Detailed explanation of the principles and advantages of CSS Flex flexible layout

Detailed explanation of the principles and advantages of CSS Flex elastic layout

Introduction:
In Web development, CSS layout is a very important concept. CSS Flex elastic layout is a widely adopted layout method, which provides flexible layout options and powerful adaptive capabilities. This article will introduce the principles and advantages of CSS Flex elastic layout in detail, and analyze it with code examples to help readers better understand and use CSS Flex elastic layout.

1. The principle of CSS Flex elastic layout
   CSS Flex elastic layout means that by using the flex property of CSS, elements can be automatically stretched and arranged to adapt to different container sizes and Device screen size. In CSS Flex layout, there are two important concepts: container and item.

   1.1 Container:
   The container refers to the parent element that applies Flex layout and sets the display attribute value to flex or inline-flex. The child elements of the container become items and are arranged according to the container's settings.
   The container can set the flex-direction attribute to change the arrangement direction of the items. Commonly used values ​​are row, column, row-reverse, and column-reverse. row indicates horizontal arrangement from left to right, column indicates vertical arrangement from top to bottom, and row-reverse and column-reverse indicate the opposite order.

   1.2 Item:
   Item refers to the direct child element of the container. In Flex layout, items adjust how they appear within the container by setting various flex properties. Commonly used flex attributes include flex-grow, flex-shrink, flex-basis, flex and order.

   • flex-grow: Define the magnification ratio of the item. The default value is 0, which means no magnification. If all items have a flex-grow property of 1, they will divide the remaining space equally.
   • flex-shrink: Define the shrinkage ratio of the item, the default value is 1. If there is insufficient space, items will be reduced according to their respective reduction ratios.
   • flex-basis: Defines the initial size of the item on the main axis. When the width is auto, the item will automatically calculate the width based on the content.
   • flex: It is the abbreviation of flex-grow, flex-shrink and flex-basis. It can set the relationship between the three attribute values.
   • order: Define the order in which items are sorted. By default, the order value of the items is 0. You can change the order of the items by modifying the order value.

2. Advantages of CSS Flex Flexible Layout
   2.1 Simplifying layout code:
   CSS Flex Flexible Layout can implement complex layout structures with less code, making the code More concise, clear and easy to maintain.

   2.2 Strong adaptability:
   CSS Flex elastic layout can automatically adjust the size and layout of the project according to the size of the container, allowing the page to adapt to different device screen sizes and resolutions.

   2.3 Flexible item arrangement:
   CSS Flex flexible layout can customize the arrangement of items in the container, which can be arranged horizontally or vertically, from left to right or top to bottom, and can Adjust the order of items by changing the order value.

   2.4 Meets a variety of application scenarios:
   CSS Flex elastic layout is suitable for a variety of different application scenarios and can be used to build web page layouts, navigation menus, picture galleries, etc.

3. Flex flexible layout code example

   HTML code:
   

   
   

   Item 1

   
   

   Item 2

   
   

   Item 3

   
   

   CSS code:
   .container {
   display: flex;
   flex-direction: row;
   justify-content: space-between;
   }

   .item {
   flex-grow: 1;
   flex-shrink: 1;
   flex-basis: 0;
   text-align: center;
   padding : 10px;
   }

   In the above code example, the .container element is set to a Flex container by setting the display property of .container to flex. By setting the .container's flex-direction property to row, items will be arranged horizontally from left to right. By setting the flex-grow property of .item to 1, when there is enough space, the item will divide the remaining space equally. By setting the flex-basis property of .item to 0, the initial width of the item is 0 and will be adaptively adjusted according to the space in the container. By setting the justify-content property of .item to space-between, the spacing of items on the main axis will automatically be evenly distributed.

Summary:
This article introduces the principle and advantages of CSS Flex elastic layout in detail, and analyzes it with code examples. CSS Flex elastic layout is a powerful layout method that can flexibly solve various complex layout requirements and improve the adaptability of the page. By flexibly using CSS Flex layout, developers can build excellent Web pages more quickly and easily.

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