Angular learning: in-depth chat about status and animation

This article will give you an in-depth understanding of the status and animation in Angular, briefly introduce the method of creating animation, and talk about key frame animation, animation callback, reusable animation, interleaved animation and other knowledge points. I hope it will be useful to everyone. Helped!

State

---

1. What is state

State represents the style of the element to be moved at different stages of movement.

2. Types of states

In Angular, there are three types of states, namely : void, *, custom

void: When the element is created in memory but has not yet This state occurs when an element is added to or deleted from the DOM [Related tutorial recommendation: "angular tutorial"]

*: The element is inserted The state after reaching the DOM tree, or the state of the element already in the DOM tree, also called the default state

custom: custom state, the element is on the page by default, from Movement from one state to another, such as the folding and unfolding of a panel.

3. Entry and exit animation

Entry animation refers to the element that appears in front of the user in the form of animation after it is created. Entry animation The status is represented by void => *, and the alias is :enter

##. The exit animation refers to a period of execution before the element is deleted. Say goodbye to animation, use
* => void for the status of exit animation, and the alias is :leave

## to get started quickly

1. Before using the animation function, you need to introduce the animation module, that is,

---

BrowserAnimationsModule

import { BrowserAnimationsModule } from "@angular/platform-browser/animations"

@NgModule({
  imports: [BrowserAnimationsModule],
})
export class AppModule {}

2. Default code analysis, todo Deleting tasks and adding tasks

<!-- 在 index.html 文件中引入 bootstrap.min.css -->
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" />

<div class="container">
  <h2 id="Todos">Todos</h2>
  <div class="form-group">
    <input (keyup.enter)="addItem(input)" #input type="text" class="form-control" placeholder="add todos" />
  </div>
  <ul class="list-group">
    <li (click)="removeItem(i)" *ngFor="let item of todos; let i = index" class="list-group-item">
      {{ item }}
    </li>
  </ul>
</div>

import { Component } from "@angular/core"

@Component({
  selector: "app-root",
  templateUrl: "./app.component.html",
  styles: []
})
export class AppComponent {
  // todo 列表
  todos: string[] = ["Learn Angular", "Learn RxJS", "Learn NgRx"]
	// 添加 todo
  addItem(input: HTMLInputElement) {
    this.todos.push(input.value)
    input.value = ""
  }
	// 删除 todo
  removeItem(index: number) {
    this.todos.splice(index, 1)
  }
}

3. Create animation

trigger method is used to create animation, specify the animation name

• ## The #transition method is used to specify the motion state of the animation, exit animation or entry animation, or custom state animation.

• The style method is used to set the style corresponding to the element in different states.

• The animate method is used to set motion parameters, such as animation motion. Time, delay event, motion form

• @Component({
    animations: [
      // 创建动画, 动画名称为 slide
      trigger("slide", [
        // 指定入场动画 注意: 字符串两边不能有空格, 箭头两边可以有也可以没有空格
        // void => * 可以替换为 :enter
        transition("void => *", [
          // 指定元素未入场前的样式
          style({ opacity: 0, transform: "translateY(40px)" }),
          // 指定元素入场后的样式及运动参数
          animate(250, style({ opacity: 1, transform: "translateY(0)" }))
        ]),
        // 指定出场动画
        // * => void 可以替换为 :leave
        transition("* => void", [
          // 指定元素出场后的样式和运动参数
          animate(600, style({ opacity: 0, transform: "translateX(100%)" }))
        ])
      ])
    ]
  })

  Note: The entry animation does not need to specify the default state of the element, Angular will clear the void state as the default state

trigger("slide", [
  transition(":enter", [
    style({ opacity: 0, transform: "translateY(40px)" }),
    animate(250)
  ]),
  transition(":leave", [
 		animate(600, style({ opacity: 0, transform: "translateX(100%)" }))
  ])
])

Note: To set the motion parameters of the animation, you need to change one parameter of the animate method to a string type

// 动画执行总时间 延迟时间 (可选) 运动形式 (可选)
animate("600ms 1s ease-out", style({ opacity: 0, transform: "translateX(100%)" }))

Keyframe animation

Keyframe animation usage

keyframes

---

Method definition

<pre class='brush:php;toolbar:false;'>transition(&quot;:leave&quot;, [ animate( 600, keyframes([ style({ offset: 0.3, transform: &quot;translateX(-80px)&quot; }), style({ offset: 1, transform: &quot;translateX(100%)&quot; }) ]) ) ])</pre>
Animation callback

Angular provides two callback functions related to animation , respectively when the animation starts executing and after the animation execution is completed

---

<li @slide (@slide.start)="start($event)" (@slide.done)="done($event)"></li>

import { AnimationEvent } from "@angular/animations"

start(event: AnimationEvent) {
  console.log(event)
}
done(event: AnimationEvent) {
  console.log(event)
}

Create reusable animation

1. Place the definition of the animation in a separate file, which is more convenient Component call.

---

import { animate, keyframes, style, transition, trigger } from "@angular/animations"

export const slide = trigger("slide", [
  transition(":enter", [
    style({ opacity: 0, transform: "translateY(40px)" }),
    animate(250)
  ]),
  transition(":leave", [
    animate(
      600,
      keyframes([
        style({ offset: 0.3, transform: "translateX(-80px)" }),
        style({ offset: 1, transform: "translateX(100%)" })
      ])
    )
  ])
])

import { slide } from "./animations"

@Component({
  animations: [slide]
})

2. Extract specific animation definitions to facilitate multiple animation calls.

import {animate, animation, keyframes, style, transition, trigger, useAnimation} from "@angular/animations"

export const slideInUp = animation([
  style({ opacity: 0, transform: "translateY(40px)" }),
  animate(250)
])

export const slideOutLeft = animation([
  animate(
    600,
    keyframes([
      style({ offset: 0.3, transform: "translateX(-80px)" }),
      style({ offset: 1, transform: "translateX(100%)" })
    ])
  )
])

export const slide = trigger("slide", [
  transition(":enter", useAnimation(slideInUp)),
  transition(":leave", useAnimation(slideOutLeft))
])

3. When calling animation, transfer the total time of movement, delay time, and movement form

export const slideInUp = animation(
  [
    style({ opacity: 0, transform: "translateY(40px)" }),
    animate("{{ duration }} {{ delay }} {{ easing }}")
  ],
  {
    params: {
      duration: "400ms",
      delay: "0s",
      easing: "ease-out"
    }
  }
)

transition(":enter", useAnimation(slideInUp, {params: {delay: "1s"}}))

Query element execution animation

Angular Provides

query

---

method to find elements and create animations for elements

<pre class='brush:php;toolbar:false;'>import { slide } from &quot;./animations&quot; animations: [ slide, trigger(&quot;todoAnimations&quot;, [ transition(&quot;:enter&quot;, [ query(&quot;h2&quot;, [ style({ transform: &quot;translateY(-30px)&quot; }), animate(300) ]), // 查询子级动画 使其执行 query(&quot;@slide&quot;, animateChild()) ]) ]) ]</pre><pre class='brush:php;toolbar:false;'>&lt;div class=&quot;container&quot; @todoAnimations&gt; &lt;h2 id=&quot;Todos&quot;&gt;Todos&lt;/h2&gt; &lt;ul class=&quot;list-group&quot;&gt; &lt;li @slide (click)=&quot;removeItem(i)&quot; *ngFor=&quot;let item of todos; let i = index&quot; class=&quot;list-group-item&quot; &gt; {{ item }} &lt;/li&gt; &lt;/ul&gt; &lt;/div&gt;</pre>By default, parent animation and child animation are executed in order, the parent animation is executed first, and then the child animation is executed. Level animation, you can use the
group

method to make it parallel

trigger("todoAnimations", [
  transition(":enter", [
    group([
      query("h2", [
        style({ transform: "translateY(-30px)" }),
        animate(300)
      ]),
      query("@slide", animateChild())
    ])
  ])
])

Interlaced animation

Angular provides the stagger method to run multiple elements When executing the same animation at the same time, delay the execution of each element's animation in turn.

---

transition(":enter", [
  group([
    query("h2", [
      style({ transform: "translateY(-30px)" }),
      animate(300)
    ]),
    query("@slide", stagger(200, animateChild()))
  ])
])

Note: The stagger method can only be used inside the query method

Custom state animation

Angular provides

state

---

method is used to define state.

1. Default code analysis

<div class="container">
  <div class="panel panel-default">
    <div class="panel-heading" (click)="toggle()">
      一套框架, 多种平台, 移动端 & 桌面端
    </div>
    <div class="panel-body">
      <p>
        使用简单的声明式模板，快速实现各种特性。使用自定义组件和大量现有组件，扩展模板语言。在几乎所有的
        IDE 中获得针对 Angular
        的即时帮助和反馈。所有这一切，都是为了帮助你编写漂亮的应用，而不是绞尽脑汁的让代码“能用”。
      </p>
      <p>
        从原型到全球部署，Angular 都能带给你支撑 Google
        大型应用的那些高延展性基础设施与技术。
      </p>
      <p>
        通过 Web Worker 和服务端渲染，达到在如今(以及未来）的 Web
        平台上所能达到的最高速度。 Angular 让你有效掌控可伸缩性。基于
        RxJS、Immutable.js 和其它推送模型，能适应海量数据需求。
      </p>
      <p>
        学会用 Angular
        构建应用，然后把这些代码和能力复用在多种多种不同平台的应用上 ——
        Web、移动 Web、移动应用、原生应用和桌面原生应用。
      </p>
    </div>
  </div>
</div>
<style>
  .container {
    margin-top: 100px;
  }
  .panel-heading {
    cursor: pointer;
  }
</style>

import { Component } from "@angular/core"

@Component({
  selector: "app-root",
  templateUrl: "./app.component.html",
  styles: []
})
export class AppComponent {
  isExpended: boolean = false
  toggle() {
    this.isExpended = !this.isExpended
  }
}

2. Create animation

trigger("expandCollapse", [
  // 使用 state 方法定义折叠状态元素对应的样式
  state(
    "collapsed",
    style({
      height: 0,
      overflow: "hidden",
      paddingTop: 0,
      paddingBottom: 0
    })
  ),
  // 使用 state 方法定义展开状态元素对应的样式
  state("expanded", style({ height: "*", overflow: "auto" })),
  // 定义展开动画
  transition("collapsed => expanded", animate("400ms ease-out")),
  // 定义折叠动画
  transition("expanded => collapsed", animate("400ms ease-in"))
])

<div class="panel-body" [@expandCollapse]="isExpended ? &#39;expanded&#39; : &#39;collapsed&#39;"></div>

Routing animation

---

1、为路由添加状态标识，此标识即为路由执行动画时的自定义状态

const routes: Routes = [
  {
    path: "",
    component: HomeComponent,
    pathMatch: "full",
    data: {
      animation: "one" 
    }
  },
  {
    path: "about",
    component: AboutComponent,
    data: {
      animation: "two"
    }
  },
  {
    path: "news",
    component: NewsComponent,
    data: {
      animation: "three"
    }
  }
]

2、通过路由插座对象获取路由状态标识，并将标识传递给动画的调用者，让动画执行当前要执行的状态是什么

<div class="routerContainer" [@routerAnimations]="prepareRoute(outlet)">
  <router-outlet #outlet="outlet"></router-outlet>
</div>

import { RouterOutlet } from "@angular/router"

export class AppComponent {
  prepareRoute(outlet: RouterOutlet) {
    return (
      outlet &&
      outlet.activatedRouteData &&
      outlet.activatedRouteData.animation
    )
  }
}

3、将 routerContainer 设置为相对定位，将它的直接一级子元素设置成绝对定位

/* styles.css */
.routerContainer {
  position: relative;
}

.routerContainer > * {
  position: absolute;
  left: 0;
  top: 0;
  width: 100%;
}

4、创建动画

trigger("routerAnimations", [
  transition("one => two, one => three, two => three", [
    query(":enter", style({ transform: "translateX(100%)", opacity: 0 })),
    group([
      query(
        ":enter",
        animate(
          "0.4s ease-in",
          style({ transform: "translateX(0)", opacity: 1 })
        )
      ),
      query(
        ":leave",
        animate(
          "0.4s ease-out",
          style({
            transform: "translateX(-100%)",
            opacity: 0
          })
        )
      )
    ])
  ]),
  transition("three => two, three => one, two => one", [
    query(
      ":enter",
      style({ transform: "translateX(-100%)", opacity: 0 })
    ),
    group([
      query(
        ":enter",
        animate(
          "0.4s ease-in",
          style({ transform: "translateX(0)", opacity: 1 })
        )
      ),
      query(
        ":leave",
        animate(
          "0.4s ease-out",
          style({
            transform: "translateX(100%)",
            opacity: 0
          })
        )
      )
    ])
  ])
])

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