Java 2D Application with Design Patterns and XML

1
Chapter 5

• Java 2D Application with Design Patterns and XML

2
Application high level view
main class (DeitelDrawing) extends JFrame
Title
menuBar
desktopPane
contentPane (border)
frame (DrawingInternalFrame)
3
Containment Hierarchy DrawingInternalFrame
(JInternalFrame)
Title
toolBar (NORTH) DrawingToolBar
contentPane (BorderLayout)
JScrollPane (CENTER)
ViewPanel (JPanel)
drawingView (extends JPanel)
JFrame is top-level, has contentPane and
menuBar. JInternalFrame is not top-level, so
toolbar etc. just goes into layout
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Sequence Diagram (instantiate DIF)
DrawingInternalFrame
DrawingModel
new
//InternalFrame observes model
add Observer
DrawingView
new (model)
getInstance
// 1 factory for Shape Controllers
ShapeControllerFactory
Drag and Drop Controller
new
getDefaultDragSource
dragSource
DragSource
create DefaultDragGestureRecognizer (drawingView)
setDropTarget
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Sequence Diagram (instantiate DIF)
DrawingInternalFrame
JPanel
new
viewPanel
add drawingView
JFileChooser/DrawingFileFiler
new
InternalFrameAdapter
// handle activate/deactivate events
addInternalFrameListener
DrawingToolBar
new
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Drawing Application Classes
DrawingView (JPanel) ltltobservergtgt
1
x, y, width, color height, etc. getXML
base abstract draw, contains
DrawingModel ltltobservablegtgt
MyShape abstract

ZoomDrawing View
MyLine
MyRectangle
MyOval
MyImage
MyText
font size, name, bold, etc.
MyShapeController Factory
1
filename, getImage
MyShapeController abstract
DrawingFile ReaderWriter
abstract startShape endShape modifyShape
1 (open/ save)
DragAndDropController ltltDragGestureListener,
DragSourceListener, DropTargetListenergtgt
BoundedShape Controller
MyLine Controller
MyText Controller
common parameter
TransferableShape ltltTransferablegtgt
AbstractDrawing Action abstract
(openAction etc.)
1
GradientIcon ltltIcongtgt
DeitelDrawing (JFrame/main)
DrawingInternalFrame ltltobservergtgt
(open/ new)
SplashScreen
1 on DrawingToolBar
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Factory Method Design Pattern

• Creates objects
• Based on criteria known at runtime
• user input
• system properties
• calculation
• etc.
• new MyShapeController method
• takes DrawingModel, class name as string
• returns controller initialized with drawing model
  and class object of correct shape

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Java Reflection

• Class class
• static method forName returns the Class object
  given a class name as a string
• can use Class object to getName, getConstructor,
  getDeclaredMethod, getPackage, getResource,
  determine if its array, primitive, etc.
• reflection enables Java to determine information
  about objects and classes at runtime.

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MyShapeController

• Sets the DrawingModel (must add shape to a model
  when drawn)
• creates mouselisteners uses Adapter class
• sets drawing attributes
• protected createNewShape method. Uses newInstance
  method to create new object. (remember forName
  created object from string)

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Singleton Design Pattern

• Ensures only one instance of object exists
• Protected, no argument constructor cant
  instantiate object directly
• provide final method getInstance()
• can read system property FACTORY_PROPERTY_KEY to
  determine whether to create subclass. Allows new
  factory to be installed at command line.

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Model-View-Controller

• The MVC architecture divides an application into
  three parts
• data components maintain the raw application data
  (model)
• presentation components provide the visual
  representation(s) of the data (view)
• input-processing components handle input from the
  user (controller)

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MVC - continued

• There can be more than one view of the data.  For
  example, a document could be viewed in outline
  format, in print preview format, and in editing
  format. 
• Multiple controllers are also possible, such as
  input from the keyboard and the mouse.   When the
  Model is changed by any Controller, it
  automatically notifies all Views.
• A variant of MVC is the delegate-model
  architecture.   Java Swing components combine the
  view and controller into a single object called a
  delegate.  In such a system, the Delegate
  modifies the Model, which in turn notifies the
  Delegate. 

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MVC - Observer design pattern

• Enables loose coupling.
• Objects interact by invoking methods declared in
  well-known interfaces, rather than invoking
  methods specific to a particular class.
• java.util.Observable represents a Model in MVC,
  or the subject in the Observer design pattern.
• The Observable class provides the method
  addObserver which takes one parameter which
  should be an implementation of the interface
  Observer from java.util.Observer.
• The Observer corresponds to the View in MVC. 
• When an Observable object is modified, it
  notifies each registered Observer. 
• An Observable object must invoke method
  setChanged and then notifyObservers. 
• The notifyObservers method invokes the update
  method of each registered Observer.

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Drag-and-Drop Controller

• Flag for whether in drag mode
• dragGestureRecognized (when user presses mouse
  and starts to drag)
• Must be in drag mode
• Get list of shapes
• Start at end (last placed) by specifying index
  for iterator
• Use contains method of MyShape to determine if
  this shape selected
• create TransferableShape
• startDrag (cursor, attach shape)
•  drop
• get Transferable from event
• find out "flavors" of transferable
• determine event (drop) location
• if JavaFileList, accept only jpeg (calls
  dropImages)
• if TransferableShape, dropShape (add shape at new
  location)
• else reject
• dragDropEnd
• if successful move
• get Transferable
• get TransferData - should be a TransferableShape

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Drag-and-Drop continued

• TransferableShape implements Transferable
• Multipurpose Internet Mail Extension (MIME) types
  text string designed to describe data in email
  attachments, now used in more general purpose way
• Creates new DataFlavor for shapes
  application/x-deitel-shape, Shape
• getTransferData returns object containing
  transfer data
• isDataFlavorSupported checks whether the object
  being dragged is supported by this app.

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JInternalFrame details

• Not a top-level container
• Add components to content pane, just like JFrame
• Must setVisible
• Doesnt generate window events. Fires internal
  frame events. App uses for ZoomDialog, to ensure
  only visible when frame is active.
• Can programmatically iconify or maximize.
• Should set location. Uses offset
  openFrameCount (a static variable of
  DrawingInternalFrame).

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XML details

• DocumentBuilderFactory provides DocumentBuilder
• Document tree representation of xml document
  (DOM)
• parse one command, translates xml document into
  DOM tree structure
• Can use dtd to validate (optional)
• Transformer writes DOM to file

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Actions in application

• setSaved- adds or removes from title,
  enables/disables saveAction
• update setSaved false
• setFileName in title
• setTitle frame zoom
• close dialog if not saved, dispose, return true
  unless cancel
• open/SaveDrawing/SaveDrawingAs
• showZoomDialog create/make visible

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Miscellaneous Details

• The SplashScreen is a JWindow borderless
  window. Also shows use of Timer class.
• The ZoomDialog is a non-modal dialog. It is an
  observer of the model DrawingView. Sets an Affine
  transform that applies to all shapes
  (graphics2D.setTransform), based on x and y scale
  factors.

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Chapter 5 Exercise

• Add a new shape option.  I chose to add a
  triangle, but you could choose a different
  shape.  I used a GeneralPath to create the shape
  and the BoundedShapeController as the
  controller.  You'll need to be sure the shape is
  Transferable. 
• Add an option for Transferable shapes to be
  copied (ACTION_COPY), not just moved.
• Be sure you can save your new shape.

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Exercise Hints

• MyShapeControllerFactory
• update supportedShapes
• MyTriangle (or whatever shape you create)
• getXML
• calls super for base attributes
• sets type
• include extra parameters (e.g., x3, y3)
• draw
• creates GeneralPath for shape
• call draw or fill function of Graphics2D
• contains
• create GeneralPath
• call contains method of GeneralPath
• DrawingFileReaderWriter
• may want to change location of shapes.dtd
• String dtd System.getProperty("user.dir")
  "\\shapes.dtd"
• update shapes.dtd if add fields to xml file
• update getShapeFromElement to create new type of
  shape, handle additional fields (if any)