gui problem

[sugard]

I have this thing that I need to accept information from a user. I have a jTextField for where the user can place the info needed (example entering his name.) My problem is this.. I need to check whether the user has placed any text in the field. Since if he did not place any text I want an informtion message to be displayed on the same screen.

I created an empty jlabel so that it would be written there.. Though i did not succeed! I tried to check if the jTextField is empty by using if (jTextField.get Text() == null) {
jLabel.setText( "Name cannot be left blank");
}

Can please someone help me.. I thank you in advance

[r035198x]

I have this thing that I need to accept information from a user. I have a jTextField for where the user can place the info needed (example entering his name.) My problem is this.. I need to check whether the user has placed any text in the field. Since if he did not place any text I want an informtion message to be displayed on the same screen.

I created an empty jlabel so that it would be written there.. Though i did not succeed! I tried to check if the jTextField is empty by using if (jTextField.get Text() == null) {
jLabel.setText( "Name cannot be left blank");
}

Can please someone help me.. I thank you in advance

Use

jTextField.getText().equals("")

instead.

[BigDaddyLH]

Another approach would be to enable the button only when the the text field holds some text:

import java.awt.*;
import javax.swing.*;
import javax.swing.event.*;
 
class Enabler implements DocumentListener {
    private JComponent target;
 
    public Enabler(JComponent target) {
        this.target = target;
    }
 
    @Override
    public void changedUpdate(DocumentEvent e) {
        adjustTarget(e);
    }
 
    @Override
    public void insertUpdate(DocumentEvent e) {
        adjustTarget(e);
    }
 
    @Override
    public void removeUpdate(DocumentEvent e) {
        adjustTarget(e);
    }
 
    private void adjustTarget(DocumentEvent e) {
        target.setEnabled(e.getDocument().getLength() > 0);
    }
}
 
public class RequiredField implements Runnable {
    public static void main(String[] args) {
        EventQueue.invokeLater(new RequiredField());
    }
 
    @Override
    public void run() {
        JFrame f = new JFrame("RequiredField");
        JTextField field = new JTextField(10);
        JButton submit = new JButton("submit");
        submit.setEnabled(false);
        field.getDocument().addDocumentListener(new Enabler(submit));
        Container cp = f.getContentPane();
        cp.setLayout(new FlowLayout());
        cp.add(new JLabel("Name (required)"));
        cp.add(field);
        cp.add(submit);
        f.pack();
        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }
}

[Stubert]

Hi there I was just wondering if you could explain what @Override does, I had a look around on Google but couldn't really come up with anything except that it overrides the method in the superclass, which understand. But are the methods you're using in a superclass?

I know this is a bit off topic but I've not came across it before.

Thanks
- Stu

[BigDaddyLH]

Threads get dull if they can't go off-topic occasionally. That was the annotation Override:
Annotations Override API

This annotation is useful because it catches typos and accidental changes. For example, consider this code:

class A {
    public void f(){}
}
 
class B extends A {
    public void f(){}
}

B overrides f. But was this on purpose or by mistake? And what if B had been written:

class B extends A {
    public void f(int x){}
}

B is no longer overriding f -- but did I mean to? If I add an annotation, the compiler will warn me of my mistake:

class B extends A {
    @Override
    public void f(int x){}
}

[Stubert]

Ahh I think I get it, the @Override annotation is used to tell the compiler that you DO want to override the method but if you have done something wrong, ie declared the method with an argument, it will warn you that you have done it incorrectly and will NOT infact be overriding the method you wanted to?

- Stu

[BigDaddyLH]

Ahh I think I get it, the @Override annotation is used to tell the compiler that you DO want to override the method but if you have done something wrong, ie declared the method with an argument, it will warn you that you have done it incorrectly and will NOT infact be overriding the method you wanted to?

- Stu

Exactly. In this thread, however I was using it pedantically, just to point out which methods I wrote were implementing methods of interface DocumentListene r.