如何在Bootstrap导航中的移动设备上显示菜单图标？

Question

When I view my site on mobile, the navbar works except there is not a mobile menu icon. That is to say, if you tap the far right of the nav bar, the <li> elements get toggled, but there is no icon in the spot where you tap to toggle the <li> elements, so users will not know to do it.

Thanks in advance for any pointers, it is much appreciated.

HTML:

<nav class="navbar navbar-light" style="background-color:#e3f2fd;">
    <div class="container-fluid">
        <!-- Brand and toggle get grouped for better mobile display -->
        <div class="navbar-header">
            <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
                <span class="sr-only">Toggle navigation</span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
                <span class="icon-bar"></span>
            </button>
            <a class="navbar-brand" href="/">
                Home
            </a>
        </div>

        <!-- Collect the nav links, forms, and other content for toggling -->
        <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
            <ul class="nav navbar-nav">
                <li><a href="/topics">All Topics</a></li>
                <li class="dropdown">
                    <a href="/topics" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">Featured Topics <span class="caret"></span></a>
                    <ul class="dropdown-menu">
                        <li><a href="/topics/US Presidents/new">U.S. Presidents</a></li>
                        <li><a href="/topics/Astronomy/new">Astronomy</a></li>
                        <li><a href="/topics/Movies/new">Movies</a></li>
                    </ul>
                </li>
                <li><a href="/newest-quizzes">Newest Quizzes<span class="sr-only">(current)</span></a></li>
                <li><a href="/create-quiz">Create</a></li>
                <li><a href="/about">About</a></li>
            </ul>

            <ul class="nav navbar-nav navbar-right">
                    <li><a href="/login">Login</a></li>
                    <li><a href="/register">Create Account</a></li>

            </ul>
        </div><!-- /.navbar-collapse -->
    </div><!-- /.container-fluid -->
</nav>

Answer 1

Could you try exchanging the class navbar-light by navbar-default or navbar-inverse on your nav element? navbar-light doesn't exist in Bootstrap 3.

Answer 2

Make sure your Bootstrap dependencies are included in the correct order. Any discrepancy will tend to break things.

Answer 3

you can style button.navbar-toggle to see that button

for example,

button.navbar-toggle {
background:#ddd !important; /* !important is just to override other styles, if any. */
}

hope that helps!