我如何射击子弹360*使用键盘，而旋转在画布中的对象?

Question

我想让我的对象在旋转或移动时朝着我的对象所面对的方向拍摄，有什么想法吗?

我是一个初学者，我开始了几天前，所以它是相当困难的我找到代码和学习他们以及我找不到一个好老师或网站。这是代码，我尝试了一些东西，但我很确定这是一个完全失败的…

var myGamePiece;
function startGame() {
bullet = new component(5, 5, 'blue', 300, 300);
myGamePiece = new component(30, 30, "red", 225, 225);
myGameArea.start();
}
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 1400;
this.canvas.height = 750;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.frameNo = 0;
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
e.preventDefault();
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
},
stop : function() {
clearInterval(this.interval);
},    
clear : function() {
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y, type) {
this.type = type;
this.width = width;
this.height = height;
this.speedx = 0;
this.speedy = 0;
this.angle = 0;
this.moveAngle = 0;
this.x = x;
this.y = y;  
this.s = x;
this.u = y;  
this.update = function() {
ctx = myGameArea.context;
ctx.save();
ctx.translate(this.x, this.y);
ctx.rotate(this.angle);
ctx.fillStyle = color;
ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height);
ctx.restore();    
}
this.newPos = function() {
this.angle += this.moveAngle * Math.PI / 180;
this.x += this.speedx;
this.y += this.speedy;
this.s += this.speed * Math.sin(this.angle);
this.u -= this.speed * Math.cos(this.angle);
}
}
function updateGameArea() {
myGameArea.clear();
myGamePiece.moveAngle = 0;
myGamePiece.speedx = 0;
myGamePiece.speedy = 0;
bullet.speed = 0;
if (myGameArea.keys && myGameArea.keys[90]) {myGamePiece.moveAngle = -3; }
if (myGameArea.keys && myGameArea.keys[88]) {myGamePiece.moveAngle = 3; }
if (myGameArea.keys && myGameArea.keys[38]) {myGamePiece.speedy= -2; }
if (myGameArea.keys && myGameArea.keys[40]) {myGamePiece.speedy= 2; }
if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.speedx= 2; }
if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.speedx= -2; }
if (myGameArea.keys && myGameArea.keys[32]) {bullet.speed= -3; }
bullet.newPos();  
bullet.update();
myGamePiece.newPos();
myGamePiece.update();
}

Answer 1

window.onload = function() {
var myGamePiece;
var bullet;
var myGameArea;
var ctx;
function startGame() {
bullet = new component(5, 5, 'blue', 300, 300);
myGamePiece = new component(30, 30, "red", 225, 225);
myGameArea.start();
}
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 1400;
this.canvas.height = 750;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.frameNo = 0;
bullet.speed = 0;
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
e.preventDefault();
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
},
stop : function() {
clearInterval(this.interval);
},    
clear : function() {
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y, type) {
this.type = type;
this.width = width;
this.height = height;
this.angle = 0;
this.moveAngle = 0;
this.x = x;
this.y = y;  
this.speed = 0;
this.speedx = 0;
this.speedy = 0;
this.update = function() {
ctx = myGameArea.context;
ctx.save();
ctx.translate(this.x, this.y);
ctx.rotate(this.angle);
ctx.fillStyle = color;
ctx.fillRect(this.width / -2, this.height / -2, this.width, this.height);
ctx.restore();    
}
this.newPos = function() {
this.angle += this.moveAngle * Math.PI / 180;
this.x += this.speedx;
this.y += this.speedy;
this.x += this.speed * Math.cos(this.angle);
this.y += this.speed * Math.sin(this.angle);
}
}
function updateGameArea() {
myGameArea.clear();
myGamePiece.moveAngle = 0;
myGamePiece.speedx = 0;
myGamePiece.speedy = 0;

if (myGameArea.keys && myGameArea.keys[90]) {myGamePiece.moveAngle = -3; }
if (myGameArea.keys && myGameArea.keys[88]) {myGamePiece.moveAngle = 3; }
if (myGameArea.keys && myGameArea.keys[38]) {myGamePiece.speedy= -2; }
if (myGameArea.keys && myGameArea.keys[40]) {myGamePiece.speedy= 2; }
if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.speedx= 2; }
if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.speedx= -2; }
if (myGameArea.keys && myGameArea.keys[32]) {
bullet.angle = myGamePiece.angle;
bullet.x = myGamePiece.x;
bullet.y = myGamePiece.y;
bullet.speed= 3; 
}
bullet.newPos();  
bullet.update();
myGamePiece.newPos();
myGamePiece.update();
}

startGame();
}

你几乎让它工作，最大的问题是子弹。速度= 0;在游戏循环中让它永远不会移动。

你也在更新这个。S和这个。但它从未在其他地方使用过，所以我修复了这部分。

this.s += this.speed * Math.sin(this.angle);
this.u -= this.speed * Math.cos(this.angle);

我还添加了一些额外的代码，所以它从红色立方体的位置触发。

最好将你的代码与我的更改进行比较，看看还有哪些更改，但我认为我已经突出了主要的一点。