss something ?

Upvotes: 1

Views: 479

Answers (2)

Chester Fung
Chester Fung

Reputation: 370

You shall use ViewPager2 with FragmentStateAdapter. See official explanation here:

Use ViewPager2 to slide between fragments: https://developer.android.com/develop/ui/views/animations/screen-slide-2

Migrate from ViewPager to ViewPager2: https://developer.android.com/develop/ui/views/animations/vp2-migration

Upvotes: 0

Rayan Hatout
Rayan Hatout

Reputation: 640

Try calling setOffscreenPageLimit() on your ViewPager in your onCreate method.

For example mViewPager.setOffscreenPageLimit(2) will make sure that no more than 3 fragments are always kept around: the current one and the two adjacent ones.

Upvotes: 1

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