I am subclassing both JFrame and JPanel objects to build a simple menu UI for a game. The menu is a PNG image that will be rendered inside the JPanel’s paintComponent(Graphics) method. I hooked a KeyListener to the JFrame in order to receive keyboard commands, and it is working (space bar exits the program). Although I am declaring a layout manager (BorderLayout), as advised by other Stack Overflow posts, JPanel’s paintComponent() is not called.
My code follows below:
public class MainScreen extends JFrame {
public MainScreen() {
super();
initialize();
}
public final void initialize() {
setLayout(new BorderLayout());
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
add(new Menu(this), BorderLayout.CENTER);
setResizable(false);
setLocationRelativeTo(null);
}
class Menu extends JPanel implements KeyListener {
JFrame frame;
Image imagem;
public Menu(JFrame frame) {
super();
this.frame = frame;
initialize();
}
public final void initialize() {
frame.removeAll();
frame.setTitle("Menu principal");
frame.setSize(new Dimension(Comuns.LARGURA, Comuns.ALTURA));
frame.addKeyListener(this);
ImageIcon icone = new ImageIcon("res\MenuScreen.png");
imagem = icone.getImage();
frame.setVisible(true);
}
@Override
public void keyTyped(KeyEvent e) {
// nada aqui
}
@Override
public void keyPressed(KeyEvent e) {
int c = e.getKeyCode();
switch (c) {
case KeyEvent.VK_1:
frame.removeKeyListener(this);
new Fase_1(frame);
break;
...
case KeyEvent.VK_SPACE:
frame.dispatchEvent(new WindowEvent(frame, WindowEvent.WINDOW_CLOSING));
break;
default:
break;
}
}
@Override
public void keyReleased(KeyEvent e) {
// nada aqui
}
@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);
Graphics2D gd = (Graphics2D) g;
if (imagem != null) {
gd.drawImage(imagem, 0, 0, frame);
}
}
@Override
public Dimension getPreferredSize() {
return new Dimension(Comuns.LARGURA, Comuns.ALTURA);
}
}
}
Answer
This question was answered in the comments by @STaefi so I’m making this answer a CW
In the public final void initialize() of Menu class, remove the frame.removeAll(); and there you go.
A good practice is to call the JFrame#setVisible after all the initialization, not int the initialization a child component.