之前在當耐特的DEMO裡看到個打飛機的游戲,然後就把他的圖片和音頻扒了了下來。。。。自己憑著玩的心情重新寫了一個。僅供娛樂哈。。。。。。我沒有用框架,所有js都是自己寫的。。。。。。所以就可以來當個簡單的教程,對那些剛玩canvas的,或許能有些幫助,樓主玩canvas也不是很久,技術不是很好,請見諒哈。
閒話不多說,先上DEMO撒:飛機游戲 樓主寫這個人純碎娛樂,沒想著寫成多正式的游戲哈。
步入主題啦:打飛機游戲文件有index.html入口文件,allSprite.js精靈的邏輯處理文件,loading.js加載處理文件以及data.js(初始化的一些數據)。
首先,正常的游戲基本上都需要一個loading,loading頁面就是用來預加載數據的,包括精靈表圖片,音頻等,因為這是個小游戲,要加載的就只有一些音頻和圖片。裡面的加載代碼主要就下面這些,其他是制作loading動畫的,那個比較簡單,就不貼了,如果有興趣的直接在DEMO裡看控制台就行了:
XML/HTML Code復制內容到剪貼板
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);
}
})
}
}
},
//再貼出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裡面用一個數組保存文件的鏈接,然後判斷這些鏈接是圖片還是音頻,如果是圖片就用preLoadImg加載,預加載圖片的代碼很簡單,就是new一個圖片對象,然後把鏈接賦給它,加載完後再回調。音頻的加載則是通過生成一個HTML5的audio dom對象,把鏈接賦給它,audio有一個事件“canplaythrough”,浏覽器預計能夠在不停下來進行緩沖的情況下持續播放指定的音頻/視頻時,會發生 canplaythrough 事件,也就是說當canplaythrough被調用時,音頻就已經被加載的差不多了,可以進行下一個音頻的加載了。就這樣當把所有東西都加載完後,再進行回調,開始游戲。
游戲開始了,一個游戲,會需要很多的對象,所以我就統一寫成了一個精靈對象,不同對象之間的每一幀的運動情況直接用behavior來分別編寫就行了。
XML/HTML Code復制內容到剪貼板
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);
}
}
}
}
寫出精靈類後,就可以通過編寫每個的painter以及behavior來生成不同的對象了。接下來就是寫painter了,painter分成兩種,一種是普通的painter,一種就是精靈表painter,因為像爆炸動畫,飛機開槍動畫,都不是一張圖片就能搞定的,所以就需要用到精靈表了:
而繪制這些就要為他們定制一個精靈表繪制器,下面這個是最簡單的精靈表繪制器,針對游戲的復雜性可以相對的修改精靈表寫法,直到合適,不過原理都大同小異,就是小修小改而已:
XML/HTML Code復制內容到剪貼板
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);
}
}
而普通的繪制器就更簡單了,直接寫一個painter,把要畫的什麼東西都寫進去就行了。
有了精靈類和精靈表繪制器後,我們就可以把星星,飛機,子彈,爆炸對象都寫出來了:下面是整個allSprite.js的代碼:
JavaScript Code復制內容到剪貼板
(function(W){
"use strict"
var planWidth = 24,
planHeight = 24,
missleWidth = 70,
missleHeight = 70,
boomWidth = 60;
//精靈類
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);
}
}
}
}
// 精靈表繪制器
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;
}
}
}
//特制飛機精靈表繪制器
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 微軟雅黑"
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);
這些繪制方法之類的都相對比較簡單。
主要說一下飛機的運動以及對象數量的控制,飛機怎麼運動?毫無疑問,通過鍵盤控制它運動,可能很多人就會想到通過keydown這個方法按下的時候通過判斷keyCode來讓飛機持續運動。但是有個問題,keydown事件不支持多鍵按下,也就是說,當你按下X鍵時,keyCode是88,與此同時你按下方向鍵後,keyCode會瞬間變成37,也就是說,如果你單純的想靠keydown來控制飛機運動,飛機就只能做一件事,要麼只可以往某個方向移動,要麼只會開槍。
所以,我們要通過keydown和keyup來實現飛機的運動,原理很容易理解:當我們按下往左的方向鍵時,我們給飛機一個往左的狀態,也就是讓飛機的toLeft屬性為true,而在動畫循環中,判斷飛機的狀態,如果toLeft為true則飛機的x值不停地減少,飛機也就會不停地往左移動,然後當我們抬起手指時觸發keyup事件,我們就再keyup事件中解除飛機往左的狀態。飛機也就停止往左移動了。其他狀態也一樣的原理,這樣寫的話,就能夠讓飛機多種狀態於一生了。可以同時開槍同時到處跑了。
實現的代碼如下:
XML/HTML Code復制內容到剪貼板
//keydown/keyup事件的綁定
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;
}
}
//飛機每一幀的狀態更新處理代碼
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);
}
就是如此簡單。
然後說下對象控制,打飛機游戲,會發射大量子彈,產生大量對象,包括爆炸啊,飛機啊,子彈等,如果不停地進行對象的生成和銷毀,會讓浏覽器的負荷變得很大,運行了一段時間後就會卡出翔了。所以,我們要用可以循環利用的對象來解決這個問題,不進行對象的銷毀,對所有對象進行保存,循環利用。
我的做法就是,在游戲初始化的時候,直接生成一定數量的對象,存放在數組裡面。當我們需要一個對象的時候,就從裡面取,當用完後,再放回數組裡面。數組裡的所有對象都有一個屬性,visible,代表對象當前是否可用。
舉個例子,當我的飛機發射一發炮彈,我需要一發炮彈,所以我就到炮彈數組裡遍歷,如果遍歷到的炮彈visible為true,也就說明該對象正在使用著,不能拿來用,所以繼續遍歷,直到遍歷到visible為false的炮彈對象,說明這個對象暫時沒人用。然後就可以拿過來重新設置屬性,投入使用了。當炮彈擊中敵人或者打出畫布外的時候,把炮彈的visible設成false,又成了一個沒人用的炮彈在數組裡存放起來等待下一次調用。
所以,我們要預算算好頁面大概要用到多少個對象,然後就預先准備好對象,這樣,在游戲進行中,不會有對象進行生成和銷毀,對游戲性能方面就有了提升了。
最後再說下音頻,游戲裡面要用到多個同樣的audio才能保證音效的不間斷性:
復制代碼
XML/HTML Code復制內容到剪貼板
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,基本上就這樣了。技術或許還不夠好,純碎做個記錄,如果代碼有不當正處,歡迎指出,共同學習。