asteroids games and simulations o-o programming in java the walker school the walker school –...
TRANSCRIPT
Asteroids
Games and SimulationsO-O Programming in Java
The Walker School
The Walker School – Games and Simulations - 2010
Asteroids
The Walker School – Games and Simulations - 2010
Take some time to play with Asteroids. What can the program do and what can’t it do?
Discovering Keyboard Controls
The Walker School – Games and Simulations - 2010
Which keyboard key is used to fire a bullet?
Explosions
The Walker School – Games and Simulations - 2010
Place an explosion into a running scenario. Does it work? What does it do?
Painting Stars
The Walker School – Games and Simulations - 2010
Create a New Scenario
The Walker School – Games and Simulations - 2010
Directions1.Create a new scenario.2.Save it as “asteriods-lastname”.
Create the World
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Directions1.Create a new subClass called “Space”.2.Leave the background empty.
Enlarge the Background
The Walker School – Games and Simulations - 2010
Directions:1.Change the size of the world (600, 400, 1).2.Change the comment.
Painting Backgrounds
The Walker School – Games and Simulations - 2010
Part IV - http://www.youtube.com/watch?v=rvZ0ErpfHKM&feature=related
Import the Java Color Library
The Walker School – Games and Simulations - 2010
Use Java to Paint Black Background
The Walker School – Games and Simulations - 2010
Create a method createStars()
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Comment it out until we create the method.
Create a Method Body
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Takes a parameter of type integer, as we stated we wanted 300 stars.
Create The Stars
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Step through this loop and explain what is happening.
For Loops
The Walker School – Games and Simulations - 2010
for (initialization; loop-condition; increment){ loop-body;}
•The initialization part declares and initializes a loop variable. This variable is often called i, and often initialized to 0.•The loop condition checks whether our loop variable is still less than a given limit. If it is, the loop will continue.•The increment section simply increments the loop variable.
Vary Star Brightness
The Walker School – Games and Simulations - 2010
Rocket Firing
The Walker School – Games and Simulations - 2010
Turning
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Flying Forward
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Flying Forward
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Calls the move() method from SmoothMover class.
What happens?
What Do We Need To Do?• Add initial movement to the rocket. • To add movement, we need to add force to the
rocket.• And we need to change its vector.• So we’ll need to call this vector from the Vector
abstract class.• The vector needs 2 variables: direction (dy) and
length (dx).
The Walker School – Games and Simulations - 2010
So where are we going to do this?
Adding Drift
The Walker School – Games and Simulations - 2010
What happens when you change the variables in the vector?
What Do We Need To Do?
• Create variables to handle each rocket image. • Add a method called ignite to checkKeys(), so
that we when hit the “up” button, the rocket image is changed.
• Define a method called ignite. It will need a boolean parameter and a void return type.
The Walker School – Games and Simulations - 2010
Create a Method Stub to Ignite Rocket
The Walker School – Games and Simulations - 2010
Remember to create an instance variable called boosterOn.
Igniting the Rocket Boosters
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Colliding with Asteroids
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What Do We Need to Do?
• If we collide with an asteroid,• Remove the rocket from the world;• Place an explosion into the world;• Show final score (game over);
The Walker School – Games and Simulations - 2010
Methods for Collision Detectionfile:///C:/Greenfoot/doc/API/index.html
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Both methods accept a parameter of type Class, which means we can check for intersections with a specific class of objects if we want to.
Which of these 2 methods do we want to use and why?
Colliding with Asteroids
The Walker School – Games and Simulations - 2010
Remember to call the method in the rocket act() method.
Creating Better Explosions
• Part I - http://www.youtube.com/watch?v=rgZ-_vQ2aIc• Part II - http://www.youtube.com/watch?v=bdv4ZgTcYyY&feature=related• Part III - http://www.youtube.com/watch?v=OFuDEt0xifM&feature=related• Part IV - http://www.youtube.com/watch?v=XMJi4_bzuLw&feature=related• Part V - http://www.youtube.com/watch?v=TKYwL8p_11A&feature=related
The Walker School – Games and Simulations - 2010
What Do We Need To Do?
• Add abstract classes SmoothMover and Vector from Greenfoot.
• Create a constructor for Debris• Update the move() method
Casting
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Create the Score Board
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Import Java Libraries
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Create the Assignment Variables
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Create the Constructors
Why are their 2 constructors?
How is this an example of overloading?
The Walker School – Games and Simulations - 2010
Make Scoreboard Image
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So, what else needs to be done?
Activity – Change Attributes
• Modify the ScoreBoard class:– Change the text shown on it.– Change the color of the text.– Change the background and frame colors.– Change the font size so that your text fits well.– Change the width of the scoreboard to suit your
text.
The Walker School – Games and Simulations - 2010
Homework – Scoreboard
• Search the Greenfoot library for other games that have scoreboards. Study how they were built. What attributes do they have that this board does not? What could you add to your scoreboard?
The Walker School – Games and Simulations - 2010
Add a Variable for the Counter
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Assign the Counter to the Constructor
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Call the Counter When Game Over
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How can you make sure that the counter is in the middle of the board without hard coding the numbers?
Ensure the Scoreboard is in the Middle of the Background
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Where do we call the gameOver() method?
Call the Game Over Method
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Example of Casting
Casting
• Casting is the technique of telling the compiler a more precise type for our object then it can work out for itself. We do this by writing the class name (Space) in parentheses before the method call. Once we have done this we can call methods defined in Space
• space.gameOver();Casting does not change the type of the object returned.
The Walker School – Games and Simulations - 2010
Add a Proton Wave
What does it do?
What doesn’t it do?
The Walker School – Games and Simulations - 2010
Import the Library
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We are going to need the Java List class because we are going to create a list of images to create a proton wave that increases in size.
Assign Variables
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How do we make the wave grow?
Add A List (Array) to Store Image Set
The Walker School – Games and Simulations - 2010
How many images will this list store?
Create a Constructer for the Wave
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Create a Method to Initialize Images
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Create a Instance Field to Set Image Count
Create a Method to Initialize Images
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Rewrite the While loop using a For loop. What needs to change?
Create a Method Stub to Grow Wave
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Call Method to Grow the Wave
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Add Statements to Grow Wave
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Square [] brackets, not curly {} brackets here
Add Sound to the Proton Wave
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Create a Method Stub to Ignite Proton Wave
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Where do we create this method?
Call Method When “Z” is Pressed
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What is the problem with the proton wave?
1. It can be released too easily!
2. It doesn’t do anything to the asteroids!
Create Reload and Delay for Wave
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Add an Instance Variable for the Delay
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Where do we create these variables?
Assign the Delay to the Constructor
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Add Delay Count to act() Method
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Program the Delay into the Wave
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Interacting with Objects in a Range
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Program a Method Stub to Check for Collision
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Purpose is to check to see if the wave touches and asteroid.
So, in what Class do we create this method?
Call it in the Wave act() Method
The Walker School – Games and Simulations - 2010
Write Statements to Check for Collision
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Why didn’t we use the “getIntersectingObjects() method?
Range is the radius of the circle (wave).
hit() Method
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What are the parameters for this method and what does it return?
Evaluating the Damage Constant
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What happens when you change the damage constant of the proton wave?
For Further Development
• Fix the score counter.• Add new asteroids when all have been cleared.• Add a level counter. Every time all asteroids are
destroyed you go up a level.• Add an end of level sound.• Add an indicator showing the load state of the
proton wave.• Add a shield.
The Walker School – Games and Simulations - 2010