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问题:

For some reason device emulation mode is not reading my media queries. It works on other sites including my own sites that I made with bootstrap, but it's not working on media queries I am using from scratch (clicking the media queries button turns the button blue but no media queries are displayed). Test file below. Is this a bug in Chrome or is there something I need to change in my file?

<!DOCTYPE html>
<!--
Media Queries Example 1
Sam Scott, Fall 2014
-->
<html>
<head>
    <title>MQ Example 1</title>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <style>
        body { font-family: sans-serif; }
        h1 { color: red; } 
        h2 { color:blue; }
        p { color:green; }

        @media (max-width: 768px) and (min-width: 481px) {
            h1 { color: green; } 
            h2 { color:red; }
            p { color:blue; }
        }

        @media (max-width:479px), print { 
            h1,h2,p { color:black; }
        }

        @media print {
            body { font-family: serif; }
        }


    </style>
</head>
<body>
    <h1>I'm a first level heading</h1>
    <p>I'm a paragraph.</p>
    <h2>I'm a second level heading</h2>
    <p>I'm another paragraph.</p>
</body>
</html>

回答1:

I fixed this problem by adding a meta tag to my page:

 <meta name="viewport" content="width=device-width">

回答2:

Device emulation in Chrome is still a WIP. To be honest I think they pushed it to Chrome a little too soon. Try using Canary (the chrome beta browser) to test the emulation, I find that it's working way better than the one in Chrome.

回答3:

The accepted answer didn't do it for me, I had to add a minimum-scale=1 as well.

<meta name="viewport" content="width=device-width, initial-scale=1, minimum-scale=1" />

回答4:

Works for me.

Just put a viewport meta tag in the head section of your page. See example:

 <head>
  <!--include the following meta tag to make chrome dev tools recognize media queries: -->
  <meta name="viewport" content="width=device-width">
</head>