How to get the current Y offset of a ScrollView

Question

ScrollView has a method for setting the x and y scroll offset, but no method for getting the current offset (all I\'m really interested is the y offset, since ScrollView onl

Answer 1

Call getScrollY() on the ScrollView

See here for the documentation: http://developer.android.com/reference/android/view/View.html#getScrollY%28%29

Answer 2

I achieve to get by the following. First get screen heigh and width.

DisplayMetrics metrics = getResources().getDisplayMetrics();
float screenWidth = metrics.widthPixels;
float screenHeight = metrics.heightPixels;

then to find out the document height (the total, what is being shown and what is out of the screen)

public float getDocumentHeight(){
    return (computeVerticalScrollRange() * screenHeight)/computeVerticalScrollExtent();
}

Finally to get the offset

public float getTopY(){
    return (getDocumentHeight() * computeVerticalScrollOffset())/computeVerticalScrollRange();
}

This give you the top of the window relative to the part of the document you are seeing so you could find the exact position of an event by

public boolean onTouchEvent(MotionEvent event) {
      int y = event.getY() + (int) getTopY();
    }

You can also do something similar to handle the width

Answer 3

Why don't you try something like this ?

targetScrollView.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
        @Override
        public void onScrollChanged() {
            int scrollX = targetScrollView.getScrollX();
            Log.d(TAG, "scrollX: " + scrollX);
        }
    });

Answer 4

What about: computeHorizontalScrollOffset() and computeVerticalScrollOffset().

Answer 5

If you are certain that you should get some value after using getScrollY() or getTop(), try to put those method inside a

yourScroolView.post(new Runnable() {
@Override
public void run() {
    Toast.makeText(getApplicationContext(),"Current Y is : "+getScrollY,Toast.LENGTH_SHORT).show();
            }
        });

Now it should work. According to my understanding about this method, it will only run after the layout being drawn. That can be one of the reason why you kept getting 0 previously. Hope it helps.