tumbleweed.java

JAVASCRIPT的界面说明JAVASCRIPT的界面说明JAVASCRIPT的界面说明JAVASCRIPT的界面说明

package net.frog_parrot.jump;

import java.util.Random;

import javax.microedition.lcdui.*;
import javax.microedition.lcdui.game.*;

/**
 * This class represents the tumbleweeds that the player 
 * must jump over.
 *
 * @author Carol Hamer
 */
public class Tumbleweed extends Sprite {

  //---------------------------------------------------------
  //   dimension fields

  /**
   * The width of the tumbleweed's bounding square.
   */
  static int WIDTH = 16;

  //---------------------------------------------------------
  //    instance fields

  /**
   * Random number generator to randomly decide when to appear.
   */
  Random myRandom = new Random();

  /**
   * whether or not this tumbleweed has been jumped over.
   * This is used to calculate the score.
   */
  boolean myJumpedOver;

  /**
   * whether or not this tumbleweed enters from the left.
   */
  boolean myLeft;

  /**
   * the Y coordinate of the tumbleweed.
   */
  int myY;

  //---------------------------------------------------------
  //   initialization

  /**
   * constructor initializes the image and animation.
   * @param left whether or not this tumbleweed enters from the left.
   */
  public Tumbleweed(boolean left) throws Exception {
    super(Image.createImage("/icons/tumbleweed.png"), 
	  WIDTH, WIDTH);
    myY = JumpManager.DISP_HEIGHT - WIDTH - 2;
    myLeft = left;
    if(!myLeft) {
      setTransform(TRANS_MIRROR);
    }
    myJumpedOver = false;
    setVisible(false);
  }

  //---------------------------------------------------------
  //   graphics

  /**
   * move the tumbleweed back to its initial (inactive) state.
   */
  void reset() {
    setVisible(false);
    myJumpedOver = false;
  }

  /**
   * alter the tumbleweed image appropriately for this frame..
   * @param left whether or not the player is moving left
   * @return how much the score should change by after this 
   *         advance.
   */
  int advance(Cowboy cowboy, int tickCount, boolean left,
	      int currentLeftBound, int currentRightBound) {
    int retVal = 0;
    // if the tumbleweed goes outside of the display 
    // region, set it to invisible since it is 
    // no longer in use.
    if((getRefPixelX() + WIDTH <= currentLeftBound) || 
       (getRefPixelX() - WIDTH >= currentRightBound)) {
      setVisible(false);
    } 
    // If the tumbleweed is no longer in use (i.e. invisible)
    // it is given a 1 in 100 chance (per game loop) 
    // of coming back into play:
    if(!isVisible()) {
      int rand = getRandomInt(100);
      if(rand == 3) {
	// when the tumbleweed comes back into play, 
	// we reset the values to what they should 
	// be in the active state:
	myJumpedOver = false;
	setVisible(true);
	// set the tumbleweed's position to the point 
	// where it just barely appears on the screen 
	// to that it can start approaching the cowboy:
	if(myLeft) {
	  setRefPixelPosition(currentRightBound, myY);
	  move(-1, 0);
	} else {
	  setRefPixelPosition(currentLeftBound, myY);
	  move(1, 0);
	}
      }
    } else {
      // when the tumbleweed is active, we advance the 
      // rolling animation to the next frame and then 
      // move the tumbleweed in the right direction across 
      // the screen.
      if(tickCount % 2 == 0) { // slow the animation down a little
	nextFrame();
      }
      if(myLeft) {
	move(-3, 0);
	// if the cowboy just passed the tumbleweed 
	// (without colliding with it) we increase the 
	// cowboy's score and set myJumpedOver to true 
	// so that no further points will be awarded 
	// for this tumbleweed until it goes offscreen 
	// and then is later reactivated:
	if((! myJumpedOver) && 
	   (getRefPixelX() < cowboy.getRefPixelX())) {
	  myJumpedOver = true;
	  retVal = cowboy.increaseScoreThisJump();
	}
      } else {
	move(3, 0);
	if((! myJumpedOver) && 
	   (getRefPixelX() > cowboy.getRefPixelX() + Cowboy.WIDTH)) {
	  myJumpedOver = true;
	  retVal = cowboy.increaseScoreThisJump();
	}
      }
    }
    return(retVal);
  }

  /**
   * Gets a random int between 
   * zero and the param upper.
   */
  public int getRandomInt(int upper) {
    int retVal = myRandom.nextInt() % upper;
    if(retVal < 0) {
      retVal += upper;
    }
    return(retVal);
  }

}