block.java

J2ME MIDP_Example_Applications

// Copyright 2003 Nokia Corporation.
//
// THIS SOURCE CODE IS PROVIDED 'AS IS', WITH NO WARRANTIES WHATSOEVER,
// EXPRESS OR IMPLIED, INCLUDING ANY WARRANTY OF MERCHANTABILITY, FITNESS
// FOR ANY PARTICULAR PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE
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// RIGHTS GRANTED HEREUNDER DOES NOT INFRINGE OR MAY NOT CAUSE INFRINGEMENT
// OF ANY PATENT OR OTHER INTELLECTUAL PROPERTY RIGHTS OWNED OR CONTROLLED
// BY THIRD PARTIES
//
// Furthermore, information provided in this source code is preliminary,
// and may be changed substantially prior to final release. Nokia Corporation
// retains the right to make changes to this source code at
// any time, without notice. This source code is provided for informational
// purposes only.
//
// Nokia and Nokia Connecting People are registered trademarks of Nokia
// Corporation.
// Java and all Java-based marks are trademarks or registered trademarks of
// Sun Microsystems, Inc.
// Other product and company names mentioned herein may be trademarks or
// trade names of their respective owners.
//
// A non-exclusive, non-transferable, worldwide, limited license is hereby
// granted to the Licensee to download, print, reproduce and modify the
// source code. The licensee has the right to market, sell, distribute and
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import java.util.Random;
import javax.microedition.lcdui.*;


// Blocks try to fly past the base, or crash into it.
// A Block can draw itself.

class Block
{
    final static int COLOR = 0xFFFFFF; // WHITE

    private final static int MIN_STRENGTH = 0; // bulletStrength
    private final static int MAX_STRENGTH = 5; // bulletStrength
    private final static int COLLIDE_BORDER = 2; // pixels
    private final static Random random = new Random();

    private final GameManager gameManager;
    private final int xMin;
    private final int xMax;
    private final int dx;
    private final int dxRandom;

    private static int dimension = 10; // default height/width in pixels
    private int dxVariable = 0;

    // A dormant block is one that has been temporarily removed from
    // the game, for example before beginning a new life.
    // When created, each block is dormant for 1.5 seconds before
    // joining the game.
    private int dormantTicks = (1500 / GameManager.MILLIS_PER_TICK);

    private int bulletHits = 0;
    private int bulletStrength = MIN_STRENGTH;
    private int x;
    private int y;


    Block(GameManager gameManager, int xMin, int xMax, int y, int dx)
    {
        this.gameManager = gameManager;
        this.xMin = xMin;
        this.xMax = xMax;
        this.y = y;

        // Set the fixed velocity component, and the default
        // variable velocity component (based on the fixed velocity).
        // Method varySpeed modifies the variable velocity component based
        // on block strength. It modifies the variable component of the
        // block speed so that as a block becomes stronger, the variable
        // component of speed becomes weaker.
        this.dx = dx;
        dxRandom = -rand(dx);
        varySpeed();

        bulletHits = 0;
        x = xMax - dimension;
    }


    private void varySpeed()
    {
        // Stronger blocks should have a 'tendency' to move
        // more slowly than weaker ones move. (Most may move
        // somewhat more slowly, but not in all cases.)
        dxVariable = ((MAX_STRENGTH - bulletStrength) * dxRandom) /
                     MAX_STRENGTH;
    }


    static void setDimension(int d)
    {
        dimension = d;
    }


    static int getDimension()
    {
        return dimension;
    }


    public void tick()
    {
        if (dormantTicks > 0)
        {
            // dormant blocks wait awhile before re-entering the game
            dormantTicks--;
        }
        else
        {
            // check if we moved off the left game edge
            if (x <= xMin)
            {
                gameManager.doBlockPassed(this);

                // become dormant for 3 seconds
                dormantTicks = (3000 / GameManager.MILLIS_PER_TICK);
                x = xMax - dimension; // initialize re-start x position
                if (bulletHits == 0)
                {
                    // If the block flew off canvas without having been shot,
                    // increase it's strength so it's more difficult to
                    // destroy in it's next life.
                    updateStrength();

                    varySpeed(); // change the variable component of speed
                }
                else
                {
                    // Reset strength and hits, to become a weak block.
                    bulletStrength = 0;
                    bulletHits = 0;

                    varySpeed(); // change the variable component of speed
                }
            }
            else
            {
                int gw = gameManager.getCanvas().getWidth();

                // The block moves left (dx + dxVariable is negative)
                x += (dx + dxVariable);
            }
        }
    }


    public void draw(Graphics g)
    {
        if (dormantTicks == 0)
        {
            int d = dimension;
            int rx = x;
            int ry = y;


            // Different blocks are drawn for bulletStrength 0 .. 5:
            //   0 : dark block with white pixel border, no diagonals
            //   1 : dark block with white pixel border, 1 white diagonal line
            //   2 : dark block with white pixel border, 2 white diagonal lines
            //   3 : white filled block with no diagonals
            //   4 : white filled block with one dark diagonal line
            //   5 : white filled block with two dark diagonal line

            g.setColor(COLOR);
            if (bulletStrength < 3)
            {
                g.drawRect(rx, ry, (d - 1), (d - 1));
                if (bulletStrength > 0)
                {
                    g.drawLine((rx + d - 1), ry, rx, (ry + d - 1));
                }
                if (bulletStrength > 1)
                {
                    g.drawLine(rx, ry, (rx + d - 1), (ry + d - 1));
                }
            }
            else
            {
                g.fillRect(rx, ry, d, d);
                g.setColor(0x000000); // BLACK
                if (bulletStrength > 3)
                {
                    g.drawLine((rx + d - 2), (ry + 1), (rx + 1), (ry + d - 2));
                }
                if (bulletStrength > 4)
                {
                    g.drawLine((rx + 1), (ry + 1), (rx + d - 2), (ry + d - 2));
                }
            }
        }
    }


    // Increase the bullet strength of the Block up to a maximum strength,
    // but reset to initial value if update would be more than the maximum.
    void updateStrength()
    {
        if (bulletStrength <= MAX_STRENGTH)
        {
            bulletStrength++;
        }
        else if (bulletStrength > MAX_STRENGTH)
        {
            bulletStrength = MIN_STRENGTH;
        }
    }


    int getPoints()
    {
        // The 'points' value of a block is based on its strength
        return (bulletStrength + 1);
    }


    boolean isCollision(Bullet b)
    {
        boolean overlaps = overlaps2D(x, y, dimension, dimension,
                                      b.getX(), b.getY(), b.getWidth(),
                                      b.getHeight());
        return ((dormantTicks == 0) && overlaps);
    }


    boolean isCollision(Base b)
    {
        // Using a phone keypad to control the {x, y} position
        // of the base may not give the player sufficient fine grained
        // control of position as they might like. One way to improve
        // this is to make the Block/Base collision detection less sensitive.
        //
        // The COLLIDE_BORDER parameter allows the collision detection
        // to be slightly more forgiving than an exact overlap.

        boolean overlaps = overlaps2D((x + COLLIDE_BORDER),
                                      (y + COLLIDE_BORDER),
                                      (dimension - (2 * COLLIDE_BORDER)),
                                      (dimension - (2 * COLLIDE_BORDER)),
                                      b.getX(),
                                      b.getY(),
                                      (b.getWidth() + b.getCannonDimension()),
                                      b.getHeight());

        return ((dormantTicks == 0) && overlaps);
    }


    boolean doBulletCollision()
    {
        if (++bulletHits > bulletStrength)
        {
            doExplode();
            return true; // block exploded
        }
        return false;
    }


    void doExplode()
    {
        dormantTicks = 30; // Remove from game for 30 ticks

        // Re-initialize some block parameters
        bulletHits = 0;
        x = xMax - dimension;
    }


    // Do two rectangles overlap?
    private static boolean overlaps2D(int x1, int y1, int w1, int h1,
        int x2, int y2, int w2, int h2)
    {
        return overlaps1D(x1, w1, x2, w2) && overlaps1D(y1, h1, y2, h2);
    }


    // Do two lines overlap?
    private static boolean overlaps1D(int p1, int l1, int p2, int l2)
    {
        return (p1 <= p2) ? ((p1 + l1) >= p2) : (p1 <= (p2 + l2));
    }


    // Return a positive random-like number
    private static int rand(int scale)
    {
        return (random.nextInt() << 1 >>> 1) % scale;
    }
}