实现DIV水平垂直居中的方法【笔记】

方案一：

初始化网页的宽度和高度，div可在浏览器窗口大小改变时，依旧居中！

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html,body{
            width: 100%;
            height: 100%;
            margin: 0;
            padding: 0;
        }
        .container{
            width: 200px;
            height: 200px;
            margin: 0 auto;
            position: relative;//设置div可移动
            background: greenyellow;
            top: 50%;margin-top: -100px;
           
        }
    </style>
</head>
<body>
    <div class="container">

    </div>
</body>
</html>

方案二：将margin-top属性改为CSS3中的 transform: translateY(-50%); 使div位置向上移动自身高度的50%

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html,body{
            width: 100%;
            height: 100%;
            margin: 0;
            padding: 0;
        }
        .container{
            width: 200px;
            height: 200px;
            margin: 0 auto;
            position: relative;
            background: greenyellow;
            top: 50%;
            transform: translateY(-50%);
           
        }
    </style>
</head>
<body>
    <div class="container">

    </div>
</body>
</html>

方案三：body开启弹性盒子布局，设置相关属性即可使DIV完成水平垂直居中

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html,body{
            width: 100%;
            height: 100%;
            margin: 0;
            padding: 0;
        }
        body{
            display: flex;
            justify-content: center;
            align-items: center;
        }
        .container{
            width: 200px;
            height: 200px;
            background: greenyellow;           
        }
    </style>
</head>
<body>
    <div class="container">

    </div>
</body>
</html>