Flex learning notes

Lu7 2021-05-03 13:17:23
flex learning notes

Flex Layout

  • flex Layout is to provide a more effective way to arrange , Allocate space in a container between alignment and items .
  • It is mainly suitable for all types of display devices and screen sizes ,flex The container expands the project to fill the available space , Or shrink them to prevent overflow .
  • Flexbox The layout is most suitable for the components and small-scale layout of the application , and Grid Layouts are used for larger layouts .



  • Spindle : The items in the elastic container will be arranged along the main axis by default from main-start To main-end.( The spindle direction can be changed , For example, it becomes vertical )
  • Side axle : The axis perpendicular to the spindle

Properties of elastic containers ( Parent container )

Define a parent container

.container {
display: flex;
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.container {
display: inline-flex;
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  • Items in elastic containers can also be set as elastic containers , Inline elements can also be set as elastic containers

flex And inline-flex The difference between

display: flex;
background-color: pink;
div span {
width: 150px;
height: 100px;
background-color: purple;
div span:nth-child(2) {
height: 150px;
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  1. When set to flex when :3.png
  2. When set to inline-flex when :2.png
  3. Be careful : There is no width or height set for the parent container ,inline-flex The parent container adapts its width and height to the child project

flex-direction( Elastic direction )

 .container {
flex-direction: row | row-reverse | column | column-reverse;
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  1. Set the spindle , Set the sub project layout direction
  2. row( The default value is ): From left to right
  3. row-reverse: From right to left
  4. column: From top to bottom
  5. column-reverse: From bottom to top
  6. 4.png

flex-wrap( Flexible packaging )

.container {
flex-wrap: nowrap | wrap | wrap-reverse;
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  1. nowrap ( Default ): All elastic items will be on one line
  2. wrap: Flexible items can wrap from top to bottom , Each line feed is arranged in the direction of the main axis
  3. wrap-reverse: Flexible items can wrap from bottom to top , Each line feed is arranged in the direction of the main axis


flex-flow( Flexible flow )

.container {
flex-flow: column wrap;
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  1. Namely flex-direction and flex-wrap It's written together , Better know how projects are arranged

justify-content( Adjust the content )

.container {
justify-content: flex-start | flex-end | center | space-between | space-around | space-evenly | start | end | left | right ... + safe | unsafe;
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  1. With spindle reference , Define the alignment of the content ( It can be understood from the concept map )

Snipaste_2021-04-26_12-18-00.png 3. space-around and space-evently The difference between

  • space-around: The spacing between each item is equal . therefore , The spacing between items is twice as large as the spacing between items and the border .( The distance from project to edge is half of the distance between projects )
  • space-evenly: Assign projects , So that the distance between any two items ( And the distance to the edge ) equal .
  • Chrome I won't support it start / end / left / right.

align-items( Item alignment )

.container {
align-items: stretch | flex-start | flex-end | center | baseline | first baseline | last baseline | start | end | self-start | self-end + ... safe | unsafe;
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  1. stretch ( Default ): Stretch to fill the container ( Still observe the minimum width / Maximum width )
  • When the subproject does not specify the width and height is , The project is stretched
  1. flex-start: The item is placed at the start of the side axis
  2. flex-end: The item is placed at the end of the side axis .
  3. center: The project is centered on the horizontal axis
  4. baseline: Project baseline alignment .( in my opinion ) The sub items in the elastic container are aligned according to the baseline position that can represent their contents .

align-content( Content alignment )

.container {
align-content: flex-start | flex-end | center | space-between | space-around | space-evenly | stretch | start | end | baseline | first baseline | last baseline + ... safe | unsafe;
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  1. normal ( Default ): Wrap the project in the default location , It's like no value is set .
  2. flex-start: Items packaged to the beginning of the container .
  3. flex-end: Items packed at the end of a container .
  4. center: The project in the center of the container
  5. space-between: Average distribution of goods ; The first line is at the beginning of the container , And the last line is at the end of the container
  6. space-around: Items are evenly distributed around each row , And have equal space
  7. space-evenly: Projects are evenly distributed , There is equal space around
  8. stretch: The line stretches to take up the rest of the space
  • Be careful : Only when the flex Containers have multiple lines flex Project time , This property is valid . If you put them in a single line , This property has no effect on the layout .
  1. Layout each line as a whole

  2. all column-* The attributes are all right flex The container has no effect on .

stay ::first-line and ::first-letter Pseudo elements don't apply to flexible containers .

Flexible projects ( Subset properties )

order( The order )

.item {
order: 5; /* default is 0 */
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  1. order Properties control where they are flex The order of occurrence in the container ( There can be negative values )

flex-grow( Flexible growth )

.item {
flex-grow: 4; /* default 0 */
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  1. This defines the ability of resilient projects to grow when necessary . It's accepted as a unitless value of proportion . It determines that the project should be in flex The amount of space available in the container .
  2. If all the projects are flex-grow Set to 1, The remaining space in the container will be evenly allocated to all subitems . If one of the children's values is 2, The remaining space will be twice that of the other children ( Or at least try ).( Adaptive with browser )
  3. Negative number is invalid .

flex-shrink( Elastic contraction )

.item {
flex-shrink: 3; /* default 1 */
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  1. If all of the items flex-shrink Attributes are 1, When space runs out , I'm going to scale it down . If a project flex-shrink The attribute is 0, Everything else 1, When there is not enough space , The former does not shrink .( It can also give you projects that you want to be fixed , Be sure to die )
  2. Negative values are not valid for this property .

flex-basis( Elastic foundation )

.item {
flex-basis: | auto; /* default auto */
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  1. Attributes that need to be understood in depth


.item {
flex: none | [ <'flex-grow'> <'flex-shrink'>? || <'flex-basis'> ]
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  1. This shorthand property is recommended , Instead of setting individual properties . Shorthand can intelligently set other values .

align-self( Self adjustment )

.item {
align-self: auto | flex-start | flex-end | center | baseline | stretch;
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  1. The arrangement of a box on the side axis
  • Traditional layout
  1. Compatibility is good.
  2. Complicated layout
  3. limitations , It can't be well laid out on the mobile end
  • flex Elastic layout
  1. It is easy to operate , The layout is extremely simple , Mobile applications are very wide
  2. PC The end browser support is poor
  3. IE11 Or earlier , Not supported or only partially supported
  4. Adaptive effects

Vertical center is really super simple

The above is from css Ruan Yifeng pink teacher


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