在Android上检测scrollview的位置

Question

I'm working on a code at android for applying a form and before completing it, user has to accept a policy. If i put a TextView inside of ScrollView and a button for accepting, user can accept directly before read. But i must force user to scroll to bottom and then make Accept button became enabled and user accepts it then continue. First i tried this inside of Dialog Window . It's getting much more complicating. Now I'm trying it to inside another activity.

Is there any way to detect Scroll View 's position has reached to end ?

Answer 1

You can use the canScrollVertically method with a setOnScrollChangeListener, exemple :

 scrollView.setOnScrollChangeListener(new View.OnScrollChangeListener() {
            @Override
            public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
                if (scrollView.canScrollVertically(1)) {
                    //user can't scroll more in bottom direction
                }
            }
        });

If the canScrollVertically is reach the user is in the bottom of the scrollView and can't scroll more. If you put a negative value like -1 the method detect if the user can scrolling up

Answer 2

You can detect it via below code

scrollView.getViewTreeObserver()
    .addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() 
{
        @Override
        public void onScrollChanged() {
            if (scrollView.getChildAt(0).getBottom()
                 <= (scrollView.getHeight() + scrollView.getScrollY())) {
                //scroll view is at bottom
            } else {
                //scroll view is not at bottom
            }
        }
    });

Answer 3

1. Fragments automatically save and restore the states of their Views, as long they have IDs assigned to it. By Assiging an Id(android:id) to scroll view, do magic for you(scroll state restored) if you are using Fragment

2. For Activity

   // save index and top position int index = mList.getFirstVisiblePosition(); View v = mList.getChildAt(0); int top = (v == null) ? 0 : (v.getTop() - mList.getPaddingTop());

// ...

// restore index and position mList.setSelectionFromTop(index, top);