DesignPatterns

DesignPatterns - Design Pa*erns + Anima/on Undo/Redo...

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Unformatted text preview: Design Pa*erns + Anima/on Undo/Redo Graphics and Hints Design Pa*erns •  Design: –  the planning –  that lays the basis for the making –  of every object –  or system •  Pa*ern: –  a type of theme –  of recurring –  events or objects Design Pa*erns in OOP •  Recipes for solving standardized problems •  Abstrac/ons of concrete problems –  How to make a class that allows only one instance of itself: •  The Singleton Design Pa*ern •  Provides a general solu/on that needs to be implemented Started from Architecture •  Architectural Pa*erns –  Lecture rooms –  Studies –  Town Squares –  Restaurants –  Etc. •  Adopted in many non ­related areas Design pa*erns •  •  •  •  •  describe… how objects communicate… without becoming entangled… in each other’s data models… and/or methods. What is a design pa*ern? •  A general recipe •  A framework •  A template •  Pre ­made solu/on Design Pa*ern Content •  •  •  •  Intent – what is the goal of the pa*ern? Applicability – when should it be used? Structure – the pa*ern descrip/on Consequences – pros and cons of using the pa*ern. Example •  The ”Singleton pa*ern” •  Ensures that one and only one instance can be created from a class private sta/c Singleton m_instance; private Singleton() { … } // private constructor public sta/c synchronized Singleton getInstance() { if (m_instance == null) // only create new first /me m_instance = new Singleton(); } return m_instance; // return the single instance Design Pa*erns vs. Libraries •  Libraries contain concrete classes –  Implement concrete solu/ons •  Design Pa*erns are abstract solu/ons –  Advice on general solu/ons •  You can’t import a design pa*ern DP Factory •  Another interes/ng Design Pa*ern •  What is a factory? –  Produc/on unit •  produces instances •  mul/ple instances of different classes –  Ask for a type and you get it! Factory Example •  A graphic Shape –  circles, rectangles, stars, etc. –  All shapes have size, and can be drawn! •  The Shape interface defines methods •  Use a ShapeFactory: public Shape getShape(String type, int size) {…} ShapeFactory, Why? •  One class provides all shapes! •  Dynamic crea/on! •  Consistent usage of Shapes –  Unless explicitly needed, we don’t have to know which Shape we have created aderwards UNDO •  The Undo/Redo mechanism should provide: –  Single Undo –  Single Redo (of Undone ac/vity) •  and, if possible: –  Undo and redo of several consecu/ve ac/on •  How can this be acheived? Command Design Pa*ern •  One way to handle queues of ac/ons! •  Important DP for the opera/on of UNDO •  Simple principle Command •  A very simple interface! –  One method execute() public interface Command { public void execute(); } Command •  All ac/vi/es are driven by the execute() method –  Encapsulate all user ac/vi/es in ”Command objects” Simple example: Macro public class IAm implements Command { public void execute() { System.out.println("I'm the command pa*ern!"); } } // An object that holds commands: public class Macro { private List commands = new ArrayList(); public void add(Command c) { commands.add(c); } public void run() { Iterator it = commands.iterator(); while(it.hasNext()) ((Command) it.next()).execute(); // Cas/ng! } } UNDO? •  The execute() method describes what happens during an edit ac/vity… •  UNDO means reversing the edi/ng ac/vity… •  In the command interface add: –  unexecute() –  reexecute() –  Describes the backward process public interface Command { public void execute(); public void unexecute(); // undo public void reexecute(); // redo } UndoManager •  UndoManager is support for UNDO in Swing •  ”edit types”  ­ the effect of a user invoked command –  each edit type must s/ll have a defini/on of the edit and its effects •  Simplifyes the management of the Undo/Redo Swing Undo •  •  •  •  •  •  UndoableEdit (Interface) AbstractUndoableEdit (Abstract class) CompoundEdit (class for sequences of undoables) UndoableEditListener (Interface) UndoableEditEvent (no/fica/on object) UndoableManager (Queue manager) –  Like EventManager •  UndoableEditSupport (Support class) Undo/Redo ­queue UndoManager op1 op2 op3 op4 Undo/Redo ­queue UndoManager op1 op2 op3 op4 op1 op2 op3 op4 Undo/Redo ­queue UndoManager op1 op2 op3 op4 op1 op2 op3 op4 op1 op2 op5 Undo •  Good example program in linked page on course homepage (Assignment 2) Add an undo/redo func/on to your Java apps with Swing Anima/on Driver Class •  Many Good Sugges/ons (these will be commented groupwise in separate email) •  Good example of a Design Pa*ern •  How to ensure OOP principles? Purspose of Anima/on Driver •  One or more Anima/ons –  Simula/on –  Real/me game (e.g. Ba*lebots) –  Other dynamic real/me anima/on with several animated objects •  One Actor controls the Anima/on process –  Singleton (suggested by one group) –  Controls Anima/on Progress Decisions? •  The amount of control in driver? •  Different anima/on speeds? •  Which objects to animate? •  How is the driver controlled? OOP Principle •  The driver needs to be free of knowledge about the respec/ve anima/ons •  Each animated object responsible for its own anima/on, e.g.: –  Driver controls general anima/on speed –  Animated object controls its own rela/ve anima/on speed Animator Pa*ern •  Interface AnimatedObject –  One primary method: /ck() –  Each /ck is one cycle in general Anima/on •  Animator –  Tracks (manages) the animated objects –  Sends /cks to all its Animated Objects –  Methods: •  addObject(AnimatedObject ao) •  removeObject(AnimatedObject ao) •  /ck() // sends /cks to all animated objects Animator Pa*ern •  Animated Object could be any class –  As long as it implements the AnimatedObject interface •  Does not have to be a graphic component! –  In fact it is easier to draw if it is not… •  A panel can host many animated graphics –  defines only paintComponent(Graphics g)! –  the graphic adds its own drawing to the Graphics environment! Animated Graphics •  Uses the paintComponent of (e.g.) Jpanel •  Implements Drawable interface: –  method: draw(Graphics g) –  the method should specify the graphic commands for the graphic •  Does not specify the paintComponent –  is not a Component, but a ”loose” graphic Jpanel paintComponent •  Each Drawable object implements the draw() method. @Override public void paintComponent(Graphics g) { Drawable d; for (Iterator<?> it = graphicObjects.iterator(); it.hasNext(); ) d = (Drawable) it.next(); // Cas/ng to Drawable d.draw(g); } Complex graphics •  Every graphic uses draw(Graphics g) to add itself to the graphics environment •  A single call to paintComponent() Animated Complex Graphics •  If we want to implement graphics that move, the class has to implement both interfaces. public class MovingStar implements Drawable, AnimatedObject { … } //here the drawing is //made in //draw(Graphics g) Anima/on Process •  Create graphic Container (JPanel?) •  Collect all graphic objects (not Swing Components) •  For every /ck: –  update the graphic objects (posi/on, size, colour, etc.) –  In paintComponent(Graphics g) draw all graphic objects on the Graphics environment g (Detour) Mixing graphics and Swing components? Don’ts in GUIs •  We will be able to do almost anything i GUI design •  But some things maybe we shouldn’t •  (but no rule without excep/on, of course) Move things for the user •  You can control the mouse pointer for the user –  java.awt.Robot library •  java.awt.Robot •  mouseMove(int x, int y); •  Should you? –  Most of the /me – NO! –  Bad GUI! •  One possible excep/on: Guding help systems The Robot is s/ll Useful! Can make screenCaptures! createScreenCapture(Rectangle screenRect) returns a BufferedImage Remove Title Bar of Window •  You can remove the Titlebar of a window •  Should you? –  Maybe, e.g. in AboutBoxes •  But remember to provide the user with control of the window! Use Anima/ons •  You can use anima/ons •  Should you? –  Yes, some/mes –  But restric/vely •  Beware of percep/on exhaus/on Use Undo •  You will be able to Undo things •  Should you? –  Yes, but only significant changes –  Don’t undo single character inser/on •  What is significant? Use graphic effects •  Swing allows you to use graphic effects –  E.g. GradientPaint, Transparency •  Should you? • Yes, but always provide an alterna/ve skin that is clear and dis/nct •  Make sure to test that the effects work on the platorm –  Make it easy to access Be Crea/ve •  It is (in principle) your imagina/on (and available /me) that sets the limits for what you can do. •  Should you? –  Yes, as long as it is good User Interface Design –  Yes, as long as it is possible to understand –  Yes, as long as it makes sense for the intended user groups Prac/ce Anima/on •  You have a large toolbox with graphics! Prac/ce using it! •  Should you? •  Yes, even if it not all will be used in the Calendar, the more you prac/ce, the more you will know about how and when you should use it! ...
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