How To Get Percentage Of Scroll In Nestedscrollview Any Time (smoothly)?

I want to change the alpha of toolbar base on scroll, like below: At first, the toolbar is transparent and by scrolling to the bottom it will more and more visible and at the end

Solution 1:

You can add an scrollListener to ScrollView.

The calculation of scrolled percentage of your scrollView:

doublepercent= ((((float) scrollY) / ((float) (scrollContentHeight - screenHeight + statusBarHeight))));

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• The top edge of the displayed part of your view: scrollY = scrollView.getScrollY()

• The scrollView has one child and scrollContentHeight = scrollView.getChildAt(0).getHeight() is the height of the content of scrollView.

• We need to calculate the max height of top edge in full scrolled state: scrollContentHeight - screenHeight + statusBarHeight

• Finished! percent = scrollY*100 / (scrollContentHeight - screenHeight + statusBarHeight)

• And set the color: view.setBackgroundColor(Color.argb((int) (255.0 * (percent/100)), r, g, b));

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scrollView.getViewTreeObserver().addOnScrollChangedListener(newViewTreeObserver.OnScrollChangedListener() {
        @OverridepublicvoidonScrollChanged() {
            intscrollY= scrollView.getScrollY();
            intscrollContentHeight= scrollView.getChildAt(0).getHeight();
            intscreenHeight= Utility.getScreenHeight(context);
            intstatusBarHeight= Utility.getStatusBarHeight(context);

            intcolor= getResources().getColor(R.color.colorPrimary);
            intr= (color >> 16) & 0xFF;
            intg= (color >> 8) & 0xFF;
            intb= (color >> 0) & 0xFF;

            doublepercent= ((((float) scrollY) / ((float) (scrollContentHeight - screenHeight + statusBarHeight))));
            if (percent >= 0 && percent <= 1)
                toolbar.setBackgroundColor(Color.argb((int) (255.0 * percent), r, g, b));
        }
    });

Solution 2:

try this

scrollview.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
            @Override
            publicvoidonScrollChanged() {
                double scrollViewHeight = scrollview.getChildAt(0).getBottom() - scrollview.getHeight();
                double getScrollY = scrollview.getScrollY();
                double scrollPosition = (getScrollY / scrollViewHeight) * 100d;
                Log.i("scrollview", "scroll Percent Y: " + (int) scrollPosition);
            }
        });

it will show the percentage from 0 to 100%

Solution 3:

Try this method:

    nestedScrollView.setOnScrollChangeListener((NestedScrollView.OnScrollChangeListener) (v, scrollX, scrollY, oldScrollX, oldScrollY) -> {
                int verticalScrollableHeight = v.getChildAt(0).getMeasuredHeight() - v.getMeasuredHeight();
                float verticalPercentage = ((float) scrollY) / verticalScrollableHeight;

Solution 4:

These answers are ignoring the effect of any top or bottom padding on the scroll view, which is effectively extra scroll span, so I found I needed:

valverticalScrollableHeight= firstChild.measuredHeight - scrollView.measuredHeight + scrollView.paddingBottom + scrollView.paddingTop
        listener(scrollView.scrollY.toFloat() / verticalScrollableHeight)