Master the flex layout skills of CSS3 and easily build a modern web interface.

Master the flex layout skills of CSS3 and easily build a modern web interface.

In today’s era of rapid development of the Internet, web design has become an important field. In order to meet users' needs for web interfaces, developers continue to explore and use new technologies to build more modern and attractive web pages. Among them, CSS3's flex layout is a technique that can help developers lay out web page elements more flexibly.

The so-called flex layout, that is, flexible box layout, is a responsive layout method that can automatically adjust the position and size of elements according to the size and layout rules of the container. Compared with the traditional box model layout, flex layout is more convenient and flexible, and can adapt to various screen sizes and device types.

Before starting to use flex layout, we first need to understand a few basic concepts. Flex layout involves the following three attributes:

1. Flex container (flex container): Elements using flex layout are called containers. By setting the display attribute to flex or inline-flex, the element can be set to be flexible. Box container.

　2. Flex item: Each sub-element in the container is called an item, and their arrangement, size and other style attributes can be set.

　3. Flex axis: The flex-direction attribute can be used to specify the arrangement direction of items in the container. The flex axis is the axis formed by the arrangement direction.

Before elaborating on the techniques of flex layout, let’s take a look at a simple example to understand the basic usage of flex layout:

<div class="container">
  <div class="item">项目1</div>
  <div class="item">项目2</div>
  <div class="item">项目3</div>
</div>

<style>
.container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.item {
  flex: 1;
  height: 100px;
  background-color: #ff9900;
}
</style>

In the above code, we create a container and Set the container to flex layout through the display attribute. Next, the alignment between items is set to space-between through the justify-content attribute, so that the intervals between items are equal. Then use the align-items attribute to set the alignment of the items on the cross axis to center, that is, vertical centering.

In the style of the project, we set the flex property to 1 so that the project can evenly distribute the remaining space. At the same time, the height of the project is set to 100px, and the background color is set for the project.

The above example demonstrates how to use flex layout to achieve the effect of bisecting a row. Below, we introduce some other commonly used flex layout techniques.

　1. Three-column layout with equal width

<div class="container">
  <div class="item">项目1</div>
  <div class="item">项目2</div>
  <div class="item">项目3</div>
</div>

<style>
.container {
  display: flex;
}

.item {
  flex: 1;
  height: 100px;
  background-color: #ff9900;
}
</style>

By setting the container to flex layout, and then setting the flex property of the item to 1, you can achieve a three-column layout with equal width.

　2. Two-column layout of equal height

<div class="container">
  <div class="left-item">左侧项目</div>
  <div class="right-item">右侧项目</div>
</div>

<style>
.container {
  display: flex;
}

.left-item {
  flex: 1;
  height: 200px;
  background-color: #ff9900;
}

.right-item {
  flex: 1;
  height: 200px;
  background-color: #00ccff;
}
</style>

By setting the container to flex layout, and then setting the flex properties of the left and right items to 1, you can achieve two columns of equal height. layout effect.

　3. Horizontal and vertical centering

<div class="container">
  <div class="item">项目</div>
</div>

<style>
.container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 300px;
  background-color: #ff9900;
}

.item {
  flex: 1;
  height: 100px;
  background-color: #00ccff;
}
</style>

By setting the container to flex layout, and then setting both the justify-content and align-items properties to center, horizontal and vertical centering can be achieved Effect.

Through the above examples, we can see that using CSS3’s flex layout technology can make it easier and more flexible to build a modern web interface. By properly setting the properties of containers and projects, we can achieve various layout effects to meet user requirements for web interfaces. In actual development, we can flexibly use various flex layout techniques as needed to build an attractive and responsive web interface.

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