Package org.eclipse.swt.widgets

Class Canvas

  • All Implemented Interfaces:
    Adaptable, Drawable
    Direct Known Subclasses:
    CLabel, Decorations, FileUpload
    public class Canvas
extends Composite
    Instances of this class provide a surface for drawing arbitrary graphics.
    Styles:
    (none)
    Events:
    (none)

    This class may be subclassed by custom control implementors who are building controls that are not constructed from aggregates of other controls. That is, they are either painted using SWT graphics calls or are handled by native methods.

    Since:
    1.0
    See Also:
    Composite

    • Constructor Detail

      • Canvas

        public Canvas​(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
        See Also:
        SWT, Widget.checkSubclass(), Widget.getStyle()

    • Method Detail

      • getAdapter

        public <T> T getAdapter​(java.lang.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 Composite
        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.

      • addPaintListener

        public void addPaintListener​(PaintListener listener)
        Adds the listener to the collection of listeners who will be notified when the receiver needs to be painted, by sending it one of the messages defined in the PaintListener interface.
        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
        Since:
        1.3
        See Also:
        PaintListener, removePaintListener(org.eclipse.swt.events.PaintListener)

      • removePaintListener

        public void removePaintListener​(PaintListener listener)
        Removes the listener from the collection of listeners who will be notified when the receiver needs to be painted.
        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
        Since:
        1.3
        See Also:
        PaintListener, addPaintListener(org.eclipse.swt.events.PaintListener)