Checkbox (Sample Document)

java.lang.Object
- java.awt.Component
- - java.awt.Checkbox

All Implemented Interfaces:

java.awt.image.ImageObserver, ItemSelectable, MenuContainer, java.io.Serializable, javax.accessibility.Accessible

public class Checkbox extends Component implements ItemSelectable, javax.accessibility.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

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

protected class Checkbox.AccessibleAWTCheckbox
This class implements accessibility support for the Checkbox class.
- Nested classes/interfaces inherited from class java.awt.Component
  Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy

Nested Classes
Modifier and Type	Class and Description
`protected class`	`Checkbox.AccessibleAWTCheckbox` This class implements accessibility support for the `Checkbox` class.

Field Summary
- 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

Constructors
Constructor and Description
`Checkbox()` Creates a check box with an empty string for its label.
`Checkbox(java.lang.String label)` Creates a check box with the specified label.
`Checkbox(java.lang.String label, boolean state)` Creates a check box with the specified label and sets the specified state.
`Checkbox(java.lang.String label, boolean state, CheckboxGroup group)` Constructs a Checkbox with the specified label, set to the specified state, and in the specified check box group.
`Checkbox(java.lang.String label, CheckboxGroup group, boolean state)` Creates a check box with the specified label, in the specified check box group, and set to the specified state.

Method Summary

Basic Attribute Methods
Modifier and Type Method and Description

javax.accessibility.AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this Checkbox.

Basic Attribute Methods
Modifier and Type	Method and Description
`javax.accessibility.AccessibleContext`	`getAccessibleContext()` Gets the AccessibleContext associated with this Checkbox.

Event Support Methods
Modifier and Type	Method and Description
`<T extends java.util.EventListener> T[]`	`getListeners(java.lang.Class<T> listenerType)` Returns an array of all the objects currently registered as `FooListener`s upon this `Checkbox`.
`protected void`	`processEvent(AWTEvent e)` Processes events on this check box.

Other Methods
Modifier and Type	Method and Description
`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.
`CheckboxGroup`	`getCheckboxGroup()` Determines this check box's group.
`ItemListener[]`	`getItemListeners()` Returns an array of all the item listeners registered on this checkbox.
`java.lang.String`	`getLabel()` Gets the label of this check box.
`java.lang.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 java.lang.String`	`paramString()` Returns a string representing the state of this `Checkbox`.
`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 the specified check box group.
`void`	`setLabel(java.lang.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, addMouseWheelListener, addPropertyChangeListener, addPropertyChangeListener, applyComponentOrientation, areFocusTraversalKeysSet, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, createVolatileImage, createVolatileImage, deliverEvent, disable, disableEvents, dispatchEvent, doLayout, enable, enable, enableEvents, enableInputMethods, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, firePropertyChange, getAlignmentX, getAlignmentY, getBackground, getBaseline, getBaselineResizeBehavior, getBounds, getBounds, getColorModel, getComponentAt, getComponentAt, getComponentListeners, getComponentOrientation, getCursor, getDropTarget, getFocusCycleRootAncestor, getFocusListeners, getFocusTraversalKeys, getFocusTraversalKeysEnabled, getFont, getFontMetrics, getForeground, getGraphics, getGraphicsConfiguration, getHeight, getHierarchyBoundsListeners, getHierarchyListeners, getIgnoreRepaint, getInputContext, getInputMethodListeners, getInputMethodRequests, getKeyListeners, getLocale, getLocation, getLocation, getLocationOnScreen, getMaximumSize, getMinimumSize, getMouseListeners, getMouseMotionListeners, getMousePosition, getMouseWheelListeners, getName, getParent, getPeer, getPreferredSize, getPropertyChangeListeners, getPropertyChangeListeners, getSize, getSize, getToolkit, getTreeLock, getWidth, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, invalidate, isBackgroundSet, isCursorSet, isDisplayable, isDoubleBuffered, isEnabled, isFocusable, isFocusCycleRoot, isFocusOwner, isFocusTraversable, isFontSet, isForegroundSet, isLightweight, isMaximumSizeSet, isMinimumSizeSet, isOpaque, isPreferredSizeSet, 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, processMouseWheelEvent, remove, removeComponentListener, removeFocusListener, removeHierarchyBoundsListener, removeHierarchyListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removeMouseWheelListener, removeNotify, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, requestFocus, requestFocusInWindow, requestFocusInWindow, reshape, resize, resize, revalidate, setBackground, setBounds, setBounds, setComponentOrientation, setCursor, setDropTarget, setEnabled, setFocusable, setFocusTraversalKeys, setFocusTraversalKeysEnabled, setFont, setForeground, setIgnoreRepaint, setLocale, setLocation, setLocation, setMaximumSize, setMinimumSize, setName, setPreferredSize, setSize, setSize, setVisible, show, show, size, toString, transferFocus, transferFocusBackward, transferFocusUpCycle, update, validate

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Constructor Detail
  - Checkbox
    
    public Checkbox() throws HeadlessException
    
    Creates a check box with an empty string for its label. The state of this check box is set to "off," and it is not part of any check box group.
    
    Throws:
    
    HeadlessException - if GraphicsEnvironment.isHeadless() returns true
    See Also:
    GraphicsEnvironment.isHeadless()
  - Checkbox
    
    public Checkbox(java.lang.String label) throws HeadlessException
    
    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.
    
    Throws:
    
    HeadlessException - if GraphicsEnvironment.isHeadless returns true
    See Also:
    GraphicsEnvironment.isHeadless()
  - Checkbox
    
    public Checkbox(java.lang.String label, boolean state) throws HeadlessException
    
    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
    
    Throws:
    
    HeadlessException - if GraphicsEnvironment.isHeadless returns true
    See Also:
    GraphicsEnvironment.isHeadless()
  - Checkbox
    
    public Checkbox(java.lang.String label, boolean state, CheckboxGroup group) throws HeadlessException
    
    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.
    state - the initial state of this check box.
    group - a check box group for this check box, or null for no group.
    
    Throws:
    
    HeadlessException - if GraphicsEnvironment.isHeadless returns true
    Since:
    
    JDK1.1
    
    See Also:
    GraphicsEnvironment.isHeadless()
  - Checkbox
    
    public Checkbox(java.lang.String label, CheckboxGroup group, boolean state) throws HeadlessException
    
    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.
    group - a check box group for this check box, or null for no group.
    state - the initial state of this check box.
    
    Throws:
    
    HeadlessException - if GraphicsEnvironment.isHeadless returns true
    Since:
    
    JDK1.1
    
    See Also:
    GraphicsEnvironment.isHeadless()
- 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 java.lang.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(String)
  - setLabel
    
    public void setLabel(java.lang.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.
    Note that this method should be primarily used to initialize the state of the checkbox. Programmatically setting the state of the checkbox will not trigger an ItemEvent. The only way to trigger an ItemEvent is by user interaction.
    
    Parameters:
    state - the boolean state of the check box
    See Also:
    getState()
  - getSelectedObjects
    
    public java.lang.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(CheckboxGroup)
  - setCheckboxGroup
    
    public void setCheckboxGroup(CheckboxGroup g)
    
    Sets this check box's group to 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.
    If the state of this check box is true and the new group already has a check box selected, this check box's state is changed to false. If the state of this check box is true and the new group has no check box selected, this check box becomes the selected checkbox for the new group and its state is true.
    
    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. Item events are sent to listeners in response to user input, but not in response to calls to setState(). If l is null, no exception is thrown and no action is performed.
    Refer to AWT Threading Issues for details on AWT's threading model.
    
    Specified by:
    
    addItemListener in interface ItemSelectable
    
    Parameters:
    l - the item listener
    Since:
    
    JDK1.1
    
    See Also:
    removeItemListener(java.awt.event.ItemListener), getItemListeners(), setState(boolean), ItemEvent, 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.
    Refer to AWT Threading Issues for details on AWT's threading model.
    
    Specified by:
    
    removeItemListener in interface ItemSelectable
    
    Parameters:
    l - the item listener
    Since:
    
    JDK1.1
    
    See Also:
    addItemListener(java.awt.event.ItemListener), getItemListeners(), ItemEvent, ItemListener
  - getItemListeners
    
    public ItemListener[] getItemListeners()
    
    Returns an array of all the item listeners registered on this checkbox.
    
    Returns:
    all of this checkbox's ItemListeners or an empty array if no item listeners are currently registered
    Since:
    
    1.4
    
    See Also:
    addItemListener(java.awt.event.ItemListener), removeItemListener(java.awt.event.ItemListener), ItemEvent, ItemListener
  - getListeners
    
    public <T extends java.util.EventListener> T[] getListeners(java.lang.Class<T> listenerType)
    Returns an array of all the objects currently registered as FooListeners upon this Checkbox. FooListeners are registered using the addFooListener method.
    You can specify the listenerType argument with a class literal, such as FooListener.class. For example, you can query a Checkbox c for its item listeners with the following code:
```
ItemListener[] ils = (ItemListener[])(c.getListeners(ItemListener.class));
```
    If no such listeners exist, this method returns an empty array.
    Overrides:
    
    getListeners in class Component
    
    Parameters:
    listenerType - the type of listeners requested; this parameter should specify an interface that descends from java.util.EventListener
    
    Returns:
    an array of all objects registered as FooListeners on this checkbox, or an empty array if no such listeners have been added
    
    Throws:
    
    java.lang.ClassCastException - if listenerType doesn't specify a class or interface that implements java.util.EventListener
    Since:
    
    1.3
    
    See Also:
    getItemListeners()
  - 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.
    Note that if the event parameter is null the behavior is unspecified and may result in an exception.
    
    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:
    - An ItemListener object is registered via addItemListener.
    - Item events are enabled via enableEvents.
    Note that if the event parameter is null the behavior is unspecified and may result in an exception.
    Parameters:
    e - the item event
    Since:
    
    JDK1.1
    
    See Also:
    ItemEvent, ItemListener, addItemListener(java.awt.event.ItemListener), Component.enableEvents(long)
  - paramString
    
    protected java.lang.String paramString()
    
    Returns a string representing the state of this Checkbox. 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 Component
    
    Returns:
    the parameter string of this check box
  - getAccessibleContext
    
    public javax.accessibility.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 javax.accessibility.Accessible
    
    Overrides:
    
    getAccessibleContext in class Component
    
    Returns:
    an AccessibleAWTCheckbox that serves as the AccessibleContext of this Checkbox
    Since:
    
    1.3

Class Checkbox

Nested Class Summary

Nested classes/interfaces inherited from class java.awt.Component

Field Summary

Fields inherited from class java.awt.Component

Fields inherited from interface java.awt.image.ImageObserver

Constructor Summary

Method Summary

Methods inherited from class java.awt.Component

Methods inherited from class java.lang.Object

Constructor Detail

Checkbox

Checkbox

Checkbox

Checkbox

Checkbox

Method Detail

addNotify

getLabel

setLabel

getState

setState

getSelectedObjects

getCheckboxGroup

setCheckboxGroup

addItemListener

removeItemListener

getItemListeners

getListeners

processEvent

processItemEvent

paramString

getAccessibleContext