Java - Check if JTextField is empty or not

Question

So I got know this is a popular question and already found the solution. But when I try this it doesn't work properly.

My JTextField is empty and the button isn't enabled. When I write something in my textfield the button doesn't get enabled.

So my program should check this field every second whether it's empty or not. As soon as someone writes something into the textfield the button should be enabled.^^

loginbt = new JButton("Login");
    loginbt.addActionListener(new loginHandler());
    add(loginbt);

    if(name.getText().equals("")) {
        loginbt.setEnabled(false);
    }else {
        loginbt.setEnabled(true);
    }

Elevate

BTW, I'll use loginbt.setEnabled(name.getText().length()!=0); – Sather

@Sather loginbt.setEnabled(name.getText().isEmpty()); – Aime

Answer 1

For that you need to add change listener (a DocumentListener which reacts for change in the text) for your JTextField, and within actionPerformed(), you need to update the loginButton to enabled/disabled depending on the whether the JTextfield is empty or not.

Below is what I found from this thread.

yourJTextField.getDocument().addDocumentListener(new DocumentListener() {
  public void changedUpdate(DocumentEvent e) {
    changed();
  }
  public void removeUpdate(DocumentEvent e) {
    changed();
  }
  public void insertUpdate(DocumentEvent e) {
    changed();
  }

  public void changed() {
     if (yourJTextField.getText().equals("")){
       loginButton.setEnabled(false);
     }
     else {
       loginButton.setEnabled(true);
    }

  }
});

Betterment

I wanted to ask whether the procedure changes if the button were to depend on more than 1 text field. Would I use the same logic to define the action or is there some other way with less code? Thanks for your time!! – Lactoscope

Then you create one DocumentListener implementation which handles that button and add them as listeners to all the textboxes? – Betterment

yes..thanks..forgot basic stuff: how to write document listener – Lactoscope

Answer 2

The following will return true if the JTextField name does not contain text:

name.getText().isEmpty();

Note

Answer 3

What you need is something called Document Listener. See How to Write a Document Listener.

Venerable

Answer 4

To Check JTextFiled is empty or not condition:

if( (billnotf.getText().length()==0)||(billtabtf.getText().length()==0))

Minda

Nice. I like this. – Beanie

Answer 5

Well, the code that renders the button enabled/disabled:

if(name.getText().equals("")) {
    loginbt.setEnabled(false);
}else {
    loginbt.setEnabled(true);
}

must be written in javax.swing.event.ChangeListener and attached to the field (see here). A change in field's value should trigger the listener to reevaluate the object state. What did you expect?

Farrow

Answer 6

use the following code :

if(name.getText().equals(""))
{
loginbt.disable();
}

Binetta

Answer 7

you can use isEmpty() or isBlank() methods regarding what you need.

---

Returns true if, and only if, length() is 0.

this.name.getText().isEmpty();

---

Returns true if the string is empty or contains only white space codepoints, otherwise false

this.name.getText().isBlank();

Dairyman

Note that isBlank() works since Java 11. – Washboard

Answer 8

Try this

if(name.getText() != null && name.getText().equals(""))
{
        loginbt.setEnabled(false);
}
else
{
        loginbt.setEnabled(true);
}

Seto

Answer 9

if(name.getText().hashCode() != 0){
    JOptionPane.showMessageDialog(null, "not empty");
}
else{
    JOptionPane.showMessageDialog(null, "empty");
}

Danettedaney

Cold you please explain why you think that this is a solution? – Defect

Answer 10

Try this one and change booleans statements around.

String text = name.getText(); 
if(!text.isEmpty()) {
    loginbt.setEnabled(true);
}else {
    loginbt.setEnabled(false);
}

In my action method it worked fine.

public void actionPerformed(ActionEvent e){
    String inputText = e.getActionCommand();
    String itext = text1.getText();
    if(inputText.equals("Submit") && !itext.isEmpty()){
        label1.setText(text1.getText());
        text1.setText("");
    }
}

Avisavitaminosis

Answer 11

You can use

`loginbt = new JButton("Login"); loginbt.addActionListener(new loginHandler()); add(loginbt);

if(String.valueOf(name.getText()).isEmpty() {
    loginbt.setEnabled(false);
}else {
    loginbt.setEnabled(true);
}

`

Rickrickard

Your answer doesn't add much to the existing ones. String.valueOf is not needed here since getText already returns a String object. – Calcimine

Answer 12

Try with keyListener in your textfield

jTextField.addKeyListener(new KeyListener() {

        @Override
        public void keyTyped(KeyEvent e) {
        }

        @Override
        public void keyPressed(KeyEvent e) {
            if (text.getText().length() >= 1) {
                button.setEnabled(true);
            } else {
                button.setEnabled(false);
            }
        }

        @Override
        public void keyReleased(KeyEvent e) {
        }

    });

Alphonsealphonsine

-1 A DocumentListener is the preferred approach. There is rarely a reason to use a KeyListener. That is old design when using AWT. Also the code would not work anyway because no text has been added to the Document when the keyPressed event is generated, so the length will still be 0 when the first event is fired. – Gavette

Thanks for the correction,i will see the DocumentListener in the future – Alphonsealphonsine

Answer 13

private void jButton4ActionPerformed(java.awt.event.ActionEvent evt) {                                         
    // Submit Button        

    String Fname = jTextField1.getText();
    String Lname = jTextField2.getText();
    String Desig = jTextField3.getText();
    String Nic = jTextField4.getText();
    String Phone = jTextField5.getText();
    String Add = jTextArea1.getText();
    String Dob = jTextField6.getText();
    // String Gender;
    // Image

    if (Fname.hashCode() == 0 || Lname.hashCode() == 0 || Desig.hashCode() == 0 || Nic.hashCode() == 0 || Phone.hashCode() == 0 || Add.hashCode() == 0)
    {
        JOptionPane.showMessageDialog(null, "Some fields are empty!");
    }
    else
    {
        JOptionPane.showMessageDialog(null, "OK");
    }
}

Aletheaalethia

Hi @HarinduLakshan, please consider adding more information to improve the quality of the answer. – Instauration

This answer has multiple issues. It doesn't clearly address the question, the variable names don't adhere to Java conventions, and it uses hashCode() rather than isEmpty() to check for missing values. It also contains unnecessary comments. – Thruster