javascript - HTML Canvas 枪功能
问题描述
我需要帮助完成按“空格”后发射子弹的功能。
我尝试使用这些
- var b = 新子弹();
- var 子弹 = []
- 子弹.push(b)
然后是这样的for循环:
- for (var i = 0; i < 6; i++) {
但我无法让它工作。基本上是一个函数,每次制作子弹时,它都会存储在一个数组中,然后空间循环通过数组在空格键上制作新的子弹。
小提琴:https ://jsfiddle.net/tmanrocks999/7mLpo8uj/652/
代码:
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
border:4px solid #d3d3d3;
background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
var myGamePiece;
var endGoalPiece;
var myEnemy1;
var bullet;
var myEnemy1Hp = 10;
var damage = 1;
var playerExp = 0;
function startGame() {
myGameArea.start();
myGamePiece = new component(30, 30, "red", 0, 240);
endGoalPiece = new component(30, 30, "black", 450, 240);
myEnemy1 = new component(30, 30, "green", 200, 240);
}
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
myGameArea.key = e.keyCode;
})
window.addEventListener('keyup', function (e) {
myGameArea.key = false;
})
},
clear : function(){
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y) {
this.gamearea = myGameArea;
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY = 0;
//this.gravity = 0.05;
//this.gravitySpeed = 0;
this.x = x;
this.y = y;
this.color = color;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = this.color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function() {
this.gravitySpeed += this.gravity;
this.x += this.speedX;
this.y += this.speedY; //+ this.gravitySpeed;
}
}
}
function jump() {
myGamePiece.gravitySpeed=-1;
}
}
function shootGun(){
bullet = new component(11, 5, "blue", myGamePiece.x+27 , myGamePiece.y+13 );
bullet.newPos();
bullet.speedX=1;
}
function updateGameArea() {
myGameArea.clear();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
if (myGameArea.key && myGameArea.key == 37) {myGamePiece.speedX = -1; }//left
if (myGameArea.key && myGameArea.key == 39) {myGamePiece.speedX = 1; }//right
if (myGameArea.key && myGameArea.key == 38) {myGamePiece.gravitySpeed = -1; }//jump
if (myGameArea.key && myGameArea.key == 32) {shootGun()}//shoot gun
//if (myGameArea.key && myGameArea.key == 40) {myGamePiece.speedY = 1; }// down
myEnemy1.update();
endGoalPiece.update();
myGamePiece.newPos();
myGamePiece.update();
bullet.newPos();
bullet.update();
}
</script>
<p>use the arrow keys on you keyboard to move the red square.</p>
<span id="myEnemy1Hp">10</span> <br>
<span id="playerExp">0<span><br> / <span id = "playerMaxExp">100</span>
</body>
</html>
我希望在空格键上通过循环遍历数组来继续创建子弹,但是在按下空格键后,每次按下空格键时只会生成 1 个项目符号并且位置会重置(我知道为什么这是我不需要解释)。
我怎样才能得到射手的错觉。
解决方案
看看这段代码:
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>STACKOVERFLOW</title>
<style>
canvas {
border: 4px solid #d3d3d3;
background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<p>use the arrow keys on you keyboard to move the red square.</p>
<span id="myEnemy1Hp">10</span> <br>
<span id="playerExp">0<span><br> / <span id = "playerMaxExp">100</span>
<script>
var myGamePiece;
var endGoalPiece;
var myEnemy1;
var bullets = [];
var myEnemy1Hp = 10;
var damage = 1;
var playerExp = 0;
function startGame() {
myGameArea.start();
myGamePiece = new component(30, 30, "red", 0, 240);
endGoalPiece = new component(30, 30, "black", 450, 240);
myEnemy1 = new component(30, 30, "green", 200, 240);
}
var myGameArea = {
canvas: document.createElement("canvas"),
start: function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function(e) {
myGameArea.key = e.keyCode;
})
window.addEventListener('keyup', function(e) {
myGameArea.key = false;
})
},
clear: function() {
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y) {
this.gamearea = myGameArea;
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY = 0;
//this.gravity = 0.05;
//this.gravitySpeed = 0;
this.x = x;
this.y = y;
this.color = color;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = this.color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function() {
this.gravitySpeed += this.gravity;
this.x += this.speedX;
this.y += this.speedY; //+ this.gravitySpeed;
}
}
function jump() {
myGamePiece.gravitySpeed = -1;
}
function shootGun() {
let bullet = new component(11, 5, "blue", myGamePiece.x + 27, myGamePiece.y + 13);
bullet.newPos();
bullet.speedX = 1;
bullets.push( bullet );
}
function updateGameArea() {
myGameArea.clear();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
if (myGameArea.key && myGameArea.key == 37) {
myGamePiece.speedX = -1;
} //left
if (myGameArea.key && myGameArea.key == 39) {
myGamePiece.speedX = 1;
} //right
if (myGameArea.key && myGameArea.key == 38) {
myGamePiece.gravitySpeed = -1;
} //jump
if (myGameArea.key && myGameArea.key == 32) {
shootGun()
} //shoot gun
//if (myGameArea.key && myGameArea.key == 40) {myGamePiece.speedY = 1; }// down
myEnemy1.update();
endGoalPiece.update();
myGamePiece.newPos();
myGamePiece.update();
bullets.forEach( (bullet)=> {
bullet.newPos()
bullet.update();
});
// bullet.newPos();
// bullet.update();
}
</script>
</body>
</html>
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