CSS 栅格(CSS Grid)

Bootstrap 的默认网格系统是十多年来 CSS 布局技术的结晶，经过了数百万人的尝试和测试。但是，Bootstrap 在创建之初并没有采用我们在浏览器中看到的许多现代 CSS 功能和技术，例如新的 CSS 网格。

如何工作

注意–我们的 CSS 网格系统从 v5.1.0 版起是试验性的，需要您自己选择！ 我们在文档的 CSS 中包含了该系统，以便为您演示，但默认情况下是禁用的。请继续阅读，了解如何在您的项目中启用它。

• CSS 网格是选择性的 通过设置 $enable-grid-classes:false禁用默认网格系统，并通过设置 $enable-cssgrid:true启用 CSS 网格。然后，重新编译 Sass。

• 用 .grid 替换 .row 实例。 .grid 类设置了 display: grid 并创建了一个 grid-template ，你可以在此基础上创建 HTML。

• 将.col-*类替换为.g-col-*类 这是因为 CSS 网格列使用的是 grid-column 属性，而不是 width 属性。

• 通过 CSS 变量设置列和间隙的大小。 在父级 .grid 中设置这些变量，然后使用 --bs-columns 和 --bs-gap 在内联或样式表中进行自定义。

未来，Bootstrap 很可能会转向混合解决方案，因为 gap 属性几乎实现了浏览器对 flexbox 的全面支持。

主要区别

与默认网格系统相比：

• Flex 实用程序对 CSS 网格列的影响并不相同。

• 缝隙（gaps）取代间隙（gutters） 。gap属性取代了默认网格系统中的水平 padding，其功能更类似于 margin。

• 因此，与.row 不同，.grid 没有负边距，也不能使用边距实用程序来更改网格间隙。默认情况下，会在水平和垂直方向应用网格间隙。更多详情，请参阅自定义部分。

• 内联和自定义样式应被视为修改器类的替代（例如，style="--bs-columns: 3;" 与 class="row-cols-3"）。

• 嵌套的工作原理与此类似，但可能需要在每个嵌套的.grid实例上重置列数。详情请参见嵌套部分。

示例

三列

通过使用 .g-col-4 类，可以在所有视口和设备上创建三列等宽的列。添加 responsive classes 可根据视口大小改变布局。

<div class="grid text-center">
  <div class="g-col-4">.g-col-4</div>
  <div class="g-col-4">.g-col-4</div>
  <div class="g-col-4">.g-col-4</div>
</div>

Responsive

Use responsive classes to adjust your layout across viewports. Here we start with two columns on the narrowest viewports, and then grow to three columns on medium viewports and above.

<div class="grid text-center">
  <div class="g-col-6 g-col-md-4">.g-col-6 .g-col-md-4</div>
  <div class="g-col-6 g-col-md-4">.g-col-6 .g-col-md-4</div>
  <div class="g-col-6 g-col-md-4">.g-col-6 .g-col-md-4</div>
</div>

Compare that to this two column layout at all viewports.

<div class="grid text-center">
  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-6">.g-col-6</div>
</div>

Wrapping

Grid items automatically wrap to the next line when there’s no more room horizontally. Note that the gap applies to horizontal and vertical gaps between grid items.

<div class="grid text-center">
  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-6">.g-col-6</div>

  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-6">.g-col-6</div>
</div>

Starts

Start classes aim to replace our default grid’s offset classes, but they’re not entirely the same. CSS Grid creates a grid template through styles that tell browsers to “start at this column” and “end at this column.” Those properties are grid-column-start and grid-column-end. Start classes are shorthand for the former. Pair them with the column classes to size and align your columns however you need. Start classes begin at 1 as 0 is an invalid value for these properties.

<div class="grid text-center">
  <div class="g-col-3 g-start-2">.g-col-3 .g-start-2</div>
  <div class="g-col-4 g-start-6">.g-col-4 .g-start-6</div>
</div>

Auto columns

When there are no classes on the grid items (the immediate children of a .grid), each grid item will automatically be sized to one column.

<div class="grid text-center">
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
</div>

This behavior can be mixed with grid column classes.

<div class="grid text-center">
  <div class="g-col-6">.g-col-6</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
  <div>1</div>
</div>

Nesting

Similar to our default grid system, our CSS Grid allows for easy nesting of .grids. However, unlike the default, this grid inherits changes in the rows, columns, and gaps. Consider the example below:

• We override the default number of columns with a local CSS variable: --bs-columns: 3.
• In the first auto-column, the column count is inherited and each column is one-third of the available width.
• In the second auto-column, we’ve reset the column count on the nested .grid to 12 (our default).
• The third auto-column has no nested content.

In practice this allows for more complex and custom layouts when compared to our default grid system.

<div class="grid text-center" style="--bs-columns: 3;">
  <div>
    First auto-column
    <div class="grid">
      <div>Auto-column</div>
      <div>Auto-column</div>
    </div>
  </div>
  <div>
    Second auto-column
    <div class="grid" style="--bs-columns: 12;">
      <div class="g-col-6">6 of 12</div>
      <div class="g-col-4">4 of 12</div>
      <div class="g-col-2">2 of 12</div>
    </div>
  </div>
  <div>Third auto-column</div>
</div>

Customizing

Customize the number of columns, the number of rows, and the width of the gaps with local CSS variables.

These CSS variables have no default value; instead, they apply fallback values that are used until a local instance is provided. For example, we use var(--bs-rows, 1) for our CSS Grid rows, which ignores --bs-rows because that hasn’t been set anywhere yet. Once it is, the .grid instance will use that value instead of the fallback value of 1.

No grid classes

Immediate children elements of .grid are grid items, so they’ll be sized without explicitly adding a .g-col class.

<div class="grid text-center" style="--bs-columns: 3;">
  <div>Auto-column</div>
  <div>Auto-column</div>
  <div>Auto-column</div>
</div>

Columns and gaps

Adjust the number of columns and the gap.

<div class="grid text-center" style="--bs-columns: 4; --bs-gap: 5rem;">
  <div class="g-col-2">.g-col-2</div>
  <div class="g-col-2">.g-col-2</div>
</div>

<div class="grid text-center" style="--bs-columns: 10; --bs-gap: 1rem;">
  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-4">.g-col-4</div>
</div>

Adding rows

Adding more rows and changing the placement of columns:

<div class="grid text-center" style="--bs-rows: 3; --bs-columns: 3;">
  <div>Auto-column</div>
  <div class="g-start-2" style="grid-row: 2">Auto-column</div>
  <div class="g-start-3" style="grid-row: 3">Auto-column</div>
</div>

Gaps

Change the vertical gaps only by modifying the row-gap. Note that we use gap on .grids, but row-gap and column-gap can be modified as needed.

<div class="grid text-center" style="row-gap: 0;">
  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-6">.g-col-6</div>

  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-6">.g-col-6</div>
</div>

Because of that, you can have different vertical and horizontal gaps, which can take a single value (all sides) or a pair of values (vertical and horizontal). This can be applied with an inline style for gap, or with our --bs-gap CSS variable.

<div class="grid text-center" style="--bs-gap: .25rem 1rem;">
  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-6">.g-col-6</div>

  <div class="g-col-6">.g-col-6</div>
  <div class="g-col-6">.g-col-6</div>
</div>

Sass

One limitation of the CSS Grid is that our default classes are still generated by two Sass variables, $grid-columns and $grid-gutter-width. This effectively predetermines the number of classes generated in our compiled CSS. You have two options here:

• Modify those default Sass variables and recompile your CSS.
• Use inline or custom styles to augment the provided classes.

For example, you can increase the column count and change the gap size, and then size your “columns” with a mix of inline styles and predefined CSS Grid column classes (e.g., .g-col-4).

<div class="grid text-center" style="--bs-columns: 18; --bs-gap: .5rem;">
  <div style="grid-column: span 14;">14 columns</div>
  <div class="g-col-4">.g-col-4</div>
</div>