JPanel on JFrame wierd problem

**IndiDev** · 02-06-2012, 06:53 PM

I tried to add a JPanel to a JFrame, everything was fine, no errors, no runtime-errors. I've set everything visible, added the JPanel to the JFrame but still don't get any output Frame. I compared it to the syntax of several Youtube Videos but it's still not showing anything. maybe someone of you can help me?

(note: the comments are in german, my native language, but they are very simple and actually not needed. You should understand the code even without comments)

Main Class:

Java Code:

public class MyMenue{

  public static void main(String[] args){
  
    Menue m = new Menue();
    MenuePanel me = new MenuePanel();
    m.setVisible(true);
    me.setVisible(true);
  }
}

Frame Class:

Java Code:

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

public class Menue extends JFrame {

 private MenuePanel mp = new MenuePanel();
 
  //Konstruktor der Klasse Menue
  public Menue(){
    super("4Gewinnt-Game");                                   //Mit dem Konstruktor von JFrame
    this.setLayout(null);                                     //kein Layoutmanager
    this.setBounds(100,100,515,555);                          //Größe und Positon
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);      //Operation beim Fenster schließen
    this.setResizable(false);                                 //Fenster veränderbar oder nicht?
    this.add(mp);                                             //fügt MenuePanel mp zu Menue hinzu
  }
  
}

Panel Class:

Java Code:

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

public class MenuePanel extends JPanel {

 private JLabel lblText;
 private JButton[] btn = new JButton[3];
 private JTextField txt1;
 private int i = 0;
 private int j;
 private int a = 0;
 JLabel l1 = new JLabel(new ImageIcon("startmenue.png"));
 MenueListener myL = new MenueListener(this);
 private Menue m = new Menue();
 
 //Konstruktor der Klasse MenuePanel
  public MenuePanel(){
    this.setLayout(null);                                            //kein Layoutmanager
    this.setBounds(0,0,515,555);                                     //Größe und Positon
    this.setBackground(Color.WHITE);                                 //Hintergrundfarbe

    l1.setBounds(0,0,515,555);


    for (j= 0; j < btn.length;j++){

     btn[j] = new JButton();
     btn[j].setBounds(150,250+a,100,23);
     a = a +25;
     if (j == 0)
      btn[0].setIcon(new ImageIcon("start.png"));
     if (j == 1)
      btn[1].setIcon(new ImageIcon("optionen.png"));
     if (j == 2)
      btn[2].setIcon(new ImageIcon("beenden.png"));
     btn[j].addActionListener(myL);
     this.add(btn[j]);
    }

     this.setLayout(null);
     this.add(l1);
     this.setBounds(0,0,515,555);
     m.add(this);

    this.setVisible(true);                             //Sichtbar oder nicht?
  }

  //Getter für btn[j]
  public JButton getBtnOp(int j){
    return this.btn[j];
  }
  
  //Getter für l1
  public JLabel getL1(){
    return this.l1;
  }

}

i didn't copy the listeners in, because they're not actually neccesary to at least show the frame.

This is the first time i tried JPanels, so I assume i forgot something at defining the JPanel...
but even then, at least the empty JFrame would show up right?

Im thankful for every piece of hint or advice.

**doWhile** · 02-06-2012, 07:04 PM

You should think carefully about how the program flows. Say you 1) create a Menue 2)this creates a MenuePanel 3) the MenuePanel has a Menue variable...which in turn goes to step 1. Repeat indefinitely == infinite loop. Be careful where you instantiate one class relative to another. I recommend reviewing closely some of the examples in the Oracle tutorials and use those code flows as a guide

And FWIW, do not use a null layout. Use an appropriate LayoutManager dependent upon how you wish your components to be organized.
A Visual Guide to Layout Managers (The Java™ Tutorials > Creating a GUI With JFC/Swing > Laying Out Components Within a Container)

**eRaaaa** · 02-06-2012, 07:05 PM

...why does the JPanel creates a JFrame and vice versa ? Why do you instantiate both at the main too and so on...thats strange!

Java Code:

class MenuePanel extends JPanel {

	private JLabel lblText;
	private JButton[] btn = new JButton[3];
	private JTextField txt1;
	private int i = 0;
	private int j;
	private int a = 0;
	JLabel l1 = new JLabel(new ImageIcon("startmenue.png"));
	

	// Konstruktor der Klasse MenuePanel
	public MenuePanel() {
		this.setLayout(null); // kein Layoutmanager
		this.setBounds(0, 0, 515, 555); // Größe und Positon
		this.setBackground(Color.WHITE); // Hintergrundfarbe

		l1.setBounds(0, 0, 515, 555);

		for (j = 0; j < btn.length; j++) {

			btn[j] = new JButton();
			btn[j].setBounds(150, 250 + a, 100, 23);
			a = a + 25;
			if (j == 0)
				btn[0].setIcon(new ImageIcon("start.png"));
			if (j == 1)
				btn[1].setIcon(new ImageIcon("optionen.png"));
			if (j == 2)
				btn[2].setIcon(new ImageIcon("beenden.png"));
			
			class Menue extends JFrame {


				// Konstruktor der Klasse Menue
				public Menue(MenuePanel panel) {
					super("4Gewinnt-Game"); // Mit dem Konstruktor von JFrame
					this.setLayout(null); // kein Layoutmanager
					this.setBounds(100, 100, 515, 555); // Größe und Positon
					this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Operation beim
																			// Fenster
																			// schließen
					this.setResizable(false); // Fenster veränderbar oder nicht?
					this.add(panel); // fügt MenuePanel mp zu Menue hinzu
				}

			}this.add(btn[j]);
		}

		this.setLayout(null);
		this.add(l1);
		this.setBounds(0, 0, 515, 555);

		this.setVisible(true); // Sichtbar oder nicht?
	}

	// Getter für btn[j]
	public JButton getBtnOp(int j) {
		return this.btn[j];
	}

	// Getter für l1
	public JLabel getL1() {
		return this.l1;
	}

}

Java Code:

class Menue extends JFrame {


	// Konstruktor der Klasse Menue
	public Menue(MenuePanel panel) {
		super("4Gewinnt-Game"); // Mit dem Konstruktor von JFrame
		this.setLayout(null); // kein Layoutmanager
		this.setBounds(100, 100, 515, 555); // Größe und Positon
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); // Operation beim
																// Fenster
																// schließen
		this.setResizable(false); // Fenster veränderbar oder nicht?
		this.add(panel); // fügt MenuePanel mp zu Menue hinzu
	}

}

Java Code:

public class MyMenue{
 
  public static void main(String[] args){
  		MenuePanel me = new MenuePanel();
		Menue m = new Menue(me);
		m.setVisible(true);
		me.setVisible(true);
  }
}

by the way: Null Layout Is Evil!