Class JTextField

public class JTextField
extends JTextComponent
implements SwingConstants

JTextField is a lightweight component that allows the editing of a single line of text. For information on and examples of using text fields, see How to Use Text Fields in The Java Tutorial.

JTextField is intended to be source-compatible with java.awt.TextField where it is reasonable to do so. This component has capabilities not found in the java.awt.TextField class. The superclass should be consulted for additional capabilities.

JTextField has a method to establish the string used as the command string for the action event that gets fired. The java.awt.TextField used the text of the field as the command string for the ActionEvent. JTextField will use the command string set with the setActionCommand method if not null, otherwise it will use the text of the field as a compatibility with java.awt.TextField.

The method setEchoChar and getEchoChar are not provided directly to avoid a new implementation of a pluggable look-and-feel inadvertently exposing password characters. To provide password-like services a separate class JPasswordField extends JTextField to provide this service with an independently pluggable look-and-feel.

The java.awt.TextField could be monitored for changes by adding a TextListener for TextEvent's. In the JTextComponent based components, changes are broadcasted from the model via a DocumentEvent to DocumentListeners. The DocumentEvent gives the location of the change and the kind of change if desired. The code fragment might look something like:

    DocumentListener myListener = ??;
     JTextField myArea = ??;
     myArea.getDocument().addDocumentListener(myListener);

The horizontal alignment of JTextField can be set to be left justified, leading justified, centered, right justified or trailing justified. Right/trailing justification is useful if the required size of the field text is smaller than the size allocated to it. This is determined by the setHorizontalAlignment and getHorizontalAlignment methods. The default is to be leading justified.

How the text field consumes VK_ENTER events depends on whether the text field has any action listeners. If so, then VK_ENTER results in the listeners getting an ActionEvent, and the VK_ENTER event is consumed. This is compatible with how AWT text fields handle VK_ENTER events. If the text field has no action listeners, then as of v 1.3 the VK_ENTER event is not consumed. Instead, the bindings of ancestor components are processed, which enables the default button feature of JFC/Swing to work.

Customized fields can easily be created by extending the model and changing the default model provided. For example, the following piece of code will create a field that holds only upper case characters. It will work even if text is pasted into from the clipboard or it is altered via programmatic changes.

 public class UpperCaseField extends JTextField {
 
     public UpperCaseField(int cols) {
         super(cols);
     }
 
     protected Document createDefaultModel() {
         return new UpperCaseDocument();
     }
 
     static class UpperCaseDocument extends PlainDocument {
 
         public void insertString(int offs, String str, AttributeSet a)
             throws BadLocationException {
 
             if (str == null) {
                 return;
             }
             char[] upper = str.toCharArray();
             for (int i = 0; i < upper.length; i++) {
                 upper[i] = Character.toUpperCase(upper[i]);
             }
             super.insertString(offs, new String(upper), a);
         }
     }
 }

Warning: Swing is not thread safe. For more information see Swing's Threading Policy.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeans™ has been added to the java.beans package. Please see XMLEncoder.

Fields

notifyAction

public static final String notifyAction

Name of the action to send notification that the contents of the field have been accepted. Typically this is bound to a carriage-return.

See Also:

Constant Field Values

Constructors

JTextField

public JTextField()

Constructs a new TextField. A default model is created, the initial string is null, and the number of columns is set to 0.

JTextField

public JTextField(String text)

Constructs a new TextField initialized with the specified text. A default model is created and the number of columns is 0.

Parameters:

text - the text to be displayed, or null

JTextField

public JTextField(int columns)

Constructs a new empty TextField with the specified number of columns. A default model is created and the initial string is set to null.

Parameters:

columns - the number of columns to use to calculate the preferred width; if columns is set to zero, the preferred width will be whatever naturally results from the component implementation

JTextField

public JTextField(String text,
                  int columns)

Constructs a new TextField initialized with the specified text and columns. A default model is created.

Parameters:

text - the text to be displayed, or null

columns - the number of columns to use to calculate the preferred width; if columns is set to zero, the preferred width will be whatever naturally results from the component implementation

JTextField

public JTextField(Document doc,
                  String text,
                  int columns)

Constructs a new JTextField that uses the given text storage model and the given number of columns. This is the constructor through which the other constructors feed. If the document is null, a default model is created.

Parameters:

doc - the text storage to use; if this is null, a default will be provided by calling the createDefaultModel method

text - the initial string to display, or null

columns - the number of columns to use to calculate the preferred width >= 0; if columns is set to zero, the preferred width will be whatever naturally results from the component implementation

Throws:

IllegalArgumentException - if columns < 0

Methods

getUIClassID

public String getUIClassID()

Gets the class ID for a UI.

Overrides:

getUIClassID in class JComponent

Returns:

the string "TextFieldUI"

See Also:

JComponent.getUIClassID(), UIDefaults.getUI(javax.swing.JComponent)

setDocument

public void setDocument(Document doc)

Associates the editor with a text document. The currently registered factory is used to build a view for the document, which gets displayed by the editor after revalidation. A PropertyChange event ("document") is propagated to each listener.

Overrides:

setDocument in class JTextComponent

Parameters:

doc - the document to display/edit

See Also:

JTextComponent.getDocument()

isValidateRoot

public boolean isValidateRoot()

Calls to revalidate that come from within the textfield itself will be handled by validating the textfield, unless the textfield is contained within a JViewport, in which case this returns false.

Overrides:

isValidateRoot in class JComponent

Returns:

if the parent of this textfield is a JViewPort return false, otherwise return true

See Also:

JComponent.revalidate(), JComponent.isValidateRoot(), Container.isValidateRoot()

getHorizontalAlignment

public int getHorizontalAlignment()

Returns the horizontal alignment of the text. Valid keys are:

• JTextField.LEFT
• JTextField.CENTER
• JTextField.RIGHT
• JTextField.LEADING
• JTextField.TRAILING

Returns:

the horizontal alignment

setHorizontalAlignment

public void setHorizontalAlignment(int alignment)

Sets the horizontal alignment of the text. Valid keys are:

• JTextField.LEFT
• JTextField.CENTER
• JTextField.RIGHT
• JTextField.LEADING
• JTextField.TRAILING

invalidate and repaint are called when the alignment is set, and a PropertyChange event ("horizontalAlignment") is fired.

Parameters:

alignment - the alignment

Throws:

IllegalArgumentException - if alignment is not a valid key

createDefaultModel

protected Document createDefaultModel()

Creates the default implementation of the model to be used at construction if one isn't explicitly given. An instance of PlainDocument is returned.

Returns:

the default model implementation

getColumns

public int getColumns()

Returns the number of columns in this TextField.

Returns:

the number of columns >= 0

setColumns

public void setColumns(int columns)

Sets the number of columns in this TextField, and then invalidate the layout.

Parameters:

columns - the number of columns >= 0

Throws:

IllegalArgumentException - if columns is less than 0

getColumnWidth

protected int getColumnWidth()

Returns the column width. The meaning of what a column is can be considered a fairly weak notion for some fonts. This method is used to define the width of a column. By default this is defined to be the width of the character m for the font used. This method can be redefined to be some alternative amount

Returns:

the column width >= 1

getPreferredSize

public Dimension getPreferredSize()

Returns the preferred size Dimensions needed for this TextField. If a non-zero number of columns has been set, the width is set to the columns multiplied by the column width.

Overrides:

getPreferredSize in class JComponent

Returns:

the dimension of this textfield

See Also:

JComponent.setPreferredSize(java.awt.Dimension), ComponentUI

setFont

public void setFont(Font f)

Sets the current font. This removes cached row height and column width so the new font will be reflected. revalidate is called after setting the font.

Overrides:

setFont in class JComponent

Parameters:

f - the new font

See Also:

Component.getFont()

addActionListener

public void addActionListener(ActionListener l)

Adds the specified action listener to receive action events from this textfield.

Parameters:

l - the action listener to be added

removeActionListener

public void removeActionListener(ActionListener l)

Removes the specified action listener so that it no longer receives action events from this textfield.

Parameters:

l - the action listener to be removed

getActionListeners

public ActionListener[] getActionListeners()

Returns an array of all the ActionListeners added to this JTextField with addActionListener().

Returns:

all of the ActionListeners added or an empty array if no listeners have been added

Since:

1.4

fireActionPerformed

protected void fireActionPerformed()

Notifies all listeners that have registered interest for notification on this event type. The event instance is lazily created. The listener list is processed in last to first order.

See Also:

EventListenerList

setActionCommand

public void setActionCommand(String command)

Sets the command string used for action events.

Parameters:

command - the command string

setAction

public void setAction(Action a)

Parameters:

a - the Action for the JTextField, or null

Since:

1.3

See Also:

Action, getAction(), configurePropertiesFromAction(javax.swing.Action), createActionPropertyChangeListener(javax.swing.Action), actionPropertyChanged(javax.swing.Action, java.lang.String)

getAction

public Action getAction()

Returns the currently set Action for this ActionEvent source, or null if no Action is set.

Returns:

the Action for this ActionEvent source, or null

Since:

1.3

See Also:

Action, setAction(javax.swing.Action)

configurePropertiesFromAction

protected void configurePropertiesFromAction(Action a)

Sets the properties on this textfield to match those in the specified Action. Refer to Swing Components Supporting Action for more details as to which properties this sets.

Parameters:

a - the Action from which to get the properties, or null

Since:

1.3

See Also:

Action, setAction(javax.swing.Action)

actionPropertyChanged

protected void actionPropertyChanged(Action action,
                                     String propertyName)

Parameters:

action - the Action associated with this textfield

propertyName - the name of the property that changed

Since:

1.6

See Also:

Action, configurePropertiesFromAction(javax.swing.Action)

createActionPropertyChangeListener

protected PropertyChangeListener createActionPropertyChangeListener(Action a)

Parameters:

a - the textfield's action

Since:

1.3

See Also:

Action, setAction(javax.swing.Action)

getActions

public Action[] getActions()

Fetches the command list for the editor. This is the list of commands supported by the plugged-in UI augmented by the collection of commands that the editor itself supports. These are useful for binding to events, such as in a keymap.

Overrides:

getActions in class JTextComponent

Returns:

the command list

postActionEvent

public void postActionEvent()

Processes action events occurring on this textfield by dispatching them to any registered ActionListener objects. This is normally called by the controller registered with textfield.

getHorizontalVisibility

public BoundedRangeModel getHorizontalVisibility()

Returns:

the visibility

See Also:

BoundedRangeModel

getScrollOffset

public int getScrollOffset()

Gets the scroll offset, in pixels.

Returns:

the offset >= 0

setScrollOffset

public void setScrollOffset(int scrollOffset)

Sets the scroll offset, in pixels.

Parameters:

scrollOffset - the offset >= 0

scrollRectToVisible

public void scrollRectToVisible(Rectangle r)

Scrolls the field left or right.

Overrides:

scrollRectToVisible in class JComponent

Parameters:

r - the region to scroll

See Also:

JViewport

paramString

protected String paramString()

Returns a string representation of this JTextField. This method is intended to be used only for debugging purposes, and the content and format of the returned string may vary between implementations. The returned string may be empty but may not be null.

Overrides:

paramString in class JTextComponent

Returns:

a string representation of this JTextField

getAccessibleContext

public AccessibleContext getAccessibleContext()

Gets the AccessibleContext associated with this JTextField. For JTextFields, the AccessibleContext takes the form of an AccessibleJTextField. A new AccessibleJTextField instance is created if necessary.

Specified by:

getAccessibleContext in interface Accessible

Overrides:

getAccessibleContext in class JTextComponent

Returns:

an AccessibleJTextField that serves as the AccessibleContext of this JTextField