APCS: AP Computer Science A @sfhs

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[[https://archive.org/details/Balloons1.screenflow|Watch old video tutorial]]

CheckList:
  - Add a method in the ''Balloon'' class called ''rise()'' which is the reverse of ''drop()''
  - Make a copy of ''BalloonFall'' to use as a starter for a new class called ''BalloonRise''
  - Change the name in ''paintComponent()'' to "Balloon Rise"
  - Change ''keyReleased'' so the new ''Balloon'' is near ''HEIGHT'' rather than 0.
  - Change ''actionPerformed'' so the balloon rises rather than falls
  - Change ''actionPerformed'' so that it removes the balloon if ''balloons.get(i).getBottom() < 0'' 
  - Modify the ''paintComponent()'' method to show the number of balloons: ''g.drawString(balloons.size()+" Balloons", WIDTH-100, 20);''
Challenges: 
  - Can you make the letter that was pressed to make the balloon drawn at the center of the balloon? (Hint: in the ''keyReleased'' method ''e.getKeyChar()'' returns the ''char'' typed
  - Can you make an application that has more ''Balloon''s drop (or rise)  randomly and typing the keys "pops" (or removes) them?
  - Instead of ''Balloon'' objects, have letters drop and have them removed when you type the letter? You can keep score and make it into a game.

<file java Balloon.java>
import java.awt.Color;
import java.awt.Graphics;

public class Balloon {
	private Color color;
	private int x,y,width,height, deltaY;

	public Balloon(int x, int y, int size) {
		this.x=x;
		this.y=y;
		this.width=size;
		this.height=size+randomInt(5,size);
		this.deltaY=randomInt(1, 5);
		int red=randomInt(0, 255);
		int green=randomInt(0, 255);
		int blue=randomInt(0, 255);
		this.color = new Color(red, green,blue);
	}
	public void draw(Graphics g){
		g.setColor(color);
		g.fillOval(x, y, width, height);
	}
	public void drop(){
		this.y+=deltaY;
	}
	public int getBottom() {
		return y+height;
	}
	public static int randomInt(int min, int max){
		return min+(int)((max-min+1)*Math.random());
	}

}

</file>


<code java BalloonDrop.java>
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.ArrayList;
 
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.Timer;
 
public class BalloonFall extends JPanel implements KeyListener, ActionListener
{
	public static int WIDTH=800;
	public static int HEIGHT=600;
    private Font titleFont, regularFont;
    private ArrayList<Balloon> balloons;
    private Timer timer;
	/**
	 * The class constructor will initialize the ArrayList&lt;Balloon&gt;
	 * and other object fields (variables), including a Timer
	 * object from the javax.swing.* library.  The timer will
	 * generate an Action Event, so that something happens
	 * in regular intervals without the user typing anything.
	 */
    public BalloonFall()
    { 	
    	//initialize variables here...
    	titleFont = new Font("Roman", Font.BOLD, 18);
    	regularFont = new Font("Helvetica", Font.PLAIN, 12);
    	balloons = new ArrayList<Balloon>();
    	timer = new Timer(10, this);
        timer.start();
    }
	/**
	 * the main method makes an instance of our application and puts it in a JFrame 
	 * that will end the application when it is closed.
	 * 
	 */
	public static void main(String[] args) {
		BalloonFall app= new BalloonFall();
		JFrame window = new JFrame("Balloon Fall");
		window.setSize(WIDTH, HEIGHT);
		window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		window.getContentPane().add(app);
		window.addKeyListener(app);
		window.setVisible(true);
 
	}
 
	/**
	 *  This is the method to change what is drawn to the screen:
	 */
	public void paintComponent(Graphics g){
		//super.paintComponent(g);
		g.setColor(Color.WHITE);
		g.fillRect(0, 0, getWidth(),getHeight());
		g.setColor(Color.BLUE);
		g.setFont(titleFont);
		g.drawString("BalloonFall version 1.0", 20, 20);
		//g.drawString(balloons.size()+" Balloons", WIDTH-100, 20);
		g.setColor(Color.BLACK);
		g.setFont(regularFont);
		g.drawString("Press a Key to make a Balloon", 20, 40);
		for (Balloon x:balloons){
			x.draw(g);
		}
 
	}
 
/**
	 * These 3 methods need to be declared to implement the KeyListener Interface
	 * that listens for keys that are typed on the keyboard
	 */
	@Override
	public void keyTyped(KeyEvent e) {}
 
	@Override
	public void keyPressed(KeyEvent e) {}
 
	@Override
	public void keyReleased(KeyEvent e) {
 
		int size = Balloon.randomInt(50, 80);
		int x = Balloon.randomInt(0, WIDTH);
		int y = Balloon.randomInt(-size, 0);
		balloons.add(new Balloon(x,y,size));
		repaint();
	}
 
	@Override
	/**
	 * This method is needed to implement the ActionListener that listens for the timer
	 * e.getKeyChar () and e.getKeyCode () will return the char (or its code)
	 */
	public void actionPerformed ( ActionEvent e) {
	// timer made an action event, so
		int i = 0;
		while ( i < balloons.size() ) {
			balloons.get(i).drop();
// 			 
                        if ( balloons.get(i).getBottom() > HEIGHT ) {
				balloons.remove (i);
			}else{
				i++;
			}
		}
		repaint ();
	}
}

</code>