一、總結關鍵點和遇到的問題
1.javascript中的繼承，最好父類只提供方法共享，屬性寫到各自子類中，避免父類和子類的構造函數混雜。
2.prototype模擬繼承的代碼，應寫在所有方法定義之前，否則原型對像被改變，方法就變成了未定義，如：
複製代碼代碼如下:
Hero.prototype = new Tank (0, 0, 0);
Hero.prototype.constructor = Hero;
Hero.prototype.addLife = function(){
this.lifetimes++;
document.querySelector("#life").innerHTML = hero.lifetimes;
}
3.canvas畫圖形時，除了畫矩形，其他的都要加上ctx.beginPath();、ctx.closePath();，否則會出現意想不到的錯誤。
4.concat函數可以合併數組，或者是元素返回一個新的數組
5.Image的src屬性賦值後就會加載圖片，但如果沒有加載完畢就畫圖片，會導致失效，所以使用onload事件處理
6.擴展Array功能，刪除指定元素
複製代碼代碼如下:
//擴展刪除指定元素
Array.prototype.deleteElement = function (obj) {
if (obj) {
for (var i = 0; i < this.length; i++) {
if (this[i] === obj) {
this.splice (i, 1);
}
}
}
}
7.定時器設置，setInterval（“fun”,1000）方法的第一個參數，可以是字符串，如"hero.say()",類似eval會去執行這串代碼，所以它可以給函數帶上參數，並且也指定了這個函數的運行上下文。但如果傳入是函數的句柄，則不能帶參數，並且不能指定上下文，除了第一種方式解決外，我用了閉包來解決這個問題
複製代碼代碼如下:
//定時器，自行運動
this.timer = setInterval ((function (context) {
return function () {
Bullet.prototype.move.call (context)
}
}) (this), 30);
我保存了當前的執行環境，並調用call方法手動執行。
8.方法的功能設計，除了功能外，應該包括執行此功能的條件檢測，如move，就應該包括什麼情況下可以移動，移動到什麼地方就不能移動了。此檢測不應該放在外部。
9.寫代碼時不應該去想設計或者優化的問題，先實現功能，再談優化，或者先設計再實現。思路要清晰，別混亂，著重於一點。
10.javascript中沒有sleep的功能，可以創建一個變量作為緩衝，來達到間隔執行的目的
二、代碼實現
1.本程序分為Bomb.js,Bullet.js,Draw.js,Tank.js,index.html,img,music,
2.最終效果
3.代碼
1.index.html
複製代碼代碼如下:
<!DOCTYPE html>
<html>
<head>
<title></title>
<meta charset="utf-8">
<style type="text/css">
body {
font: 14px "sans-serif"
}
#Map {
background-color: #000000;
}
.show {
float: left
}
#guide {
float: left;
width: 200px;
height: 390px;
margin-left: 5px;
background: #CCCCCC;
padding: 5px;
}
</style>
<script type="text/javascript" src="Tank.js"></script>
<script type="text/javascript" src="Bullet.js"></script>
<script type="text/javascript" src="Bomb.js"></script>
<script type="text/javascript" src="Draw.js"></script>
<script type="text/javascript">
window.onload = function () {
//畫布信息
width = document.getElementById ('Map').width;
height = document.getElementById ('Map').height;
ctx = document.getElementById ('Map').getContext ('2d');
//初始頁面
var starImg = new Image ();
starImg.src = "img/star.jpg";
starImg.onload = function () {
ctx.drawImage (starImg, 0, 0, width, height);
}
//鍵盤監聽回車開始遊戲
document.body.onkeydown = function () {
var keycode = event.keyCode;
switch (keycode) {
case 13:
//初始化參數
init ()
//刷新頁面
setInterval (draw, 30);
document.body.onkeydown = gameControl;
break;
}
}
}
function init () {
//玩家和電腦
hero = new Hero (100, 300, 0);
enemys = [];
for (var i = 0; i < 3; i++) {
enemys.push (new Enemy (100 + i * 50, 0, 2));
}
//合併數組
allTank = enemys.concat (hero);
//炸彈
Bombs = [];
im = new Image ();
im2 = new Image ();
im3 = new Image ();
im.src = "img/bomb_3.gif";
im2.src = "img/bomb_2.gif";
im3.src = "img/bomb_1.gif";
}
function gameControl () {
var keycode = event.keyCode;
switch (keycode) {
case 65:
hero.moveLeft ();
break;//左
case 83:
hero.moveDown ();
break;//下
case 87:
hero.moveUp ();
break;//上
case 68:
hero.moveRight ();
break;//右
case 74:
hero.shot ();
break;
case 49:
hero.addLife ()
break;
}
}
//擴展刪除指定元素
Array.prototype.deleteElement = function (obj) {
if (obj) {
for (var i = 0; i < this.length; i++) {
if (this[i] === obj) {
this.splice (i, 1);
}
}
}
}
</script>
</head>
<body>
<div>
<canvas id="Map">
</canvas>
<audio id="music" autoplay="autoplay">
<source src="music/111.wav">
</audio>
</div>
<div id="guide">
<p>按下回車鍵開始遊戲</p>
<p>按下1鍵增加生命,默認是1</p>
<p>剩餘生命數:<label id="life">1</label></p>
<div id="data">
</div>
</div>
</body>
</html>
2.Draw.js
複製代碼代碼如下:
/**
* Created by Alane on 14-3-18.
*/
function draw(){
//檢測子彈和坦克生死
checkDead();
//清空畫布
ctx.clearRect(0,0,500,400);
//畫玩家
if(!hero.isdead){
drawTank(hero);
}else{
hero.cutLife();
}
//畫敵人坦克
for (var i = 0; i < enemys.length; i++) {
drawTank(enemys[i]);
}
//畫敵人子彈
for(var j=0;j<enemys.length;j++){
var temp = enemys[j].bulletsList;
for (var i = 0; i < temp.length; i++) {
drawBullet(temp[i]);
}
}
//畫玩家子彈
var temp = hero.bulletsList;
for (var i = 0; i < temp.length; i++) {
drawBullet(temp[i]);
}
//畫炸彈
for(var i=0;i<Bombs.length;i++){
drawBown(Bombs[i]);
}
}
function drawTank(tank){
var x = tank.x;
var y = tank.y;
ctx.fillStyle = tank.color;
if(tank.direct == 0 || tank.direct ==2){
ctx.fillRect(x, y, 5,30);
ctx.fillRect(x+15, y, 5,30);
ctx.fillRect(x+6, y+8, 8,15);
ctx.strokeStyle = tank.color;
ctx.lineWidth = '1.5';
if(tank.direct == 0){
ctx.beginPath();
ctx.moveTo(x+10,y-2);
ctx.lineTo(x+10,y+8);
ctx.closePath();
}else{
ctx.beginPath();
ctx.moveTo(x+10,y+24);
ctx.lineTo(x+10,y+32);
ctx.closePath();
}
ctx.stroke();
}else{
ctx.fillRect(x, y, 30,5);
ctx.fillRect(x, y+15, 30,5);
ctx.fillRect(x+8, y+6, 15,8);
ctx.strokeStyle = '#FF0000';
ctx.lineWidth = '1.5';
if(tank.direct == 3){
ctx.beginPath();
ctx.moveTo(x-2,y+10);
ctx.lineTo(x+8,y+10);
ctx.closePath();
}else{
ctx.beginPath();
ctx.moveTo(x+24,y+10);
ctx.lineTo(x+32,y+10);
ctx.closePath();
}
ctx.stroke();
}
}
function drawBullet(bullet){
ctx.fillStyle = bullet.color;
ctx.beginPath();
ctx.arc(bullet.x,bullet.y,2,360,true);
ctx.closePath();
ctx.fill();
}
function drawBown (obj){
if(obj.life>8){
ctx.drawImage(im,obj.x,obj.y,50,50);
}else if(obj.life>4){
ctx.drawImage(im2,obj.x,obj.y,50,50);
}else{
ctx.drawImage(im3,obj.x,obj.y,50,50);
}
obj.lifeDown();
if(obj.life<=0){
Bombs.deleteElement(obj);
}
}
function checkDead(){
//檢測敵人子彈生死
for(var j=0;j<enemys.length;j++){
var temp = enemys[j].bulletsList;
for (var i = 0; i < temp.length; i++) {
var o = temp[i];
if(o.isdead){
temp.deleteElement(o);
}
}
}
//檢測玩家子彈生死
var temp = hero.bulletsList;
for (var i = 0; i < temp.length; i++) {
var o = temp[i];
if(o.isdead){
temp.deleteElement(o);
}
}
//檢測敵人坦克生死
for (var i = 0; i < enemys.length; i++) {
var o = enemys[i];
if(o.isdead){
enemys.deleteElement(o);
}
}
}
Bomb.js
複製代碼代碼如下:
/**
* Created by Alane on 14-3-18.
*/
function Bomb(x,y){
this.life = 12;
this.x = x;
this.y = y;
}
Bomb.prototype.lifeDown = function(){
this.life--;
}
Tank.js
複製代碼代碼如下:
/**
* Created by Alane on 14-3-7.
*/
/**
* direct 0 上
* 1 右
* 2 下
* 3 左
* @param x
* @param y
* @param direct
* @constructor
*/
//************************************************ ******************************************/
//坦克父類
function Tank (x, y, direct) {
this.speed = 2;
}
Tank.prototype.moveUp = function () {
//邊界檢測
if (this.y < 0) {
//換方向
this.changeDirect ();
return;
}
this.y -= this.speed;
this.direct = 0;
}
Tank.prototype.moveDown = function () {
if (this.y > height - 30) {
this.changeDirect ();
return;
}
this.y += this.speed;
this.direct = 2;
}
Tank.prototype.moveLeft = function () {
if (this.x < 0) {
this.changeDirect ();
return;
}
this.x -= this.speed;
this.direct = 3;
}
Tank.prototype.moveRight = function () {
if (this.x > width - 30) {
this.changeDirect ();
return;
}
this.x += this.speed;
this.direct = 1;
}
//變換方向
Tank.prototype.changeDirect = function () {
while (true) {
var temp = Math.round (Math.random () * 3);
if (this.direct != temp) {
this.direct = temp;
break;
}
}
//alert("x="+this.x+" y="+this.y+" direct="+this.direct)
}
//射擊子彈
Tank.prototype.shot = function () {
if(this.isdead){
return;
}
if (this.bulletsList.length < this.maxBulletSize) {
//新建子彈
var bullet = null;
switch (this.direct) {
case 0:
bullet = new Bullet (this.x + 10, this.y - 2, 0, this.color);
break;
case 1:
bullet = new Bullet (this.x + 32, this.y + 10, 1, this.color);
break;
case 2:
bullet = new Bullet (this.x + 10, this.y + 32, 2, this.color);
break;
case 3:
bullet = new Bullet (this.x - 2, this.y + 10, 3, this.color);
break;
}
//放入彈夾
this.bulletsList.push (bullet);
}
}
//************************************************ ******************************************/
//玩家
function Hero (x, y, direct) {
this.lifetimes = 5;
this.isdead = false;
this.color = '#FF0000';
this.x = x;
this.y = y;
this.direct = direct;
this.bulletsList = [];
this.maxBulletSize = 10;
this.newlife = null;
}
Hero.prototype = new Tank (0, 0, 0);
Hero.prototype.constructor = Hero;
Hero.prototype.addLife = function(){
this.lifetimes++;
document.querySelector("#life").innerHTML = hero.lifetimes;
}
Hero.prototype.cutLife = function(){
if(this.lifetimes>=1 && !this.newlife){
this.lifetimes--;
this.newlife = setTimeout("hero.newLife()",2000);
}
}
Hero.prototype.newLife = function(){
this.isdead = false;
clearTimeout(hero.newlife);
hero.newlife = null;
document.querySelector("#life").innerHTML = hero.lifetimes;
}
//************************************************ ******************************************/
//敵人坦克
function Enemy (x, y, direct) {
this.isdead = false;
this.color = 'blue';
this.x = x;
this.y = y;
this.direct = direct;
this.bulletsList = [];
this.maxBulletSize = 1;
//定時器,自動移動
this.timer1 = setInterval ((function (context) {
return function () {
//移動
Enemy.prototype.move.call (context);
}
}) (this), 30);
//定時器,射擊
this.timer2 = setInterval ((function (context) {
return function () {
//射擊
Tank.prototype.shot.call (context);
}
}) (this), 2000);
//定時器,變換方向
this.timer3 = setInterval ((function (context) {
return function () {
//射擊
Tank.prototype.changeDirect.call (context);
}
}) (this), 3000);
}
Enemy.prototype = new Tank (0, 0, 0);
Enemy.prototype.constructor = Enemy;
Enemy.prototype.move = function () {
switch (this.direct) {
case 0:
this.moveUp ();
break;
case 1:
this.moveRight ();
break;
case 2:
this.moveDown ();
break;
case 3:
this.moveLeft ();
break;
}
}
Bullet.js
複製代碼代碼如下:
/**
* Created by Alane on 14-3-11.
*/
function Bullet (x, y, direct, color) {
this.isdead = false;
this.x = x;
this.y = y;
this.direct = direct;
this.speed = 4;
this.color = color;
//定時器，自行運動
this.timer = setInterval ((function (context) {
return function () {
Bullet.prototype.move.call (context)
}
}) (this), 30);
}
Bullet.prototype.move = function () {
switch (this.direct) {
case 0:
this.y -= this.speed;
break;
case 1:
this.x += this.speed;
break;
case 2:
this.y += this.speed;
break;
case 3:
this.x -= this.speed;
break;
}
//邊界檢測
if (this.y < 0 || this.x > width || this.y > height || this.x < 0) {
clearInterval (this.timer);
this.isdead = true;
}
//碰撞檢測檢測敵人坦克
for(var i=0;i<allTank.length;i++){
var temp = allTank[i];
if(temp.isdead){
continue;
}
switch (temp.direct){
case 0:
case 2:if(this.x>temp.x && this.x<temp.x+20 && this.y>temp.y&& this.y<temp.y+30){
if(this.color == temp.color){
break;
}
Bombs.push(new Bomb(temp.x-10,temp.y-10));
clearInterval (this.timer);
this.isdead = true;
temp.isdead = true;
}break
case 1:
case 3:if(this.x>temp.x && this.x<temp.x+30 && this.y>temp.y&& this.y<temp.y+20){
if(this.color == temp.color){
break;
}
Bombs.push(new Bomb(temp.x-10,temp.y-10));
clearInterval (this.timer);
this.isdead = true;
temp.isdead = true;
}break;
}
}
}
源碼下載