html - Bootstrap 4 布局在与表单一起使用时无法按预期工作

Question

我正在使用 Bootstrap 4 处理表单。现在，当将表单与网格类一起使用时，它实际上并没有像预期的那样工作。输出可以在这里看到 http://www.henryspike.tk/testform

我的预期是看到整个 12 列分为 4-4-4，每列包含一个输入字段，但它堆叠起来。

<div class="row">
                    <div class="col-md-12 offset-md-1">
                        <div class="row">
                            <form class="form">
                                <div class="col-md-4">
                                    <div class="form-group">
                                        <label for="name">Name</label>
                                        <input class="form-control" type="text" name="name" id="name" placeholder="eg. John Doe" required>
                                    </div>
                                </div>
                                <div class="col-md-4">
                                    <div class="form-group">
                                        <label for="email">Name</label>
                                        <input class="form-control" type="email" name="email" id="email" placeholder="someone@example.com" required>
                                    </div>
                                </div>
                                <div class="col-md-4">
                                    <div class="form-group">
                                        <label for="username">Name</label>
                                        <input class="form-control" type="text" name="username" id="username" placeholder="eg. JDoe12" required>
                                    </div>
                                </div>
                            </form>
                        </div>
                    </div>
                </div>

Answer 1

col- 应始终是 row 的直接子级..

http://www.codeply.com/go/moFmNMMuPs

<div class="row">
    <div class="col-md-12">
        <form class="row form">
            <div class="col-md-4">
                <div class="form-group">
                    <label for="name">Name</label>
                    <input class="form-control" type="text" name="name" id="name" placeholder="eg. John Doe" required="">
                </div>
            </div>
            <div class="col-md-4">
                <div class="form-group">
                    <label for="email">Name</label>
                    <input class="form-control" type="email" name="email" id="email" placeholder="someone@example.com" required="">
                </div>
            </div>
            <div class="col-md-4">
                <div class="form-group">
                    <label for="username">Name</label>
                    <input class="form-control" type="text" name="username" id="username" placeholder="eg. JDoe12" required="">
                </div>
            </div>
        </form>
    </div>
</div>