Repaint a circle

Question

I want to repaint a circle whenever a button is pressed.

Currently, I have it whenever I press a button, it prints to the console what button I pressed. For example, if I press the "Paint Red" button, I want it to fill the circle with red, and the same with the other colors as well. I'm trying to wrap my head around the whole paint/paintComponent difference.

This is what I have so far...

public class testCircle extends JPanel {

public void paint(Graphics g)
{
    setSize(500,500);

    int R = (int) (Math.random( )*256);
    int G = (int)(Math.random( )*256);
    int B= (int)(Math.random( )*256);
    Color randomColor = new Color(R, G, B);
    g.setColor(randomColor);
    g.drawOval(75, 100, 200,200);
    g.fillOval(75, 100, 200, 200);
}

public static void main(String[] args)
{

     JFrame frame = new JFrame();
     frame.setSize(400, 400);
     testCircle circlePanel = new testCircle();
     frame.add(circlePanel);



     JButton redButton = new JButton("Paint Red");
     redButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent event)
         {
             System.out.println("Red Button Pressed!");  
         }
     });
     JButton blueButton = new JButton("Paint Blue");
     blueButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent event)
         {
             System.out.println("Blue Button Pressed!");
         }
     });

     JButton greenButton = new JButton("Paint Green");
     greenButton.addActionListener(new ActionListener() {
         public void actionPerformed(ActionEvent event)
         {
             System.out.println("Green Button Pressed!");
         }
     });

     redButton.setPreferredSize(new Dimension(100,100));
     blueButton.setPreferredSize(new Dimension(100,100));
     greenButton.setPreferredSize(new Dimension(100,100));

     frame.setLayout(new FlowLayout());
     frame.add(redButton);
     frame.add(blueButton);
     frame.add(greenButton);
     frame.setVisible(true);
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}

score 3 · Answer 1 · edited May 23 '17 at 12:19

Consider these changes to your code:

As discussed here, Swing programs should override paintComponent() instead of overriding paint().
Give your panel an attribute for currentColor.
```
private Color currentColor;
```
Let each button's ActionListener set currentColor and invoke repaint().
```
currentColor = color;
repaint();
```
Use Action for to encapsulate your program's functionality.

A complete example is examined here.

score 0 · Answer 2 · answered Oct 09 '16 at 07:52

0

You don't trigger a "repaint" anywhere in your code. That should work:

 redButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent event) {
                System.out.println("Red Button Pressed!");
                frame.invalidate();
                frame.validate();
            }
        });

answered Oct 09 '16 at 07:52

PeterMmm

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1

You shouldn't have to `validate()` the entire `Container`; it should be possible to `repaint()` just the panel, as outlined [here](http://stackoverflow.com/a/39941735/230513). – trashgod Oct 09 '16 at 08:57

Repaint a circle

2 Answers2