JavaScript Canvas 乒乓球游戏

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JavaScript

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.6.4/jquery.min.js"></script>  
<style type="text/css">
canvas{
   border:1px solid green;
}
</style>
</head>  
<body>  
  <canvas id="canvas" width="300" height="500"></canvas>  
  <script type="text/javascript">
//BEGIN LIBRARY CODE
  var x = 150;
  var y = 150;
  var dx = 2;
  var dy = 4;
  var WIDTH;
  var HEIGHT;
  var ctx;
var intervalId;
  function init() {
    ctx = $('#canvas')[0].getContext("2d");
    WIDTH = $("#canvas").width();
    HEIGHT = $("#canvas").height();
    intervalId= setInterval(draw, 10);
  }

  function circle(x,y,r) {
    ctx.beginPath();
    ctx.fillStyle = "red"; 
    ctx.arc(x, y, r, 0, Math.PI*2, true);
    ctx.closePath();
    ctx.fill();
  }

  function rect(x,y,w,h) {
    ctx.beginPath();
    ctx.rect(x,y,w,h);
    ctx.closePath();
    ctx.fill();
  }

  function clear() {
    ctx.clearRect(0, 0, WIDTH, HEIGHT);
  }

  //END LIBRARY CODE
var paddlex;
var paddleh;
var paddlew;

function init_paddle() {
  paddlex = WIDTH / 2;
  paddleh = 10;
  paddlew = 75;
}
rightDown = false;
leftDown = false;

//set rightDown or leftDown if the right or left keys are down
function onKeyDown(evt) {
  if (evt.keyCode == 39) rightDown = true;
  else if (evt.keyCode == 37) leftDown = true;
}

//and unset them when the right or left key is released
function onKeyUp(evt) {
  if (evt.keyCode == 39) rightDown = false;
  else if (evt.keyCode == 37) leftDown = false;
}

$(document).keydown(onKeyDown);
$(document).keyup(onKeyUp);
       
var canvasMinX;
var canvasMaxX;

function init_mouse() {
  canvasMinX = $("#canvas").offset().left;
  canvasMaxX = canvasMinX + WIDTH;
}

function onMouseMove(evt) {
  if (evt.pageX > canvasMinX && evt.pageX < canvasMaxX) {
    paddlex = evt.pageX - canvasMinX;
  }
}

$(document).mousemove(onMouseMove);
     
var bricks;
var NROWS;
var NCOLS;
var BRICKWIDTH;
var BRICKHEIGHT;
var PADDING;

function initbricks() {
  NROWS = 5;
  NCOLS = 5;
  BRICKWIDTH = (WIDTH/NCOLS) - 1;
  BRICKHEIGHT = 15;
  PADDING = 1;

  bricks = new Array(NROWS);
  for (i=0; i < NROWS; i++) {
    bricks[i] = new Array(NCOLS);
    for (j=0; j < NCOLS; j++) {
      bricks[i][j] = 1;
    }
  }
}
       
function draw() {
  clear();

  circle(x, y, 10);

  if (rightDown) paddlex += 5;
  else if (leftDown) paddlex -= 5;
  rect(paddlex, HEIGHT-paddleh, paddlew, paddleh);

  //draw bricks
  for (i=0; i < NROWS; i++) {
    for (j=0; j < NCOLS; j++) {
      if (bricks[i][j] == 1) {
    	ctx.fillStyle = "green";
        rect((j * (BRICKWIDTH + PADDING)) + PADDING,
             (i * (BRICKHEIGHT + PADDING)) + PADDING,
             BRICKWIDTH, BRICKHEIGHT);
      }
    }
  }

  //have we hit a brick?
  rowheight = BRICKHEIGHT + PADDING;
  colwidth = BRICKWIDTH + PADDING;
  row = Math.floor(y/rowheight);
  col = Math.floor(x/colwidth);
  //if so, reverse the ball and mark the brick as broken
  if (y < NROWS * rowheight && row >= 0 && col >= 0 && bricks[row][col] == 1) {
    dy = -dy;
    bricks[row][col] = 0;
  }

  if (x + dx > WIDTH || x + dx < 0)
    dx = -dx;

  if (y + dy < 0)
    dy = -dy;
  else if (y + dy > HEIGHT) {
    if (x > paddlex && x < paddlex + paddlew)
      dy = -dy;
    else
      clearInterval(intervalId);
  }

  x += dx;
  y += dy;
}

init();
init_paddle();
init_mouse();
initbricks();
  </script>  

</body>  
</html>

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