Introduction to Bumpers

Transcription

1 Software Engineering II: Project Organization & Management SS 2009 Introduction to Bumpers Prof. Bernd Bruegge, Ph.D. Applied Software Engineering Technische Universitaet Muenchen 1

2 Development of an Interactive Game Several cars are driving in a rectangular game board. Some cars are fast, others are slower The number of cars is arbitrary, but fixed at delivery time The player controls a certain car ( DrivenCar ) with the mouse The initial direction of each car is chosen by random The cars can collide with each other and with the border of the game board Each collision between cars leads to a winner and a looser The looser stops at the point of collision ( crashes ) If a car encounters the game border, it is bounced back depending on its speed and direction ( physical laws are followed ) 2

3 Development of an Interactive Game (2) The Goal: The player wins, if all opposing cars ( RobotCars ) are eliminated by colliding with them in the right way 3

4 Analysis and Design Questions How do we represent the game field? How do we model the cars? How do we animate all the cars simultaneously? What do we do, when a car hits the edge? How do we compute the new route? How do we compute a collision? Do we compute a new route for the winner? How do we control the driven car with the mouse? 4

5 Analysis: Use Cases Generating the game board Starting the Music Generating one or more cars Moving a car Starting the game Quitting the game Car hits another car Car hits border of game board Determining a collision 5

6 Analysis: Identification of Classes Generating the Gameboard Starting the Music Generating one or more cars Moving a car Starting the game Quitting the game Car hits another car Car hits border of game board Determining a collision Car Gameboard Referee Music 6

7 Object Model for GameBoard, Referee and Car 7

8 Analysis: Classification of Cars ( Taxonomy in the Application Domain ) Car UserCar FastCar SlowCar 8

9 A Game with one Opposing Car In Gameboard.java (bumpers:cars:gameboard.java) you determine the number of opponent cars (robot cars) 9

10 Object Design of Collisions How do we check for collisions? Where do we place the collision code? We have two possibilities: With the game field or with the cars If we want to make the game extensible, the type of collision is probably a function of the car type (most certainly of its size) If we let the cars determine the collisions, then every type car depends on every other type of car Example: When we introduce a new type of car, say a slow car, we have to modify every existing type of car, to implement collisions with slow cars. The maintainability of the game is much higher, if the game field handles the collisions. 10

11 Detailed Design of Collision Each car is represented by its bounding box This is the smallest rectangle, that contains all pixels of the picture of the car We get bounding box of a picture by calling getsize() followed by calling getposition(). (0,0) A collision occurs, if two given bounding boxes have at least one pixel in common (intersects()). Small problem: The picture of a car rarely resembles a rectangle, the bounding box often contains pixels that don t belong to the picture of the car. (x,y) h w To compensate for the empty space, we reduce the bounding box to 3/4 of its original size (with growth()), and place its center slightly to the lower left (with translate()). Remaining Problem: Who is the winner of the collision? 11

12 Detecting Collisions public void movecars() { // First each car makes a move // Then we check for collisions for (int i = 0; i < cars.length; i++{ if (cars[i].iscrunched( )) {continue;} Car crashedcar = collisionstrategy.detectcollision( drivencar, cars[i]); if(crashedcar!= null){ BANG.play(); crashedcar.setcrunched(); if(drivencar.iscrunched()){ stopgame(); }else{ // check if player won }}} Referee +startgame() + stopgame() + movecars() public Car detectcollision(car car1, Car car2){ Point p1 = car1.getposition( ); Dimension d1 = car1.getsize( ); Rectangle r1 = new Rectangle(p1, d1); r1.translate(p1.x / 8, p1.y / 8); r1.grow(-1 * d1.width / 4, -1 * d1.height / 4); Point p2 = car2.getposition( ); Dimension d2 = car2.getsize( ); Rectangle r2 = new Rectangle(p2, d2); r2.translate(p2.x / 8, p2.y / 8); r2.grow(-1 * d2.width / 4, -1 * d2.height / 4); if (r1.intersects(r2)) { if (p1.y > p2.y){return car2; }else{ return car1;} } return null; } Car +boolean * iscrunched() + Point getposition() + Dimension getsize() + setcrunched() 12

13 Relationship between Referee und Collisions Referee + movecars() + setcollisionstrategy(collisionstrategy) CollisionStrategy + detectcollision(car, Car) + getname() DefaultCollision LowerCarWinColision Is this a Bridge or a Strategy Pattern? 13

14 Strategy Pattern in Bumpers Client Strategy Game Toolbar + ItemStateChanged(ItemEvent) Referee + movecars() + setcollisionstrategy(collisionstrategy) CollisionStrategy + detectcollision(car, Car) + getname() DefaultCollision LowerCarWinColision Policy: e.g. User interface events 14

15 InstrumentFactory + createspeedometer(usercar) + createrotationspersecond(usercar) + createspeedcontroller(usercar) + creategps(usercar) + createbodyview(usercar) Abstract Factory Pattern in Bumpers EUFactory USFactory Instrument # thecar: UserCar + updateinstrument() Speedometer SpeedController GPS Body RotationsPerSecond US... EU... US... EU... US... EU... US... EU... US... EU... 15

16 Adapter Pattern in Bumpers InstrumentPanel Instruments # thecar + updateinstrument() AnalogSpeedometer - angle + getmaxangle() + setangle(int) AnalogSpeedometerAdapter - speedometer + updateinstrument() 16