How to use flex in uniapp

With the rapid development of mobile Internet, more and more developers are beginning to use cross-platform technology to develop applications. In cross-platform development, uniapp is a very popular framework, because uniapp can quickly develop applications that support multiple platforms at the same time. In uniapp development, flex layout is a very powerful layout method that can help developers quickly achieve various complex layout effects. Below, we will introduce how to use flex layout in uniapp.

1. Overview

Flex layout, also known as elastic layout, is a modern CSS3 layout method that can be used to achieve complex layout effects. In flex layout, container elements can adapt to the size and proportions of their child elements without specifying explicit pixel or percentage dimensions. This makes layout more flexible and simpler.

flex layout can also be used in uniapp to achieve various layout effects. Developers of uniapp can use the uniapp plug-in uni-app-plus-flexible to quickly integrate and use flex layout.

2. Use flex layout

1. Introduce uni-app-plus-flexible plug-in

Before using flex layout, you need to install and use uni first -app-plus-flexible plugin. The uni-app-plus-flexible plug-in is a plug-in that allows the uniapp application to adapt to different devices and adjust the rem base value. This plug-in needs to be installed before using it.

npm install -D uni-app-plus-flexible

After the installation is complete, import and use the plug-in in the project's main.js file:

import Vue from 'vue'
import App from './App'
import uniFlex from 'uni-app-plus-flexible'  // 引入uniapp插件
Vue.use(uniFlex) // 注册uniapp插件
Vue.config.productionTip = false

App.mpType = 'app'

const app = new Vue({
  ...App
})
app.$mount()

2. Use flex layout in the layout file

To use flex layout in the layout file, you only need to add the display:flex style to the container element. As shown in the following code:

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

<style>
.container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}
.item {
  background-color: #f5f5f5;
  border: 1px solid #cccccc;
  padding: 20px;
}

.item-1 {
  flex: 1;
}
.item-2 {
  flex: 2;
}
.item-3 {
  flex: 3;
}
</style>

In the above code, we create a container containing only three child elements. We style the container element to display:flex; and assign different flex values ​​to its child elements. With these simple settings, you can implement a simple centered box based on flex layout.

In uniapp, flex layout has the following characteristics:

• The direct child elements of the flexible container are inline elements by default. You can set the flex-direction attribute A value of row or row-reverse turns it into a row-level element.
• The child elements of the flex container are flex box elements by default. You can set the flex: [none | [ <positive-number> | auto ]{1,3} ] attribute value Change its default behavior.
• Elements in the flexible container can also be passed through justify-content, align-items, align-self, flex- Attributes such as wrap and order are used to control the range, alignment, order, etc. of flexible elements.
• Compared with ordinary CSS layout syntax, the use of flex layout can help us more easily implement various complex layout requirements, such as bisecting containers, vertical centering, equally divided grids, etc.

3. Summary

In short, flex layout is an indispensable part of the uniapp development process. It allows developers to easily implement various layout effects without having to set a lot of pixels and percentages like traditional layout methods. Although the syntax of flex layout is relatively new, it is also simple to understand and use. For developers who use flex layout in uniapp, it will greatly improve development efficiency and make the application more outstanding.

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