I am trying to draw an incredibly basic shape using swing in Java, however for some reason it does not seem to be working. This is code that I downloaded from my lecturer that he showed us in a lecture, but when I run it the window opens but nothing is drawn and I have no idea why.
package graphicsEx;
import java.awt.*;
import java.awt.geom.*;
import javax.swing.*;
public class Lecture1Example extends JPanel{
// This is where the JPanel gets (re-)painted when the screen is refreshed.
public void paintComponent(Graphics g) {
// Cast to Graphics2D for more features.
Graphics2D g2D = (Graphics2D) g;
Rectangle2D rect = new Rectangle2D.Double(20,30,40,50);
g2D.setColor(Color.red);
g2D.draw(rect);
g2D.fill(rect);
}
public static void main(String args[]) {
JFrame frame = new JFrame("Playing with Graphics");
frame.setSize(500, 400);
frame.setVisible(true);
frame.setContentPane(new Lecture1Example());
}
}
I am using the Eclipse IDE.
Dear user1821475's lecturer:
Swing GUI objects should be constructed and manipulated only on the event dispatch thread .
"Subclasses of Swing components which have a UI delegate (vs. direct subclasses of JComponent
), should invoke super.paintComponent()
within their paintComponent
override.
"As a convenience add
and its variants, remove
and setLayout
have been overridden to forward to the contentPane
as necessary."
The outermost Container
should be setVisible()
only after invoking pack()
and other methods affecting geometry.
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