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:
Restriction:
This class is not intended to be subclassed by clients.

  • 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:

  • 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:

    • 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:

    • 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:

    • 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