getWidth and getHeight of JPanel

[Kareem Mesbah]

hi, what's up all ?
I've question that is related to methods getWidth(); and getHeight(); of class JPanel.
actually I was trying to draw rainbow using fillArc(); method
then I already created my JFrame object that will hold this JPanel object and set its size to 400*400
I've noticed something, that when I getWidth and getHeight of the JPanel I get384, 362 respectively. they're not equal to the width and the height of the JFrame which I set earlier.
and that's ok, they're different objects and each one has its own attributes.
but I want to know depending on what the JPanel sets its size?

I've discovered that the JPanel's width and height are always less than the JFrame's width and height by 16 and 38 respectively.

here's my code

import java.awt.Color;import java.awt.Graphics;


import javax.swing.JPanel;




public class DrawingArcs extends JPanel {
    private static final Color VIOLET = new Color (128, 0, 128);
    private static final Color INDIGO = new Color (75, 0, 130);
    private Color[] colors = {Color.WHITE, Color.WHITE, VIOLET,
                             INDIGO,Color.BLUE, Color.GREEN,
                             Color.YELLOW, Color.ORANGE, Color.RED};
    
    public DrawingArcs () {
        setBackground(Color.WHITE);
    }// end constructor
    
    @Override
    protected void paintComponent(Graphics g) {
        
        super.paintComponent(g);
        
        int radius = 20;
        int centerX = getWidth()/2;
        int centerY = getHeight()-10;


        for (int counter = colors.length; counter > 0; counter--) {
            
            g.setColor(colors[counter-1]);//setting color
            g.fillArc(centerX-counter*radius, centerY-counter*radius, counter*radius*2, counter*radius*2,0,180);//drawing rainbow
            
        }// end for


    }// end paintComponent
    
}

and here's the main method

import javax.swing.JFrame;



public class RainbowTest {


    
    public static void main(String[] args) {
        
        DrawingArcs arcs = new DrawingArcs();
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 250);
        frame.add(arcs);
        frame.setVisible(true);


    }// end main


}

[pbrockway2]

The frame is always going to be bigger than the panel you add because the frame will include things like the title bar.

The actual size of components depends on the LayoutManager of whatever container they are added to. Use of layout managers in this way enables a gui to be "fluid" - that is, components will be change their size and position depending on the overall size of the gui.

If you haven't seen it before there is a whole section on Creating a GUI (including layout) in Oracle's Tutorial.

[Kareem Mesbah]

thanks :)

[pbrockway2]

You're welcome.