actor.java

J2ME Game Programming的隋书源代码

/**
 * A dynamic moving object capable of existing in a World.
 */

import javax.microedition.lcdui.Graphics;

import net.jscience.math.kvm.MathFP;

abstract public class Actor
{
   public static final int FP_MINUS_1 = MathFP.toFP("-1.0");
   public static final int FP_MINUS_05 = MathFP.toFP("-0.5");
   public static final int FP_MINUS_01 = MathFP.toFP("-0.1");
   public static final int FP_225 = MathFP.toFP("22.5");
   public static final int FP_PI2 = MathFP.mul(MathFP.PI, MathFP.toFP(2));
   public static final int FP_DEGREES_PER_RAD = MathFP.div(MathFP.toFP(360), FP_PI2);
   public static final int FP_ONE = MathFP.toFP("1");

   // lookup table for cos and sin value (0 to 359)
   static int[] lookupCosFP = new int[360];
   static int[] lookupSinFP = new int[360];

   // static init
   {
      for (int i = 0; i < 360; i++)
         lookupCosFP[i] = MathFP.cos(getRadiansFromAngle(i));
      for (int i = 0; i < 360; i++)
         lookupSinFP[i] = MathFP.sin(getRadiansFromAngle(i));
   }
   // Actor types - we place them all in here so we can check the type of
   // a actor instance without doing an expensive instanceof test. This is
   // (of course) a horrible corruption of the intent of an abstract Actor
   // class - it's considered worth it for the performance gain.

   public static final int SHIP_START = 0;
   public static final int PLAYER_SHIP = SHIP_START + 1;

   public static final int ENEMY_SHIP_START = SHIP_START + 2;
   public static final int ENEMY_DRONE = SHIP_START + 3;
   public static final int ENEMY_AI_START = SHIP_START + 4;
   public static final int ENEMY_TURRET = SHIP_START + 5;
   public static final int ENEMY_FIGHTER = SHIP_START + 6;
   public static final int SHIP_END = SHIP_START + 7;

   public static final int BULLET_START = 1000;
   public static final int PLASMA_CANNON = BULLET_START + 1;
   public static final int BULLET_END = BULLET_START + 2;

   private int type;							// type of actor (instead of subclassing)
   private int xFP, yFP;              	// current position
   private int x, y;							// integer versions (stored for speed)
   private int startingX, startingY;	// where the actor starts (used for restart)
   private int startingDir;				// starting direction (used for restart)
   private int lastXFP, lastYFP;
   private int xVelFP, yVelFP;        	// current velocity
   private int xAccFP, yAccFP;        	// current acceleration
   private int thrustFP;
   private int spinFP;                	// current spin rate (in degrees per second)
   private int maxSpinRate;           	// maximum spin rate (in degrees per second)
   private int maxVelFP;					// maximum velocity
   private int bounceVelFP;  			   // velocity to variance when bouncing off an impact
   private int realDir;                // actual direction in degrees
   private int alignedDir;             // aligned direction
   private int alignedDivDegreesFP;   	// degrees per facing division
   private boolean wantAlignment;		// turn auto alignment on

   private long fluff = 0;
   private boolean autoSpinning;			// we set a flag to avoid over calling setSpin()
   private int targetAngle;

   protected Actor owner;
   protected World world;
   private boolean collidable;			// can anything collide with us?
   private boolean visible;				// whether we should be drawn or not

   private Actor nextLinked;				// link to next actor
   private Actor prevLinked;				// link to previous actor

   public Actor()
   {
   }

   public Actor(World w)
   {
      world = w;
   }

   /**
    * Initializes an Actor. The alignedDivArg sets the number of distinct angles
    * this Actor can face. A Ship with 16 facing images has 16 aligned
    * divisions, which translates to an aligned division of 22.5 degrees (360
    * divided by 16). The aligned direction is used by the Actor class to make
    * sure it can only face an angle that can be drawn.
    * @param startX The starting x position of the new Actor.
    * @param startY The starting y position of the new Actor.
    * @param startDirection The starting direction
    * @param alignedDivArg The number of aligned angle divisions.
    * @param maxVelFPArg The maximum velocity.
    * @param thrustFPArg The starting thrust.
    * @param bounceVelFPArg The level of bounce when colliding with something.
    * @param maxSpinRateArg The maximum turn rate in degrees per second.
    */
   public void init(Actor newOwner, int startX, int startY, int thrustFPArg,
                    int speedFPArg, int maxVelFPArg, int startDirection, 
                    int alignedDivArg, int bounceVelFPArg, int maxSpinRateArg)
   {
      setX(startX);
      setY(startY);
      owner = newOwner;
      startingX = x;
      startingY = y;
      startingDir = startDirection;

      maxVelFP = maxVelFPArg;
      maxSpinRate = maxSpinRateArg;

      wantAlignment = false;
      if (alignedDivArg > 0)
      {
         alignedDivDegreesFP = MathFP.div(360, alignedDivArg);
         wantAlignment = true;
      }
      setDirection(startDirection);
      setThrust(thrustFPArg);
      setVel(speedFPArg);

      bounceVelFP = bounceVelFPArg;
      collidable = true;
      visible = true;
   }

   // typically used to restart state for a level (ie. when the player dies)
   public void reset()
   {
      setX(startingX);
      setY(startingY);
      setDirection(startingDir);
      setSpin(0);
      setVel(0);
   }

   public final Actor getNextLinked()
   {
      return nextLinked;
   }

   public final void setNextLinked(Actor nextLinked)
   {
      this.nextLinked = nextLinked;
   }

   public final Actor getPrevLinked()
   {
      return prevLinked;
   }

   public final void setPrevLinked(Actor prevLinked)
   {
      this.prevLinked = prevLinked;
   }

   public final int getType()
   {
      return type;
   }

   public final void setType(int type)
   {
      this.type = type;
   }

   public int getStartingY()
   {
      return startingY;
   }

   public int getStartingX()
   {
      return startingX;
   }

   public final void setStartingPos(int startingX, int startingY)
   {
      this.startingX = startingX;
      this.startingY = startingY;
   }

   public final boolean isEnemyShip()
   {
      return (type > ENEMY_SHIP_START && type < SHIP_END);
   }

   public final boolean isBullet()
   {
      return (type > BULLET_START && type < BULLET_END);
   }

   public final Actor getOwner()
   {
      return owner;
   }

   public final void setOwner(Actor owner)
   {
      this.owner = owner;
   }

   public final void deactivate()
   {
      collidable = false;
      visible = false;
   }

   /**
    * Get a rudamentary distance from this Actor to another (uses basic x, y
    * coords rather than the centre to save time - typically you only need an
    * approx distance anyway.
    */
   public final int distanceTo(Actor another)
   {
      return distance(x, y, another.getX(), another.getY());
   }

   public final void setCollidable(boolean b)
   {
      collidable = b;
   }

   public final boolean isCollidable()
   {
      return collidable;
   }

   public final boolean isVisible()
   {
      return visible;
   }

   public final void setVisible(boolean visible)
   {
      this.visible = visible;
   }

   /**
    * Abstract render method that must be implemented by derived classes.
    * This method is intended to be called by a Actor manager (such as a
    * World class) to draw Actors on the screen.
    * @param graphics The graphics context upon which to draw.
    * @param offsetX The amount to offset the x drawing position by.
    * @param offsetY The amount to offset the y drawing position by.
    */
   public void render(Graphics graphics, int offsetX, int offsetY)
   {
   }

   /**
    * Abstract method to return the width of the Actor.
    */
   abstract public int getWidth();

   /**
    * Abstract method to return the height of the Actor.
    */
   abstract public int getHeight();

   /**
    * Changes the current speed of the actor by setting the velocity based on
    * the current (aligned) direction.
    * @param speedArg The speed to travel at.
    */
   public final void setVel(int speedArg)
   {
      xVelFP = MathFP.mul(MathFP.toFP(speedArg), lookupCosFP[alignedDir]);
      yVelFP = MathFP.mul(MathFP.toFP(speedArg), -lookupSinFP[alignedDir]);
      // If you change this remember to change the cycle code
      if (xVelFP > maxVelFP)
         xVelFP = maxVelFP;
      else if (xVelFP < -maxVelFP) xVelFP = -maxVelFP;
      if (yVelFP > maxVelFP)
         yVelFP = maxVelFP;
      else if (yVelFP < -maxVelFP) yVelFP = -maxVelFP;
   }

   /**
    * Set the direction (in degrees; east = 0). We also set the alignedDir
    * to the closest angle available.
    */
   public final void setDirection(int d)
   {
      realDir = d;
      if (realDir < 0) realDir = (359 + (realDir));   // add the neg value
      if (realDir > 359) realDir = (d - 360);

      // set the facing direction to be the closest alignment
      if (wantAlignment)
      {
         alignedDir = getAlignedDirection(realDir);
      }
      else
         alignedDir = realDir;

   }

   /**
    * Gets the closest aligned direction to the passed in direction (in
    * degrees).
    * @param dir The direction to align (in degrees).
    * @return A direction which aligns to the number of divisions the Actor
    * supports.
    */
   public final int getAlignedDirection(int dir)
   {
      int fp = MathFP.toInt(MathFP.div(MathFP.toFP(dir), alignedDivDegreesFP));
      int ad = MathFP.toInt(MathFP.mul(MathFP.toFP(fp), alignedDivDegreesFP));
      if (ad < 0) ad = 0;
      if (ad > 359) ad = 0;
      return ad;
   }

   /**
    * @return The current aligned direction.
    */
   public final int getDirection()
   {
      return alignedDir;
   }

   /**
    * @return The current real direction (not aligned).
    */
   public final int getRealDirection()
   {
      return realDir;
   }

   /**
    * @return The World object that contains this Actor.
    */
   public final World getWorld()
   {