Bootstrap无法使用rails app

Question

我安装了bootstrap但是我的rails应用程序无法正常工作。 我的application.css

/*
 * This is a manifest file that'll be compiled into application.css, which will include all the files
 * listed below.
 *
 * Any CSS and SCSS file within this directory, lib/assets/stylesheets, or any plugin's
 * vendor/assets/stylesheets directory can be referenced here using a relative path.
 *
 * You're free to add application-wide styles to this file and they'll appear at the bottom of the
 * compiled file so the styles you add here take precedence over styles defined in any other CSS/SCSS
 * files in this directory. Styles in this file should be added after the last require_* statement.
 * It is generally better to create a new file per style scope.
 *
 *= require_self
 *= require_tree .

 */

custom.css.scss

@import "bootstrap-sprockets";
@import "bootstrap";

的Gemfile

gem 'bootstrap-sass', '~> 3.3.7'
gem 'sass-rails', '~> 5.0'  
gem 'autoprefixer-rails'
gem 'sprockets-rails', '~> 3.2.1'

的application.js

//= require rails-ujs
//= require bootstrap-sprockets
//= require turbolinks
//= require_tree .

以下是导航栏的来源： -