Java: need an explanation about graphics

Question

Java: need an explanation about graphics

I would like to know a little more about Graphics and how to use it.

I have this class:

public class Rectangle 
{
    private int x, y, length, width;
    // constructor, getters and setters

    public void drawItself(Graphics g)
    {
        g.drawRect(x, y, length, width);
    }
}

And a very simple shot like this:

public class LittleFrame extends JFrame 
{
    Rectangle rec = new Rectangle(30,30,200,100);      

    public LittleFrame()
    {
        this.getContentPane().setBackground(Color.LIGHT_GRAY);
        this.setSize(600,400);
        this.setVisible(true);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

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

I just want to add this rectangle to the LittleFrame container. But I don't know how to do it.

+3

java swing graphics

Rob 23 jan. 13 at 8:16

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1 answer

Dan D. · Accepted Answer · 2013-01-23T08:26:57+0000

I suggest you create an additional class that extends JPanel

as shown below:

import java.awt.Graphics;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JPanel;

public class GraphicsPanel extends JPanel {

    private List<Rectangle> rectangles = new ArrayList<Rectangle>();

    public void addRectangle(Rectangle rectangle) {
        rectangles.add(rectangle);
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        for (Rectangle rectangle : rectangles) {
            rectangle.drawItself(g);
        }
    }
}

Then in your class, LittleFrame

you will need to add this new panel to the frame's content panel and add yours Rectangle

to the list of rectangles to be colored. At the end of the constructor LittleFrame

add:

GraphicsPanel panel = new GraphicsPanel();
panel.addRectangle(rec);
getContentPane().add(panel);

Java: need an explanation about graphics

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