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:

Drawable

public class Button
extends Control

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

Styles:

ARROW, CHECK, PUSH, RADIO, TOGGLE, FLAT, WRAP

UP, DOWN, 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 not intended to be subclassed.

See Also:

• Button snippets
• SWT Example: ControlExample
• Sample code and further information

Restriction:

This class is not intended to be subclassed by clients.

Field Summary

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

handle

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 the user, by sending it one of the messages defined in the SelectionListener 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 or if the receiver is an ARROW button.
void	removeSelectionListener(SelectionListener listener)	Removes the listener from the collection of listeners who will be notified when the control is selected by the user.
void	setAlignment(int alignment)	Controls how text, images and arrows will be displayed in the receiver.
void	setBackground(Color color)	Sets the button's background color to the color specified by the argument, or to the default system color for the control if the argument is null.
boolean	setFocus()	Causes the receiver to have the keyboard focus, such that all keyboard events will be delivered to it.
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 string)	Sets the receiver's text.

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

addControlListener, addDragDetectListener, addFocusListener, addGestureListener, addHelpListener, addKeyListener, addMenuDetectListener, addMouseListener, addMouseMoveListener, addMouseTrackListener, addMouseWheelListener, addPaintListener, addTouchListener, addTraverseListener, computeSize, computeSize, dragDetect, dragDetect, forceFocus, getAccessible, getBackground, getBackgroundImage, getBorderWidth, getBounds, getCursor, getDragDetect, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getMonitor, getOrientation, getParent, getRegion, getShell, getSize, getTextDirection, getToolTipText, getTouchEnabled, getVisible, internal_dispose_GC, internal_new_GC, isEnabled, isFocusControl, isReparentable, isVisible, moveAbove, moveBelow, pack, pack, print, redraw, redraw, removeControlListener, removeDragDetectListener, removeFocusListener, removeGestureListener, removeHelpListener, removeKeyListener, removeMenuDetectListener, removeMouseListener, removeMouseMoveListener, removeMouseTrackListener, removeMouseWheelListener, removePaintListener, removeTouchListener, removeTraverseListener, requestLayout, setBackgroundImage, setBounds, setBounds, setCapture, setCursor, setDragDetect, setEnabled, setFont, setForeground, setLayoutData, setLocation, setLocation, setMenu, setOrientation, setParent, setRedraw, setRegion, setSize, setSize, setTextDirection, setToolTipText, setTouchEnabled, setVisible, toControl, toControl, toDisplay, toDisplay, traverse, traverse, traverse, update

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

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

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eclipse.swt.graphics.Drawable

isAutoScalable

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

Method Details

addSelectionListener

public void addSelectionListener(SelectionListener listener)

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

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

When the SWT.RADIO style bit is set, the widgetSelected method is also called when the receiver loses selection because another item in the same radio group was selected by the user. During widgetSelected the application can use getSelection() to determine the current selected state of the receiver.

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

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

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:

3.4

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

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

getText

public String getText()

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

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

removeSelectionListener

public void removeSelectionListener(SelectionListener listener)

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

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)

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 unless the receiver is an ARROW button, in which case, the argument indicates the direction of the arrow (one of LEFT, RIGHT, UP or DOWN).

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

setBackground

public void setBackground(Color color)

Sets the button's background color to the color specified by the argument, or to the default system color for the control if the argument is null.

Note: This is custom paint operation and only affects SWT.PUSH and SWT.TOGGLE buttons. If the native button has a 3D look an feel (e.g. Windows 7), this method will cause the button to look FLAT irrespective of the state of the SWT.FLAT style. For SWT.CHECK and SWT.RADIO buttons, this method delegates to Control.setBackground(Color).

Overrides:

setBackground in class Control

Parameters:

color - the new color (or null)

Throws:

IllegalArgumentException -

• ERROR_INVALID_ARGUMENT - if the argument 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

setFocus

public boolean setFocus()

Description copied from class: Control

Causes the receiver to have the keyboard focus, such that all keyboard events will be delivered to it. Focus reassignment will respect applicable platform constraints.

Overrides:

setFocus in class Control

Returns:

true if the control got focus, and false if it was unable to.

See Also:

• Control.forceFocus()

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.

Note that a Button can display an image and text simultaneously.

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

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:

3.4

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

setText

public void setText(String string)

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 emphasized in a platform specific manner. The mnemonic indicator character '&' can be escaped by doubling it in the string, causing a single '&' to be displayed.

Note that a Button can display an image and text simultaneously on Windows (starting with XP), GTK+ and OSX. On other platforms, a Button that has an image and text set into it will display the image or text that was set most recently.

Also note, if control characters like '\n', '\t' etc. are used in the string, then the behavior is platform dependent.

Parameters:

string - 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