/*--------------------------------------------------
* AnimationCanvas.java
*
* Show a ball that bounces around on a canvas
* Each time we hit a wall we change the ball color
* We also clear the screen after 'n' number of
* hits against the wall
* The "left" and "right" keys change the ball size
* The "Fire" key resets the display, however,
* it leaves the ball size the same.
*
* Example from the book:     Core J2ME Technology
* Copyright John W. Muchow   http://www.CoreJ2ME.com
* You are free to use/modify this source code.
*-------------------------------------------------*/
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
import java.util.*;

class AnimationCanvas extends Canvas implements CommandListener
{
  private Animation midlet;         // Main midlet
  private Command cmExit;          // Exit midlet
  private int    keyFire,           // Reset ball
                 keyRight,          // Increase ball radius
                 keyLeft;           // Decrease ball radius
  private boolean clearBackground = false; // Clear background
  private Random random;            // Random number
  int x_loc,                        // Current x & y locations
      y_loc,
      radius,                       // Ball radius
      red,                          // rgb colors
      green,
      blue,
      x_dir,                // Next x & y positions of ball
      y_dir,
      start_x,              // Where ball starts
      start_y,
      directionChanged = 0; // How many times we've hit a wall
  private static final int MAX_CHANGES = 50;

  /*--------------------------------------------------
  * Constructor
  *-------------------------------------------------*/
  public AnimationCanvas(Animation midlet)
  {
    // Save reference to main midlet
    this.midlet = midlet;

    random = new java.util.Random();

    // Determine starting location and direction of ball
    init();
    radius = 7;

    // Create exit command and "Fire" key
    cmExit = new Command("Exit", Command.EXIT, 1);

    keyFire =  getKeyCode(FIRE);
    keyRight = getKeyCode(RIGHT);
    keyLeft = getKeyCode(LEFT);

    addCommand(cmExit);
    setCommandListener(this);
  }

  /*--------------------------------------------------
  * Paint a new ball, clearing the screen as asked
  *-------------------------------------------------*/
  protected void paint(Graphics g)
  {
    // Max edge hits, reset everything
    if (directionChanged > MAX_CHANGES)
      init();

    // Clear the background
    if (clearBackground)
    {
      g.setColor(255, 255, 255);
	    g.fillRect(0, 0, getWidth(), getHeight());
      clearBackground = !clearBackground;
    }

    // Set color and draw another ball
    g.setColor(red, green, blue);
    g.fillArc( x_loc, y_loc, radius, radius, 0, 360);
  }

  /*--------------------------------------------------
  * Initialize starting location and direction of ball
  *-------------------------------------------------*/
  private void init()
  {
    // Start close to the middle
    x_loc = getWidth() / 2;
    y_loc = getHeight() / 2;

    // The direction the ball is heading
    x_dir = (random.nextInt() % 10);
    if (x_dir == 0)  x_dir = 1;

    y_dir = (random.nextInt() % 10);
    if (y_dir == 0)  y_dir = 1;

    directionChanged = 0;
    clearBackground = true;
    changeColor();
  }

  /*--------------------------------------------------
  * Change the colors.
  * I am counting on the implemention to substitute
  * a use-able color if any of these are out of the
  * devices supported range
  *-------------------------------------------------*/
  protected void changeColor()
  {
    // The shift is to remove any sign (negative) bit
    red = (random.nextInt() >>> 1) % 256;
    green = (random.nextInt() >>> 1) % 256;
    blue = (random.nextInt() >>> 1) % 256;
  }

  /*--------------------------------------------------
  * Event handling
  *-------------------------------------------------*/
  public void commandAction(Command c, Displayable d)
  {
    if (c == cmExit)
      midlet.exitMIDlet();
  }

  /*--------------------------------------------------
  * Reset ball is "Fire" key is pressed
  *-------------------------------------------------*/
  protected void keyPressed(int keyCode)
  {
    // Restart
    if (keyCode == keyFire)
      init();
    // Decrease ball size
    else if (keyCode == keyLeft)
      radius = Math.max(1, --radius);
    else if (keyCode == keyRight)
    // Increase ball size
     radius = Math.min(getWidth() / 4, ++radius);
  }
}