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Detailed explanation of css3 flex layout examples
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- 2017-06-17 14:36:471716browse
flex Layout is the most frequently used and outstanding function in css3. It is a bit complicated. It is divided into attributes applied to the container and attributes on the project, that is, on the parent element. of and attributes on child elements.
Attributes on the parent element
-
display: flex
<style>p{display: flex; background-color: yellow;}b{background-color: red;}</style><body> <p> <b>a</b><b>b</b><b>c</b><b>d</b><b>e</b><b>f</b><b>g</b><b>h</b><b>i</b> </p></body>When the parent element is set to
flexAfter, its parent element itself will appear as a block-level element. If you want to appear as an inline element, you can useinline-flex. All child elements, whether block-level or inline, will immediately become inline layout. This is due to the default values of other attributes and can be modified later.
- ##flex-
<style>p{display: flex; background-color: yellow; margin: 5px;}p.row{ flex-direction: row;}p.row-reverse{ flex-direction: row-reverse;}p.column{ flex-direction: column;}p.column-reverse{ flex-direction: column-reverse;}b{background-color: red;}</style><body> <p class="row"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="row-reverse"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="column"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="column-reverse"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>flex-direction
Decision Arrangement direction of child elements, default valuerow.
##flex-wrap <style>p{display: flex; background-color: yellow; margin: 5px; }p.nowrap{ flex-wrap: nowrap;}p.wrap{ flex-wrap: wrap;}p.wrap-reverse{ flex-wrap: wrap-reverse;}b{background-color: red; width: 100px;}</style><body> <p class="nowrap"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="wrap"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="wrap-reverse"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>flex-wrapDetermines how the child element should be handled when it exceeds one line. The default value
nowrapwill compress the width of child elements,wrapwill wrap a new line, andwrap-reversewill add a new line upwards. Note: This is discussed under the premise that the main axis is the X-axis.
##justify-content
<style>b{background-color: red; }p{display: flex; background-color: yellow; margin: 5px; }p.start{ justify-content: flex-start;}p.end{justify-content: flex-end;}p.center{ justify-content: center;}p.space-between{ justify-content: space-between;}p.space-around{ justify-content: space-around;}</style><body> <p class="start"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="end"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="center"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-between"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-around"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>justify-content
Determines whether the child element is on the main axis (currently the X axis ), the default value isflex-start. The distance between space-between and space-around is divided equally by the excess space, but the latter will also count the space for the left and right ends.
##align-items
<style>b{background-color: red; width: 40px;}b:nth-child(1){}b:nth-child(2){font-size: 30px; height: 40px;}b:nth-child(3){height: 50px;}b:nth-child(4){height: 60px;}p{display: flex; flex-wrap: wrap; background-color: yellow; margin: 5px; }p.start{ align-items: flex-start;}p.end{ align-items: flex-end;}p.center{ align-items: center;}p.baseline{ align-items: baseline;}p.stretch{ align-items: stretch;}</style><body> <p class="start"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="end"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="center"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="baseline"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="stretch"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>Determine the secondary axis (currently the Y axis) The alignment of elements. The default value
stretch means that when the child element does not set a height, it will fill the height of the parent class.
align-content
<style>b{background-color: red; width: 100px;}p{display: flex; flex-wrap: wrap; background-color: yellow; margin: 5px; height: 70px;}p.start{ align-content: flex-start;}p.end{ align-content: flex-end;}p.center{ align-content: center;}p.space-between{ align-content: space-between;}p.space-around{ align-content: space-around;}p.stretch{ align-content: stretch;}</style><body> <p class="start"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="end"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="center"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-between"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="space-around"> <b>a</b><b>b</b><b>c</b><b>d</b> </p> <p class="stretch"> <b>a</b><b>b</b><b>c</b><b>d</b> </p></body>indicates that when the child element has multiple lines, each line Position on the secondary axis (currently the Y axis). The default value
stretch means changing the height of each row of child elements until the parent element is filled.
Attributes on child elements
order
<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; }b.test{order: -1;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>- order
means arranging elements of the same level from small to large, the default value is
0.
##flex-grow
<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; }b.test{flex-grow: 1; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>flex-grow - means when the main axis (currently the X axis) is on When there is remaining space, the proportion occupied by dividing the space equally. The default value is
0
, which means it does not occupy space. The current space bisection ratio is0 : 0 : 1 : 0
##flex-shrink, so c occupies all remaining space.<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; width: 100px; flex-shrink: 0;}b.test{flex-shrink: 1; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>
flex-shrink means when the main axis (currently the X axis) space When it is not enough to fill all the sub-elements, how should the sub-elements be compressed? The default value is - 1
, which means
1 : 1 : 1 : 1, that is, equal-ratio compression. The current ratio is
0: 0: 1: 0, indicating that all space is compressed by c.##flex-basis<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; flex-grow: 1;}b.test{flex-basis: 100px; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>
means when the main axis (currently the X axis) is on The position occupied before dividing the space equally. When the main axis is the X-axis, it is equivalent to setting
flex-basis width - . When the main axis is the Y-axis, it is equivalent to setting
height
. The default valueauto
means equal towidthorheight.##align-self<style>p{display: flex; background-color: yellow; margin: 5px;}b{background-color: red; flex-grow: 1;}b:nth-child(1){height: 20px;}b:nth-child(2){height: 40px;}b:nth-child(3){height: 50px;}b:nth-child(4){height: 60px;}b.test{align-self: flex-end; background-color: green;}</style><body> <p class="start"> <b>a</b><b>b</b><b class="test">c</b><b>d</b> </p></body>align-self表示当前元素可以覆盖父元素align-items所决定的副轴（当前为Y轴）上的方向。默认auto，即不设置。可选择与align-items一致，auto | flex-start | flex-end | center | baseline | stretch。
特别注意，为简化布局理解，上面事例都使用了默认的 flex-direction:row 作为子元素排序方向为基础。如果改为 flex-direction:column ，主轴将为变成 Y 轴，而副轴将变成 X 轴，所有属性的效果将会改变，这个留给读者自行实践。
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