这篇文章主要介绍“如何利用HTML5 Canvas制作一个简单的打飞机游戏”,在日常操作中,相信很多人在如何利用HTML5 Canvas制作一个简单的打飞机游戏问题上存在疑惑,小编查阅了各式资料,整理出简单好用的操作方法,希望对大家解答”如何利用HTML5 Canvas制作一个简单的打飞机游戏”的疑惑有所帮助!接下来,请跟着小编一起来学习吧!
步入主题: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:
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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。
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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.length;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:
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:
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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:
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(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.length;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<this.cells.length || this.isloop){
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<planHeight/2? sprite.top : sprite.top-sprite.velocityY;
}
if(sprite.toLeft){
sprite.left = sprite.left<planWidth/2? sprite.left : sprite.left-sprite.velocityX;
}
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<sprite.fireLevel;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<audio.length;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<missles.length;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<sprite.fireLevel;i++){
this.addMissle(sprite , sprite.rotateAngle-i*missleAngle);
this.addMissle(sprite , sprite.rotateAngle+i*missleAngle);
}
},
addMissle:function(sprite , angle){
for(var j=0;j<missles.length;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:
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//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<planHeight/2? sprite.top : sprite.top-sprite.velocityY;
}
if(sprite.toLeft){
spritesprite.left = sprite.left<planWidth/2? sprite.left : sprite.left-sprite.velocityX;
}
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:
XML/HTML Code复制内容到剪贴板
var audio = document.getElementsByTagName("audio");
for(var i=0;i<audio.length;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。
源码地址:https://github.com/whxaxes/canvas-test/tree/gh-pages/src/Game-demo/planGame
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