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问题:

I'm trying to create a full width page using Bootstrap. I have a setup similar to this:

<body>
    <div class="container-fluid">
        <div class="row">
            The first row goes here
        </div>
        <div class="row">
            The second row goes here
        </div>
        <div class="row">
            The third row goes here
        </div>
    </div>
</body>

If I wanted to create a row inside a row, how would I do that? This is what I am trying to achieve:

<body>
    <div class="container-fluid">
        <div class="row">
            <div class="row text-center">
                <h1>Some title</h1>
            </div>
            <div class="row">
                <div class="col-md-2"></div>
                <div class="col-md-4">
                    Grid perhaps
                </div>
                <div class="col-md-4">
                    More grid
                </div>
                <div class="col-md-2"></div>
            </div>
        </div>
    </div>
</body>

So basically I want to put the title on one row and some grids on another row. The tricky part here is, I want to place some columns that are 4 columns wide in the middle, and then have "2 columns padding" on the left and right.

My question may sound like others, but is unique because of the padding. How do I make this layout properly?

回答1:

Bootstrap has a smart (but delicate) gutters system providing "natural" (margins + paddings) for content on all devices ¹.

This system is based on two simple assumptions:

columns are immediate children of .rows ²
content is placed inside columns

That's why, if you want to place a .row inside another .row (to further divide one of your cols), you'd have to use this markup:

<div class="row">
  <div class="col-12">
     <div class="row">
        <div class="col-md-4 offset-md-2">
           Grid perhaps
        </div>
        <div class="col-md-4">
           More grid
        </div>
     </div>
  </div>
</div>

The above doesn't make much sense by itself (you could just use the markup of the child row and you'd get the same result). But it's useful when you want to offset (or limit) an entire area of a layout, like this:

<div class="row">
  <div class="col-md-8 offset-md-2 col-sm-10 offset-sm-1 col offset-0">
     <div class="row">
        <div class="col-md-6">Grid</div>
        <div class="col-md-6">More grid</div>
        <div class="col-md-6">Grid</div>
        <div class="col-md-6">More grid</div>
        <div class="col-md-6">Grid</div>
        <div class="col-md-6">More grid</div>
        <div class="col-md-6">Grid</div>
        <div class="col-md-6">More grid</div>
        <div class="col-md-6">Grid</div>
        <div class="col-md-6">More grid</div>
     </div>
  </div>
</div>

See this fiddle for a live example.

¹ To get rid of Bootstrap's gutters (in v4), one would need to apply no-gutters class on .row.

² This is a "general principle", not a "strict rule". Other elements are allowed (and even recommended) as direct children of .rows (such as column breaks). At the other end, other elements extend from .rows (such as .form-rows), thus inheriting the gutters system and being valid column parents.

回答2:

A .row should not be the immediate child of another .row. From the Bootstrap docs:

"Content should be placed within columns, and only columns may be immediate children of rows."

I don't understand why you think you need a row in a row, and what's wrong with just using your layout w/o the nested row. Do you realize that col-12 is the width of a full row?

<div class="container-fluid">
    <div class="row">
        <div class="col-12 text-center">
            <h1>Some title</h1>
        </div>
    </div>
    <div class="row">
        <div class="col-md-2">

        </div>
        <div class="col-md-4">
            Grid perhaps
        </div>
        <div class="col-md-4">
            More grid
        </div>
        <div class="col-md-2">

        </div>
    </div>
</div>

http://www.codeply.com/go/jfrWn4QDf1

Bootstrap 4, the same rule applies:

"Rows are wrappers for columns. Each column has horizontal padding (called a gutter) for controlling the space between them... In a grid layout, content must be placed within columns and only columns may be immediate children of rows" __ Bootstrap 4.1 Docs