CODEWITHSUNDEEP
javaswingjframejbutton
user4450842
user4450842

Reputation:

Why aren't the JButtons displayed on the JFrame?

When I run the program the window and all it's properties are right, but the buttons won't show up, any idea of what I've done wrong?

I have two classes window and TimeTable0:

Here's window:

package timetable0;

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

public class window extends JFrame {

    JButton bt1,bt2,bt3,bt4 = new JButton();
    JPanel panel = new JPanel();

    public void ventana() {

        setResizable(false);
        setTitle("Time Table");
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(400,550);
        setVisible(true);

        bt1.setText("Show Grades");
        bt2.setText("Show Time Table");
        bt3.setText("");
        bt4.setText("");

        panel.add(bt1);
        panel.add(bt2);
        panel.add(bt3);
        panel.add(bt4);

    }

    public void actions (){

        bt1.addActionListener((ActionEvent e) -> {
            System.out.println("");
               });
        bt2.addActionListener((ActionEvent e) -> {
            System.out.println("");
               });
        bt3.addActionListener((ActionEvent e) -> {
            System.out.println("");
               });
        bt4.addActionListener((ActionEvent e) -> {
            System.out.println("");
               });

    }

}

And here's TimeTable0:

package timetable0;

public class TimeTable0 {
    public static void main(String[] args) {
        window menu = new window();

        menu.ventana();
        menu.actions();
    }
}

Upvotes: 1

Views: 88

Answers (5)

Xun Chenlong
Xun Chenlong

Reputation: 1622

Initialize buttons one by one:

JButton bt1 = new JButton();
JButton bt2 = new JButton();
JButton bt3 = new JButton();
JButton bt4 = new JButton();

Add panel to your frame after you add buttons to your panel:

    panel.add(bt1);
    panel.add(bt2);
    panel.add(bt3);
    panel.add(bt4);

    setContentPane(panel);

Upvotes: 0

user3437460
user3437460

Reputation: 17474

You didn't show much codes there, but you should at least try to do this instead:

Note that JButton bt1,bt2,bt3,bt4 = new JButton(); is different from writing it as below:

JButton bt1 = new JButton();
JButton bt2 = new JButton();
JButton bt3 = new JButton();
JButton bt4 = new JButton();

Doing JButton bt1,bt2,bt3,bt4 = new JButton();, you are only creating a JButton object for bt4 and not the rest.

You have also forgotten to add your JPanel into your JFrame.

add(panel);  //Add panel to frame

Upvotes: 0

deezy
deezy

Reputation: 1480

You will need to initialize the buttons and add panel to the JFrame. Also, try moving the setVisible(true) statement to the end of the ventana() method so that it is displayed after the components are added.

public void Ventana() {
    bt1 = new JButton("Show Grades");
    bt2 = new JButton("Show Time Table");
    bt3 = new JButton();
    bt4 = new JButton();
    ...
    panel.add(bt4);

    add(panel);
    setVisible(true); //moved from top
}

Upvotes: 0

user3437460
user3437460

Reputation: 17474

I would have done it this way if you really want to extends your class to a JFrame.

public class Window extends JFrame {

    JButton bt1,bt2,bt3,bt4;  //Do initialization in the constructor, not here
    JPanel panel;

    public Window() {
        createComponents();
        addComponents();
        initFrame();
    }

    private void createComponents(){
        panel = new JPanel();
        panel.setPreferredSize(new Dimension(800, 600));
        bt1 = new JButton("Show Grades");
        bt2 = new JButton("Show Time Table");
        bt3 = new JButton("btn 3");
        bt4 = new JButton("btn 4");        
    }
    private void addComponents(){
        panel.add(bt1);
        panel.add(bt2);
        panel.add(bt3);
        panel.add(bt4);
        add(panel);  
    }
    private void initFrame(){
        setResizable(false);
        setTitle("Time Table");
        setVisible(true);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setLocationRelativeTo(null);         
    }
}

Usually I would prefer to extends a class to JPanel instead of extending it to JFrame. After that create a JFrame in the main() and add your customized JPanel into it.

Upvotes: 1

durron597
durron597

Reputation: 32343

  1. You aren't adding the JPanel to the frame.

    panel.add(bt1);
panel.add(bt2);
panel.add(bt3);
panel.add(bt4);
setContentPane(panel);

  2. You aren't running the program on the Event Dispatch Thread:

    public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
        @Override
        public void run() {
            window menu = new window();
            menu.ventana();
            menu.actions();
        }
    });
}

  3. You aren't creating all four buttons:

    JButton bt1 = new JButton();
JButton bt2 = new JButton();
JButton bt3 = new JButton();
JButton bt4 = new JButton();

Upvotes: 4

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