用HTML5实现动画
要在HTML5中实现动画,可以使用以下几种方法:CSS动画、使用<canvas>元素和JavaScript来实现动画、使用JavaScript动画库。重点介绍前两种。
一、CSS 动画
CSS3 动画:使用CSS3的动画属性和关键帧(keyframes)来创建动画效果。通过定义动画的开始状态、结束状态和过渡效果,可以实现平滑的动画效果。
先看一个简单的例子:
html
<html>
<head>
<meta charset="UTF-8" />
<title>在HTML5中用CSS3实现简单动画</title>
<style>
.box {
width: 100px;
height: 100px;
background-color: red;
animation: myAnimation 2s infinite;
}
@keyframes myAnimation {
0% { transform: translateX(0px); }
50% { transform: translateX(200px); }
100% { transform: translateX(0px); }
}
</style>
</head>
<body>
<div class="box"></div>
</body>
</html>
我这里命名为:CSS3简单动画.html
用浏览器打开,运行效果:
下面给出一个小车动画
由两部分组成:
HTML文件和CSS文件,为方便使用,我将这两个文件放在同一文件夹中。
HTML 文件,我这里命名为:CSS3小车动画.html,源码如下:
html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>在HTML5中用CSS3实现动画</title>
<link rel="stylesheet" type="text/css" href="car.css">
</head>
<body>
<div id="container">
<div id="car">
<div id="chassis"></div>
<div id="backtire" class="tire">
<div class="hr"></div>
<div class="vr"></div>
</div>
<div id="fronttire" class="tire">
<div class="hr"></div>
<div class="vr"></div>
</div>
</div>
<div id="grass"></div>
</div>
</body>
</html>
CSS 文件,我这里命名为:car.css,源码如下:
css
/*定义动画:从-400px的位置移动到1600px的位置 */
@keyframes carAnimation {
0% { left: -400px; } /* 指定初始位置*/
100% { left: 1600px; } /* 指定最终位置*/
}
#car {
position: absolute;
width: 400px;
height: 210px;
top: 300px;
left: 50px;
animation: carAnimation 10s infinite linear;
}
#chassis {
position: absolute;
width: 400px;
height: 130px;
background: #FF9900;
border: 2px solid #FF6600;
}
.tire {
position: absolute;
bottom: 0;
height: 120px;
width: 120px;
border-radius: 60px;
background: #0099FF;
border: 1px solid #3300FF;
animation: tyreAnimation 10s infinite linear;
}
#fronttire {
right: 20px;
}
#backtire {
left: 20px;
}
@keyframes tyreAnimation {
0% { transform: rotate(0); }
100% { transform: rotate(1800deg); }
}
#grass {
position: absolute;
width: 100%;
height: 130px;
bottom: 0;
background: linear-gradient(bottom, #33CC00, #66FF22);
}
.hr {
position: absolute;
background: #3300FF;
height: 2px;
width: 100%;
top: 60px;
}
.vr {
position: absolute;
background: #3300FF;
width: 2px;
height: 100%;
left: 60px;
top: 0;
}
我这里命名为:CSS3简单动画.html
用浏览器打开,运行效果:
二、使用<canvas> 元素和JavaScript 来实现动画
先看一个简单的例子:
html
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>在HTML5中用canvas+JS简单动画</title>
</head>
<body>
<canvas id="myCanvas" width="400" height="200"></canvas>
<script>
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
var x = 0;
var dx = 2; // 方块的移动速度以及方向
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.fillRect(x, 50, 50, 50);
// 更新方块的位置
x += dx;
// 如果方块触碰到画布的右边缘或左边缘,反转方向
if (x + 50 > canvas.width || x < 0) {
dx = -dx;
}
requestAnimationFrame(draw);
}
draw();
</script>
</body>
</html>
我这里命名为:canvas+JS简单动画.html
运行效果:
下面给出一个小车动画
由两部分组成
HTML文件和JavaScript文件,为方便使用,我将这两个文件放在同一文件夹中。
HTML 文件,我这里命名为:canvas+JS小车动画.html,源码如下:
html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>在HTML5中用canvas+JS小车动画</title>
<style>
body {
margin: 0;
overflow: hidden;
}
canvas {
display: block;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<script src="car.js"></script>
</body>
</html>
JavaScript 文件,我这里命名为:car.js,源码如下:
javascript
const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
// Set canvas full screen
canvas.width = window.innerWidth;
canvas.height = window.innerHeight-120; //
const car = {
x: 50,
y: canvas.height - 180, //
width: 200,
height: 100,
wheelRadius: 40,
wheelOffset: 25,
wheelRotation: 0
};
function drawCar(x, y, width, height, wheelRadius, wheelOffset, wheelRotation) {
// Draw car body
ctx.fillStyle = 'orange';
ctx.fillRect(x, y, width, height);
// Draw wheels
const wheelPositions = [
{ x: x + wheelOffset, y: y + height },
{ x: x + width - wheelOffset, y: y + height }
];
wheelPositions.forEach(wheelPos => {
ctx.save();
ctx.translate(wheelPos.x, wheelPos.y);
ctx.rotate(wheelRotation);
// Draw wheel
ctx.beginPath();
ctx.arc(0, 0, wheelRadius, 0, Math.PI * 2);
ctx.fillStyle = 'blue';
ctx.fill();
// Draw spokes
ctx.beginPath();
ctx.moveTo(-wheelRadius, 0);
ctx.lineTo(wheelRadius, 0);
ctx.moveTo(0, -wheelRadius);
ctx.lineTo(0, wheelRadius);
ctx.strokeStyle = 'white';
ctx.lineWidth = 4;
ctx.stroke();
ctx.restore();
});
}
function animate() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Draw ground
ctx.fillStyle = 'green';
ctx.fillRect(0, canvas.height - 50, canvas.width, 50);
// Update wheel rotation
car.wheelRotation += 0.05;
// Draw car
drawCar(car.x, car.y, car.width, car.height, car.wheelRadius, car.wheelOffset, car.wheelRotation);
// Move car
car.x += 2;
if (car.x > canvas.width) {
car.x = -car.width;
}
requestAnimationFrame(animate);
}
animate();
用浏览器打开,效果如下:
修改上面源码,将两个文件合二为一,并添加几个控制按钮"暂停/继续"、"快"、"慢",并实现相关功能:
点击pauseResumeBtn按钮会切换动画的暂停和继续状态。
点击speedUpBtn按钮会增加小车的速度。
点击speedDownBtn按钮会减慢小车的速度,但速度不能小于1。
源码如下:
html
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>在HTML5中用canvas+JS小车可控动画</title>
<style>
body {
margin: 0;
overflow: hidden;
}
canvas {
display: block;
}
</style>
</head>
<body>
<canvas id="canvas"></canvas>
<button id="pauseResumeBtn">暂停/继续</button>
<button id="speedUpBtn">快</button>
<button id="speedDownBtn">慢</button>
<script>
const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
// Set canvas full screen
canvas.width = window.innerWidth;
canvas.height = window.innerHeight - 120; //
const car = {
x: 50,
y: canvas.height - 180, //
width: 200,
height: 100,
wheelRadius: 40,
wheelOffset: 25,
wheelRotation: 0,
speed: 2
};
let isPaused = false;
function drawCar(x, y, width, height, wheelRadius, wheelOffset, wheelRotation) {
// Draw car body
ctx.fillStyle = 'orange';
ctx.fillRect(x, y, width, height);
// Draw wheels
const wheelPositions = [
{ x: x + wheelOffset, y: y + height },
{ x: x + width - wheelOffset, y: y + height }
];
wheelPositions.forEach(wheelPos => {
ctx.save();
ctx.translate(wheelPos.x, wheelPos.y);
ctx.rotate(wheelRotation);
// Draw wheel
ctx.beginPath();
ctx.arc(0, 0, wheelRadius, 0, Math.PI * 2);
ctx.fillStyle = 'blue';
ctx.fill();
// Draw spokes
ctx.beginPath();
ctx.moveTo(-wheelRadius, 0);
ctx.lineTo(wheelRadius, 0);
ctx.moveTo(0, -wheelRadius);
ctx.lineTo(0, wheelRadius);
ctx.strokeStyle = 'white';
ctx.lineWidth = 4;
ctx.stroke();
ctx.restore();
});
}
function animate() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Draw ground
ctx.fillStyle = 'green';
ctx.fillRect(0, canvas.height - 50, canvas.width, 50);
// Update wheel rotation
car.wheelRotation += 0.05;
// Draw car
drawCar(car.x, car.y, car.width, car.height, car.wheelRadius, car.wheelOffset, car.wheelRotation);
// Move car
car.x += car.speed;
if (car.x > canvas.width) {
car.x = -car.width;
}
if (!isPaused) {
requestAnimationFrame(animate);
}
}
// Button event listeners
document.getElementById('pauseResumeBtn').addEventListener('click', function() {
isPaused = !isPaused;
if (!isPaused) {
animate();
}
});
document.getElementById('speedUpBtn').addEventListener('click', function() {
car.speed += 1;
});
document.getElementById('speedDownBtn').addEventListener('click', function() {
if (car.speed > 1) {
car.speed -= 1;
}
});
animate();
</script>
</body>
</html>
我这里保存命名为:canvas+JS小车可控动画.html
用浏览器打开,效果如下:
三、使用JavaScript 动画库
使用JavaScript动画库(如Anime.js、Velocity.js、Three.js等)可以更方便地创建复杂的动画效果,我没有深入学习了解,在此就不介绍了。
附录:
CSS3动画详解(图文教程) https://www.cnblogs.com/qianguyihao/p/8435182.html
anime.js 简单入门教程https://www.cnblogs.com/joyco773/p/10734850.html
Velocity.js 中文文档https://www.cnblogs.com/guandekuan/p/6643988.html