Grid system
Working Mechanism
Official website: https://v4.bootcss.com/docs/layout/grid/
About flex: https://www.cnblogs.com/py-peng/p/12346058.html
The change from 3 to 4 is still quite large. On the whole, the grid system is more flexible, but the compatibility is not as good as before.
row
Row is no longer a simple margin around -15px, but a flexible layout flex.
col
Since the row is a flexible layout, the column also needs to be changed.
And added a new column width, col-auto
| Extra small <576px |
Small ≥576px |
Medium ≥768px |
Large ≥992px |
Extra large ≥1200px |
|
|---|---|---|---|---|---|
| Max container width | None (auto) | 540px | 720px | 960px | 1140px |
| Class prefix | .col- |
.col-sm- |
.col-md- |
.col-lg- |
.col-xl- |
| # of columns | 12 | ||||
| Gutter width | 30px (15px on each side of a column) | ||||
| Nestable | Yes | ||||
| Column ordering | Yes | ||||
Automatic
After understanding the new grid system, we give some layout demonstrations.
Equal width
<div class="container"> <div class="row"> <div class="col"> 1 of 2 </div> <div class="col"> 2 of 2 </div> </div> <div class="row"> <div class="col"> 1 of 3 </div> <div class="col"> 2 of 3 </div> <div class="col"> 3 of 3 </div> </div> </div>
Multi-line equal width
<div class="container"> <div class="row"> <div class="col">col</div> <div class="col">col</div> <div class="w-100"></div> <div class="col">col</div> <div class="col">col</div> </div> </div>
The principle of .w-100
Auto width
In fact, you can also see in the previous application that it automatically fills the width, because they are in a flexible layout.
<div class="container"> <div class="row"> <div class="col"> 1 of 3 </div> <div class="col-6"> 2 of 3 (wider) </div> <div class="col"> 3 of 3 </div> </div> <div class="row"> <div class="col"> 1 of 3 </div> <div class="col-5"> 2 of 3 (wider) </div> <div class="col"> 3 of 3 </div> </div> </div>
Variable-width content
<div class="container"> <div class="row justify-content-md-center"> <div class="col col-lg-2"> 1 of 3 </div> <div class="col-md-auto"> Variable width content </div> <div class="col col-lg-2"> 3 of 3 </div> </div> <div class="row"> <div class="col"> 1 of 3 </div> <div class="col-md-auto"> Variable width content </div> <div class="col col-lg-2"> 3 of 3 </div> </div> </div>
Responsive
Different breakpoints
<div class="container"> <div class="row"> <div class="col">col</div> <div class="col">col</div> <div class="col">col</div> <div class="col">col</div> </div> <div class="row"> <div class="col-8">col-8</div> <div class="col-4">col-4</div> </div> </div>
Mix and match
<div class="container"> <!-- Stack the columns on mobile by making one full-width and the other half-width --> <div class="row"> <div class="col-md-8">.col-md-8</div> <div class="col-6 col-md-4">.col-6 .col-md-4</div> </div> <!-- Columns start at 50% wide on mobile and bump up to 33.3% wide on desktop --> <div class="row"> <div class="col-6 col-md-4">.col-6 .col-md-4</div> <div class="col-6 col-md-4">.col-6 .col-md-4</div> <div class="col-6 col-md-4">.col-6 .col-md-4</div> </div> <!-- Columns are always 50% wide, on mobile and desktop --> <div class="row"> <div class="col-6">.col-6</div> <div class="col-6">.col-6</div> </div> </div>
Ranks
<div class="container"> <div class="row row-cols-2"> <div class="col">Column</div> <div class="col">Column</div> <div class="col">Column</div> <div class="col">Column</div> </div> </div>
<div class="container"> <div class="row row-cols-3"> <div class="col">Column</div> <div class="col">Column</div> <div class="col">Column</div> <div class="col">Column</div> </div> </div>
Alignment
Vertical alignment
<div class="container"> <div class="row align-items-start"> <div class="col"> One of three columns </div> <div class="col"> One of three columns </div> <div class="col"> One of three columns </div> </div>
<div class="row align-items-center"> <div class="col"> One of three columns </div> <div class="col"> One of three columns </div> <div class="col"> One of three columns </div> </div>
<div class="row align-items-end"> <div class="col"> One of three columns </div> <div class="col"> One of three columns </div> <div class="col"> One of three columns </div> </div> </div>
<div class="container"> <div class="row"> <div class="col align-self-start"> One of three columns </div> <div class="col align-self-center"> One of three columns </div> <div class="col align-self-end"> One of three columns </div> </div> </div>
Row actually operates: align-items, the items below it (column) will be aligned according to this.
col actually operates: align-self, which allows you to use different alignments.
It looks like this:
<div class="container-fluid"> <div class="row align-items-start"> <div class="col"></div> <div class="col align-self-center"></div> <div class="col"></div> </div> </div>
Horizontal alignment
<div class="container"> <div class="row justify-content-start"> <div class="col-4"> One of two columns </div> <div class="col-4"> One of two columns </div> </div> <div class="row justify-content-center"> <div class="col-4"> One of two columns </div> <div class="col-4"> One of two columns </div> </div> <div class="row justify-content-end"> <div class="col-4"> One of two columns </div> <div class="col-4"> One of two columns </div> </div> <div class="row justify-content-around"> <div class="col-4"> One of two columns </div> <div class="col-4"> One of two columns </div> </div> <div class="row justify-content-between"> <div class="col-4"> One of two columns </div> <div class="col-4"> One of two columns </div> </div> </div>
row margin
Sometimes you don't use container, container-fluid, the default row is about -15px outside, when you want the row to be around 0, you only need to use .no-gutters
<div class="row no-gutters"> <div class="col-sm-6 col-md-8">.col-sm-6 .col-md-8</div> <div class="col-6 col-md-4">.col-6 .col-md-4</div> </div>
col line break
In flexbox, splitting a column into new rows requires a little trick: add an element with a width of 100%, no matter where you want to pack the column as a new row.
<div class="container"> <div class="row"> <div class="col-6 col-sm-3">.col-6 .col-sm-3</div> <div class="col-6 col-sm-3">.col-6 .col-sm-3</div> <!-- Force next columns to break to new line --> <div class="w-100"></div> <div class="col-6 col-sm-3">.col-6 .col-sm-3</div> <div class="col-6 col-sm-3">.col-6 .col-sm-3</div> </div> </div>
Sort
Order
The smaller the value, the higher the priority. The default is 0.
<div class="container"> <div class="row"> <div class="col"> First in DOM, no order applied </div> <div class="col order-12"> Second in DOM, with a larger order </div> <div class="col order-1"> Third in DOM, with an order of 1 </div> </div> </div>
You can also order-first order-lastsort by: the values they represent are: -1, 13.
<div class="container"> <div class="row"> <div class="col order-last"> First in DOM, ordered last </div> <div class="col"> Second in DOM, unordered </div> <div class="col order-first"> Third in DOM, ordered first </div> </div> </div>
Offset column
Can understand the col-md-offset * in bootstrap3, changed the name.
<div class="container"> <div class="row"> <div class="col-md-4">.col-md-4</div> <div class="col-md-4 offset-md-4">.col-md-4 .offset-md-4</div> </div> <div class="row"> <div class="col-md-3 offset-md-3">.col-md-3 .offset-md-3</div> <div class="col-md-3 offset-md-3">.col-md-3 .offset-md-3</div> </div> <div class="row"> <div class="col-md-6 offset-md-3">.col-md-6 .offset-md-3</div> </div> </div>
Margin utilities
Due to the characteristics of flexible layout, you can use ml, mr to separate with blanks.
<div class="container"> <div class="row"> <div class="col-md-4">.col-md-4</div> <div class="col-md-4 ml-auto">.col-md-4 .ml-auto</div> </div> <div class="row"> <div class="col-md-3 ml-md-auto">.col-md-3 .ml-md-auto</div> <div class="col-md-3 ml-md-auto">.col-md-3 .ml-md-auto</div> </div> <div class="row"> <div class="col-auto mr-auto">.col-auto .mr-auto</div> <div class="col-auto">.col-auto</div> </div> </div>
