CODEWITHSUNDEEP
androidandroid-viewpagerandroid-support-library
Denis Steinman
Denis Steinman

Reputation: 7799

ViewPager became show incorrect pages after update of the support libraries

I updated the Google support libraries to rev. 23.2.0. And ViewPager became show wrong page views.
ViewPager uses a custom page transformer:

private class ZoomOutPageTransformer implements ViewPager.PageTransformer {

    private static final float MIN_SCALE = 0.85f;

    private float mCenterOffset;
    private boolean mIsFixedCenterOffset = false;

    public void transformPage(View view, float position) {
        final int pageWidth = view.getWidth();
        final int pageHeight = view.getHeight();

        if(!mIsFixedCenterOffset) {
            mCenterOffset = position;
            mIsFixedCenterOffset = true;
        }

        position -= mCenterOffset;

        if (position <= 1) {
            final float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
            final float vertMargin = pageHeight * (1 - scaleFactor) / 2;
            final float horzMargin = pageWidth * (1 - scaleFactor) / 2;

            if (position < 0) {
                view.setTranslationX(horzMargin - vertMargin / 2);
            } else {
                view.setTranslationX(-horzMargin + vertMargin / 2);
            }

            view.setScaleX(scaleFactor);
            view.setScaleY(scaleFactor);
        }
    }
}

And has page margin:

ViewPager viewPager = (ViewPager) v.findViewById(R.id.vpDaySlider);
mAdapter = new DayPagerAdapter(getActivity(), fm, mWeekNumber);
viewPager.setAdapter(mAdapter);
viewPager.addOnPageChangeListener(this);
viewPager.setPageTransformer(false, new ZoomOutPageTransformer());
Point display = SettingsManager.getDisplaySize(getContext());
final int padding = (int)(display.x * 0.1);
viewPager.setPageMargin(padding);

Now, it looks like below:
enter image description here
I even don't know where bug is... How to fix it? I need to page fills parent space and scales down only on scrolling.
Warning in LogCat:

W/FragmentManager: moveToState: Fragment state for DayFragment{24ec179 #2 id=0x7f0c00b4} not updated inline; expected state 3 found 2

ADDED I realized what a bug. ZoomOutPageTransformer fixes the first position of page. And it must be 0 or nearly at zero but after update the first value of position > 1 (for example 1.1 on my phone) but the next (second) value is real page position (for my phone: 0).
Because of what is happening? I think it's a wrong behaviour of ViewPager.

Upvotes: 2

Views: 5093

Answers (1)

Denis Steinman
Denis Steinman

Reputation: 7799

I fixed this bug so:

private static class ZoomOutPageTransformer implements ViewPager.PageTransformer {

        private static final float MIN_SCALE = 0.85f;

        private ViewPager mViewPager;
        private float mPositionFixer;
        private boolean isSetFixer = false;

        public  ZoomOutPageTransformer(ViewPager viewPager) {
            mViewPager = viewPager;
        }

        public void transformPage(View view, float position) {
            final int pageWidth = view.getWidth();
            final int pageHeight = view.getHeight();

            if(!isSetFixer) {
                final int mClientWidth = mViewPager.getMeasuredWidth() -
                        mViewPager.getPaddingLeft() - mViewPager.getPaddingRight();
                mPositionFixer = ((float)mViewPager.getPaddingStart()) / mClientWidth;
                isSetFixer = true;
            }

            position -= mPositionFixer;

            if (position <= 1) {
                final float scaleFactor = Math.max(MIN_SCALE, 1 - Math.abs(position));
                final float vertMargin = pageHeight * (1 - scaleFactor) / 2;
                final float horzMargin = pageWidth * (1 - scaleFactor) / 2;

                if (position < 0) {
                    view.setTranslationX(horzMargin - vertMargin / 2);
                } else {
                    view.setTranslationX(-horzMargin + vertMargin / 2);
                }

                view.setScaleX(scaleFactor);
                view.setScaleY(scaleFactor);
            }
        }
    }

Although I cannot understand this bug in Support libraries rev. 23.2.0.

Upvotes: 4

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