1) Add a mouseHandler class that extends mouseAdapter and implements mousePressed and mouseReleased methods. Get startPoint from mousePressed and endPoint from mouseReleased.
2) add mouseHandler as a MouseListener to your PaintCanvas (paintCanvasInstance.addMouseListener()), Java will automatically call those methods and pass in the MouseEvent for you when you click and release
3) Call a run method on mouseHandler mouseReleased method that calls createShapeCommand class.
4-1) CreateShapeCommand/MoveShapeCommand/SelectShapeCommand classes uses command pattern uml design, implements ICommand interface which has a single run(Point start, Point end, ApplicationState appState) method
Like->public interface ICommand {void run(Point start, Point end, ApplicationState appState);} , it will pass along start and end pointing of the mouse and store application state in run method. Create/Select/Move are the corresponding mouseModes.
When draw is selected, createShapeCommand will have methods to create the selected shape.
When move is selected- shape is moved.
When select is selected, shape is selected(highlighted).
5) Implement strategy pattern for Triangle, Rectangle and Ellipse classes with IShapeStrategy interface. Rectangle will have all the shape properties derived from the user's currently selected shape, color choice, shadingType preference.
5-1)Add addShape(IShape shape) method from createShapeCommand and add this shape to ShapeList(this is a different class , that adds shapes passed in by addShape method).ShapeList uses collection list. Every time user selects a shape , this gets persisted in the ShapeList.
6) When addShape is called, it should notify PaintCanvas class - For this please implement Observer pattern here. PaintCanvas will be the observer and shapes getting added to the shapelist is the subject. Once addShape method adds selected shape to the shapeliest, update method will notify PaintCanvas.
6-1) Create a listener class that has a method that makes paintCanvas to call drawRect() method on Graphics2D to draw rectangle and other Graphics2D methods to draw triangle (drawTriangle()and ellipse(drawPolygon())
[[[Overall->
Pick a shape from GUI ellipse, triangle, rectangle
Pick a primary and secondary color
Select shading type
click and drag mouse to Draw shape on the screen, be able to select the shape and move the shape]]]
Command pattern:
Implement ICommand interface and below 3 classes:
CreateShapeCommand-will be used to create a user selected shape
MoveShapeCommand-will be used to move the shape on the screen/canvas
SelectShapeCommand-will be used to select the shape on the screen
Observer pattern
Implement ISubject and Observer interface
When shape is added via addShape(Ishape shape) method to the collectionList (ShapeList), paintcanvas(is the observer) is notified.. Subject is shape getting added to shapeList, update PaintCanvas which will call listener to implement different draw methods
Static Factory
ShapeFactory
Rectangle /Triangle/Ellipse static class with shape properties.
Singleton method
The application state should persist from beginning to end so use singleton method for application state.
Attachment:- src.zip