Animation with HSA2

Basic HSA2 (and Swing) drawing commands:

We've already learned the following drawing commands:	There are also the following Swing commands that have been simplified for HSA2:
gc.drawString() gc.drawLine() gc.drawOval() gc.drawRect() gc.fillOval() gc.fillRect() gc.drawPolygon() ←optional gc.fillPolygon() ←optional gc.setColor() gc.setFont()	gc.setBackgroundColor() gc.clear() [follows setBackgroundColor] gc.getDrawWidth() gc.getDrawHeight() gc.setStroke() gc.setAntiAlias() gc.showDialog() gc.showInputDialog() gc.sleep()

Other:

Making a colour
Color c = new Color(r,g,b); //where r,g,b are numbers representing red, green, blue values and which range from 0 to 255.

Making a new Font:
Font f = new Font("Arial", Font.PLAIN, 24); //the second parameter can be PLAIN, BOLD, or ITALIC
IMPORTANT: Don’t create fonts inside a loop. They take up a lot of CPU time.

Organizing a Graphics Program (HSA2, not Swing)

Comparison

Typical Graphics program

Typical Text-based program


public class BestGraphics {

	public static void main (String[] args) {   
		new BestGraphics();
	}

	//global variables
	GraphicsConsole gc = new GraphicsConsole();
	int health = 50;

	BestGraphics() {
		//do stuff ... most of the program goes here
		drawGraphics();
	}

	//other methods go here, most will be void
	void drawGraphics(){
		//draw healthbar
		gc.drawRect(10,10, 100, 20);
		gc.fillRect(10,10, health, 20);
	}
}


public class BestProgram {

	//global variables: all must be static
	static int secretNum = 78;

	public static void main(String[] args) {
		//do stuff ...
		int x = calculateSomething(56);
	}

	//other methods can go here, but they must all be static
	static int printAnswer(int num) {
		int result = secretNum * num;
		return result;
	}
}

Nothing needs to be static.

Constructors

The line “new BestGraphics()” makes a new BestGraphics object from the BestGraphics class that we are writing.
This is all that we are putting in main(){};
When you make an object, it looks for a CONSTRUCTOR which has information on how to make the object.
The constructor is just the name of the class with (). No void in front of it.
So BestGraphics(){ } is a constructor, but void BestGraphics() { } is not.
You can also pass information to a constructor.
For example: gc = new GraphicsConsole(); gc = new GraphicsConsole(1000,900); gc = new GraphicsConsole(100,900,"Title of Window");

Everything needs to be static. We'll learn about static in Grade 12 when we learn about objects.

Organizing a Graphics Program: Game Loop

public class ProgramName {

	public static void main(String[] args){
		new ProgramName();
	}

	//global variables
	GraphicsConsole gc = new GraphicsConsole();
	Ball b;
	Enemy e;


	//***** constructor ******
	ProgramName(){

		setup();
		
		while(true) {    --> start loop

			//move whatever needs moving
			moveBall();
			moveEnemies();
			movePlayer();
			moveSolarSystem();

			//check for whatever collisions might occur
			hitWall();		//player hits wall
			shootEnemy();		//bullet hits enemy
			deathByBlackHole();	//solar system hits black hole

			drawGraphics();	// ALL graphic drawing goes here and is put inside a "synchronized(gc){ }" code block.

			gc.sleep(n);	//sleep for some number of milliseconds to let the graphics get drawn properly
	
		}  <--- end loop (go back to start)

		//any program cleanup goes here, which is AFTER the loop exits
		//write out high score to a file ...
		gc.showDialog("Thanks for playing","Game Over");
		gc.close();
	}

	//all other methods go here:
	void setup() {
		...
	}
	void moveBall() {
		...
	}
	void shootEnemy() {
		...
	}

Summary of Game Loop

First understand that the while() will keep looping. Everything inside the purple lines will happen over and over again.
Pressing 'Q' or 'q' will quit the loop.
The program will then proceed to the lines after the loop:
gc.showDialog("Thanks for playing","Game Over"); gc.close();

Before we run the loop, we need to set up the screen. I’ve made a subprogram called setup() to do this.
Subprograms are called methods (functions or subroutines). For simple graphics, they normally have void in front of them.
Other methods each do one specific task: moveBall, checkCollisions, drawGraphics.