如何使这个ActionListener完全重绘JFrame？

Question

private static final long serialVersionUID = 1L;
String[] options = {"1","2","4","8","16","20","40","100","400"} ;
int[] optionsNum = {1,2,4,8,16,20,40,100,400};
JComboBox<String> box = new JComboBox<>(options);
JLabel prompt = new JLabel("How complex do you want the circle to be?");
ImageIcon image;

Circle p = new Circle(1);
int boxindex = 0;

public CircleDrawer(){
    image = new ImageIcon(p.getImage());
    box.setSelectedIndex(boxindex);
    setLayout(new FlowLayout());
    add(new JLabel(image));
    add(prompt);
    add(box);
    pack();
    setSize(851, 950);
    setTitle("Circle Drawer");
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    box.addActionListener(this);

}

public void actionPerformed(ActionEvent e) {
    if (e.getSource() == box){
        boxindex = box.getSelectedIndex();
        p.setComplexity(optionsNum[boxindex]);
        image = new ImageIcon(p.getImage());
        add(new JLabel(image));
        validate();
    }
}

public static void main(String[] args) {
    CircleDrawer f = new CircleDrawer();
    f.setVisible(true);
}

Basically, I have this code. It references a class called Circle , which calculates some points on the outer edge of a circle and draws them using a paintComponent . In this class, there is a method called getImage , which takes what the paintComponent method drew and puts it into a BufferedImage.

public BufferedImage getImage() {

    BufferedImage hello = new BufferedImage(805, 805, BufferedImage.TYPE_INT_ARGB);
    Graphics g = hello.getGraphics();
    paintComponent( g );

    return hello;
}

Like so.

The problem I'm running into is that I can't find a way for it to completely re-draw the JFrame . I've tried clearing the JFrame within the actionPerformed method using removeAll() and then COMPLETELY setting up the frame all over again ( add all of the components, pack , setSize , setTitle , etc) and then repaint , revalidate , or just validate it.

If I simply have it add the image and then validate it, I can see the image being updated, but it's just getting tacked on at the end of the JFrame (just like I would expect it to using a FlowLayout ) but that's not the behavior I need. It just shows that it is sort of working.

My question is this: How do I make it re-draw the JFrame when the user changes options inside of the JComboBox ?

Answer 1

Graphics g = hello.getGraphics();
paintComponent( g );

Don't use getGraphics() and never invoke paintComponent() directly. Swing will invoke the proper painting methods are required.

 add(new JLabel(image));
 validate();

When you add (remove) components from a visible GUI the general structure of the code is:

add(...);
revalidate(); // to invoke the layout manager
repaint(); to repaint the components