TEXT FIELDS

The TextField class implements a single-line text-entry area, usually called an edit control.
Text fields allow the user to enter strings and to edit the text using the arrow keys, cut and
paste keys, and mouse selections. TextField is a subclass of TextComponent. TextField
defines the following constructors:
TextField( )
TextField(int numChars)
TextField(String str)
TextField(String str, int numChars)
The first version creates a default text field. The second form creates a text field that
is numChars characters wide. The third form initializes the text field with the string
contained in str. The fourth form initializes a text field and sets its width.
TextField (and its superclass TextComponent) provides several methods that allow
you to utilize a text field. To obtain the string currently contained in the text field, call
getText( ). To set the text, call setText( ). These methods are as follows:
String getText( )
void setText(String str)
Here, str is the new string.

The user can select a portion of the text in a text field. Also, you can select a portion
of text under program control by using select( ). Your program can obtain the currently
selected text by calling getSelectedText( ). These methods are shown here:
String getSelectedText( )
void select(int startIndex, int endIndex)
getSelectedText( ) returns the selected text. The select( ) method selects the characters
beginning at startIndex and ending at endIndex–1.
You can control whether the contents of a text field may be modified by the user
by calling setEditable( ). You can determine editability by calling isEditable( ). These
methods are shown here:
boolean isEditable( )
void setEditable(boolean canEdit)
isEditable( ) returns true if the text may be changed and false if not. In setEditable( ),
if canEdit is true, the text may be changed. If it is false, the text cannot be altered.
There may be times when you will want the user to enter text that is not displayed,
such as a password. You can disable the echoing of the characters as they are typed
by calling setEchoChar( ). This method specifies a single character that the TextField
will display when characters are entered (thus, the actual characters typed will not be
shown). You can check a text field to see if it is in this mode with the echoCharIsSet( )
method. You can retrieve the echo character by calling the getEchoChar( ) method.
These methods are as follows:
void setEchoChar(char ch)
boolean echoCharIsSet( )
char getEchoChar( )
Here, ch specifies the character to be echoed.
Handling a TextField
Since text fields perform their own editing functions, your program generally will not
respond to individual key events that occur within a text field. However, you may want
to respond when the user presses ENTER. When this occurs, an action event is generated.
Here is an example that creates the classic user name and password screen:
// Demonstrate text field.
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
/*



*/
public class TextFieldDemo extends Applet
implements ActionListener {
TextField name, pass;
public void init() {
Label namep = new Label("Name: ", Label.RIGHT);
Label passp = new Label("Password: ", Label.RIGHT);
name = new TextField(12);
pass = new TextField(8);
pass.setEchoChar('?');
add(namep);
add(name);
add(passp);
add(pass);
// register to receive action events
name.addActionListener(this);
pass.addActionListener(this);
}
// User pressed Enter.
public void actionPerformed(ActionEvent ae) {
repaint();
}
public void paint(Graphics g) {
g.drawString("Name: " + name.getText(), 6, 60);
g.drawString("Selected text in name: "
+ name.getSelectedText(), 6, 80);
g.drawString("Password: " + pass.getText(), 6, 100);
}
}