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:

CHECK, PUSH, RADIO, TOGGLE, FLAT

LEFT, RIGHT, CENTER

Events:

Selection

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

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

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

Constructor Summary

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

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.
int	getAlignment() Returns a value which describes the position of the text or image in the receiver.
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.
java.lang.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 and images will be displayed in 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(java.lang.String string) Sets the receiver's text.

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

addControlListener, addFocusListener, addKeyListener, addMouseListener, addMouseMoveListener, addPaintListener, addTraverseListener, computeSize, computeSize, forceFocus, getBackground, getBorderWidth, getBounds, getEnabled, getFont, getForeground, getLayoutData, getLocation, getMenu, getParent, getShell, getSize, getToolTipText, getVisible, isEnabled, isFocusControl, isReparentable, isVisible, moveAbove, moveBelow, pack, pack, redraw, redraw, removeControlListener, removeFocusListener, removeKeyListener, removeMouseListener, removeMouseMoveListener, removePaintListener, removeTraverseListener, setBackground, setBounds, setBounds, setCapture, setEnabled, setFocus, setFont, setForeground, setLayoutData, setLocation, setLocation, setMenu, setParent, setRedraw, setSize, setSize, setToolTipText, setVisible, toControl, toControl, toDisplay, toDisplay, traverse, update

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

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:

java.lang.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 Detail

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:

java.lang.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.

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

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 java.lang.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

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:

java.lang.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 and images 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

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:

java.lang.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

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(java.lang.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 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:

string - the new text

Throws:

java.lang.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