asteroids games and simulations o-o programming in java the walker school the walker school –...

Asteroids

Games and SimulationsO-O Programming in Java

The Walker School

The Walker School – Games and Simulations - 2010

Asteroids


Take some time to play with Asteroids. What can the program do and what can’t it do?

Discovering Keyboard Controls


Which keyboard key is used to fire a bullet?

Explosions


Place an explosion into a running scenario. Does it work? What does it do?

Painting Stars


Create a New Scenario


Directions1.Create a new scenario.2.Save it as “asteriods-lastname”.

Create the World


Directions1.Create a new subClass called “Space”.2.Leave the background empty.

Enlarge the Background


Directions:1.Change the size of the world (600, 400, 1).2.Change the comment.

Painting Backgrounds


Part IV - http://www.youtube.com/watch?v=rvZ0ErpfHKM&feature=related

http://www.youtube.com/watch?v=rvZ0ErpfHKM&feature=related

Import the Java Color Library


Use Java to Paint Black Background


Create a method createStars()


Comment it out until we create the method.

Create a Method Body


Takes a parameter of type integer, as we stated we wanted 300 stars.

Create The Stars


Step through this loop and explain what is happening.

For Loops


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


Rocket Firing


Turning


Flying Forward


Flying Forward


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).


So where are we going to do this?

Adding Drift


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.


Create a Method Stub to Ignite Rocket


Remember to create an instance variable called boosterOn.

Igniting the Rocket Boosters


Colliding with Asteroids


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);


Methods for Collision Detectionfile:///C:/Greenfoot/doc/API/index.html


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


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


http://www.youtube.com/watch?v=rgZ-_vQ2aIc

http://www.youtube.com/watch?v=bdv4ZgTcYyY&feature=related

http://www.youtube.com/watch?v=OFuDEt0xifM&feature=related

http://www.youtube.com/watch?v=XMJi4_bzuLw&feature=related

http://www.youtube.com/watch?v=TKYwL8p_11A&feature=related

What Do We Need To Do?

• Add abstract classes SmoothMover and Vector from Greenfoot.

• Create a constructor for Debris• Update the move() method

Casting


Create the Score Board


Import Java Libraries


Create the Assignment Variables


Create the Constructors

Why are their 2 constructors?

How is this an example of overloading?


Make Scoreboard Image


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.


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?


Add a Variable for the Counter


Assign the Counter to the Constructor


Call the Counter When Game Over


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


Where do we call the gameOver() method?

Call the Game Over Method


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.


Add a Proton Wave

What does it do?

What doesn’t it do?


Import the Library


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


How do we make the wave grow?

Add A List (Array) to Store Image Set


How many images will this list store?

Create a Constructer for the Wave


Create a Method to Initialize Images


Create a Instance Field to Set Image Count

Create a Method to Initialize Images


Rewrite the While loop using a For loop. What needs to change?

Create a Method Stub to Grow Wave


Call Method to Grow the Wave


Add Statements to Grow Wave


Square [] brackets, not curly {} brackets here

Add Sound to the Proton Wave


Create a Method Stub to Ignite Proton Wave


Where do we create this method?

Call Method When “Z” is Pressed


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


Add an Instance Variable for the Delay


Where do we create these variables?

Assign the Delay to the Constructor


Add Delay Count to act() Method


Program the Delay into the Wave


Interacting with Objects in a Range


Program a Method Stub to Check for Collision


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


Write Statements to Check for Collision


Why didn’t we use the “getIntersectingObjects() method?

Range is the radius of the circle (wave).

hit() Method


What are the parameters for this method and what does it return?

Evaluating the Damage Constant


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.


asteroids games and simulations o-o programming in java the walker school the walker school –...

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