Changing scroll bar color programmatically - codenameone

Question

I have a requirement to change the color of the scroll bar based on some user selection.
In a typical form, I have switch case where is I am setting the scroll bar color using:
#Override
protected void beforeTopic(final Form f) {
int scrollColor=0x000000;
switch(userSelectedTopic)
{
case 1:
scrollColor=0x59be8a;
break;
case 2:
scrollColor = 0xff3333;
break;
.
.
.
}
// setting color to scroll thumb
Style s = UIManager.getInstance().getComponentStyle("ScrollThumb");
System.out.println(scrollColor);
s.setFgColor(scrollColor);
s.setBgColor(scrollColor);
s.setBgTransparency(255);
UIManager.getInstance().setComponentStyle("ScrollThumb", s);
s = UIManager.getInstance().getComponentStyle("ScrollThumb");
System.out.println("-->>"+s.getFgColor());
}
What happens is that the color code is picked properly for the first time.
When this form is invoked again, with a different user selection, the color code value changes as per the switch statement. The style attributes also change.
However, the initial color applied to the thumb prevails!
What could be the issue?
I tried f.refreshTheme(); but this does not seem to work. It just sustains the first applied color

Answer 1

That won't work. getComponentStyle will always return a copy which is the way it should be. Otherwise when you do something like getUnselectedStyle().setFgColor() you will change the color of all the components.
One way to do that is to update the theme, you can define another theme that just sets the color of the scroll then apply it using addThemeProps of the UIManager and then invoke refreshTheme() on the form.
The alternative is to derive the scrollable component and paint the scroll yourself or hide the scroll entirely and paint it yourself using the glasspane or something like that.