Class ResourceManager

  • Direct Known Subclasses:
    DeviceResourceManager, LocalResourceManager

    public abstract class ResourceManager
    extends Object
    This class manages SWT resources. It manages reference-counted instances of resources such as Fonts, Images, and Colors, and allows them to be accessed using descriptors. Everything allocated through the registry should also be disposed through the registry. Since the resources are shared and reference counted, they should never be disposed directly.

    ResourceManager handles correct allocation and disposal of resources. It differs from the various JFace *Registry classes, which also map symbolic IDs onto resources. In general, you should use a *Registry class to map IDs onto descriptors, and use a ResourceManager to convert the descriptors into real Images/Fonts/etc.

    Since:
    3.1
    • Constructor Detail

      • ResourceManager

        public ResourceManager()
    • Method Detail

      • getDevice

        public abstract Device getDevice()
        Returns the Device for which this ResourceManager will create resources
        Returns:
        the Device associated with this ResourceManager
        Since:
        3.1
      • create

        public abstract Object create​(DeviceResourceDescriptor descriptor)
        Returns the resource described by the given descriptor. If the resource already exists, the reference count is incremented and the exiting resource is returned. Otherwise, a new resource is allocated. Every call to this method should have a corresponding call to destroy(DeviceResourceDescriptor).

        If the resource is intended to live for entire lifetime of the resource manager, a subsequent call to destroy(DeviceResourceDescriptor) may be omitted and the resource will be cleaned up when the resource manager is disposed. This pattern is useful for short-lived LocalResourceManagers, but should never be used with the global resource manager since doing so effectively leaks the resource.

        The resources returned from this method are reference counted and may be shared internally with other resource managers. They should never be disposed outside of the ResourceManager framework, or it will cause exceptions in other code that shares them. For example, never call Resource.dispose() on anything returned from this method.

        Callers may safely downcast the result to the resource type associated with the descriptor. For example, when given an ImageDescriptor, the return value of this method will always be an Image.

        Parameters:
        descriptor - descriptor for the resource to allocate
        Returns:
        the newly allocated resource (not null)
        Throws:
        DeviceResourceException - if unable to allocate the resource
        Since:
        3.1
      • destroy

        public abstract void destroy​(DeviceResourceDescriptor descriptor)
        Deallocates a resource previously allocated by create(DeviceResourceDescriptor). Descriptors are compared by equality, not identity. If the same resource was created multiple times, this may decrement a reference count rather than disposing the actual resource.
        Parameters:
        descriptor - identifier for the resource
        Since:
        3.1
      • get

        public final Object get​(DeviceResourceDescriptor descriptor)

        Returns a previously-allocated resource or allocates a new one if none exists yet. The resource will remain allocated for at least the lifetime of this resource manager. If necessary, the resource will be deallocated automatically when the resource manager is disposed.

        The resources returned from this method are reference counted and may be shared internally with other resource managers. They should never be disposed outside of the ResourceManager framework, or it will cause exceptions in other code that shares them. For example, never call Resource.dispose() on anything returned from this method.

        Callers may safely downcast the result to the resource type associated with the descriptor. For example, when given an ImageDescriptor, the return value of this method may be downcast to Image.

        This method should only be used for resources that should remain allocated for the lifetime of the resource manager. To allocate shorter-lived resources, manage them with create, and destroy rather than this method.

        This method should never be called on the global resource manager, since all resources will remain allocated for the lifetime of the app and will be effectively leaked.

        Parameters:
        descriptor - identifier for the requested resource
        Returns:
        the requested resource. Never null.
        Throws:
        DeviceResourceException - if the resource does not exist yet and cannot be created for any reason.
        Since:
        3.3
      • createImage

        public final Image createImage​(ImageDescriptor descriptor)

        Creates an image, given an image descriptor. Images allocated in this manner must be disposed by destroyImage(ImageDescriptor), and never by calling Resource.dispose().

        If the image is intended to remain allocated for the lifetime of the ResourceManager, the call to destroyImage may be omitted and the image will be cleaned up automatically when the ResourceManager is disposed. This should only be done with short-lived ResourceManagers, as doing so with the global manager effectively leaks the resource.

        Parameters:
        descriptor - descriptor for the image to create
        Returns:
        the Image described by this descriptor (possibly shared by other equivalent ImageDescriptors)
        Throws:
        DeviceResourceException - if unable to allocate the Image
        Since:
        3.1
      • createImageWithDefault

        public final Image createImageWithDefault​(ImageDescriptor descriptor)
        Creates an image, given an image descriptor. Images allocated in this manner must be disposed by destroyImage(ImageDescriptor), and never by calling Resource.dispose().
        Parameters:
        descriptor - descriptor for the image to create
        Returns:
        the Image described by this descriptor (possibly shared by other equivalent ImageDescriptors)
        Since:
        3.1
      • getDefaultImage

        protected abstract Image getDefaultImage()
        Returns the default image that will be returned in the event that the intended image is missing.
        Returns:
        a default image that will be returned in the event that the intended image is missing.
        Since:
        3.1
      • destroyImage

        public final void destroyImage​(ImageDescriptor descriptor)
        Undoes everything that was done by createImage(ImageDescriptor).
        Parameters:
        descriptor - identifier for the image to dispose
        Since:
        3.1
      • createColor

        public final Color createColor​(ColorDescriptor descriptor)
        Allocates a color, given a color descriptor. Any color allocated in this manner must be disposed by calling destroyColor(ColorDescriptor), or by an eventual call to dispose(). Resource.dispose() must never been called directly on the returned color.
        Parameters:
        descriptor - descriptor for the color to create
        Returns:
        the Color described by the given ColorDescriptor (not null)
        Throws:
        DeviceResourceException - if unable to create the color
        Since:
        3.1
      • createColor

        public final Color createColor​(RGB descriptor)
        Allocates a color, given its RGB value. Any color allocated in this manner must be disposed by calling destroyColor(RGB), or by an eventual call to dispose(). Resource.dispose() must never been called directly on the returned color.
        Parameters:
        descriptor - descriptor for the color to create
        Returns:
        the Color described by the given ColorDescriptor (not null)
        Throws:
        DeviceResourceException - if unable to create the color
        Since:
        3.1
      • destroyColor

        public final void destroyColor​(RGB descriptor)
        Undoes everything that was done by a call to createColor(RGB).
        Parameters:
        descriptor - RGB value of the color to dispose
        Since:
        3.1
      • destroyColor

        public final void destroyColor​(ColorDescriptor descriptor)
        Undoes everything that was done by a call to createColor(ColorDescriptor).
        Parameters:
        descriptor - identifier for the color to dispose
        Since:
        3.1
      • createFont

        public final Font createFont​(FontDescriptor descriptor)
        Returns the Font described by the given FontDescriptor. Any Font allocated in this manner must be deallocated by calling disposeFont(...), or by an eventual call to dispose(). The method Resource.dispose() must never be called directly on the returned font.
        Parameters:
        descriptor - description of the font to create
        Returns:
        the Font described by the given descriptor
        Throws:
        DeviceResourceException - if unable to create the font
        Since:
        3.1
      • destroyFont

        public final void destroyFont​(FontDescriptor descriptor)
        Undoes everything that was done by a previous call to createFont(FontDescriptor).
        Parameters:
        descriptor - description of the font to destroy
        Since:
        3.1
      • dispose

        public void dispose()
        Disposes any remaining resources allocated by this manager.
      • find

        public abstract Object find​(DeviceResourceDescriptor descriptor)
        Returns a previously allocated resource associated with the given descriptor, or null if none exists yet.
        Parameters:
        descriptor - descriptor to find
        Returns:
        a previously allocated resource for the given descriptor or null if none.
        Since:
        3.1
      • disposeExec

        public void disposeExec​(Runnable r)
        Causes the run() method of the runnable to be invoked just before the receiver is disposed. The runnable can be subsequently canceled by a call to cancelDisposeExec.
        Parameters:
        r - runnable to execute.
      • cancelDisposeExec

        public void cancelDisposeExec​(Runnable r)
        Cancels a runnable that was previously scheduled with disposeExec. Has no effect if the given runnable was not previously registered with disposeExec.
        Parameters:
        r - runnable to cancel