Resize drawing to match frame size

Question

I've written an app that custom draws everything inside paint() based on fixed pixel positions. Then I disabled resize of the frame so its always visible.

However, now I would like to be able to resize it but I dont want to change my drawling code. I was hoping I could grab the 300x300 square of the Graphics g object and resize it to the JFrame current size after all of my drawling code, but I have no idea what I'm doing.

Here sample code. In this I want the 100x100 square to remain in the middle, proportionate to the resized JFrame:

package DrawAndScale;

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

public class DASFrame extends javax.swing.JFrame {
    public DASFrame() {
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        this.setSize(300, 300);
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new DASFrame().setVisible(true);
            }
        });
    }

    @Override
    public void paint(Graphics g) {
        g.setColor(Color.BLACK);
        g.fill3DRect(100, 100, 100, 100, true);
    }
}

Thanks.

Answer 1

Assuming you rename your method that paints for 300x300 as paint300, define a buffered image:

@Override public void paint(Graphics g) {
     Image bufferImage = createImage(300, 300);  // empty image
     paint300(bufferImage.getGraphics());  // fill the image
     g.drawImage(bufferImage, 0, 0, null);  // send the image to graphics device
}

Above is when you want to draw at full size (300x300). If your window is resized:

@Override public void paint(Graphics g) {
     Image bufferImage = createImage(300, 300);  
     paint300(bufferImage.getGraphics());
     int width = getWidth();
     int height = getHeight(); 
     CropImageFilter crop = 
         new CropImageFilter((300 - width)/2, (300 - height)/2 , width, height);
     FilteredImageSource fis = new FilteredImageSource(bufferImage, crop);
     Image croppedImage = createImage(fis);
     g.drawImage(croppedImage, 0, 0, null);
}

The new classes are from from java.awt.image.*.

I didn't test this code. It's just to send you in the right direction.

Answer 2

if you want to painting Custom paint then look for JLabel or JPanel and including Icon/ImageIcon inside, simple example about that

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

public class MainComponentPaint extends JFrame {

    private static final long serialVersionUID = 1L;

    public MainComponentPaint() {
        setTitle("Customize Preffered Size Test");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }

    public void display() {
        add(new CustomComponent());
        pack();
        setMinimumSize(getSize());
        setPreferredSize(getSize());
    SwingUtilities.invokeLater(new Runnable() {

        @Override
        public void run() {
            setVisible(true);
        }
    });
    }

    public static void main(String[] args) {
        MainComponentPaint main = new MainComponentPaint();
        main.display();
    }
}

class CustomComponent extends JComponent {

    private static final long serialVersionUID = 1L;

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(50, 50);
    }

    @Override
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        int w = getWidth();
        int h = getHeight();
        for (int i = 0; i < Math.max(w, h); i += 20) {
            g.drawLine(i, 0, i, h);
            g.drawLine(0, i, w, i);
        }
    }
}

Answer 3

Not an expert, but you could just scale the Graphics2D object (the passed Graphics is in fact a Graphics2D instance), where the x and y ratios are the ratios of the fixed size you chose to draw and the actual size of the frame.

See http://download.oracle.com/javase/6/docs/api/java/awt/Graphics2D.html#scale%28double,%20double%29

Answer 4

You could do this with some math.

public void paint(Graphics g){
    int height = 100;
    int width = 100;

    int x = (this.getWidth() / 2) - (width / 2);
    int y = (this.getHeight() / 2) - (height / 2);

    g.setColor(Color.BLACK);
    g.fill3DRect(x, y, width, height, true);

}

Or if you wanted to keep the width and height of the box with the same proportion, use int width = this.getWidth() / 3; and int height = this.getHeight() / 3.

The other option is to use Graphics2D.scale(), as JB pointed out, the passed Graphics object is actually a Graphics2D object.