JavaTM 2 Platform
Std. Ed. v1.3.1

java.awt
Class Checkbox

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Checkbox
All Implemented Interfaces:
Accessible, ImageObserver, ItemSelectable, MenuContainer, Serializable

public class Checkbox
extends Component
implements ItemSelectable, Accessible

A check box is a graphical component that can be in either an "on" (true) or "off" (false) state. Clicking on a check box changes its state from "on" to "off," or from "off" to "on."

The following code example creates a set of check boxes in a grid layout:


 setLayout(new GridLayout(3, 1));
 add(new Checkbox("one", null, true));
 add(new Checkbox("two"));
 add(new Checkbox("three"));
 

This image depicts the check boxes and grid layout created by this code example:

The button labeled one is in the "on" state, and the other two are in the "off" state. In this example, which uses the GridLayout class, the states of the three check boxes are set independently.

Alternatively, several check boxes can be grouped together under the control of a single object, using the CheckboxGroup class. In a check box group, at most one button can be in the "on" state at any given time. Clicking on a check box to turn it on forces any other check box in the same group that is on into the "off" state.

Since:
JDK1.0
See Also:
GridLayout, CheckboxGroup, Serialized Form

Inner Class Summary
protected  class Checkbox.AccessibleAWTCheckbox
          This class implements accessibility support for the Checkbox class.
 
Inner classes inherited from class java.awt.Component
Component.AccessibleAWTComponent
 
Fields inherited from class java.awt.Component
BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
 
Fields inherited from interface java.awt.image.ImageObserver
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
 
Constructor Summary
Checkbox()
          Creates a check box with no label.
Checkbox(String label)
          Creates a check box with the specified label.
Checkbox(String label, boolean state)
          Creates a check box with the specified label and sets the specified state.
Checkbox(String label, boolean state, CheckboxGroup group)
          Creates a check box with the specified label, in the specified check box group, and set to the specified state.
Checkbox(String label, CheckboxGroup group, boolean state)
          Constructs a Checkbox with the specified label, set to the specified state, and in the specified check box group.
 
Method Summary
 void addItemListener(ItemListener l)
          Adds the specified item listener to receive item events from this check box.
 void addNotify()
          Creates the peer of the Checkbox.
 AccessibleContext getAccessibleContext()
          Gets the AccessibleContext associated with this Checkbox.
 CheckboxGroup getCheckboxGroup()
          Determines this check box's group.
 String getLabel()
          Gets the label of this check box.
 EventListener[] getListeners(Class listenerType)
          Return an array of all the listeners that were added to the Checkbox with addXXXListener(), where XXX is the name of the listenerType argument.
 Object[] getSelectedObjects()
          Returns an array (length 1) containing the checkbox label or null if the checkbox is not selected.
 boolean getState()
          Determines whether this check box is in the "on" or "off" state.
protected  String paramString()
          Returns the parameter string representing the state of this check box.
protected  void processEvent(AWTEvent e)
          Processes events on this check box.
protected  void processItemEvent(ItemEvent e)
          Processes item events occurring on this check box by dispatching them to any registered ItemListener objects.
 void removeItemListener(ItemListener l)
          Removes the specified item listener so that the item listener no longer receives item events from this check box.
 void setCheckboxGroup(CheckboxGroup g)
          Sets this check box's group to be the specified check box group.
 void setLabel(String label)
          Sets this check box's label to be the string argument.
 void setState(boolean state)
          Sets the state of this check box to the specified state.
 
Methods inherited from class java.awt.Component
action, add, addComponentListener, addFocusListener, addHierarchyBoundsListener, addHierarchyListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, addPropertyChangeListener, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getComponentOrientation, getCursor, getDropTarget, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getInputContext, getInputMethodRequests, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getName, getParent, getPeer, getPreferredSize, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isDisplayable, isDoubleBuffered, 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, postEvent, preferredSize, prepareImage, prepareImage, print, printAll, processComponentEvent, processFocusEvent, processHierarchyBoundsEvent, processHierarchyEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, resize, resize, setBackground, setBounds, setBounds, setComponentOrientation, 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, wait, wait, wait
 

Constructor Detail

Checkbox

public Checkbox()
Creates a check box with no label. The state of this check box is set to "off," and it is not part of any check box group.

Checkbox

public Checkbox(String label)
Creates a check box with the specified label. The state of this check box is set to "off," and it is not part of any check box group.
Parameters:
label - a string label for this check box, or null for no label.

Checkbox

public Checkbox(String label,
                boolean state)
Creates a check box with the specified label and sets the specified state. This check box is not part of any check box group.
Parameters:
label - a string label for this check box, or null for no label.
state - the initial state of this check box.

Checkbox

public Checkbox(String label,
                boolean state,
                CheckboxGroup group)
Creates a check box with the specified label, in the specified check box group, and set to the specified state.
Parameters:
label - a string label for this check box, or null for no label.
state - the initial state of this check box.
group - a check box group for this check box, or null for no group.
Since:
JDK1.1

Checkbox

public Checkbox(String label,
                CheckboxGroup group,
                boolean state)
Constructs a Checkbox with the specified label, set to the specified state, and in the specified check box group.
Parameters:
label - a string label for this check box, or null for no label.
group - a check box group for this check box, or null for no group.
state - the initial state of this check box.
Since:
JDK1.1
Method Detail

addNotify

public void addNotify()
Creates the peer of the Checkbox. The peer allows you to change the look of the Checkbox without changing its functionality.
Overrides:
addNotify in class Component
See Also:
Toolkit.createCheckbox(java.awt.Checkbox), Component.getToolkit()

getLabel

public String getLabel()
Gets the label of this check box.
Returns:
the label of this check box, or null if this check box has no label.
See Also:
setLabel(java.lang.String)

setLabel

public void setLabel(String label)
Sets this check box's label to be the string argument.
Parameters:
label - a string to set as the new label, or null for no label.
See Also:
getLabel()

getState

public boolean getState()
Determines whether this check box is in the "on" or "off" state. The boolean value true indicates the "on" state, and false indicates the "off" state.
Returns:
the state of this check box, as a boolean value.
See Also:
setState(boolean)

setState

public void setState(boolean state)
Sets the state of this check box to the specified state. The boolean value true indicates the "on" state, and false indicates the "off" state.
Parameters:
state - the boolean state of the check box.
See Also:
getState()

getSelectedObjects

public Object[] getSelectedObjects()
Returns an array (length 1) containing the checkbox label or null if the checkbox is not selected.
Specified by:
getSelectedObjects in interface ItemSelectable
See Also:
ItemSelectable

getCheckboxGroup

public CheckboxGroup getCheckboxGroup()
Determines this check box's group.
Returns:
this check box's group, or null if the check box is not part of a check box group.
See Also:
setCheckboxGroup(java.awt.CheckboxGroup)

setCheckboxGroup

public void setCheckboxGroup(CheckboxGroup g)
Sets this check box's group to be the specified check box group. If this check box is already in a different check box group, it is first taken out of that group.
Parameters:
g - the new check box group, or null to remove this check box from any check box group.
See Also:
getCheckboxGroup()

addItemListener

public void addItemListener(ItemListener l)
Adds the specified item listener to receive item events from this check box. If l is null, no exception is thrown and no action is performed.
Specified by:
addItemListener in interface ItemSelectable
Parameters:
l - the item listener
Since:
JDK1.1
See Also:
ItemEvent, ItemListener, removeItemListener(java.awt.event.ItemListener)

removeItemListener

public void removeItemListener(ItemListener l)
Removes the specified item listener so that the item listener no longer receives item events from this check box. If l is null, no exception is thrown and no action is performed.
Specified by:
removeItemListener in interface ItemSelectable
Parameters:
l - the item listener
Since:
JDK1.1
See Also:
ItemEvent, ItemListener, addItemListener(java.awt.event.ItemListener)

getListeners

public EventListener[] getListeners(Class listenerType)
Return an array of all the listeners that were added to the Checkbox with addXXXListener(), where XXX is the name of the listenerType argument. For example, to get all of the ItemListener(s) for the given Checkbox c, one would write:
 ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.class))
 
If no such listener list exists, then an empty array is returned.
Overrides:
getListeners in class Component
Parameters:
listenerType - Type of listeners requested
Returns:
all of the listeners of the specified type supported by this checkbox
Since:
1.3

processEvent

protected void processEvent(AWTEvent e)
Processes events on this check box. If the event is an instance of ItemEvent, this method invokes the processItemEvent method. Otherwise, it calls its superclass's processEvent method.
Overrides:
processEvent in class Component
Parameters:
e - the event.
Since:
JDK1.1
See Also:
ItemEvent, processItemEvent(java.awt.event.ItemEvent)

processItemEvent

protected void processItemEvent(ItemEvent e)
Processes item events occurring on this check box by dispatching them to any registered ItemListener objects.

This method is not called unless item events are enabled for this component. Item events are enabled when one of the following occurs:

Parameters:
e - the item event.
Since:
JDK1.1
See Also:
ItemEvent, ItemListener, addItemListener(java.awt.event.ItemListener), Component.enableEvents(long)

paramString

protected String paramString()
Returns the parameter string representing the state of this check box. This string is useful for debugging.
Overrides:
paramString in class Component
Returns:
the parameter string of this check box.

getAccessibleContext

public AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this Checkbox. For checkboxes, the AccessibleContext takes the form of an AccessibleAWTCheckbox. A new AccessibleAWTCheckbox is created if necessary.
Specified by:
getAccessibleContext in interface Accessible
Overrides:
getAccessibleContext in class Component
Returns:
an AccessibleAWTCheckbox that serves as the AccessibleContext of this Checkbox

JavaTM 2 Platform
Std. Ed. v1.3.1

Submit a bug or feature
For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

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