sprite.java

J2ME Game Programming的隋书源代码

/**
 * A state manager for a game sprite. Use in conjunction with an ImageSet in
 * order to draw animated, multi-state sprites on screen. For each instance of
 * an animated graphics you should create one corresponding Sprite object.
 * Graphics are shared using a common ImageSet. To animate you must call this
 * class's cycle method.
 */

import javax.microedition.lcdui.Graphics;

public class Sprite
{
   private int currentFrame;
   private int currentState;
   private long currentStateBegan;		// time this currentState started
   private ImageSet imageSet;
   private long lastFrameChange;
   private int totalCycles;

   public Sprite(ImageSet is, int startingState, int startingFrame)
   {
      imageSet = is;
      setState(startingState, false);
      currentFrame = startingFrame;
   }

   public final void setFrame(int f)
   {
      currentFrame = f;
   }

   public final void setState(int s, boolean force)
   {
      if (currentState != s || force)
      {
         currentState = s;
         currentFrame = 0;
         totalCycles = 0;
         currentStateBegan = System.currentTimeMillis();
      }
   }

   public final void reset()
   {
      currentFrame = 0;
      totalCycles = 0;
      currentStateBegan = 0;
      lastFrameChange = 0;
   }

   public final long getWhenStateBegan()
   {
      return currentStateBegan;
   }

   public final long getTimeInCurrentState()
   {
      return (System.currentTimeMillis() - currentStateBegan);
   }

   public final int getCurrentState()
   {
      return currentState;
   }

   public final int getCurrentFrame()
   {
      return currentFrame;
   }

   public final void draw(Graphics target, int targetX, int targetY)
   {
      imageSet.draw(target, currentState, currentFrame, targetX, targetY);
   }

   public final void cycle(long deltaMS)
   {
      // change frame if we are animating (and enough time has passed)
      if (imageSet.getTotalFrames(currentState) > 1 &&
              imageSet.getAnimTime(currentState) > 0)
      {
         long deltaTime = System.currentTimeMillis() - lastFrameChange;
         if (deltaTime > imageSet.getAnimTimePerFrame(currentState))
         {
            currentFrame++;
            lastFrameChange = System.currentTimeMillis();
            if (currentFrame >= imageSet.getTotalFrames(currentState))
            {
               currentFrame = 0;
               totalCycles++;
            }
         }
      }
   }

   public final int getTotalCycles()
   {
      return totalCycles;
   }

}