Trying to get a square change color on button click

[Timothy Oldbean]

EDIT: Obviously a beginners question! Probably in the wrong forum, please feel free to move mods! Apologies!

I thought I'd help myself understanding the GUI and ActionListener proces a bit better by sussing out how to do something simple like putting a button and a rectangle on a screen and then having it change color from blue to red on buttonclick.

Appears I've ended up in a swamp and everytime I move I get sucked farther in.

I soon found out I have no clue how to easily change the color of something when clicking a button so I thought I'd fake it first by simply running a different color panel on mouseclick. And that failed miserably too! Trying to use the boolean swoosh in two different classes is not the way to go. So a little help, hint or push in the right direction would be greatly appreciated!

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

public class KnopOefen implements ActionListener {
	
	JFrame frame;
	

	public static void main(String[] args) {
		boolean swoosh = true;
		KnopOefen knop = new KnopOefen();
		knop.go();
		
	}
	
	public void go() {
		frame = new JFrame();
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		
		JButton button = new JButton("Click to make the square red!");
		button.addActionListener(this);
		
		Rectangle recty = new Rectangle();
		

		frame.getContentPane().add(BorderLayout.SOUTH, button);
		frame.getContentPane().add(BorderLayout.CENTER, recty);
		frame.setSize(300,300);
		frame.setVisible(true);
	}
	
	public void actionPerformed(ActionEvent event) {
		boolean swoosh = false;
		KnopOefen knip = new KnopOefen();
		knip.go();
	}

}

import java.awt.*;
import javax.swing.*;

public class Rectangle extends JPanel{
	
		
		public void paintComponent(Graphics g) {
			
			if (swoosh == false) {
			g.setColor(Color.blue);
			
			g.fillRect(20, 50, 100, 100);
			
			}  else {
			g.setColor(Color.red);
			
			g.fillRect(20, 50, 100, 100);	
			}
		 }
	}

[Timothy Oldbean]

I'm trying to get the boolean to work in another class through using getter and setter but now I've run into a new problem. I get an error on the getter method.

public class KnopOefen implements ActionListener {
	private boolean swoosh = true;
	JFrame frame;
	
	public void setSwoosh(boolean swoosh) {
		this.swoosh = swoosh;
		
	public boolean getSwoosh() {
		return swoosh;
	}
	}

[Timothy Oldbean]

Stuck for hours and as soon as I post here I start getting somewhere.

I think I've got the getter and setter part sorted now:

public class KnopOefen implements ActionListener {
	private boolean swoosh = true;
	JFrame frame;
	
	boolean getSwoosh() {
		return swoosh;
	}
	void setSwoosh(boolean swoosh) {
		this.swoosh = swoosh;
	}

The challenge I have now is to get the value of boolean swoosh into the if else statement which I'm wrongly attempting to do like so at the moment:

import java.awt.*;
import javax.swing.*;

public class Rectangle extends JPanel{

boolean swish = getSwoosh();

		public void paintComponent(Graphics g) {
			
			if (swish == true) {
			g.setColor(Color.blue);
			
			g.fillRect(20, 50, 100, 100);
			
			}  else {
			g.setColor(Color.red);
			
			g.fillRect(20, 50, 100, 100);	
			}
		 }
}
		

[Michael Dunn]

you've a number of things around the wrong way

comments should be self-explanatory

compile/run, the clicking the button numerous times will alternate between the two colors

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

 class MyRectangle extends JPanel{//Rectangle class already exists

   boolean swoosh;//needs it here
   public void setSwoosh(boolean trueFalse){swoosh = trueFalse;}
   public boolean getSwoosh(){return swoosh;}
   @Override
    protected void paintComponent(Graphics g) {

      //if (swoosh == false) {
     // g.setColor(Color.blue);

      //g.fillRect(20, 50, 100, 100);

      //}  else {
      //g.setColor(Color.red);

      //g.fillRect(20, 50, 100, 100);
      //}
      super.paintComponent(g);//almost always needed
      g.setColor(swoosh? Color.red:Color.blue);
      g.fillRect(20, 50, 100, 100);//only need it once, after setting color to blue or red
     }
  }
class KnopOefen implements ActionListener {

  JFrame frame;
  MyRectangle recty;//listener needs to reference it

  public static void main(String[] args) {
    //boolean swoosh = true;
    //KnopOefen knop = new KnopOefen();
    //knop.go();
    new KnopOefen().go();

  }

  public void go() {
    frame = new JFrame();
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    JButton button = new JButton("Click to make the square red!");
    button.addActionListener(this);

    //MyRectangle recty = new MyRectangle();//moved declaration to class field
    recty = new MyRectangle();

    frame.getContentPane().add(BorderLayout.SOUTH, button);
    frame.getContentPane().add(BorderLayout.CENTER, recty);
    frame.setSize(300,300);
    frame.setVisible(true);
  }

  public void actionPerformed(ActionEvent event) {
    //boolean swoosh = false;
    //KnopOefen knip = new KnopOefen();
    //knip.go();
    recty.setSwoosh(!recty.getSwoosh());
    recty.repaint();
  }

}

note: if you had added 'recty' anywhere else but center, it would not have shown up (try adding it to NORTH).
without components, it normally needs to have a preferredSize set

[Timothy Oldbean]

Thanks a lot Michael!

I'm going to take my time tomorrow comparing your code to mine and see where I went wrong. By the first look of it I see you doing a couple of things I haven't seen yet and thus don't understood so I might have a couple of extra questions later after I try to find it out myself.