检测滚动视图到达顶部 - Android

Question

我已经使用滚动视图使用我的Android应用activity_main.xml中.卷轴工作得很好.但问题是我需要添加一个Scroll to top按钮,这样如果用户开始滚动按钮应该是可见的,如下面的链接..

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

我需要在Android中执行此操作..

Answer 1

使用以下代码检测滚动的顶部.

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;
        }
    });

Answer 2

 scrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
            @Override
            public void onScrollChanged() {
                if (scrollView != null) {
                    if (scrollView.getScrollY()==0) {
                        Toast.makeText(getContext(),"top",Toast.LENGTH_SHORT).show();
                    } else {

                    }
                }
            }
        });