I am looking for a way to put example text into a swing JTextField and have it grayed out. The example text should then disappear as soon as any thing is entered into that text field. Some what similar to what stackoverflow does when a user is posting a question with the title field.
I would like it if it was already a extended implementation of JTextField so that I can just drop it in as a simple replacement. Anything from swingx would work. I guess if there is not an easy way to do this my option will probably be to override the paint method of JTextField do something that way maybe.
Thanks
The Text Prompt class provides the required functionality without using a custom JTextField (or JPasswordField).
It allows you to specify a prompt that is displayed when the text field is empty. As soon as you type text the prompt is removed.
The prompt is actually a JLabel so you can customize the font, style, colour, transparency etc..:
JTextField tf7 = new JTextField(10);
TextPrompt tp7 = new TextPrompt("First Name", tf7);
tp7.setForeground( Color.RED );
Some examples of customizing the look of the prompt:
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import javax.swing.event.*;
import javax.swing.text.*;
/**
* The TextPrompt class will display a prompt over top of all text component when
* the Document of the text field is empty. The Show property is used to
* determine the visibility of the prompt.
*
* The Font and foreground Color of the prompt will default to those properties
* of the parent text component. You are free to change the properties after
* class construction.
*/
public class TextPrompt extends JLabel
implements FocusListener, DocumentListener
{
public enum Show
{
ALWAYS,
FOCUS_GAINED,
FOCUS_LOST;
}
private JTextComponent component;
private Document document;
private Show show;
private boolean showPromptOnce;
private int focusLost;
public TextPrompt(String text, JTextComponent component)
{
this(text, component, Show.ALWAYS);
}
public TextPrompt(String text, JTextComponent component, Show show)
{
this.component = component;
setShow( show );
document = component.getDocument();
setText( text );
setFont( component.getFont() );
setForeground( component.getForeground() );
setBorder( new EmptyBorder(component.getInsets()) );
setHorizontalAlignment(JLabel.LEADING);
component.addFocusListener( this );
document.addDocumentListener( this );
component.setLayout( new BorderLayout() );
component.add( this );
checkForPrompt();
}
/**
* Convenience method to change the alpha value of the current foreground
* Color to the specifice value.
*
* @param alpha value in the range of 0 - 1.0.
*/
public void changeAlpha(float alpha)
{
changeAlpha( (int)(alpha * 255) );
}
/**
* Convenience method to change the alpha value of the current foreground
* Color to the specifice value.
*
* @param alpha value in the range of 0 - 255.
*/
public void changeAlpha(int alpha)
{
alpha = alpha > 255 ? 255 : alpha < 0 ? 0 : alpha;
Color foreground = getForeground();
int red = foreground.getRed();
int green = foreground.getGreen();
int blue = foreground.getBlue();
Color withAlpha = new Color(red, green, blue, alpha);
super.setForeground( withAlpha );
}
/**
* Convenience method to change the style of the current Font. The style
* values are found in the Font class. Common values might be:
* Font.BOLD, Font.ITALIC and Font.BOLD + Font.ITALIC.
*
* @param style value representing the the new style of the Font.
*/
public void changeStyle(int style)
{
setFont( getFont().deriveFont( style ) );
}
/**
* Get the Show property
*
* @return the Show property.
*/
public Show getShow()
{
return show;
}
/**
* Set the prompt Show property to control when the promt is shown.
* Valid values are:
*
* Show.AWLAYS (default) - always show the prompt
* Show.Focus_GAINED - show the prompt when the component gains focus
* (and hide the prompt when focus is lost)
* Show.Focus_LOST - show the prompt when the component loses focus
* (and hide the prompt when focus is gained)
*
* @param show a valid Show enum
*/
public void setShow(Show show)
{
this.show = show;
}
/**
* Get the showPromptOnce property
*
* @return the showPromptOnce property.
*/
public boolean getShowPromptOnce()
{
return showPromptOnce;
}
/**
* Show the prompt once. Once the component has gained/lost focus
* once, the prompt will not be shown again.
*
* @param showPromptOnce when true the prompt will only be shown once,
* otherwise it will be shown repeatedly.
*/
public void setShowPromptOnce(boolean showPromptOnce)
{
this.showPromptOnce = showPromptOnce;
}
/**
* Check whether the prompt should be visible or not. The visibility
* will change on updates to the Document and on focus changes.
*/
private void checkForPrompt()
{
if (document.getLength() > 0)
{
setVisible( false );
return;
}
// Prompt has already been shown once, remove it
if (showPromptOnce && focusLost > 0)
{
setVisible(false);
return;
}
// Check the Show property and component focus to determine if the
// prompt should be displayed.
if (component.hasFocus())
{
if (show == Show.ALWAYS
|| show == Show.FOCUS_GAINED)
setVisible( true );
else
setVisible( false );
}
else
{
if (show == Show.ALWAYS
|| show == Show.FOCUS_LOST)
setVisible( true );
else
setVisible( false );
}
}
// Implement FocusListener
public void focusGained(FocusEvent e)
{
checkForPrompt();
}
public void focusLost(FocusEvent e)
{
focusLost++;
checkForPrompt();
}
// Implement DocumentListener
public void insertUpdate(DocumentEvent e)
{
checkForPrompt();
}
public void removeUpdate(DocumentEvent e)
{
checkForPrompt();
}
public void changedUpdate(DocumentEvent e) {}
}
I would always check the TextPrompt link from above for the most current version of the class.
If you can use external librairies, the Swing components from Jide software have what you are looking for; it’s called LabeledTextField (javadoc) and it’s part of the JIDE Common Layer (Open Source Project) – which is free. It’s doing what mklhmnn suggested.
How about initialize the text field with default text and give it a focus listener such that when focus is gained, if the text .equals the default text, call selectAll() on the JTextField.
Rather than overriding, put a value in the field and add a KeyListener that would remove the value when a key stroke is registered. Maybe also have it change the foreground.
You could wrap this up into your own custom JTextField class that would take the default text in a constructor.