Package org.eclipse.swt.widgets

Class Button

java.lang.Object

org.eclipse.swt.widgets.Widget

org.eclipse.swt.widgets.Control

org.eclipse.swt.widgets.Button

All Implemented Interfaces:

Adaptable, Drawable

public class Button
extends Control

Instances of this class represent a selectable user interface object that issues notification when pressed and released.

Styles:

CHECK, PUSH, RADIO, TOGGLE, FLAT, WRAP

LEFT, RIGHT, CENTER

Events:

Selection

Note: Only one of the styles ARROW, CHECK, PUSH, RADIO, and TOGGLE may be specified.

Note: Only one of the styles LEFT, RIGHT, and CENTER may be specified.

Note: Only one of the styles UP, DOWN, LEFT, and RIGHT may be specified when the ARROW style is specified.

IMPORTANT: This class is intended to be subclassed only within the SWT implementation.

Since:

1.0

Constructor Summary

Constructors

Constructor	Description
Button(Composite parent, int style)	Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

Method Summary

Modifier and Type	Method	Description
void	addSelectionListener(SelectionListener listener)	Adds the listener to the collection of listeners who will be notified when the control is selected, by sending it one of the messages defined in the SelectionListener interface.
Point	computeSize(int wHint, int hHint, boolean changed)	Returns the preferred size of the receiver.
<T> T	getAdapter(Class<T> adapter)	Implementation of the Adaptable interface.
int	getAlignment()	Returns a value which describes the position of the text or image in the receiver.
boolean	getGrayed()	Returns true if the receiver is grayed, and false otherwise.
Image	getImage()	Returns the receiver's image if it has one, or null if it does not.
boolean	getSelection()	Returns true if the receiver is selected, and false otherwise.
String	getText()	Returns the receiver's text, which will be an empty string if it has never been set.
void	removeSelectionListener(SelectionListener listener)	Removes the listener from the collection of listeners who will be notified when the control is selected.
void	setAlignment(int alignment)	Controls how text, images and arrows will be displayed in the receiver.
void	setData(String key, Object value)	Sets the application defined property of the receiver with the specified name to the given value.
void	setGrayed(boolean grayed)	Sets the grayed state of the receiver.
void	setImage(Image image)	Sets the receiver's image to the argument, which may be null indicating that no image should be displayed.
void	setSelection(boolean selected)	Sets the selection state of the receiver, if it is of type CHECK, RADIO, or TOGGLE.
void	setText(String text)	Sets the receiver's text.

Methods inherited from class org.eclipse.swt.widgets.Control

addControlListener, addDragDetectListener, addFocusListener, addGestureListener, addHelpListener, addKeyListener, addMenuDetectListener, addMouseListener, addTouchListener, addTraverseListener, computeSize, forceFocus, getAccessible, getBackground, getBackgroundImage, getBorderWidth, getBounds, getCursor, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getMonitor, getOrientation, getParent, getShell, getSize, getToolTipText, getTouchEnabled, getVisible, isEnabled, isFocusControl, isReparentable, isVisible, moveAbove, moveBelow, pack, pack, redraw, redraw, removeControlListener, removeDragDetectListener, removeFocusListener, removeGestureListener, removeHelpListener, removeKeyListener, removeMenuDetectListener, removeMouseListener, removeTouchListener, removeTraverseListener, requestLayout, setBackground, setBackgroundImage, setBounds, setBounds, setCursor, setEnabled, setFocus, setFont, setForeground, setLayoutData, setLocation, setLocation, setMenu, setOrientation, setParent, setRedraw, setSize, setSize, setToolTipText, setTouchEnabled, setVisible, toControl, toControl, toDisplay, toDisplay, update

Methods inherited from class org.eclipse.swt.widgets.Widget

addDisposeListener, addListener, checkSubclass, checkWidget, dispose, getData, getData, getDisplay, getListeners, getStyle, isDisposed, isListening, notifyListeners, removeDisposeListener, removeListener, removeListener, reskin, setData, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

Button

public Button(Composite parent,
 int style)

Constructs a new instance of this class given its parent and a style value describing its behavior and appearance.

The style value is either one of the style constants defined in class SWT which is applicable to instances of this class, or must be built by bitwise OR'ing together (that is, using the int "|" operator) two or more of those SWT style constants. The class description lists the style constants that are applicable to the class. Style bits are also inherited from superclasses.

Parameters:

parent - a composite control which will be the parent of the new instance (cannot be null)

style - the style of control to construct

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the parent is null

SWTException -

• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the parent
• ERROR_INVALID_SUBCLASS - if this class is not an allowed subclass

See Also:

• SWT.CHECK
• SWT.PUSH
• SWT.RADIO
• SWT.TOGGLE
• SWT.FLAT
• SWT.LEFT
• SWT.RIGHT
• SWT.CENTER
• Widget.checkSubclass()
• Widget.getStyle()

Method Details

setText

public void setText(String text)

Sets the receiver's text.

This method sets the button label. The label may include the mnemonic character but must not contain line delimiters.

Mnemonics are indicated by an '&' that causes the next character to be the mnemonic. When the user presses a key sequence that matches the mnemonic, a selection event occurs. On most platforms, the mnemonic appears underlined but may be emphasised in a platform specific manner. The mnemonic indicator character '&' can be escaped by doubling it in the string, causing a single '&' to be displayed.

Parameters:

text - the new text

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the text is null

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getText

public String getText()

Returns the receiver's text, which will be an empty string if it has never been set.

Returns:

the receiver's text

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getSelection

public boolean getSelection()

Returns true if the receiver is selected, and false otherwise.

When the receiver is of type CHECK or RADIO, it is selected when it is checked. When it is of type TOGGLE, it is selected when it is pushed in. If the receiver is of any other type, this method returns false.

Returns:

the selection state

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setSelection

public void setSelection(boolean selected)

Sets the selection state of the receiver, if it is of type CHECK, RADIO, or TOGGLE.

When the receiver is of type CHECK or RADIO, it is selected when it is checked. When it is of type TOGGLE, it is selected when it is pushed in.

Parameters:

selected - the new selection state

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getGrayed

public boolean getGrayed()

Returns true if the receiver is grayed, and false otherwise. When the widget does not have the CHECK style, return false.

Returns:

the grayed state of the checkbox

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

Since:

1.2

setGrayed

public void setGrayed(boolean grayed)

Sets the grayed state of the receiver. This state change only applies if the control was created with the SWT.CHECK style.

Parameters:

grayed - the new grayed state

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

Since:

1.2

getImage

public Image getImage()

Returns the receiver's image if it has one, or null if it does not.

Returns:

the receiver's image

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setImage

public void setImage(Image image)

Sets the receiver's image to the argument, which may be null indicating that no image should be displayed.

Parameters:

image - the image to display on the receiver (may be null)

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the image has been disposed

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

getAlignment

public int getAlignment()

Returns a value which describes the position of the text or image in the receiver. The value will be one of LEFT, RIGHT or CENTER unless the receiver is an ARROW button, in which case, the alignment will indicate the direction of the arrow (one of LEFT, RIGHT, UP or DOWN)

Returns:

the alignment

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

setAlignment

public void setAlignment(int alignment)

Controls how text, images and arrows will be displayed in the receiver. The argument should be one of LEFT, RIGHT or CENTER .

Parameters:

alignment - the new alignment

Throws:

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

computeSize

public Point computeSize(int wHint,
 int hHint,
 boolean changed)

Description copied from class: Control

Returns the preferred size of the receiver.

The preferred size of a control is the size that it would best be displayed at. The width hint and height hint arguments allow the caller to ask a control questions such as "Given a particular width, how high does the control need to be to show all of the contents?" To indicate that the caller does not wish to constrain a particular dimension, the constant SWT.DEFAULT is passed for the hint.

If the changed flag is true, it indicates that the receiver's contents have changed, therefore any caches that a layout manager containing the control may have been keeping need to be flushed. When the control is resized, the changed flag will be false, so layout manager caches can be retained.

Overrides:

computeSize in class Control

Parameters:

wHint - the width hint (can be SWT.DEFAULT)

hHint - the height hint (can be SWT.DEFAULT)

changed - true if the control's contents have changed, and false otherwise

Returns:

the preferred size of the control.

See Also:

• Layout
• Control.getBorderWidth()
• Control.getBounds()
• Control.getSize()
• Control.pack(boolean)
• "computeTrim, getClientArea for controls that implement them"

addSelectionListener

public void addSelectionListener(SelectionListener listener)

Adds the listener to the collection of listeners who will be notified when the control is selected, by sending it one of the messages defined in the SelectionListener interface.

widgetSelected is called when the control is selected. widgetDefaultSelected is not called.

Parameters:

listener - the listener which should be notified

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the listener is null

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

See Also:

• SelectionListener
• removeSelectionListener(org.eclipse.swt.events.SelectionListener)
• SelectionEvent

removeSelectionListener

public void removeSelectionListener(SelectionListener listener)

Removes the listener from the collection of listeners who will be notified when the control is selected.

Parameters:

listener - the listener which should no longer be notified

Throws:

IllegalArgumentException -

• ERROR_NULL_ARGUMENT - if the listener is null

SWTException -

• ERROR_WIDGET_DISPOSED - if the receiver has been disposed
• ERROR_THREAD_INVALID_ACCESS - if not called from the thread that created the receiver

See Also:

• SelectionListener
• addSelectionListener(org.eclipse.swt.events.SelectionListener)

setData

public void setData(String key,
 Object value)

Description copied from class: Widget

Sets the application defined property of the receiver with the specified name to the given value.

Applications may associate arbitrary objects with the receiver in this fashion. If the objects stored in the properties need to be notified when the widget is disposed of, it is the application's responsibility to hook the Dispose event on the widget and do so.

Overrides:

setData in class Control

Parameters:

key - the name of the property

value - the new value for the property

See Also:

• Widget.getData(String)

getAdapter

public <T> T getAdapter(Class<T> adapter)

Description copied from class: Widget

Implementation of the Adaptable interface.

IMPORTANT: This method is not part of the RWT public API. It is marked public only so that it can be shared within the packages provided by RWT. It should never be accessed from application code.

Specified by:

getAdapter in interface Adaptable

Overrides:

getAdapter in class Control

Parameters:

adapter - the lookup class

Returns:

an object that can be cast to the given class or null if there is no adapter associated with the given class.