我正在创建一个JS乒乓球比赛，但是乒乓球比赛中的球在几秒后开始滞后。我试图停止动画帧，优化我的代码以获得更好的性能并重写球的代码，但没有工作。有人能帮帮我吗？
HTML（无CSS）
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Pong</title>
</head>
<body>
<canvas id="canvas" width="800" height="400" style="background: #000"></canvas>
</body>
</html>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>
<script src="main.JS"></script>
Javascript（使用jQuery）
/*
Created : 7 / 18 / 2016
*/
//Bottom comment is used to define JQuery
/*jslint browser: true*/
/*global $, jQuery, alert*/
//Define variables
var canvas, ctx;
var ballX, ballY; //Balls x and y pos
var ballSpeedX, ballSpeedY; //Speed of ball x and y pos
var paddleY, paddleHeight, paddleWidth, aiY; //PaddleY = paddle's y pos and paddleHeight = Centering mouse on paddle
//Score variables
var aiScore, playerScore;
//Set functions
//Gets mouse pos
function getMousePos(e) {
"use strict";
//Define variables
var rect, root, mouseX, mouseY;
rect = canvas.getBoundingClientRect(); //Get canvas outline
root = document.documentElement; //Get html document
mouseX = e.clientX - rect.left - root.scrollLeft;
mouseY = e.clientY - rect.top - root.scrollTop;
//Return x and y pos to page
return {
x: mouseX,
y: mouseY
};
}
//Move ai function
function moveAI() {
"use strict";
var aiYCenter = aiY + paddleHeight / 2;
if (aiYCenter < ballY - 35) {
aiY += 6;
} else if (aiYCenter > ballY + 35) {
aiY -= 6;
}
}
//Animate objects
function animate() {
"use strict";
//Animate ball
ballX += ballSpeedX;
ballY += ballSpeedY;
//Make ai move
moveAI();
return false;
}
function resetBall() {
"use strict";
ballX = canvas.width / 2;
ballY = canvas.height / 2;
//Flip ball
ballSpeedX = -ballSpeedX;
return false;
}
//Detect collisiom
function collision() {
"use strict";
//Right wall
if (ballX > canvas.width) {
//If player paddle hits ball
if (ballY > aiY && ballY < aiY + paddleHeight) {
ballSpeedX = -ballSpeedX;
} else {
//If player paddle doesn't hit ball
resetBall(); //Reset ball function
playerScore += 1; //If ai scores add 1 point to ai's score
}
}
//Left wall
if (ballX < 0) {
//If player paddle hits ball
if (ballY > paddleY && ballY < paddleY + paddleHeight) {
ballSpeedX = -ballSpeedX;
} else {
//If player paddle doesn't hit ball
resetBall(); //Reset ball function
aiScore += 1; //If ai scores add 1 point to ai's score
}
}
if (ballY > canvas.height) { //If ballY does outside of 800px
ballSpeedY = -ballSpeedY;
}
if (ballY <= 0) { //If ballY goes outside of 0px
ballSpeedY = -ballSpeedY;
}
return false;
}
//Make paddle move
function movePaddle(e) {
"use strict";
var pos = getMousePos(e);
paddleY = pos.y - paddleHeight / 2; //Set paddleY to y pos of function and center user's mouse on the paddle
return false;
}
//Draw objects
function draw() {
"use strict";
ctx.clearRect(0, 0, canvas.width, canvas.height); //Clear canvas after animation frame
ctx.fillStyle = "white"; //Set color
//Draw ball
ctx.beginPath();
ctx.arc(ballX, ballY, 10, 0, Math.PI * 2, true);
ctx.fill();
//Draw player paddle
ctx.fillRect(0, paddleY, paddleWidth, paddleHeight);
//Draw ai
ctx.fillRect(canvas.width - paddleWidth, aiY, paddleWidth, paddleHeight);
//Score boarc
ctx.font = "30px Roboto";
//Draw score
ctx.fillText(playerScore, 100, 100); //Player score
ctx.fillText(aiScore, canvas.width - 100, 100);
return false;
}
//When document is ready
$("document").ready(function () {
"use strict";
//Get canvas and set its context
canvas = $("#canvas")[0];
ctx = canvas.getContext("2d");
//Set values to variables
//Set fps
var fps = 30;
ballX = 100;
ballY = 100;
ballSpeedX = 2;
ballSpeedY = 2;
paddleHeight = 100; //Used for centering mouse on paddle
paddleY = canvas.height / 2 - paddleHeight / 1.5; //Set paddle's y pos
paddleWidth = 10; //Width of paddle
//Score variables
aiScore = 0;
playerScore = 0;
aiY = canvas.height / 2 - paddleHeight / 1.5; //Height of ai player
setInterval(function () {
animate();
collision();
$(canvas).bind("mousemove", movePaddle); //Move paddle
draw();
}, fps / 1000);
return false;
});
答案 0 :(得分：1)
我做了一些修改，以考虑代码中的帧速率。
请尝试下面的那个。
//Set fps
var fps = 30, frameInterval = 1000/fps, lastTime = new Date().getTime();; // I would increase fps to 60
$(document).ready(function () {
"use strict";
//Get canvas and set its context
canvas = $("#canvas")[0];
ctx = canvas.getContext("2d");
//Set values to variables
ballX = 100;
ballY = 100;
ballSpeedX = 2;
ballSpeedY = 2;
paddleHeight = 100; //Used for centering mouse on paddle
paddleY = canvas.height / 2 - paddleHeight / 1.5; //Set paddle's y pos
paddleWidth = 10; //Width of paddle
//Score variables
aiScore = 0;
playerScore = 0;
aiY = canvas.height / 2 - paddleHeight / 1.5; //Height of ai player
$(canvas).bind("mousemove", movePaddle); //Bind once only
window.requestAnimationFrame(run);
return false;
});
function run() {
var now = new Date().getTime();
var elapsed = now - lastTime;
if(elapsed > frameInterval) {
animate();
collision();
draw();
lastTime = now;
}
window.requestAnimationFrame(run);
}
让我知道它是否有效。