Using Java's 2d Graphics Outside of the Main Class

Question

I have a class called survival that contains the main method, an initializes the program. Instead of putting the code for graphics int this class, how can I move it into a new class which is separate from survival?

Here is Survival.java:

package survival;
import javax.swing.*;

public class Survival extends JFrame { 
    private static int applicationWidth = 1024;
    private static int applicationHeight = 768;

    public Survival() {
        setTitle("Survival");
        setResizable(false);
        setSize(applicationWidth, applicationHeight);
        setVisible(true);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

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

Here is GraphicsDisplay.java:

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

public class GraphicsDisplay extends JPanel {
   @Override public void paintComponent(Graphics g) {
       g.fillOval(50, 50, 100, 100);
   }
}

beware: the paintComponent is invalid if the panel reports itself as being opaque (as it does by default) — kleopatra, Dec 15 '11 at 12:39

score 3 · Accepted Answer · edited May 23 '17 at 10:08

It seems like you can just add() an instance of GraphicsDisplay in the Survival constructor.

...
setResizable(false);
add(new GraphicsDisplay());
setSize(applicationWidth, applicationHeight);
...

In this case, GraphicsDisplay acts as a view of your implicit, circular model. You might look at how this example separates classes in the Model–View–Controller pattern.

Because GraphicsDisplay is a custom component that is rendered entirely by your program, consider overriding getPreferredSize() to define the panel's geometry. Then the enclosing frame can just use pack() without knowing anything about other display panels used in the game. This LissajousPanel is an example.

KV Prajapati · Answer 2 · 2011-12-15T12:53:17.810

2

You have to extend the JPanel (JComponent) and override a paintComponent(Graphics g) method.

For instance,

public class MyPanel extends JPanel
{ 
   @Override
   public void paintComponent(Graphics g) {
       super.paintComponent(g); // suggestion of @kleopatra
   }
}

edited Dec 15 '11 at 12:53

answered Dec 15 '11 at 02:39

KV Prajapati

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Can you modify the code I added to describe what you are showing? – Conner Ruhl Dec 15 '11 at 05:12
-1 for a) empty paintComponent override b) getGraphics - that's _not_ how custom painting is done in Swing – kleopatra Dec 15 '11 at 12:43
1

thanks :-) to clarify even more, you might add a comment inside the methods which hints at doing the custom painting there – kleopatra Dec 15 '11 at 13:02

score 0 · Answer 3 · answered Dec 15 '11 at 05:22

0

In the Constructor add the component (JPanel) to the container (JFrame):

public Survival() {
    setTitle("Survival");
    setResizable(false);
    setSize(applicationWidth, applicationHeight);

    this.getContentPane().add( new GraphicsDisplay() );

    setVisible(true);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
}

answered Dec 15 '11 at 05:22

Singleton

1

1

"As a conveniance `add` and its variants, `remove` and `setLayout` have been overridden to forward to the `contentPane` as necessary."—[`JFrame`](http://docs.oracle.com/javase/7/docs/api/javax/swing/JFrame.html) – trashgod Dec 15 '11 at 06:22

Using Java's 2d Graphics Outside of the Main Class

3 Answers3