Class BaseApplet

java.lang.Object
  |
  +--java.awt.Component
        |
        +--java.awt.Container
              |
              +--java.awt.Panel
                    |
                    +--java.applet.Applet
                          |
                          +--BaseApplet

Direct Known Subclasses:

BaseApplet2, LatticeApplet

public abstract class BaseApplet

extends java.applet.Applet

implements java.awt.event.ActionListener, java.awt.event.ItemListener

Base class for this set of applets, incorporating miscellaneous helper methods.

• Automatic double buffering (based on applet parameter)
• Automatic repainting and buffer adjustment on resize
• Fix for checkboxes in Mozilla
• Standard AppletInfo and parameterInfo methods
• Font changes (based on applet parameter)

See Also:

Serialized Form

Inner Class Summary

protected class	BaseApplet.MozillaWorkaround Manually adjusts selected checkbox in a CheckboxGroup, fixing a problem experienced with Mozilla.
protected class	BaseApplet.ResizeListener Recreates buffer and repaints when size of applet is changed.

Inner classes inherited from class java.awt.Component

java.awt.Component.AWTTreeLock

Field Summary

protected java.awt.Image	buffer The image used for buffering
protected int	GRAPH_MARGIN
protected boolean	refresh true if the buffer has been invalidated, else false
protected BaseApplet.ResizeListener	resizeListener Instance of ResizeListener used to detect size changes
protected boolean	safetyLimit true if extra range checks are enabled, else false
protected boolean	useBuffer true if buffering is enabled, else false

Fields inherited from class java.applet.Applet

serialVersionUID, stub

Fields inherited from class java.awt.Panel

base, nameCounter, serialVersionUID

Fields inherited from class java.awt.Container

component, containerListener, containerSerializedDataVersion, dispatcher, layoutMgr, maxSize, ncomponents, serialVersionUID

Fields inherited from class java.awt.Component

actionListenerK, adjustmentListenerK, appContext, assert, background, BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, changeSupport, componentListener, componentListenerK, componentOrientation, componentSerializedDataVersion, containerListenerK, cursor, dropTarget, enabled, eventMask, focusListener, focusListenerK, font, foreground, hasFocus, height, incRate, inputMethodListener, inputMethodListenerK, isInc, isPacked, itemListenerK, keyListener, keyListenerK, LEFT_ALIGNMENT, locale, LOCK, minSize, mouseListener, mouseListenerK, mouseMotionListener, mouseMotionListenerK, name, nameExplicitlySet, newEventsOnly, ownedWindowK, parent, peer, peerFont, popups, prefSize, RIGHT_ALIGNMENT, serialVersionUID, textListenerK, TOP_ALIGNMENT, valid, visible, width, windowListenerK, x, y

Constructor Summary

BaseApplet()

Method Summary

abstract void	actionPerformed(java.awt.event.ActionEvent ae) Subclasses should at least provide an empty implementation of this method.
protected void	changeFont() Used internally to read and apply font settings
protected abstract void	doPaint(java.awt.Graphics g) Called by forcePaint() to actually perform the painting.
void	forcePaint(java.awt.Graphics g) Forces the buffer to be regenerated, then painted onto the specified Graphics object.
java.lang.String	getAppletInfo() Unless overridden, returns (C) 2002 University of Southampton, UK"
java.lang.String[][]	getParameterInfo() Unless overridden, returns parameter descriptions for fontname fontsize usebuffer safety
void	init() Performs extra intialisation specific to this class
void	itemStateChanged(java.awt.event.ItemEvent ie) Default ItemListener implementation, calls actionPerformed(null)
void	paint(java.awt.Graphics g) Paints the applet onto the specified Graphics object.
void	refresh() Invalidates the buffer contents and repaints the applet
void	start() Applets should use this method to perform any final initialisation necessary to "activate" the applet
void	stop() When this method is called, the applet should cease any user interaction.
void	update(java.awt.Graphics g) Method overridden to save clearing the screen.

Methods inherited from class java.applet.Applet

destroy, getAppletContext, getAudioClip, getAudioClip, getCodeBase, getDocumentBase, getImage, getImage, getLocale, getParameter, isActive, newAudioClip, play, play, resize, resize, setStub, showStatus

Methods inherited from class java.awt.Panel

, addNotify, constructComponentName

Methods inherited from class java.awt.Container

add, add, add, add, add, addContainerListener, addImpl, applyOrientation, countComponents, deliverEvent, dispatchEventImpl, dispatchEventToSelf, doLayout, eventEnabled, findComponentAt, findComponentAt, getAlignmentX, getAlignmentY, getComponent, getComponentAt, getComponentAt, getComponentCount, getComponents_NoClientCode, getComponents, getCursorTarget, getInsets, getLayout, getMaximumSize, getMinimumSize, getMouseEventTarget, getPreferredSize, getWindow, initIDs, insets, invalidate, invalidateTree, isAncestorOf, layout, lightweightPrint, list, list, locate, minimumSize, nextFocus, paintComponents, paramString, postProcessKeyEvent, postsOldMouseEvents, preferredSize, preProcessKeyEvent, print, printComponents, printOneComponent, processContainerEvent, processEvent, proxyEnableEvents, proxyRequestFocus, readObject, remove, remove, removeAll, removeContainerListener, removeNotify, setCursor, setFocusOwner, setFont, setLayout, transferFocus, updateCursor, validate, validateTree, writeObject

Methods inherited from class java.awt.Component

action, add, addComponentListener, addFocusListener, addInputMethodListener, addKeyListener, addMouseListener, addMouseMotionListener, addPropertyChangeListener, addPropertyChangeListener, areInputMethodsEnabled, bounds, checkImage, checkImage, coalesceEvents, contains, contains, createImage, createImage, disable, disableEvents, dispatchEvent, enable, enable, enableEvents, enableInputMethods, firePropertyChange, getBackground, getBounds, getBounds, getColorModel, getComponentOrientation, getCursor, getDropTarget, getFont_NoClientCode, getFont, getFontMetrics, getForeground, getGraphics, getHeight, getInputContext, getInputMethodRequests, getIntrinsicCursor, getLocation, getLocation, getLocationOnScreen, getName, getNativeContainer, getParent_NoClientCode, getParent, getPeer, getSize, getSize, getToolkit, getToolkitImpl, getTreeLock, getWidth, getWindowForObject, getX, getY, gotFocus, handleEvent, hasFocus, hide, imageUpdate, inside, isDisplayable, isDoubleBuffered, isEnabled, isEnabledImpl, isFocusTraversable, isLightweight, isOpaque, isShowing, isValid, isVisible, keyDown, keyUp, list, list, list, location, lostFocus, mouseDown, mouseDrag, mouseEnter, mouseExit, mouseMove, mouseUp, move, nextFocus, paintAll, postEvent, prepareImage, prepareImage, printAll, processComponentEvent, processFocusEvent, processInputMethodEvent, processKeyEvent, processMouseEvent, processMouseMotionEvent, remove, removeComponentListener, removeFocusListener, removeInputMethodListener, removeKeyListener, removeMouseListener, removeMouseMotionListener, removePropertyChangeListener, removePropertyChangeListener, repaint, repaint, repaint, repaint, requestFocus, reshape, setBackground, setBounds, setBounds, setComponentOrientation, setDropTarget, setEnabled, setForeground, setLocale, setLocation, setLocation, setName, setSize, setSize, setVisible, show, show, size, toString, transferFocus

Methods inherited from class java.lang.Object

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

Field Detail

buffer

protected java.awt.Image buffer

The image used for buffering

useBuffer

protected boolean useBuffer

true if buffering is enabled, else false

refresh

protected boolean refresh

true if the buffer has been invalidated, else false

safetyLimit

protected boolean safetyLimit

true if extra range checks are enabled, else false

resizeListener

protected BaseApplet.ResizeListener resizeListener

Instance of ResizeListener used to detect size changes

GRAPH_MARGIN

protected int GRAPH_MARGIN

Constructor Detail

BaseApplet

public BaseApplet()

Method Detail

init

public void init()

Performs extra intialisation specific to this class

Overrides:

init in class java.applet.Applet

start

public void start()

Applets should use this method to perform any final initialisation necessary to "activate" the applet

Overrides:

start in class java.applet.Applet

stop

public void stop()

When this method is called, the applet should cease any user interaction. In particular, any threads explicitly started should be stopped, any external resources should be closed. This method should negate the action of start().

Overrides:

stop in class java.applet.Applet

actionPerformed

public abstract void actionPerformed(java.awt.event.ActionEvent ae)

Subclasses should at least provide an empty implementation of this method.

Specified by:

actionPerformed in interface java.awt.event.ActionListener

itemStateChanged

public void itemStateChanged(java.awt.event.ItemEvent ie)

Default ItemListener implementation, calls actionPerformed(null)

Specified by:

itemStateChanged in interface java.awt.event.ItemListener

changeFont

protected void changeFont()

Used internally to read and apply font settings

getAppletInfo

public java.lang.String getAppletInfo()

Unless overridden, returns (C) 2002 University of Southampton, UK"

Overrides:

getAppletInfo in class java.applet.Applet

getParameterInfo

public java.lang.String[][] getParameterInfo()

Unless overridden, returns parameter descriptions for

• fontname
• fontsize
• usebuffer
• safety

Overrides:

getParameterInfo in class java.applet.Applet

refresh

public void refresh()

Invalidates the buffer contents and repaints the applet

update

public void update(java.awt.Graphics g)

Method overridden to save clearing the screen. Since we are pasting the contents of a buffer, the prior state of the display area is immaterial.

Overrides:

update in class java.awt.Container

paint

public void paint(java.awt.Graphics g)

Paints the applet onto the specified Graphics object. If buffering is enabled and the buffer has not been invalidated, then the contents of the buffer will be painted. Otherwise, forcePaint() will be called to regenerate the buffer.

Overrides:

paint in class java.awt.Container

Parameters:

g - The Graphics object on which to paint

forcePaint

public void forcePaint(java.awt.Graphics g)

Forces the buffer to be regenerated, then painted onto the specified Graphics object.

Parameters:

g - The Graphics object on which to paint

doPaint

protected abstract void doPaint(java.awt.Graphics g)

Called by forcePaint() to actually perform the painting. Subclasses should implement this method as if it were the standard paint() method; buffering will then take place transparently.

Parameters:

g - The Graphics object on which to paint