Package org.eclipse.jface.resource

Class LocalResourceManager

  • public final class LocalResourceManager
extends ResourceManager
    A local registry that shares its resources with some global registry. LocalResourceManager is typically used to safeguard against leaks. Clients can use a nested registry to allocate and deallocate resources in the global registry. Calling dispose() on the nested registry will deallocate everything allocated for the nested registry without affecting the rest of the global registry.

    A nested registry can be used to manage the resources for, say, a dialog box.

    Since:
    3.1

    • Constructor Detail

      • LocalResourceManager

        public LocalResourceManager​(ResourceManager parentRegistry)
        Creates a local registry that delegates to the given global registry for all resource allocation and deallocation.
        Parameters:
        parentRegistry - global registry

      • LocalResourceManager

        public LocalResourceManager​(ResourceManager parentRegistry,
                            Control owner)
        Creates a local registry that wraps the given global registry. Anything allocated by this registry will be automatically cleaned up with the given control is disposed. Note that registries created in this way should not be used to allocate any resource that must outlive the given control.
        Parameters:
        parentRegistry - global registry that handles resource allocation
        owner - control whose disposal will trigger cleanup of everything in the registry.

    • Method Detail

      • getDevice

        public Device getDevice()
        Description copied from class: ResourceManager
        Returns the Device for which this ResourceManager will create resources
        Specified by:
        getDevice in class ResourceManager
        Returns:
        the Device associated with this ResourceManager

      • allocate

        protected Object allocate​(DeviceResourceDescriptor descriptor)
                   throws DeviceResourceException
        Called the first time a resource is requested. Should allocate and return a resource of the correct type.
        Parameters:
        descriptor - identifier for the resource to allocate
        Returns:
        the newly allocated resource
        Throws:
        DeviceResourceException - Thrown when allocation of an SWT device resource fails

      • deallocate

        protected void deallocate​(Object resource,
                          DeviceResourceDescriptor descriptor)
        Called the last time a resource is dereferenced. Should release any resources reserved by allocate(...).
        Parameters:
        resource - resource being deallocated
        descriptor - identifier for the resource

      • getDefaultImage

        protected Image getDefaultImage()
        Description copied from class: ResourceManager
        Returns the default image that will be returned in the event that the intended image is missing.
        Specified by:
        getDefaultImage in class ResourceManager
        Returns:
        a default image that will be returned in the event that the intended image is missing.

      • create

        public final Object create​(DeviceResourceDescriptor descriptor)
                    throws DeviceResourceException
        Description copied from class: ResourceManager
        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 ResourceManager.destroy(DeviceResourceDescriptor).

        If the resource is intended to live for entire lifetime of the resource manager, a subsequent call to ResourceManager.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.

        Specified by:
        create in class ResourceManager
        Parameters:
        descriptor - descriptor for the resource to allocate
        Returns:
        the newly allocated resource (not null)
        Throws:
        DeviceResourceException - if unable to allocate the resource

      • dispose

        public void dispose()
        Deallocates any resources allocated by this registry that have not yet been deallocated.
        Overrides:
        dispose in class ResourceManager
        Since:
        3.1

      • find

        public Object find​(DeviceResourceDescriptor descriptor)
        Description copied from class: ResourceManager
        Returns a previously allocated resource associated with the given descriptor, or null if none exists yet.
        Specified by:
        find in class ResourceManager
        Parameters:
        descriptor - descriptor to find
        Returns:
        a previously allocated resource for the given descriptor or null if none.