<!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>