java.awt
Class Toolkit

java.lang.Object
  |
  +--java.awt.Toolkit

public abstract class Toolkit

extends Object

This class is the abstract superclass of all actual implementations of the Abstract Window Toolkit. Subclasses of Toolkit are used to bind the various components to particular native toolkit implementations.

Most applications should not call any of the methods in this class directly. The methods defined by Toolkit are the "glue" that joins the platform-independent classes in the java.awt package with their counterparts in java.awt.peer. Some methods defined by Toolkit query the native operating system directly.

Since:

JDK1.0

Constructor Summary

Toolkit()

Method Summary

void	addAWTEventListener(AWTEventListener listener, long eventMask) Adds an AWTEventListener to receive all AWTEvents dispatched system-wide that conform to the given eventMask.
abstract void	beep() Emits an audio beep.
abstract int	checkImage(Image image, int width, int height, ImageObserver observer) Indicates the construction status of a specified image that is being prepared for display.
Image	createImage(byte[] imagedata) Creates an image which decodes the image stored in the specified byte array.
abstract Image	createImage(byte[] imagedata, int imageoffset, int imagelength) Creates an image which decodes the image stored in the specified byte array, and at the specified offset and length.
abstract Image	createImage(ImageProducer producer) Creates an image with the specified image producer.
abstract Image	createImage(String filename) Returns an image which gets pixel data from the specified file.
abstract Image	createImage(URL url) Returns an image which gets pixel data from the specified URL.
abstract ColorModel	getColorModel() Determines the color model of this toolkit's screen.
static Toolkit	getDefaultToolkit() Gets the default toolkit.
abstract String[]	getFontList() Deprecated. see GraphicsEnvironment.getAvailableFontFamilyNames()
abstract FontMetrics	getFontMetrics(Font font) Deprecated. This returns integer metrics for the default screen.
abstract Image	getImage(String filename) Returns an image which gets pixel data from the specified file, whose format can be either GIF, JPEG or PNG.
abstract Image	getImage(URL url) Returns an image which gets pixel data from the specified URL.
int	getMenuShortcutKeyMask() Determines which modifier key is the appropriate accelerator key for menu shortcuts.
static String	getProperty(String key, String defaultValue) Gets a property with the specified key and default.
abstract int	getScreenResolution() Returns the screen resolution in dots-per-inch.
abstract Dimension	getScreenSize() Gets the size of the screen.
abstract Clipboard	getSystemClipboard() Gets the singleton instance of the system Clipboard which interfaces with clipboard facilities provided by the native platform.
EventQueue	getSystemEventQueue() Get the application's or applet's EventQueue instance.
protected abstract EventQueue	getSystemEventQueueImpl()
protected void	loadSystemColors(int[] systemColors) Fills in the integer array that is supplied as an argument with the current system color values.
abstract boolean	prepareImage(Image image, int width, int height, ImageObserver observer) Prepares an image for rendering.
void	removeAWTEventListener(AWTEventListener listener) Removes an AWTEventListener from receiving dispatched AWTEvents.
abstract void	sync() Synchronizes this toolkit's graphics state.

Methods inherited from class java.lang.Object

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

Constructor Detail

Toolkit

public Toolkit()

Method Detail

loadSystemColors

protected void loadSystemColors(int[] systemColors)

Fills in the integer array that is supplied as an argument with the current system color values.

Since:

JDK1.1

getScreenSize

public abstract Dimension getScreenSize()

Gets the size of the screen.

Returns:

the size of this toolkit's screen, in pixels.

getScreenResolution

public abstract int getScreenResolution()

Returns the screen resolution in dots-per-inch.

Returns:

this toolkit's screen resolution, in dots-per-inch.

getColorModel

public abstract ColorModel getColorModel()

Determines the color model of this toolkit's screen.

ColorModel is an abstract class that encapsulates the ability to translate between the pixel values of an image and its red, green, blue, and alpha components.

This toolkit method is called by the getColorModel method of the Component class.

Returns:

the color model of this toolkit's screen.

See Also:

ColorModel, Component.getColorModel()

getFontList

public abstract String[] getFontList()

Deprecated. see GraphicsEnvironment.getAvailableFontFamilyNames()

Returns the names of the available fonts in this toolkit.

For 1.1, the following font names are deprecated (the replacement name follows):

• TimesRoman (use Serif)
• Helvetica (use SansSerif)
• Courier (use Monospaced)

The ZapfDingbats fontname is also deprecated in 1.1 but the characters are defined in Unicode starting at 0x2700, and as of 1.1 Java supports those characters.

Returns:

the names of the available fonts in this toolkit.

See Also:

GraphicsEnvironment.getAvailableFontFamilyNames()

getFontMetrics

public abstract FontMetrics getFontMetrics(Font font)

Deprecated. This returns integer metrics for the default screen.

Gets the screen device metrics for rendering of the font.

Parameters:

font - a font.

Returns:

the screen metrics of the specified font in this toolkit.

See Also:

GraphicsEnvironment.getScreenDevices()

sync

public abstract void sync()

Synchronizes this toolkit's graphics state. Some window systems may do buffering of graphics events.

This method ensures that the display is up-to-date. It is useful for animation.

getDefaultToolkit

public static Toolkit getDefaultToolkit()

Gets the default toolkit.

If there is a system property named "awt.toolkit", that property is treated as the name of a class that is a subclass of Toolkit.

If the system property does not exist, then an implementation-dependent default toolkit is used.

Also loads additional classes into the VM, using the property 'assistive_technologies' specified in the Sun reference implementation by a line in the 'accessibility.properties' file. The form is "assistive_technologies=..." where the "..." is a comma-separated list of assistive technology classes to load. Each class is loaded in the order given and a single instance of each is created using Class.forName(class).newInstance(). This is done just after the AWT toolkit is created. All errors are handled via an AWTError exception.

Returns:

the default toolkit.

Throws:

AWTError - if a toolkit could not be found, or if one could not be accessed or instantiated.

getImage

public abstract Image getImage(String filename)

Returns an image which gets pixel data from the specified file, whose format can be either GIF, JPEG or PNG. The underlying toolkit attempts to resolve multiple requests with the same filename to the same returned Image. Since the mechanism required to facilitate this sharing of Image objects may continue to hold onto images that are no longer of use for an indefinate period of time, developers are encouraged to implement their own caching of images by using the createImage variant wherever available.

Parameters:

filename - the name of a file containing pixel data in a recognized file format.

Returns:

an image which gets its pixel data from the specified file.

See Also:

createImage(java.lang.String)

getImage

public abstract Image getImage(URL url)

Returns an image which gets pixel data from the specified URL. The pixel data referenced by the specified URL must be in one of the following formats: GIF, JPEG or PNG. The underlying toolkit attempts to resolve multiple requests with the same URL to the same returned Image. Since the mechanism required to facilitate this sharing of Image objects may continue to hold onto images that are no longer of use for an indefinate period of time, developers are encouraged to implement their own caching of images by using the createImage variant wherever available.

Parameters:

url - the URL to use in fetching the pixel data.

Returns:

an image which gets its pixel data from the specified URL.

See Also:

createImage(java.net.URL)

createImage

public abstract Image createImage(String filename)

Returns an image which gets pixel data from the specified file. The returned Image is a new object which will not be shared with any other caller of this method or its getImage variant.

Parameters:

filename - the name of a file containing pixel data in a recognized file format.

Returns:

an image which gets its pixel data from the specified file.

See Also:

getImage(java.lang.String)

createImage

public abstract Image createImage(URL url)

Returns an image which gets pixel data from the specified URL. The returned Image is a new object which will not be shared with any other caller of this method or its getImage variant.

Parameters:

url - the URL to use in fetching the pixel data.

Returns:

an image which gets its pixel data from the specified URL.

See Also:

getImage(java.net.URL)

prepareImage

public abstract boolean prepareImage(Image image,
                                     int width,
                                     int height,
                                     ImageObserver observer)

Prepares an image for rendering.

If the values of the width and height arguments are both -1, this method prepares the image for rendering on the default screen; otherwise, this method prepares an image for rendering on the default screen at the specified width and height.

The image data is downloaded asynchronously in another thread, and an appropriately scaled screen representation of the image is generated.

This method is called by components prepareImage methods.

Information on the flags returned by this method can be found with the definition of the ImageObserver interface.

Parameters:

image - the image for which to prepare a screen representation.

width - the width of the desired screen representation, or -1.

height - the height of the desired screen representation, or -1.

observer - the ImageObserver object to be notified as the image is being prepared.

Returns:

true if the image has already been fully prepared; false otherwise.

See Also:

Component.prepareImage(java.awt.Image, java.awt.image.ImageObserver), Component.prepareImage(java.awt.Image, int, int, java.awt.image.ImageObserver), ImageObserver

checkImage

public abstract int checkImage(Image image,
                               int width,
                               int height,
                               ImageObserver observer)

Indicates the construction status of a specified image that is being prepared for display.

If the values of the width and height arguments are both -1, this method returns the construction status of a screen representation of the specified image in this toolkit. Otherwise, this method returns the construction status of a scaled representation of the image at the specified width and height.

This method does not cause the image to begin loading. An application must call prepareImage to force the loading of an image.

This method is called by the component's checkImage methods.

Information on the flags returned by this method can be found with the definition of the ImageObserver interface.

Parameters:

image - the image whose status is being checked.

width - the width of the scaled version whose status is being checked, or -1.

height - the height of the scaled version whose status is being checked, or -1.

observer - the ImageObserver object to be notified as the image is being prepared.

Returns:

the bitwise inclusive OR of the ImageObserver flags for the image data that is currently available.

See Also:

prepareImage(java.awt.Image, int, int, java.awt.image.ImageObserver), Component.checkImage(java.awt.Image, java.awt.image.ImageObserver), Component.checkImage(java.awt.Image, int, int, java.awt.image.ImageObserver), ImageObserver

createImage

public abstract Image createImage(ImageProducer producer)

Creates an image with the specified image producer.

Parameters:

producer - the image producer to be used.

Returns:

an image with the specified image producer.

See Also:

Image, ImageProducer, Component.createImage(java.awt.image.ImageProducer)

createImage

public Image createImage(byte[] imagedata)

Creates an image which decodes the image stored in the specified byte array.

The data must be in some image format, such as GIF or JPEG, that is supported by this toolkit.

Parameters:

imagedata - an array of bytes, representing image data in a supported image format.

Returns:

an image.

Since:

JDK1.1

createImage

public abstract Image createImage(byte[] imagedata,
                                  int imageoffset,
                                  int imagelength)

Creates an image which decodes the image stored in the specified byte array, and at the specified offset and length. The data must be in some image format, such as GIF or JPEG, that is supported by this toolkit.

Parameters:

imagedata - an array of bytes, representing image data in a supported image format.

imageoffset - the offset of the beginning of the data in the array.

imagelength - the length of the data in the array.

Returns:

an image.

Since:

JDK1.1

beep

public abstract void beep()

Emits an audio beep.

Since:

JDK1.1

getSystemClipboard

public abstract Clipboard getSystemClipboard()

Gets the singleton instance of the system Clipboard which interfaces with clipboard facilities provided by the native platform. This clipboard enables data transfer between Java programs and native applications which use native clipboard facilities.

In addition to any and all formats specified in the flavormap.properties file, or other file specified by the AWT.DnD.flavorMapFileURL Toolkit property, text returned by the system Clipboard's getTransferData() method is available in the following flavors:

• DataFlavor.stringFlavor
• DataFlavor.plainTextFlavor (deprecated)

As with java.awt.datatransfer.StringSelection, if the requested flavor is DataFlavor.plainTextFlavor, or an equivalent flavor, a Reader is returned. Note: The behavior of the system Clipboard's getTransferData() method for DataFlavor.plainTextFlavor, and equivalent DataFlavors, is inconsistent with the definition of DataFlavor.plainTextFlavor . Because of this, support for DataFlavor.plainTextFlavor, and equivalent flavors, is deprecated.

Each actual implementation of this method should first check if there is a security manager installed. If there is, the method should call the security manager's checkSystemClipboardAccess method to ensure it's ok to to access the system clipboard. If the default implementation of checkSystemClipboardAccess is used (that is, that method is not overriden), then this results in a call to the security manager's checkPermission method with an AWTPermission("accessClipboard") permission.

Returns:

the system Clipboard

Since:

JDK1.1

See Also:

Clipboard, StringSelection, DataFlavor.stringFlavor, DataFlavor.plainTextFlavor, Reader, AWTPermission

getMenuShortcutKeyMask

public int getMenuShortcutKeyMask()

Determines which modifier key is the appropriate accelerator key for menu shortcuts.

Menu shortcuts, which are embodied in the MenuShortcut class, are handled by the MenuBar class.

By default, this method returns Event.CTRL_MASK. Toolkit implementations should override this method if the Control key isn't the correct key for accelerators.

Returns:

the modifier mask on the Event class that is used for menu shortcuts on this toolkit.

Since:

JDK1.1

See Also:

MenuBar, MenuShortcut

getProperty

public static String getProperty(String key,
                                 String defaultValue)

Gets a property with the specified key and default. This method returns defaultValue if the property is not found.

getSystemEventQueue

public final EventQueue getSystemEventQueue()

Get the application's or applet's EventQueue instance. Depending on the Toolkit implementation, different EventQueues may be returned for different applets. Applets should therefore not assume that the EventQueue instance returned by this method will be shared by other applets or the system.

First, if there is a security manager, its checkAwtEventQueueAccess method is called. If the default implementation of checkAwtEventQueueAccess is used (that is, that method is not overriden), then this results in a call to the security manager's checkPermission method with an AWTPermission("accessEventQueue") permission.

Returns:

the EventQueue object.

Throws:

SecurityException - if a security manager exists and its SecurityManager.checkAwtEventQueueAccess() method denies access to the EventQueue.

See Also:

AWTPermission

getSystemEventQueueImpl

protected abstract EventQueue getSystemEventQueueImpl()

addAWTEventListener

public void addAWTEventListener(AWTEventListener listener,
                                long eventMask)

Adds an AWTEventListener to receive all AWTEvents dispatched system-wide that conform to the given eventMask.

First, if there is a security manager, its checkPermission method is called with an AWTPermission("listenToAllAWTEvents") permission. This may result in a SecurityException.

eventMask is a bitmask of event types to receive. It is constructed by bitwise OR-ing together the event masks defined in AWTEvent.

Note: event listener use is not recommended for normal application use, but are intended solely to support special purpose facilities including support for accessibility, event record/playback, and diagnostic tracing. If listener is null, no exception is thrown and no action is performed.

Parameters:

listener - the event listener.

eventMask - the bitmask of event types to receive

Throws:

SecurityException - if a security manager exists and its checkPermission method doesn't allow the operation.

Since:

1.2

See Also:

AWTEventListener, addAWTEventListener(java.awt.event.AWTEventListener, long), AWTEvent, SecurityManager.checkPermission(java.security.Permission), AWTPermission

removeAWTEventListener

public void removeAWTEventListener(AWTEventListener listener)

Removes an AWTEventListener from receiving dispatched AWTEvents.

First, if there is a security manager, its checkPermission method is called with an AWTPermission("listenToAllAWTEvents") permission. This may result in a SecurityException.

Note: event listener use is not recommended for normal application use, but are intended solely to support special purpose facilities including support for accessibility, event record/playback, and diagnostic tracing. If listener is null, no exception is thrown and no action is performed.

Parameters:

listener - the event listener.

Throws:

SecurityException - if a security manager exists and its checkPermission method doesn't allow the operation.

Since:

1.2

See Also:

AWTEventListener, addAWTEventListener(java.awt.event.AWTEventListener, long), AWTEvent, SecurityManager.checkPermission(java.security.Permission), AWTPermission