利用HTML5 Canvas制作一个简单的打飞机游戏

10/24/2015来源:HTML教程人气:1525

  之前在当耐特的DEMO里看到个打飞机的游戏,然后就把他的图片和音频扒了了下来。。。。自己凭着玩的心情重新写了一个。仅供娱乐哈。。。。。。我没有用框架,所有js都是自己写的。。。。。。所以就可以来当个简单的教程,对那些刚玩canvas的,或许能有些帮助,楼主玩canvas也不是很久,技术不是很好,请见谅哈。

  闲话不多说,先上DEMO撒:飞机游戏 楼主写这个人纯碎娱乐,没想着写成多正式的游戏哈。

  步入主题啦:打飞机游戏文件有index.html入口文件,allSPRite.js精灵的逻辑处理文件,loading.js加载处理文件以及data.js(初始化的一些数据)。

  首先,正常的游戏基本上都需要一个loading,loading页面就是用来预加载数据的,包括精灵表图片,音频等,因为这是个小游戏,要加载的就只有一些音频和图片。里面的加载代码主要就下面这些,其他是制作loading动画的,那个比较简单,就不贴了,如果有兴趣的直接在DEMO里看控制台就行了:

  xml/HTML Code复制内容到剪贴板

  loadImg:function(datas){

  var _this = this;

  var dataIndex = 0;

  li();

  function li(){

  if(datas[dataIndex].indexOf("mp3")>=0){

  var audio = document.createElement("audio");

  document.body.appendChild(audio);

  audio.preload = "auto";

  audio.src = datas[dataIndex];

  audio.oncanplaythrough = function(){

  this.oncanplaythrough = null;

  dataIndex++;

  if(dataIndex===datas.length){

  _this.percent = 100;

  }else {

  _this.percent = parseInt(dataIndex/datas.length*100);

  li.call(_this);

  }

  }

  }else {

  preLoadImg(datas[dataIndex] , function(){

  dataIndex++;

  if(dataIndex===datas.length){

  _this.percent = 100;

  } else {

  _this.percent = parseInt(dataIndex/datas.length*100);

  li.call(_this);

  }

  })

  }

  }

  },

  //再贴出preLoadImg的方法

  function preLoadImg(src , callback){

  var img = new Image();

  img.src = src;

  if(img.complete){

  callback.call(img);

  }else {

  img.onload = function(){

  callback.call(img);

  }

  }

  }

  我先在data.js里面用一个数组保存文件的链接,然后判断这些链接是图片还是音频,如果是图片就用preLoadImg加载,预加载图片的代码很简单,就是new一个图片对象,然后把链接赋给它,加载完后再回调。音频的加载则是通过生成一个HTML5的audio dom对象,把链接赋给它,audio有一个事件“canplaythrough”,浏览器预计能够在不停下来进行缓冲的情况下持续播放指定的音频/视频时,会发生 canplaythrough 事件,也就是说当canplaythrough被调用时,音频就已经被加载的差不多了,可以进行下一个音频的加载了。就这样当把所有东西都加载完后,再进行回调,开始游戏。

  游戏开始了,一个游戏,会需要很多的对象,所以我就统一写成了一个精灵对象,不同对象之间的每一帧的运动情况直接用behavior来分别编写就行了。

  XML/HTML Code复制内容到剪贴板

  W.Sprite = function(name , painter , behaviors , args){

  if(name !== undefined) this.name = name;

  if(painter !== undefined) this.painter = painter;

  this.top = 0;

  this.left = 0;

  this.width = 0;

  this.height = 0;

  this.velocityX = 3;

  this.velocityY = 2;

  this.visible = true;

  this.animating = false;

  this.behaviors = behaviors;

  this.rotateAngle = 0;

  this.blood = 50;

  this.fullBlood = 50;

  if(name==="plan"){

  this.rotateSpeed = 0.05;

  this.rotateLeft = false;

  this.rotateRight = false;

  this.fire = false;

  this.firePerFrame = 10;

  this.fireLevel = 1;

  }else if(name==="star"){

  this.width = Math.random()*2;

  this.speed = 1*this.width/2;

  this.lightLength = 5;

  this.cacheCanvas = document.createElement("canvas");

  thisthis.cacheCtx = this.cacheCanvas.getContext('2d');

  thisthis.cacheCanvas.width = this.width+this.lightLength*2;

  thisthis.cacheCanvas.height = this.width+this.lightLength*2;

  this.painter.cache(this);

  }else if(name==="badPlan"){

  this.badKind = 1;

  this.speed = 2;

  this.rotateAngle = Math.PI;

  }else if(name==="missle"){

  this.width = missleWidth;

  }else if(name==="boom"){

  this.width = boomWidth;

  }else if(name==="food"){

  this.width = 40;

  this.speed = 3;

  this.kind = "LevelUP"

  }

  this.toLeft = false;

  this.toTop = false;

  this.toRight = false;

  this.toBottom = false;

  this.outArcRadius = Math.sqrt((this.width/2*this.width/2)*2);

  if(args){

  for(var arg in args){

  this[arg] = args[arg];

  }

  }

  }

  Sprite.prototype = {

  constructor:Sprite,

  paint:function(){

  if(this.name==="badPlan"){this.update();}

  if(this.painter !== undefined && this.visible){

  if(this.name!=="badPlan") {

  this.update();

  }

  if(this.name==="plan"||this.name==="missle"||this.name==="badPlan"){

  ctx.save();

  ctx.translate(this.left , this.top);

  ctx.rotate(this.rotateAngle);

  this.painter.paint(this);

  ctx.restore();

  }else {

  this.painter.paint(this);

  }

  }

  },

  update:function(time){

  if(this.behaviors){

  for(var i=0;i

  this.behaviors[i].execute(this,time);

  }

  }

  }

  }

  写出精灵类后,就可以通过编写每个的painter以及behavior来生成不同的对象了。接下来就是写painter了,painter分成两种,一种是普通的painter,一种就是精灵表painter,因为像爆炸动画,飞机开枪动画,都不是一张图片就能搞定的,所以就需要用到精灵表了:

2015511181456172.png (168×24)
2015511181533636.png (896×64)

  而绘制这些就要为他们定制一个精灵表绘制器,下面这个是最简单的精灵表绘制器,针对游戏的复杂性可以相对的修改精灵表写法,直到合适,不过原理都大同小异,就是小修小改而已:

  XML/HTML Code复制内容到剪贴板

  var SpriteSheetPainter = function(cells){

  this.cells = cells || [];

  this.cellIndex = 0;

  }

  SpriteSheetPainter.prototype = {

  advance:function(){

  if(this.cellIndex === this.cells.length-1){

  this.cellIndex = 0;

  }

  else this.cellIndex++;

  },

  paint:function(sprite){

  var cell = this.cells[this.cellIndex];

  context.drawImage(spritesheet , cell.x , cell.y , cell.w , cell.h , sprite.left , sprite.top , cell.w , cell.h);

  }

  }

  而普通的绘制器就更简单了,直接写一个painter,把要画的什么东西都写进去就行了。

  有了精灵类和精灵表绘制器后,我们就可以把星星,飞机,子弹,爆炸对象都写出来了:下面是整个allSprite.js的代码:

  javaScript Code复制内容到剪贴板

  (function(W){

  "use strict"

  var planWidth = 24,

  planHeight = 24,

  missleWidth = 70,

  missleHeight = 70,

  boomWidth = 60;

  //精灵类

  W.Sprite = function(name , painter , behaviors , args){

  if(name !== undefined) this.name = name;

  if(painter !== undefined) this.painter = painter;

  this.top = 0;

  this.left = 0;

  this.width = 0;

  this.height = 0;

  this.velocityX = 3;

  this.velocityY = 2;

  this.visible = true;

  this.animating = false;

  this.behaviors = behaviors;

  this.rotateAngle = 0;

  this.blood = 50;

  this.fullBlood = 50;

  if(name==="plan"){

  this.rotateSpeed = 0.05;

  this.rotateLeft = false;

  this.rotateRight = false;

  this.fire = false;

  this.firePerFrame = 10;

  this.fireLevel = 1;

  }else if(name==="star"){

  this.width = Math.random()*2;

  this.speed = 1*this.width/2;

  this.lightLength = 5;

  this.cacheCanvas = document.createElement("canvas");

  this.cacheCtx = this.cacheCanvas.getContext('2d');

  this.cacheCanvas.width = this.width+this.lightLength*2;

  this.cacheCanvas.height = this.width+this.lightLength*2;

  this.painter.cache(this);

  }else if(name==="badPlan"){

  this.badKind = 1;

  this.speed = 2;

  this.rotateAngle = Math.PI;

  }else if(name==="missle"){

  this.width = missleWidth;

  }else if(name==="boom"){

  this.width = boomWidth;

  }else if(name==="food"){

  this.width = 40;

  this.speed = 3;

  this.kind = "LevelUP"

  }

  this.toLeft = false;

  this.toTop = false;

  this.toRight = false;

  this.toBottom = false;

  this.outArcRadius = Math.sqrt((this.width/2*this.width/2)*2);

  if(args){

  for(var arg in args){

  this[arg] = args[arg];

  }

  }

  }

  Sprite.prototype = {

  constructor:Sprite,

  paint:function(){

  if(this.name==="badPlan"){this.update();}

  if(this.painter !== undefined && this.visible){

  if(this.name!=="badPlan") {

  this.update();

  }

  if(this.name==="plan"||this.name==="missle"||this.name==="badPlan"){

  ctx.save();

  ctx.translate(this.left , this.top);

  ctx.rotate(this.rotateAngle);

  this.painter.paint(this);

  ctx.restore();

  }else {

  this.painter.paint(this);

  }

  }

  },

  update:function(time){

  if(this.behaviors){

  for(var i=0;i

  this.behaviors[i].execute(this,time);

  }

  }

  }

  }

  // 精灵表绘制器

  W.SpriteSheetPainter = function(cells , isloop , endCallback , spritesheet){

  this.cells = cells || [];

  this.cellIndex = 0;

  this.dateCount = null;

  this.isloop = isloop;

  this.endCallback = endCallback;

  this.spritesheet = spritesheet;

  }

  SpriteSheetPainter.prototype = {

  advance:function(){

  this.cellIndex = this.isloop?(this.cellIndex===this.cells.length-1?0:this.cellIndex+1):(this.cellIndex+1);

  },

  paint:function(sprite){

  if(this.dateCount===null){

  this.dateCount = new Date();

  }else {

  var newd = new Date();

  var tc = newd-this.dateCount;

  if(tc>40){

  this.advance();

  this.dateCount = newd;

  }

  }

  if(this.cellIndex

  var cell = this.cells[this.cellIndex];

  ctx.drawImage(this.spritesheet , cell.x , cell.y , cell.w , cell.h , sprite.left-sprite.width/2 , sprite.top-sprite.width/2 , cell.w , cell.h);

  } else if(this.endCallback){

  this.endCallback.call(sprite);

  this.cellIndex = 0;

  }

  }

  }

  //特制飞机精灵表绘制器

  W.controllSpriteSheetPainter = function(cells , spritesheet){

  this.cells = cells || [];

  this.cellIndex = 0;

  this.dateCount = null;

  this.isActive = false;

  this.derection = true;

  this.spritesheet = spritesheet;

  }

  controllSpriteSheetPainter.prototype = {

  advance:function(){

  if(this.isActive){

  this.cellIndex++;

  if(this.cellIndex === this.cells.length){

  this.cellIndex = 0;

  this.isActive = false;

  }

  }

  },

  paint:function(sprite){

  if(this.dateCount===null){

  this.dateCount = new Date();

  }else {

  var newd = new Date();

  var tc = newd-this.dateCount;

  if(tc>sprite.firePerFrame){

  this.advance();

  this.dateCount = newd;

  }

  }

  var cell = this.cells[this.cellIndex];

  ctx.drawImage(this.spritesheet , cell.x , cell.y , cell.w , cell.h , -planWidth/2 , -planHeight/2 , cell.w , cell.h);

  }

  }

  W.planBehavior = [

  {execute:function(sprite,time){

  if(sprite.toTop){

  sprite.top = sprite.top

  }

  if(sprite.toLeft){

  sprite.left = sprite.left

  }

  if(sprite.toRight){

  sprite.left = sprite.left>canvas.width-planWidth/2? sprite.left : sprite.left+sprite.velocityX;

  }

  if(sprite.toBottom){

  sprite.top = sprite.top>canvas.height-planHeight/2? sprite.top : sprite.top+sprite.velocityY;

  }

  if(sprite.rotateLeft){

  sprite.rotateAngle -= sprite.rotateSpeed;

  }

  if(sprite.rotateRight){

  sprite.rotateAngle += sprite.rotateSpeed;

  }

  if(sprite.fire&&!sprite.painter.isActive){

  sprite.painter.isActive = true;

  this.shot(sprite);

  }

  },

  shot:function(sprite){

  this.addMissle(sprite , sprite.rotateAngle);

  var missleAngle = 0.1

  for(var i=1;i

  this.addMissle(sprite , sprite.rotateAngle-i*missleAngle);

  this.addMissle(sprite , sprite.rotateAngle+i*missleAngle);

  }

  var audio = document.getElementsByTagName("audio");

  for(var i=0;i

  console.log(audio[i].paused)

  if(audio[i].src.indexOf("shot")>=0&&audio[i].paused){

  audio[i].play();

  break;

  }

  }

  },

  addMissle:function(sprite , angle){

  for(var j=0;j

  if(!missles[j].visible){

  missles[j].left = sprite.left;

  missles[j].top = sprite.top;

  missles[j].rotateAngle = angle;

  var missleSpeed = 20;

  missles[j].velocityX = missleSpeed*Math.sin(-missles[j].rotateAngle);

  missles[j].velocityY = missleSpeed*Math.cos(-missles[j].rotateAngle);

  missles[j].visible = true;

  break;

  }

  }

  }

  }

  ]

  W.starBehavior = [

  {execute:function(sprite,time){

  if(sprite.top > canvas.height){

  sprite.left = Math.random()*canvas.width;

  sprite.top = Math.random()*canvas.height - canvas.height;

  }

  sprite.top += sprite.speed;

  }}

  ]

  W.starPainter = {

  paint:function(sprite){

  ctx.drawImage(sprite.cacheCanvas , sprite.left-sprite.width/2-sprite.lightLength , sprite.top-sprite.width/2-sprite.lightLength)

  },

  cache:function(sprite){

  sprite.cacheCtx.save();

  var opacity = 0.5,addopa = 1/sprite.lightLength;

  sprite.cacheCtx.fillStyle = "rgba(255,255,255,0.8)";

  sprite.cacheCtx.beginPath();

  sprite.cacheCtx.arc(sprite.width/2+sprite.lightLength , sprite.width/2+sprite.lightLength , sprite.width/2 , 0 , 2*Math.PI);

  sprite.cacheCtx.fill();

  for(var i=1;i<=sprite.lightLength;i+=2){

  opacity-=addopa;

  sprite.cacheCtx.fillStyle = "rgba(255,255,255,"+opacity+")";

  sprite.cacheCtx.beginPath();

  sprite.cacheCtx.arc(sprite.width/2+sprite.lightLength , sprite.width/2+sprite.lightLength , sprite.width/2+i , 0 , 2*Math.PI);

  sprite.cacheCtx.fill();

  }

  }

  }

  W.foodBehavior = [

  {execute:function(sprite,time){

  sprite.top += sprite.speed;

  if(sprite.top > canvas.height+sprite.width){

  sprite.visible = false;

  }

  }}

  ]

  W.foodPainter = {

  paint:function(sprite){

  ctx.fillStyle = "rgba("+parseInt(Math.random()*255)+","+parseInt(Math.random()*255)+","+parseInt(Math.random()*255)+",1)"

  ctx.font="15px 微软雅黑"

  ctx.textAlign = "center";

  ctx.textBaseline = "middle";

  ctx.fillText(sprite.kind , sprite.left , sprite.top);

  }

  }

  W.missleBehavior = [{

  execute:function(sprite,time){

  sprite.left -= sprite.velocityX;

  sprite.top -= sprite.velocityY;

  if(sprite.left<-missleWidth/2||sprite.top<-missleHeight/2||sprite.left>canvas.width+missleWidth/2||sprite.top<-missleHeight/2){

  sprite.visible = false;

  }

  }

  }];

  W.misslePainter = {

  paint:function(sprite){

  var img = new Image();

  img.src="../planGame/image/plasma.png"

  ctx.drawImage(img , -missleWidth/2+1 , -missleHeight/2+1 , missleWidth , missleHeight);

  }

  }

  W.badPlanBehavior = [{

  execute:function(sprite,time){

  if(sprite.top > canvas.height || !sprite.visible){

  var random = Math.random();

  if(point>=200&&point<400){

  sprite.fullBlood = 150;

  if(random<0.1){

  sprite.badKind = 2;

  sprite.fullBlood = 250;

  }

  }else if(point>=400&&point<600){

  sprite.fullBlood = 250;

  if(random<0.2){

  sprite.badKind = 2;

  sprite.fullBlood = 400;

  }

  if(random<0.1){

  sprite.badKind = 3;

  sprite.fullBlood = 600;

  }

  }else if(point>=600){

  sprite.fullBlood = 500;

  if(random<0.4){

  sprite.badKind = 2;

  sprite.fullBlood = 700;

  }

  if(random<0.2){

  sprite.badKind = 3;

  sprite.fullBlood = 1000;

  }

  }

  sprite.visible = true;

  sprite.blood = sprite.fullBlood;

  sprite.left = Math.random()*(canvas.width-2*planWidth)+planWidth;

  sprite.top = Math.random()*canvas.height - canvas.height;

  }

  sprite.top += sprite.speed;

  },

  shot:function(sprite){

  this.addMissle(sprite , sprite.rotateAngle);

  var missleAngle = 0.1

  for(var i=1;i

  this.addMissle(sprite , sprite.rotateAngle-i*missleAngle);

  this.addMissle(sprite , sprite.rotateAngle+i*missleAngle);

  }

  },

  addMissle:function(sprite , angle){

  for(var j=0;j

  if(!missles[j].visible){

  missles[j].left = sprite.left;

  missles[j].top = sprite.top;

  missles[j].rotateAngle = angle;

  var missleSpeed = 20;

  missles[j].velocityX = missleSpeed*Math.sin(-missles[j].rotateAngle);

  missles[j].velocityY = missleSpeed*Math.cos(-missles[j].rotateAngle);

  missles[j].visible = true;

  break;

  }

  }

  }

  }];

  W.badPlanPainter = {

  paint:function(sprite){

  var img = new Image();

  img.src="../planGame/image/ship.png"

  switch(sprite.badKind){

  case 1:ctx.drawImage(img , 96 , 0 , planWidth , planWidth , -planWidth/2 , -planHeight/2 , planWidth , planWidth);

  break;

  case 2:ctx.drawImage(img , 120 , 0 , planWidth , planWidth , -planWidth/2 , -planHeight/2 , planWidth , planWidth);

  break;

  case 3:ctx.drawImage(img , 144 , 0 , planWidth , planWidth , -planWidth/2 , -planHeight/2 , planWidth , planWidth);

  break;

  }

  ctx.strokeStyle = "#FFF";

  ctx.fillStyle = "#F00";

  var bloodHeight = 1;

  ctx.strokeRect(-planWidth/2-1 , planHeight+bloodHeight+3 , planWidth+2 , bloodHeight+2);

  ctx.fillRect(planWidth/2-planWidth*sprite.blood/sprite.fullBlood , planHeight+bloodHeight+3 , planWidth*sprite.blood/sprite.fullBlood , bloodHeight);

  }

  }

  W.planSize = function(){

  return {

  w:planWidth,

  h:planHeight

  }

  }

  })(window);

  这些绘制方法之类的都相对比较简单。

  主要说一下飞机的运动以及对象数量的控制,飞机怎么运动?毫无疑问,通过键盘控制它运动,可能很多人就会想到通过keydown这个方法按下的时候通过判断keyCode来让飞机持续运动。但是有个问题,keydown事件不支持多键按下,也就是说,当你按下X键时,keyCode是88,与此同时你按下方向键后,keyCode会瞬间变成37,也就是说,如果你单纯的想靠keydown来控制飞机运动,飞机就只能做一件事,要么只可以往某个方向移动,要么只会开枪。

  所以,我们要通过keydown和keyup来实现飞机的运动,原理很容易理解:当我们按下往左的方向键时,我们给飞机一个往左的状态,也就是让飞机的toLeft属性为true,而在动画循环中,判断飞机的状态,如果toLeft为true则飞机的x值不停地减少,飞机也就会不停地往左移动,然后当我们抬起手指时触发keyup事件,我们就再keyup事件中解除飞机往左的状态。飞机也就停止往左移动了。其他状态也一样的原理,这样写的话,就能够让飞机多种状态于一生了。可以同时开枪同时到处跑了。

  实现的代码如下:

  XML/HTML Code复制内容到剪贴板

  //keydown/keyup事件的绑定

  window.onkeydown = function(event){

  switch(event.keyCode){

  case 88:myplan.fire = true;

  break;

  case 90:myplan.rotateLeft=true;

  break;

  case 67:myplan.rotateRight=true;

  break;

  case 37:myplan.toLeft = true;

  break;

  case 38:myplan.toTop = true;

  break;

  case 39:myplan.toRight = true;

  break;

  case 40:myplan.toBottom = true;

  break;

  }

  }

  window.onkeyup = function(event){

  switch(event.keyCode){

  case 88:myplan.fire = false;

  break;

  case 90:myplan.rotateLeft=false;

  break;

  case 67:myplan.rotateRight=false;

  break;

  case 37:myplan.toLeft = false;

  break;

  case 38:myplan.toTop = false;

  break;

  case 39:myplan.toRight = false;

  break;

  case 40:myplan.toBottom = false;

  break;

  }

  }

  //飞机每一帧的状态更新处理代码

  execute:function(sprite,time){

  if(sprite.toTop){

  spritesprite.top = sprite.top

  }

  if(sprite.toLeft){

  spritesprite.left = sprite.left

  }

  if(sprite.toRight){

  spritesprite.left = sprite.left>canvas.width-planWidth/2? sprite.left : sprite.left+sprite.velocityX;

  }

  if(sprite.toBottom){

  spritesprite.top = sprite.top>canvas.height-planHeight/2? sprite.top : sprite.top+sprite.velocityY;

  }

  if(sprite.rotateLeft){

  sprite.rotateAngle -= sprite.rotateSpeed;

  }

  if(sprite.rotateRight){

  sprite.rotateAngle += sprite.rotateSpeed;

  }

  if(sprite.fire&&!sprite.painter.isActive){

  sprite.painter.isActive = true;

  this.shot(sprite);

  }

  就是如此简单。

  然后说下对象控制,打飞机游戏,会发射大量子弹,产生大量对象,包括爆炸啊,飞机啊,子弹等,如果不停地进行对象的生成和销毁,会让浏览器的负荷变得很大,运行了一段时间后就会卡出翔了。所以,我们要用可以循环利用的对象来解决这个问题,不进行对象的销毁,对所有对象进行保存,循环利用。

  我的做法就是,在游戏初始化的时候,直接生成一定数量的对象,存放在数组里面。当我们需要一个对象的时候,就从里面取,当用完后,再放回数组里面。数组里的所有对象都有一个属性,visible,代表对象当前是否可用。

  举个例子,当我的飞机发射一发炮弹,我需要一发炮弹,所以我就到炮弹数组里遍历,如果遍历到的炮弹visible为true,也就说明该对象正在使用着,不能拿来用,所以继续遍历,直到遍历到visible为false的炮弹对象,说明这个对象暂时没人用。然后就可以拿过来重新设置属性,投入使用了。当炮弹击中敌人或者打出画布外的时候,把炮弹的visible设成false,又成了一个没人用的炮弹在数组里存放起来等待下一次调用。

  所以,我们要预算算好页面大概要用到多少个对象,然后就预先准备好对象,这样,在游戏进行中,不会有对象进行生成和销毁,对游戏性能方面就有了提升了。

  最后再说下音频,游戏里面要用到多个同样的audio才能保证音效的不间断性:

  复制代码

  XML/HTML Code复制内容到剪贴板

  var audio = document.getElementsByTagName("audio");

  for(var i=0;i

  console.log(audio[i].paused)

  if(audio[i].src.indexOf("boom")>=0&&audio[i].paused){

  audio[i].play();

  break;

  }

  }

  好吧,基本上就这样了。技术或许还不够好,纯碎做个记录,如果代码有不当正处,欢迎指出,共同学习。