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Class java.awt.swing.JLabel

java.lang.Object
    |
    +----java.awt.Component
            |
            +----java.awt.Container
                    |
                    +----java.awt.swing.JComponent
                            |
                            +----java.awt.swing.JLabel
Subclasses:
DefaultTableCellRenderer

public class JLabel
extends JComponent
implements SwingConstants, Accessible
A display area for a short text string or an image, or both. A label does not react to input events. As a result, it cannot get the keyboard focus. A label can, however, display a keyboard alternative as a convenience for a nearby component that has a keyboard alternative but can't display it.

A JLabel object can display either text, an image, or both. You can specify where in the label's display area the label's contents are aligned by setting the vertical and horizontal alignment. By default, labels are vertically centered in their display area. Text-only labels are left-aligned, by default; image-only labels are horizontally centered, by default.

You can also specify the position of the text relative to the image. By default, text is to the right of the image, with the text and image vertically aligned.

Finally, you can use the setIconTextGap method to specify how many pixels should appear between the text and the image. The default is 4 pixels.

See How to Use Labels in The Java Tutorial for further documentation.

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 Swing1.0 applications. It will not be possible to load serialized Swing1.0 objects with future releases of Swing. The JDK1.2 release of Swing will be the compatibility baseline for the serialized form of Swing objects.


Inner Class Summary
 JLabel.AccessibleJLabel
The class used to obtain the accessible role for this object.
 
Inner classes inherited from class java.awt.swing.JComponent
 JComponent.AccessibleJComponent
 

Field Summary
Component  labelFor
--- Accessibility Support ---
 
Fields inherited from class java.awt.swing.JComponent
 accessibleContext, listenerList, TOOL_TIP_TEXT_KEY, ui, UNDEFINED_CONDITION, WHEN_ANCESTOR_OF_FOCUSED_COMPONENT, WHEN_FOCUSED, WHEN_IN_FOCUSED_WINDOW
 
Fields inherited from class java.awt.Component
 BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
 

Constructor Summary
 JLabel(String text, Icon icon, int horizontalAlignment)
Creates a JLabel instance with the specified text, image, and horizontal alignment.
 JLabel(String text, int horizontalAlignment)
Creates a JLabel instance with the specified text and horizontal alignment.
 JLabel(String text)
Creates a JLabel instance with the specified text.
 JLabel(Icon image, int horizontalAlignment)
Creates a JLabel instance with the specified image and horizontal alignment.
 JLabel(Icon image)
Creates a JLabel instance with the specified image.
 JLabel()
Creates a JLabel instance with no image and with an empty string for the title.
 

Method Summary
int  checkHorizontalKey(int key, String message)
Verify that key is a legal value for the horizontalAlignment or horizontalTextPosition properties.
int  checkVerticalKey(int key, String message)
Verify that key is a legal value for the verticalAlignment or verticalTextPosition properties.
AccessibleContext  getAccessibleContext()
Get the AccessibleContext of this object
Icon  getDisabledIcon()
Returns the value of the disabledIcon property if it's been set, If it hasn't been set and the value of the icon property is an ImageIcon, we compute a "grayed out" version of the icon and update the disabledIcon property with that.
int  getDisplayedMnemonic()
Return the keycode that indicates a mnemonic key.
int  getHorizontalAlignment()
Returns the alignment of the label's contents along the X axis.
int  getHorizontalTextPosition()
Returns the horizontal position of the label's text, relative to its image.
Icon  getIcon()
Returns the graphic image (glyph, icon) that the label displays.
int  getIconTextGap()
Returns the amount of space between the text and the icon displayed in this label.
Component  getLabelFor()
Get the component this is labelling.
String  getText()
Returns the text string that the label displays.
java.awt.swing.plaf.LabelUI  getUI()
Returns the L&F object that renders this component.
String  getUIClassID()
Returns a string that specifies the name of the l&f class that renders this component.
int  getVerticalAlignment()
Returns the alignment of the label's contents along the Y axis.
int  getVerticalTextPosition()
Returns the vertical position of the label's text, relative to its image.
void  setDisabledIcon(Icon disabledIcon)
Set the icon to be displayed if this JLabel is "disabled", i.e.
void  setDisplayedMnemonic(int key)
Specify a keycode that indicates a mnemonic key.
void  setDisplayedMnemonic(char aChar)
 
void  setFont(Font font)
Sets the font used to display the label's text.
void  setHorizontalAlignment(int alignment)
Sets the alignment of the label's contents along the X axis.
void  setHorizontalTextPosition(int x)
Sets the horizontal position of the label's text, relative to its image.
void  setIcon(Icon icon)
Defines the icon this component will display.
void  setIconTextGap(int iconTextGap)
If both the icon and text properties are set, this property defines the space between them.
void  setLabelFor(Component c)
Set the component this is labelling.
void  setText(String text)
Defines the single line of text this component will display.
void  setUI(java.awt.swing.plaf.LabelUI ui)
Sets the L&F object that renders this component.
void  setVerticalAlignment(int alignment)
Sets the alignment of the label's contents along the Y axis.
void  setVerticalTextPosition(int textPosition)
Sets the vertical position of the label's text, relative to its image.
void  updateUI()
Notification from the UIFactory that the L&F has changed.
 
Methods inherited from class java.awt.swing.JComponent
 addAncestorListener, addNotify, addPropertyChangeListener, addVetoableChangeListener, computeVisibleRect, contains, createToolTip, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, fireVetoableChange, getAccessibleContext, getActionForKeyStroke, getAlignmentX, getAlignmentY, getAutoscrolls, getBorder, getBounds, getClientProperty, getComponentGraphics, getConditionForKeyStroke, getDebugGraphicsOptions, getGraphics, getHeight, getInsets, getLocation, getMaximumSize, getMinimumSize, getNextFocusableComponent, getPreferredSize, getRegisteredKeyStrokes, getRootPane, getSize, getToolTipLocation, getToolTipText, getToolTipText, getTopLevelAncestor, getUIClassID, getVisibleRect, getWidth, getX, getY, grabFocus, hasFocus, isDoubleBuffered, isFocusCycleRoot, isFocusTraversable, isLightweightComponent, isManagingFocus, isOpaque, isOptimizedDrawingEnabled, isPaintingTile, isRequestFocusEnabled, isValidateRoot, paint, paintBorder, paintChildren, paintComponent, paintImmediately, paintImmediately, processComponentKeyEvent, processFocusEvent, processKeyEvent, processMouseMotionEvent, putClientProperty, registerKeyboardAction, registerKeyboardAction, removeAncestorListener, removeNotify, removePropertyChangeListener, removeVetoableChangeListener, repaint, repaint, requestDefaultFocus, requestFocus, resetKeyboardActions, reshape, revalidate, scrollRectToVisible, setAlignmentX, setAlignmentY, setAutoscrolls, setBorder, setBounds, setDebugGraphicsOptions, setDoubleBuffered, setMaximumSize, setMinimumSize, setNextFocusableComponent, setOpaque, setPreferredSize, setRequestFocusEnabled, setToolTipText, setUI, setVisible, unregisterKeyboardAction, update, updateUI
 
Methods inherited from class java.awt.Container
 add, add, add, add, add, addContainerListener, addImpl, addNotify, countComponents, deliverEvent, doLayout, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents, getInsets, getLayout, getMaximumSize, getMinimumSize, getPreferredSize, insets, invalidate, isAncestorOf, layout, list, list, locate, minimumSize, paint, paintComponents, paramString, preferredSize, print, printComponents, processContainerEvent, processEvent, remove, remove, removeAll, removeContainerListener, removeNotify, setLayout, update, validate, validateTree
 
Methods inherited from class java.awt.Component
 action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addNotify, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBounds, getColorModel, getComponentAt, getComponentAt, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getHeight, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getName, getParent, getPeer, getPreferredSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isDisplayable, isEnabled, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, layout, list, list, list, list, list, locate, location, lostFocus, minimumSize, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paint, paintAll, paramString, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processEvent, processFocusEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, resize, resize, setBackground, setBounds, setBounds, setCursor, setDropTarget, setEnabled, setFont, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus, update, validate
 
Methods inherited from class java.lang.Object
 clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

labelFor

protected Component labelFor
--- Accessibility Support ---
Constructor Detail

JLabel

public JLabel(String text,
              Icon icon,
              int horizontalAlignment)
Creates a JLabel instance with the specified text, image, and horizontal alignment. The label is centered vertically in its display area. The text is to the right of the image.
Parameters:
text - The text to be displayed by the label.
icon - The image to be displayed by the label.
horizontalAlignment - One of the following constants defined in SwingConstants: LEFT, CENTER, or RIGHT.

JLabel

public JLabel(String text,
              int horizontalAlignment)
Creates a JLabel instance with the specified text and horizontal alignment. The label is centered vertically in its display area.
Parameters:
text - The text to be displayed by the label.
horizontalAlignment - One of the following constants defined in SwingConstants: LEFT, CENTER, or RIGHT.

JLabel

public JLabel(String text)
Creates a JLabel instance with the specified text. The label is aligned against the left side of its display area, and centered vertically.
Parameters:
text - The text to be displayed by the label.

JLabel

public JLabel(Icon image,
              int horizontalAlignment)
Creates a JLabel instance with the specified image and horizontal alignment. The label is centered vertically in its display area.
Parameters:
icon - The image to be displayed by the label.
horizontalAlignment - One of the following constants defined in SwingConstants: LEFT, CENTER, or RIGHT.

JLabel

public JLabel(Icon image)
Creates a JLabel instance with the specified image. The label is centered vertically and horizontally in its display area.
Parameters:
icon - The image to be displayed by the label.

JLabel

public JLabel()
Creates a JLabel instance with no image and with an empty string for the title. The label is centered vertically in its display area. The label's contents, once set, will be displayed at the left of the label's display area.
Method Detail

getUI

public java.awt.swing.plaf.LabelUI getUI()
Returns the L&F object that renders this component.
Returns:
LabelUI object

setUI

public void setUI(java.awt.swing.plaf.LabelUI ui)
Sets the L&F object that renders this component.
Parameters:
ui - the LabelUI L&F object
See Also:
getUI

updateUI

public void updateUI()
Notification from the UIFactory that the L&F has changed.
Overrides:
updateUI in class JComponent
See Also:
updateUI

getUIClassID

public String getUIClassID()
Returns a string that specifies the name of the l&f class that renders this component.
Returns:
String "LabelUI"
Overrides:
getUIClassID in class JComponent
See Also:
getUIClassID, getUI

getText

public String getText()
Returns the text string that the label displays.
Returns:
a String
See Also:
setText

setText

public void setText(String text)
Defines the single line of text this component will display. If the value of text is null or empty string, nothing is displayed.

The default value of this property is null.

This is a JavaBeans bound property.

See Also:
setVerticalTextPosition, setHorizontalTextPosition, setIcon

getIcon

public Icon getIcon()
Returns the graphic image (glyph, icon) that the label displays.
Returns:
an Icon
See Also:
setIcon

setIcon

public void setIcon(Icon icon)
Defines the icon this component will display. If the value of icon is null, nothing is displayed.

The default value of this property is null.

This is a JavaBeans bound property.

See Also:
setVerticalTextPosition, setHorizontalTextPosition, getIcon

getDisabledIcon

public Icon getDisabledIcon()
Returns the value of the disabledIcon property if it's been set, If it hasn't been set and the value of the icon property is an ImageIcon, we compute a "grayed out" version of the icon and update the disabledIcon property with that.
Returns:
The value of the disabledIcon property.
See Also:
setDisabledIcon, ImageIcon

setDisabledIcon

public void setDisabledIcon(Icon disabledIcon)
Set the icon to be displayed if this JLabel is "disabled", i.e. JLabel.setEnabled(false).

The default value of this property is null.

Parameters:
disabledIcon - the Icon to display when the component is disabled
See Also:
getDisabledIcon, setEnabled

setDisplayedMnemonic

public void setDisplayedMnemonic(int key)
Specify a keycode that indicates a mnemonic key. This property is used when the label is part of a larger component. If the labelFor property of the label is not null, the label will call the requestFocus method of the component specified by the labelFor property when the mnemonic is activated.
See Also:
getLabelFor, setLabelFor

setDisplayedMnemonic

public void setDisplayedMnemonic(char aChar)

getDisplayedMnemonic

public int getDisplayedMnemonic()
Return the keycode that indicates a mnemonic key. This property is used when the label is part of a larger component. If the labelFor property of the label is not null, the label will call the requestFocus method of the component specified by the labelFor property when the mnemonic is activated.
Returns:
int value for the mnemonic key
See Also:
getLabelFor, setLabelFor

checkHorizontalKey

protected int checkHorizontalKey(int key,
                                 String message)
Verify that key is a legal value for the horizontalAlignment or horizontalTextPosition properties.
Parameters:
key - the property value to check
message - the IllegalArgumentException detail message
Throws:
IllegalArgumentException - if key isn't LEFT, CENTER, or RIGHT.
See Also:
setHorizontalAlignment, setHorizontalTextPosition

checkVerticalKey

protected int checkVerticalKey(int key,
                               String message)
Verify that key is a legal value for the verticalAlignment or verticalTextPosition properties.
Parameters:
key - the property value to check
message - the IllegalArgumentException detail message
Throws:
IllegalArgumentException - if key isn't TOP, CENTER, or BOTTOM.
See Also:
setVerticalAlignment, setVerticalTextPosition

getIconTextGap

public int getIconTextGap()
Returns the amount of space between the text and the icon displayed in this label.
Returns:
an int equal to the number of pixels between the text and the icon.
See Also:
setIconTextGap

setIconTextGap

public void setIconTextGap(int iconTextGap)
If both the icon and text properties are set, this property defines the space between them.

The default value of this property is 4 pixels.

This is a JavaBeans bound property.

See Also:
getIconTextGap

getVerticalAlignment

public int getVerticalAlignment()
Returns the alignment of the label's contents along the Y axis.
Returns:
The value of the verticalAlignment property, one of the following constants defined in SwingConstants: TOP, CENTER, or BOTTOM.
See Also:
SwingConstants, setVerticalAlignment

setVerticalAlignment

public void setVerticalAlignment(int alignment)
Sets the alignment of the label's contents along the Y axis.

The default value of this property is CENTER.

This is a JavaBeans bound property.

Parameters:
alignment - One of the following constants defined in SwingConstants: TOP, CENTER (the default), or BOTTOM.
See Also:
SwingConstants, getVerticalAlignment

getHorizontalAlignment

public int getHorizontalAlignment()
Returns the alignment of the label's contents along the X axis.
Returns:
The value of the horizontalAlignment property, one of the following constants defined in SwingConstants: LEFT, CENTER, or RIGHT.
See Also:
setHorizontalAlignment, SwingConstants

setHorizontalAlignment

public void setHorizontalAlignment(int alignment)
Sets the alignment of the label's contents along the X axis.

This is a JavaBeans bound property.

Parameters:
alignment - One of the following constants defined in SwingConstants: LEFT (the default for text-only labels), CENTER (the default for image-only labels), or RIGHT.
See Also:
SwingConstants, getHorizontalAlignment

getVerticalTextPosition

public int getVerticalTextPosition()
Returns the vertical position of the label's text, relative to its image.
Returns:
One of the following constants defined in SwingConstants: TOP, CENTER, or BOTTOM.
See Also:
setVerticalTextPosition, SwingConstants

setVerticalTextPosition

public void setVerticalTextPosition(int textPosition)
Sets the vertical position of the label's text, relative to its image.

The default value of this property is CENTER.

This is a JavaBeans bound property.

Parameters:
textPosition - One of the following constants defined in SwingConstants: TOP, CENTER (the default), or BOTTOM.
See Also:
SwingConstants, getVerticalTextPosition

getHorizontalTextPosition

public int getHorizontalTextPosition()
Returns the horizontal position of the label's text, relative to its image.
Returns:
One of the following constants defined in SwingConstants: LEFT, CENTER, or RIGHT.
See Also:
SwingConstants

setHorizontalTextPosition

public void setHorizontalTextPosition(int x)
Sets the horizontal position of the label's text, relative to its image.
Parameters:
x - One of the following constants defined in SwingConstants: LEFT, CENTER, or RIGHT (the default).
See Also:
SwingConstants

setFont

public void setFont(Font font)
Sets the font used to display the label's text.
Parameters:
font - The font to use.
Overrides:
setFont in class Component

getAccessibleContext

public AccessibleContext getAccessibleContext()
Get the AccessibleContext of this object
Implements:
getAccessibleContext in interface Accessible
Returns:
the AccessibleContext of this object
Overrides:
getAccessibleContext in class JComponent

getLabelFor

public Component getLabelFor()
Get the component this is labelling.
Returns:
the Component this is labelling. Can be null if this does not label a Component. If the displayedMnemonic property is set and the labelFor property is also set, the label will call the requestFocus method of the component specified by the labelFor property when the mnemonic is activated.
See Also:
getDisplayedMnemonic, setDisplayedMnemonic

setLabelFor

public void setLabelFor(Component c)
Set the component this is labelling. Can be null if this does not label a Component. If the displayedMnemonic property is set and the labelFor property is also set, the label will call the requestFocus method of the component specified by the labelFor property when the mnemonic is activated.
Parameters:
c - the Component this label is for, or null if the label is not the label for a component
See Also:
getDisplayedMnemonic, setDisplayedMnemonic

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