TextField User Name Password Validation

After Button, the most used AWT component is TextField. TextField is useful to take input from the user and also to display output to the user by the programmer. User can write and edit the text in the TextField. Programmatically, the TextField can be made non-editable. Pressing Enter key generates ActionEvent and can be handled by ActionListener.

Limitations of TextField

One small limitation of TextField is it allows entering or displaying only one line of text; of course of any length. Anyhow, this limitation is overcome with TextArea, another AWT component.

Following is the class signature

public class TextField extends TextComponent

The super class of TextField is TextComponent and also for TextArea.

Example code on TextField User Name Password Validation

The following program comes with 3 text fields. In two text fields, user enters name and password. In the third text field, the programmer displays the result of validation.

import java.awt.*;
import java.awt.event.*;
public class UserPassValidation extends Frame implements ActionListener
{
  TextField nameField, passField, resultField;
  Label lab1, lab2, lab3;
  public UserPassValidation()
  {                       // set layout
    setLayout(new GridLayout(3, 2, 0, 10));  
    setBackground(Color.pink);  // fill the gap with color
                         // create components
    nameField = new TextField(15);
    passField = new TextField(15);
    resultField = new TextField(15);
    lab1 = new Label("Enter User Name");
    lab2 = new Label("Enter Password");
    lab3 = new Label("Display Result");
    	             // register the listener
    passField.addActionListener(this);
    	            // beautification
    passField.setEchoChar('*');
    resultField.setEditable(false);

    add(lab1);   add(nameField);
    add(lab2);   add(passField);
    add(lab3);   add(resultField);

    setTitle("User Name & Password Validation");
    setSize(300, 300);
    setVisible(true);
   }
   public void actionPerformed(ActionEvent e)
   {                   // get the values entered by the user
     String str1 = nameField.getText();
     String str2 = passField.getText();
                        // some validation code
     if(str1.equals("snrao") && str2.equals("java"))
     {
       resultField.setText("VALID");
     }
     else
     {
       resultField.setText("INVALID, TRY AGAIN");
     }
   }
   public static void main(String args[])
   {
     new UserPassValidation();
   }
}

Three text fields, nameField, passField, resultField and three labels, lab1, lab2, lab3 are created.

passField.addActionListener(this);

The text field passField is registered with ActionListener using addActionListener() method of TextField. Pressing Enter key in passField generates an event but pressing Enter key in nameField and resultField do not have any event handling as they are not registered with ActionListener (as not required in the program).

passField.setEchoChar(‘*’);
resultField.setEditable(false);

passField is meant for entering password. Password should be secret and for this reason passField characters entered by the user are echoed (displayed) as *. resultField is not allowed by the user to enter any text as it is meant for the programmer to display the result.

String str1 = nameField.getText();
resultField.setText(“VALID”);

Two methods exist in TextField used very often – getText() and setText(). getText() returns the text entered by the user in the text field and setText() method places the text in the text field.

Another program on text field is given Java TextField – Setting Properties where properties for the text field are given with different methods of TextField. For practice, a text field with applet is given in TextField Applet – Adding Two Numbers. The frame you get do not close when clicked over the close icon on the title bar of the frame. It requires extra code close icon to work.