Angular 8 - Animations

Animation gives the web application a refreshing look and rich user interaction. In HTML, animation is basically the transformation of HTML element from one CSS style to another over a specific period of time. For example, an image element can be enlarged by changing its width and height.
If the width and height of the image is changed from initial value to final value in steps over a period of time, say 10 seconds, then we get an animation effect. So, the scope of the animation depends on the feature / property provided by the CSS to style a HTML element.
Angular provides a separate module BrowserAnimationModule to do the animation. BrowserAnimationModule provides an easy and clear approach to do animation.
Let us learn how to configure animation module in this chapter.
Follow below mentioned steps to configure animation module, BrowserAnimationModule in an application.
Import BrowserAnimationModule in AppModule.
import { BrowserAnimationsModule } from '@angular/platform-browser/animations'; 
@NgModule({ 
   imports: [ 
      BrowserModule, 
      BrowserAnimationsModule 
   ], 
   declarations: [ ], 
   bootstrap: [ ] 
}) 
export class AppModule { }
Import animation function in the relevant components.
import { state, style, transition, animate, trigger } from '@angular/animations'
Add animations metadata property in the relevant component.
@Component({ 
   animations: [ 
      // animation functionality goes here 
   ] 
}) 
export class MyAnimationComponent
In angular, we need to understand the five core concept and its relationship to do animation.
State
State refers the specific state of the component. A component can have multiple defined state. The state is created using state() method. state() method has two arguments.
name − Unique name of the state.
name − Unique name of the state.
style − Style of the state defined using style() method.
style − Style of the state defined using style() method.
animations: [ 
   ... 
   state('start', style( { width: 200px; } )) 
   ... 
]
Here, start is the name of the state.
Style
Style refers the CSS style applied in a particular state. style() method is used to style the particular state of a component. It uses the CSS property and can have multiple items.
animations: [ 
   ... 
   state('start', style( { width: 200px; opacity: 1 } )) 
   ... 
]
Here, start state defines two CSS property, width with value 200px and opacity with value 1.
Transition refers the transition from one state to another. Animation can have multiple transition. Each transition is defined using transition() function. transition() takes two argument.
Specifies the direction between two transition state. For example, start => end refers that the initial state is start and the final state is end. Actually, it is an expression with rich functionality.
Specifies the direction between two transition state. For example, start => end refers that the initial state is start and the final state is end. Actually, it is an expression with rich functionality.
Specifies the animation details using animate() function.
Specifies the animation details using animate() function.
animations: [ 
   ... 
   transition('start => end', [ 
      animate('1s') 
   ])
   ... 
]
Here, transition() function defines the transition from start state to end state with animation defined in animate() method.
Animation defines the way the transition from one state to another take place. animation() function is used to set the animation details. animate() takes a single argument in the form of below expression −
duration delay easing

duration − refers the duration of the transition. It is expressed as 1s, 100ms, etc.,
duration − refers the duration of the transition. It is expressed as 1s, 100ms, etc.,
delay − refers the delay time to start the transition. It is expressed similar to duration
delay − refers the delay time to start the transition. It is expressed similar to duration
easing − refers how do to accelerates / decelerates the transition in the given time duration.
easing − refers how do to accelerates / decelerates the transition in the given time duration.
Every animation needs a trigger to start the animation. trigger() method is used to set all the animation information such as state, style, transition and animation in one place and give it a unique name. The unique name is used further to trigger the animation.
animations: [ 
   trigger('enlarge', [ 
      state('start', style({ 
         height: '200px', 
      })), 
      state('end', style({ 
         height: '500px', 
      })), 
      transition('start => end', [ 
         animate('1s') 
      ]), 
      transition('end => start', [ 
         animate('0.5s') 
   ]) ]), 
]

Here, enlarge is the unique name given to the particular animation. It has two state and related styles. It has two transition one from start to end and another from end to start. End to start state do the reverse of the animation.
Trigger can be attached to an element as specified below −
<div [@triggerName]="expression">...</div>;

For example,
<img [@enlarge]="isEnlarge ? 'end' : 'start'">...</img>;

Here,
@enlarge − trigger is set to image tag and attrached to an expression.
@enlarge − trigger is set to image tag and attrached to an expression.
If isEnlarge value is changed to true, then end state will be set and it triggers start => end transition.
If isEnlarge value is changed to true, then end state will be set and it triggers start => end transition.
If isEnlarge value is changed to false, then start state will be set and it triggers end => start transition.
If isEnlarge value is changed to false, then start state will be set and it triggers end => start transition.
Let us write a new angular application to better understand the animation concept by enlarging an image with animation effect.
Open command prompt and create new angular application.
cd /go/to/workspace 
ng new animation-app 
cd animation-app
Configure BrowserAnimationModule in the AppModule (src/app/app.module.ts)
import { BrowserModule } from '@angular/platform-browser'; 
import { NgModule } from '@angular/core' 
import { BrowserAnimationsModule } from '@angular/platform-browser/animations'; 
import { AppComponent } from './app.component'; @NgModule({ 
   declarations: [ 
      AppComponent 
   ], 
   imports: [ 
      BrowserModule, 
      BrowserAnimationsModule 
   ], 
   providers: [], 
   bootstrap: [AppComponent] 
}) 
export class AppModule { }
Open AppComponent (src/app/app.component.ts) and import necessary animation functions.
import { state, style, transition, animate, trigger } from '@angular/animations';
Add animation functionality, which will animate the image during the enlarging / shrinking of the image.
@Component({
   selector: 'app-root',
   templateUrl: './app.component.html',
   styleUrls: ['./app.component.css'],
   animations: [
      trigger('enlarge', [
         state('start', style({
            height: '150px'
         })),
         state('end', style({
            height: '250px'
         })),
         transition('start => end', [
            animate('1s 2s')
         ]),
         transition('end => start', [
            animate('1s 2s')
         ])
      ])
   ]
})
Open AppComponent template, src/app/app.component.html and remove sample code. Then, include a header with application title, image and a button to enlarge / shrink the image.
<h1>{{ title }}</h1> 
<img src="assets/puppy.jpeg" style="height: 200px" /> <br /> 
<button>{{ this.buttonText }}</button>
Write a function to change the animation expression.
export class AppComponent { 
   title = 'Animation Application'; 
   isEnlarge: boolean = false; 
   buttonText: string = "Enlarge"; 
   triggerAnimation() { 
      this.isEnlarge = !this.isEnlarge; 
      if(this.isEnlarge) 
         this.buttonText = "Shrink"; 
      else 
         this.buttonText = "Enlarge"; 
   } 
}
Attach the animation in the image tag. Also, attach the click event for the button.
<h1>{{ title }}</h1>
<img [@enlarge]="isEnlarge ? 'end' : 'start'" src="assets/puppy.jpeg" style="height: 200px" />
<br />
<button (click)='triggerAnimation()'>{{ this.buttonText }}</button>
The complete AppComponent code is as follows −
import { Component } from '@angular/core';
import { state, style, transition, animate, trigger } from '@angular/animations';

@Component({
   selector: 'app-root',
   templateUrl: './app.component.html',
   styleUrls: ['./app.component.css'],
   animations: [
      trigger('enlarge', [
         state('start', style({
            height: '150px'
         })),
         state('end', style({
            height: '250px'
         })),
         transition('start => end', [
            animate('1s 2s')
         ]),
         transition('end => start', [
            animate('1s 2s')
         ])
      ])
   ]
})
export class AppComponent {
   title = 'Animation Application';
   isEnlarge: boolean = false;
   buttonText: string = "Enlarge";


   triggerAnimation() {
      this.isEnlarge = !this.isEnlarge;

      if(this.isEnlarge) 
         this.buttonText = "Shrink";
      else
         this.buttonText = "Enlarge";
   }
}
The complete AppComponent template code is as follows −
<h1>{{ title }}</h1>
<img [@enlarge]="isEnlarge ? 'end' : 'start'" src="assets/puppy.jpeg" style="height: 200px" />
<br />
<button (click)='triggerAnimation()'>{{ this.buttonText }}</button>
Run the application using below command −
ng serve
Click the enlarge button, it will enlarge the image with animation. The result will be as shown below −
Click the button again to shrink it. The result will be as shown below −

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