Get current Frame Size? Autoadjusting GUI to frame size?

[Zigster]

What I'm trying to do, is print a circle in the middle of the JFrame, and have it stay in the middle when I resize the JFrame by with the mouse after I have run it. Similar, for instance, to how this website readjusts everything when you resize the browser window.

What is the best way to do this? How can I find the size of the JFrame if people resize it with the mouse?

Thanks!

[DarrylBurke]

Print a circle? do you mean paint?

Lets see what you've tired so far, in the form of a SSCCE (Short, Self Contained, Correct (Compilable), Example).

db

[Zigster]

package Main;

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

public class DrawingColor{
	public static void main(String[] args) {
		DrawingColor d = new DrawingColor();
	}

	public DrawingColor(){
		JFrame frame = new JFrame("Drawing with Alpha");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().add(new ArenaComponent());
		frame.setSize(800,600);
		frame.setVisible(true);  
	}

	public class ArenaComponent extends JComponent{
		public void paint(Graphics g){

			g.setColor(Color.black);
			g.fillOval(240,10, 420,570);
			g.setColor(Color.white);
			g.fillOval(250,20,400,550); 
			g.setColor(Color.red);
			g.fillOval(400,100,10,10);
		}
	}
}

I want it to always be in the centre, even when I resize the frame with the mouse, but I don't know how to check what the frame size is and to automatically update when it changes.

[DarrylBurke]

First off, the recommended method to override for custom painting in a Swing component is paintComponent(...), not paint(...).

Within a painting method override in a JComponent subclass, you can use methods of the class such as getWidth() and getHeight() and compute the desired location from the returned int values.

You don't need to check the size of the frame.

db

[Zigster]

Thankyou DarrylBurke, it works!

package Main;

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

public class DrawArena{
	public static void main(String[] args) {
		new DrawArena();
	}

	public DrawArena(){
		JFrame frame = new JFrame("Drawing with Alpha");
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().add(new ArenaComponent());
		frame.setSize(800,600);
		frame.setVisible(true);
	}

	public class ArenaComponent extends JComponent{
		public void paintComponent(Graphics g){

			g.setColor(Color.black);
			g.fillOval(getWidth()/2-((getWidth()/2+20)/2),10, getWidth()/2+20,getHeight()-30);
			g.setColor(Color.white);
			g.fillOval(getWidth()/2-getWidth()/4,20,getWidth()/2,getHeight()-50); 
			g.setColor(Color.red);
			g.fillOval(400,100,10,10);
			System.out.println(getWidth());
		}
	}
}

[DarrylBurke]

Now learn to construct and deal with Swing components on the EDT: Lesson: Concurrency in Swing (The Java™ Tutorials > Creating a GUI With JFC/Swing)

Failure to honor Swing's single threaded rule can lead to intermittent buggy behavior that is next to impossible to analyze.

db

[DarrylBurke]

Also, that code can be made vastly more readable by assigning int variables instead of resorting to repeatedly calling the same methods, observing the coding conventions in respect of horizontal whitespace, and adding a bit of vertical whitespace.

        public void paintComponent(Graphics g){

            int w = getWidth();
            int h = getHeight();
            // System.out.println(w);

            g.setColor(Color.black);
            g.fillOval(w / 2 - ((w/2 + 20) / 2), 10, w / 2 + 20, h - 30);

            g.setColor(Color.white);
            g.fillOval(w / 2 - w / 4, 20, w / 2, h - 50); 

            g.setColor(Color.red);
            g.fillOval(400, 100, 10, 10);
        }

When extending a subclass of JComponent, it's good practice to invoke the super implementation of the overridden paintComponent(...), unless you are very sure that you're painting the entire area of the component.

db

[Zigster]

Thanks, I did what you suggested with the ints and spacing, and I will read some tutorials about Concurrency and JComponent.