[applet development] detailed explanation of host environment

Learning objectives of this section ：

In depth understanding of the host environment composition of applets

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1. The host environment of the applet

Mobile wechat is the host environment of small programs , Applets take advantage of the capabilities provided by the host environment , It can realize many functions that ordinary web pages cannot complete . for example ： The applet calls the... Provided by wechat API Realize code scanning , Payment and other functions .

The content contained in the hosting environment of the applet ：

• Communication model
• Operating mechanism
• Components
• API

2. Communication model

1. The subject of communication

The main body of communication in the applet is Render layer and Logic layer , among ：

1. WXML Templates and WXSS Styles work in the render layer
2. JS Scripts work at the logical level

2. Communication model of applet

The communication model of the applet is divided into two parts ：

1. Render layer and Logic layer Communication between
2. Logic layer and Third party servers Communication between

Both are forwarded through wechat clients

3. Operating mechanism

1. The startup process of the applet

1. Download the code package of the applet to the local
2. analysis app.json Global profile
3. perform app.js Applet entry file , call App() Create an instance of the applet
4. Rendering applet home page
5. Applet startup completed

2. The process of page rendering

1. Load the of the parsing page .json The configuration file
2. To load a page .wxml Templates and .wxss style
3. Execute the .js file , call Page() Create page instances
4. Page rendering complete

4. Components

1. Classification of components in applet ：

The components in the applet are also composed of Host environment Provided , Developers can quickly build a beautiful page structure based on components . Officials divide the components of small programs into 9 Categories: , Namely ：

1. View container
2. Basic content </blue>
3. Form components
4. Navigation components
5. Body assembly
6. map Map components
7. canvas Canvas components
8. Opening ability
9. Accessibility

2. Common view container class components

view

• Normal view area
• Be similar to HTML Medium div, Is a block level element
• Commonly used to achieve the layout effect of the page

for example ： Use flex Achieve horizontal layout .

wxml Code :

<view class="container1"><view>A</view><view>B</view><view>C</view></view>

wxss Code ：

.container1 view{  width:100px;  height:100px;  text-align: center;  line-height: 100px;}.container1 view:nth-child(1){  background-color: aquamarine;}.container1 view:nth-child(2){  background-color: azure;}.container1 view:nth-child(3){  background-color: darkorange;}.container1 {  display: flex;  justify-content: space-around;}

Realization effect ：

scroll-view

• Scrollable view area
• It is often used to achieve the effect of scrolling lists

utilize scroll-view Achieve the effect of scrolling up and down

wxml Code :

<scroll-view class="container1" scroll-y><view>A</view><view>B</view><view>C</view></scroll-view>

Modified wxss Code ：

.container1 {  border:1px solid red;  height:110px;  /* Use scroll-view Set a fixed height */

Realization effect ：

swiper and swiper-item

• Carousel map container assembly and Shuffling figure item Components

Using these two components can achieve the effect of rotating pictures ：

wxml Code :

<swiper class="swiper-container" indicator-dots="true" indicator-color="white" indicator-active-color="red" autoplay="true" interval="1000" circular><swiper-item><view class="item">A</view></swiper-item><swiper-item>  <view class="item">B</view></swiper-item><swiper-item>  <view class="item">C</view></swiper-item></swiper>

wxss Code ：

.swiper-container{  height:150px;}.item{  height:100%;  line-height: 150px;  text-align: center;}swiper-item:nth-child(1) .item{  background-color: aquamarine;}swiper-item:nth-child(2) .item{  background-color: azure;}swiper-item:nth-child(3) .item{  background-color: darkorange;}

Realization effect ：

3. Common basic content components

text

• Text component
• Be similar to HTML Medium span label , It's an in-line element

Long press the selected text content

<view> Long press to select the text content :<text user-select>HelloWorld!</text></view>

rich-text

• Rich text component
• Support HTML The string is rendered as WXML structure

hold HTML The string is rendered as the corresponding UI structure

<rich-text nodes="<h1 style='color:red'> title </h1>"> </rich-text>

4. Other common components

button

• Button components
• Functional ratio HTML Medium button Rich buttons
• adopt open-type Attribute can call various functions provided by wechat （ Customer service 、 forward 、 Get user authorization 、 Access to user information, etc ）

image

• Picture components
• image The default width of the component is about 300px、 The height is about 240px

navigator

• Page navigation component
• Be similar to HTML Medium a link , Realize page Jump

5.API

In the applet API Is provided by the host environment , Through these rich applets API, Developers can easily call the capabilities provided by wechat , for example ： Realize payment , Scan code and other functions .

Applet API Of 3 Big classification ：

Event monitoring API

• characteristic ： With on start , Used to monitor the trigger of some events
• give an example ：wx.onWindowResize(function callback) Listen for window size changes

Sync API

• characteristic 1： With Sync At the end of the API It's all synchronous API
• characteristic 2： Sync API The results of the implementation of , You can get directly through the return value of the function , If the execution fails, an exception will be thrown
• give an example ：wx.setStorageSync(‘key’, ‘value’) Write content to local storage

asynchronous API

• characteristic ： Be similar to jQuery Medium $.ajax(options) function , Need to pass through success、fail、complete Receive the result of the call
• give an example ：wx.request() Initiate a network data request , adopt success The callback function receives data

6. summary

In this section, we learned about the hosting environment of the applet and the specific contents of the hosting environment of the applet .