Android : onscrollchanged() is getting called multiple times

I have this custom scrollview, and I want to auto scroll my calendar to a particular event in calendar. but everytime it is scrolling to the end, after debug I get to know that, onscrollchanged() method is getting called twice. can you help me with this. I am new to android.

public class ObservableScrollView extends ScrollView {
private OnScrollListener mScrollListener;

public ObservableScrollView(Context context, AttributeSet attrs) {
    super(context, attrs);
}

@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
    super.onScrollChanged(l, t, oldl, oldt);
    if (mScrollListener != null) {
        mScrollListener.onScrollChanged(this);
    }
}

public boolean isScrollPossible() {
    return computeVerticalScrollRange() > getHeight();
}

public void setOnScrollListener(OnScrollListener listener) {
    mScrollListener = listener;
}

public static interface OnScrollListener {
    public void onScrollChanged(ObservableScrollView view);
}
}

Thanks in advance.