自定义有监听器的ScrollView

public class ObservableScrollView extends ScrollView {
 
    public ObservableScrollView(Context context) {
        super(context);
    }
 
    public ObservableScrollView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
 
    public ObservableScrollView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }
 
    public interface OnScrollChangedListener {
        public void onScrollChanged(int x, int y, int oldX, int oldY);
    }
 
    private OnScrollChangedListener onScrollChangedListener;
 
    public void setOnScrollListener(OnScrollChangedListener onScrollChangedListener) {
        this.onScrollChangedListener = onScrollChangedListener;
    }
 
    @Override
    protected void onScrollChanged(int x, int y, int oldX, int oldY) {
        super.onScrollChanged(x, y, oldX, oldY);
        if (onScrollChangedListener != null) {
            onScrollChangedListener.onScrollChanged(x, y, oldX, oldY);
        }
    }
}

参考自：http://stormzhang.com/android/2015/02/01/android-observable-scrollview/