HTML5游戏开发系列教程9(译)

时间：2024-11-09 16:34:32

原文地址：http://www.script-tutorials.com/html5-game-development-lesson-9/

今天我们将继续使用canvas来进行HTML5游戏开发系列的文章。这次我准备了一个新游戏，是基于第4篇的游戏，但是增加了火球，敌人和碰撞检测。故，我们的龙可以发射火球来杀死敌人，并且记录分数。这样该游戏就有更多的交互性。

之前的翻译文章可以点击这里：http://www.cnblogs.com/pigzhu/p/3234255.html

第一步：HTML

首先是我们基础的html代码：

 <!DOCTYPE html>

 <html lang="en" >

     <head>

         <meta charset="utf-8" />

         <title>HTML5 Game Development - Lesson 9 | Script Tutorials</title>

         <link href="css/main.css" rel="stylesheet" type="text/css" />

         <!--[if lt IE 9]>

           <script src="http://html5shiv.googlecode.com/svn/trunk/html5.js"></script>

         <![endif]-->

         <script src="js/jquery-2.0.0.min.js"></script>

         <script src="js/script.js"></script>

     </head>

     <body>

         <header tabindex="0">

             <h2>HTML5 Game Development - Lesson 9</h2>

             <a  href="http://www.script-tutorials.com/html5-game-development-lesson-9/" class="stuts">Back to original tutorial on <span>Script Tutorials</span></a>

         </header>

         <div class="container">

             <canvas id="scene" width="1000" height="600" tabindex="1"></canvas>

         </div>

     </body>

 </html>

第二步：CSS

接着这里是CSS样式。

css/main.css

这次依然不打算显示出CSS文件的内容了，因为仅仅只是些页面布局样式。你可以在源代码包里找到该文件。

第三步：JS

js/script.js

 // 内部变量

 var canvas, ctx;

 var backgroundImage;

 var iBgShiftX = 100;

 var dragon, enemy = null; // 游戏中两个主要实体对象

 var balls = [];

 var enemies = [];

 var dragonW = 75; // 龙的宽度

 var dragonH = 70; // 龙的高度

 var iSprPos = 0; // 初始帧的位置

 var iSprDir = 0; // 初始龙的朝向

 var iEnemyW = 128; // 敌人的宽度

 var iEnemyH = 128; // 敌人的高度

 var iBallSpeed = 10; // 火球的速度

 var iEnemySpeed = 2; // 敌人的速度

 var dragonSound; // 龙的声音

 var wingsSound; // 翅膀的声音

 var explodeSound, explodeSound2; // 爆炸声音

 var laughtSound; // 敌人从左边逃出，嘲笑的声音

 var bMouseDown = false; // 鼠标是否按下

 var iLastMouseX = 0;

 var iLastMouseY = 0;

 var iScore = 0;

 // -------------------------------------------------------------

 // 龙

 function Dragon(x, y, w, h, image) {

     this.x = x;

     this.y = y;

     this.w = w;

     this.h = h;

     this.image = image;

     this.bDrag = false;

 }

 // 球

 function Ball(x, y, w, h, speed, image) {

     this.x = x;

     this.y = y;

     this.w = w;

     this.h = h;

     this.speed = speed;

     this.image = image;

 }

 // 敌人

 function Enemy(x, y, w, h, speed, image) {

     this.x = x;

     this.y = y;

     this.w = w;

     this.h = h;

     this.speed = speed;

     this.image = image;

 }

 // -------------------------------------------------------------

 // 获得位于x和y之间的随机数。

 function getRand(x, y) {

     return Math.floor(Math.random() * y) + x;

 }

 // draw functions :

 function drawScene() { // main drawScene function

     ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height); // 清除这个画布

     // 画背景

     iBgShiftX += 4;

     if (iBgShiftX >= 1045) {

         iBgShiftX = 0;

     }

     ctx.drawImage(backgroundImage, 0 + iBgShiftX, 0, 1000, 940, 0, 0, 1000, 600);

     // 更新帧的位置

     iSprPos++;

     if (iSprPos >= 9) {

         iSprPos = 0;

     }

     // 当鼠标被按下，龙朝着鼠标移动

     if (bMouseDown) {

         if (iLastMouseX > dragon.x) {

             dragon.x += 5;

         }

         if (iLastMouseY > dragon.y) {

             dragon.y += 5;

         }

         if (iLastMouseX < dragon.x) {

             dragon.x -= 5;

         }

         if (iLastMouseY < dragon.y) {

             dragon.y -= 5;

         }

     }

     // 绘制龙

     ctx.drawImage(dragon.image, iSprPos * dragon.w, iSprDir * dragon.h, dragon.w, dragon.h,

      dragon.x - dragon.w / 2, dragon.y - dragon.h / 2, dragon.w, dragon.h);

     // 如果有火球则绘制

     if (balls.length > 0) {

         for (var key in balls) {

             if (balls[key] != undefined) {

                 ctx.drawImage(balls[key].image, balls[key].x, balls[key].y);

                 balls[key].x += balls[key].speed;

                 if (balls[key].x > canvas.width) {  //超出屏幕，移除

                     delete balls[key];

                 }

             }

         }

     }

     // 如果有敌人则绘制

     if (enemies.length > 0) {

         for (var ekey in enemies) {

             if (enemies[ekey] != undefined) {

                 ctx.drawImage(enemies[ekey].image, enemies[ekey].x, enemies[ekey].y);

                 enemies[ekey].x += enemies[ekey].speed;

                 if (enemies[ekey].x < - iEnemyW) {  //敌人没有被击中，从左边消失，并发出嘲笑声音

                     delete enemies[ekey];

                     laughtSound.currentTime = 0;

                     laughtSound.play();

                 }

             }

         }

     }

     // 检测是否击中敌人

     if (balls.length > 0) {

         for (var key in balls) {

             if (balls[key] != undefined) {

                 if (enemies.length > 0) {

                     for (var ekey in enemies) {

                         if (enemies[ekey] != undefined && balls[key] != undefined) {

                             if (balls[key].x + balls[key].w > enemies[ekey].x && balls[key].y + balls[key].h > enemies[ekey].y

                                 && balls[key].y < enemies[ekey].y + enemies[ekey].h) {

                                 delete enemies[ekey];

                                 delete balls[key];

                                 iScore++;

                                 explodeSound2.currentTime = 0;

                                 explodeSound2.play();

                             }

                         }

                     }

                 }

             }

         }

     }

     // 绘制分数

     ctx.font = '16px Verdana';

     ctx.fillStyle = '#fff';

     ctx.fillText('Score: ' + iScore * 10, 900, 580);

     ctx.fillText('Plese click "1" to cast fireball', 100, 580);

 }

 // -------------------------------------------------------------

 // 初始化

 $(function(){

     canvas = document.getElementById('scene');

     ctx = canvas.getContext('2d');

     var width = canvas.width;

     var height = canvas.height;

     // 加载背景图片

     backgroundImage = new Image();

     backgroundImage.src = 'images/hell.jpg';

     backgroundImage.onload = function() {

     }

     backgroundImage.onerror = function() {

         console.log('Error loading the background image.');

     }

     //初始化各种声音

     dragonSound = new Audio('media/dragon.wav');

     dragonSound.volume = 0.9;

     laughtSound = new Audio('media/laught.wav');

     laughtSound.volume = 0.9;

     explodeSound = new Audio('media/explode1.wav');

     explodeSound.volume = 0.9;

     explodeSound2 = new Audio('media/explosion.wav');

     explodeSound2.volume = 0.9;

     wingsSound = new Audio('media/wings.wav');

     wingsSound.volume = 0.9;

     wingsSound.addEventListener('ended', function() { // loop wings sound

         this.currentTime = 0;

         this.play();

     }, false);

     wingsSound.play();

     // 加载各种图片

     var oBallImage = new Image();

     oBallImage.src = 'images/fireball.png';

     oBallImage.onload = function() { }

     var oEnemyImage = new Image();

     oEnemyImage.src = 'images/enemy.png';

     oEnemyImage.onload = function() { }

     var oDragonImage = new Image();

     oDragonImage.src = 'images/dragon.gif';

     oDragonImage.onload = function() {

         dragon = new Dragon(400, 300, dragonW, dragonH, oDragonImage);

     }

     $('#scene').mousedown(function(e) { // 处理鼠标按下

         var mouseX = e.layerX || 0;

         var mouseY = e.layerY || 0;

         if(e.originalEvent.layerX) { // jquery 1.7之后用下面这种方式

             mouseX = e.originalEvent.layerX;

             mouseY = e.originalEvent.layerY;

         }

         bMouseDown = true;

         if (mouseX > dragon.x- dragon.w/2 && mouseX < dragon.x- dragon.w/2 +dragon.w &&

             mouseY > dragon.y- dragon.h/2 && mouseY < dragon.y-dragon.h/2 +dragon.h) {

             dragon.bDrag = true;

             dragon.x = mouseX;

             dragon.y = mouseY;

         }

     });

     $('#scene').mousemove(function(e) { // 处理鼠标移动

         var mouseX = e.layerX || 0;

         var mouseY = e.layerY || 0;

         if(e.originalEvent.layerX) {

             mouseX = e.originalEvent.layerX;

             mouseY = e.originalEvent.layerY;

         }

         // 保存上次鼠标的位置

         iLastMouseX = mouseX;

         iLastMouseY = mouseY;

         // 执行龙的拖动

         if (dragon.bDrag) {

             dragon.x = mouseX;

             dragon.y = mouseY;

         }

         // 根据鼠标的位置，改变龙的方向

         if (mouseX > dragon.x && Math.abs(mouseY-dragon.y) < dragon.w/2) {

             iSprDir = 0;

         } else if (mouseX < dragon.x && Math.abs(mouseY-dragon.y) < dragon.w/2) {

             iSprDir = 4;

         } else if (mouseY > dragon.y && Math.abs(mouseX-dragon.x) < dragon.h/2) {

             iSprDir = 2;

         } else if (mouseY < dragon.y && Math.abs(mouseX-dragon.x) < dragon.h/2) {

             iSprDir = 6;

         } else if (mouseY < dragon.y && mouseX < dragon.x) {

             iSprDir = 5;

         } else if (mouseY < dragon.y && mouseX > dragon.x) {

             iSprDir = 7;

         } else if (mouseY > dragon.y && mouseX < dragon.x) {

             iSprDir = 3;

         } else if (mouseY > dragon.y && mouseX > dragon.x) {

             iSprDir = 1;

         }

     });

     $('#scene').mouseup(function(e) { // 处理鼠标释放事件

         dragon.bDrag = false;

         bMouseDown = false;

         // play dragon sound

         dragonSound.currentTime = 0;

         dragonSound.play();

     });

     $(window).keydown(function(event){ // 按键1，开火

         switch (event.keyCode) {

             case 49: // '1' key

                 balls.push(new Ball(dragon.x, dragon.y, 32, 32, iBallSpeed, oBallImage));

                 // play explode sound #1

                 explodeSound.currentTime = 0;

                 explodeSound.play();

                 break;

         }

     });

     setInterval(drawScene, 30); // loop drawScene

     // 随机生产出敌人

     var enTimer = null;

     function addEnemy() {

         clearInterval(enTimer);

         var randY = getRand(0, canvas.height - iEnemyH);

         enemies.push(new Enemy(canvas.width, randY, iEnemyW, iEnemyH, - iEnemySpeed, oEnemyImage));

         var interval = getRand(5000, 10000);

         enTimer = setInterval(addEnemy, interval); // loop drawScene

     }

     addEnemy();

 });

在上面代码的开始处，我增加了两个新对象，球和敌人。每个对象都有他们自己的属性集(比如位置，大小，图片，速度)，然后通过‘drawScene’方法来绘制他们，在该方法底部，你可以看到处理球和敌人的碰撞检测代码：

 // 检测是否击中敌人

     if (balls.length > 0) {

         for (var key in balls) {

             if (balls[key] != undefined) {

                 if (enemies.length > 0) {

                     for (var ekey in enemies) {

                         if (enemies[ekey] != undefined && balls[key] != undefined) {

                             if (balls[key].x + balls[key].w > enemies[ekey].x && balls[key].y + balls[key].h > enemies[ekey].y

                                 && balls[key].y < enemies[ekey].y + enemies[ekey].h) {

                                 delete enemies[ekey];

                                 delete balls[key];

                                 iScore++;

                                 explodeSound2.currentTime = 0;

                                 explodeSound2.play();

                             }

                         }

                     }

                 }

             }

         }

     }

最后，我们通过下面的代码不定时间的增加敌人：

 // 随机生产出敌人

     var enTimer = null;

     function addEnemy() {

         clearInterval(enTimer);

         var randY = getRand(0, canvas.height - iEnemyH);

         enemies.push(new Enemy(canvas.width, randY, iEnemyW, iEnemyH, - iEnemySpeed, oEnemyImage));

         var interval = getRand(5000, 10000);

         enTimer = setInterval(addEnemy, interval); // loop drawScene

     }

     addEnemy();

第四步：Custom files

  • images/dragon.gif, images/enemy.png, images/fireball.png, images/hell.jpg

  • media/dragon.wav, media/explode1.wav, media/explosion.wav, media/laught.wav, media/wings.wav

上面所有的文件都在源码包里。

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