How to create a gui in java?

Question

I need to create a gui in java which will take a string from a user and then user will click on submit button.On clicking the submit button,the user will do some processing on the string and then give output on screen(gui).

I have written the following code till now but when I run this code,it doesn't give any output.

public class userinterface extends javax.swing.JFrame {
   
    public userinterface() {
        initComponents();
    }
                   
    private javax.swing.JButton jButton1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JPanel jPanel3;
    private javax.swing.JPanel jPanel5;
    private javax.swing.JTextField jTextField1;
    // End of variables declaration                   
    
    public void show() {
        String str = jTextField1.getText();
                        
        jButton1.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                //Execute when button is pressed
                System.out.println("You clicked the button,str");
            }
        });
    }

    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new userinterface().setVisible(true);
                userinterface obj = new userinterface();
                obj.show();
            }
        });
    }

}

Please tell me where am I doing wrong ? How can I make the output display on gui screen?

Thanks.

Answer 1

Your problem is you've overridden the essential method show() without realizing it, and this prevents the JFrame from displaying. Change the name of this method to something different:

public void myShow() {
  // String str = jTextField1.getText(); // not useful

  jButton1.addActionListener(new ActionListener() {
     public void actionPerformed(ActionEvent e) {
        // Execute when button is pressed
        System.out.println("You clicked the button,str");
     }
  });
}

public static void main(String args[]) {
  java.awt.EventQueue.invokeLater(new Runnable() {
     public void run() {
        // new userinterface().setVisible(true);
        userinterface obj = new userinterface();
        // obj.show();
        obj.myShow();
        obj.setVisible(true);
     }
  });
}

This is another reason that we all should strive not to extend classes unless absolutely necessary, since doing so can occasionally cause very difficult to debug errors.

I was able to debug this by placing println's throughout your code and seeing that show() was being called even when it wasn't explicitly being called by me.

Answer 2

JFrame frame = new JFrame();
JPanel panel = new JPanel();
JLabel label = new JLabel("this is GUI boi");

frame.setSize(500, 500);
panel.add(label);
frame.add(panel);
frame.setVisible(true);

1. you have to instantiate all the gui components
2. you have to call the setVisible() method of the JFrame
3. you have to set a width and height of the JFrame
4. you have add the components to a parent component(like a label to a panel and that panel to a frame)