<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style type="text/css">
body,html{
height:100%;
width:100%;
}
.c1{
height:100%;
width: 100%;
background: #030f1c;
}
</style>
</head>
<body>
<div class="c1"></div>
<button>点击全屏预览</button>
</body>
</html>