Detect scroll view reaching its top - Android

Question

I have used scrollview in my Android app using activity_main.xml. The scroll is working perfectly. But the thing is i need to add a Scroll to top button so that if the user starts scrolling the button should be visible like the link below..

http://webdesignerwall.com/demo/scroll-to-top/scrolltotop.html?

I need to do this in Android..

Answer 1

Use the below code to detect the top of the scroll.

final ViewTreeObserver.OnScrollChangedListener onScrollChangedListener = new
            ViewTreeObserver.OnScrollChangedListener() {

                @Override
                public void onScrollChanged() {
                    if (scrollview.getScrollY() == 0) {
                        swipeRefreshLayout.setEnabled(true);
                    } else
                        swipeRefreshLayout.setEnabled(false);
                }
            };
    scrollview.setOnTouchListener(new View.OnTouchListener() {
        private ViewTreeObserver observer;

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if (observer == null) {
                observer = scrollview.getViewTreeObserver();
                observer.addOnScrollChangedListener(onScrollChangedListener);
            } else if (!observer.isAlive()) {
                observer.removeOnScrollChangedListener(onScrollChangedListener);
                observer = scrollview.getViewTreeObserver();
                observer.addOnScrollChangedListener(onScrollChangedListener);
            }
            return false;
        }
    });