Introduction to Angular animations link
Animation provides the illusion of motion: HTML elements change styling over time. Well-designed animations can make your application more fun and straightforward to use, but they aren't just cosmetic. Animations can improve your application and user experience in a number of ways:
- Without animations, web page transitions can seem abrupt and jarring
- Motion greatly enhances the user experience, so animations give users a chance to detect the application's response to their actions
- Good animations intuitively call the user's attention to where it is needed
Typically, animations involve multiple style transformations over time. An HTML element can move, change color, grow or shrink, fade, or slide off the page. These changes can occur simultaneously or sequentially. You can control the timing of each transformation.
Angular's animation system is built on CSS functionality, which means you can animate any property that the browser considers animatable. This includes positions, sizes, transforms, colors, borders, and more. The W3C maintains a list of animatable properties on its CSS Transitions page.
About this guide link
This guide covers the basic Angular animation features to get you started on adding Angular animations to your project.
The features described in this guide —and the more advanced features described in the related Angular animations guides— are demonstrated in an example application available as a
Prerequisites link
The guide assumes that you're familiar with building basic Angular apps, as described in the following sections:
- Tutorial
- Architecture Overview
Getting started link
The main Angular modules for animations are
@angular/animations
and
@angular/platform-browser
.
When you create a new project using the CLI, these dependencies are automatically added to your project.
To get started with adding Angular animations to your project, import the animation-specific modules along with standard Angular functionality.
Step 1: Enabling the animations module link
Import
BrowserAnimationsModule
, which introduces the animation capabilities into your Angular root application module.
import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
@NgModule({
imports: [
BrowserModule,
BrowserAnimationsModule
],
declarations: [ ],
bootstrap: [ ]
})
export class AppModule { }
NOTE
:
When you use the CLI to create your app, the root application module
app.module.ts
is placed in the
src/app
folder.
Step 2: Importing animation functions into component files link
If you plan to use specific animation functions in component files, import those functions from
@angular/animations
.
import { Component, HostBinding } from '@angular/core';
import {
trigger,
state,
style,
animate,
transition,
// ...
} from '@angular/animations';
NOTE
:
See a summary of available animation functions at the end of this guide.
Step 3: Adding the animation metadata property link
In the component file, add a metadata property called
animations:
within the
@Component()
decorator.
You put the trigger that defines an animation within the
animations
metadata property.
@Component({
selector: 'app-root',
templateUrl: 'app.component.html',
styleUrls: ['app.component.css'],
animations: [
// animation triggers go here
]
})
Animating a transition link
Let's animate a transition that changes a single HTML element from one state to another.
For example, you can specify that a button displays either
Open
or
Closed
based on the user's last action.
When the button is in the
open
state, it's visible and yellow.
When it's the
closed
state, it's translucent and blue.
In HTML, these attributes are set using ordinary CSS styles such as color and opacity.
In Angular, use the
style()
function to specify a set of CSS styles for use with animations.
Collect a set of styles in an animation state, and give the state a name, such as
open
or
closed
.
Let's create a new
open-close
component to animate with simple transitions.
Run the following command in terminal to generate the component:
ng g component open-close
This will create the component at
src/app/open-close.component.ts
.
Animation state and styles link
Use Angular's
state()
function to define different states to call at the end of each transition.
This function takes two arguments:
A unique name like
open
or
closed
and a
style()
function.
Use the
style()
function to define a set of styles to associate with a given state name.
You must use
camelCase
for style attributes that contain dashes, such as
backgroundColor
or wrap them in quotes, such as
'background-color'
.
Let's see how Angular's
state()
function works with the
style()
function to set CSS style attributes.
In this code snippet, multiple style attributes are set at the same time for the state.
In the
open
state, the button has a height of 200 pixels, an opacity of 1, and a yellow background color.
// ...
state('open', style({
height: '200px',
opacity: 1,
backgroundColor: 'yellow'
})),
In the following
closed
state, the button has a height of 100 pixels, an opacity of 0.8, and a background color of blue.
state('closed', style({
height: '100px',
opacity: 0.8,
backgroundColor: 'blue'
})),
Transitions and timing link
In Angular, you can set multiple styles without any animation. However, without further refinement, the button instantly transforms with no fade, no shrinkage, or other visible indicator that a change is occurring.
To make the change less abrupt, you need to define an animation
transition
to specify the changes that occur between one state and another over a period of time.
The
transition()
function accepts two arguments:
The first argument accepts an expression that defines the direction between two transition states, and the second argument accepts one or a series of
animate()
steps.
Use the
animate()
function to define the length, delay, and easing of a transition, and to designate the style function for defining styles while transitions are taking place.
Use the
animate()
function to define the
keyframes()
function for multi-step animations.
These definitions are placed in the second argument of the
animate()
function.
Animation metadata: duration, delay, and easing link
The
animate()
function (second argument of the transition function) accepts the
timings
and
styles
input parameters.
The
timings
parameter takes either a number or a string defined in three parts.
animate (duration)
or
animate ('duration delay easing')
The first part,
duration
, is required.
The duration can be expressed in milliseconds as a number without quotes, or in seconds with quotes and a time specifier.
For example, a duration of a tenth of a second can be expressed as follows:
-
As a plain number, in milliseconds:
100 -
In a string, as milliseconds:
'100ms' -
In a string, as seconds:
'0.1s'
The second argument,
delay
, has the same syntax as
duration
.
For example:
-
Wait for 100ms and then run for 200ms:
'0.2s 100ms'
The third argument,
easing
, controls how the animation accelerates and decelerates during its runtime.
For example,
ease-in
causes the animation to begin slowly, and to pick up speed as it progresses.
-
Wait for 100ms, run for 200ms. Use a deceleration curve to start out fast and slowly decelerate to a resting point:
'0.2s 100ms ease-out' -
Run for 200ms, with no delay. Use a standard curve to start slow, accelerate in the middle, and then decelerate slowly at the end:
'0.2s ease-in-out' -
Start immediately, run for 200ms. Use an acceleration curve to start slow and end at full velocity:
'0.2s ease-in'
NOTE
:
See the Material Design website's topic on Natural easing curves for general information on easing curves.
This example provides a state transition from
open
to
closed
with a 1-second transition between states.
transition('open => closed', [
animate('1s')
]),
In the preceding code snippet, the
=>
operator indicates unidirectional transitions, and
<=>
is bidirectional.
Within the transition,
animate()
specifies how long the transition takes.
In this case, the state change from
open
to
closed
takes 1 second, expressed here as
1s
.
This example adds a state transition from the
closed
state to the
open
state with a 0.5-second transition animation arc.
transition('closed => open', [
animate('0.5s')
]),
NOTE
:
Some additional notes on using styles within
state
and
transition
functions.
-
Use
state()to define styles that are applied at the end of each transition, they persist after the animation completes -
Use
transition()to define intermediate styles, which create the illusion of motion during the animation -
When animations are disabled,
transition()styles can be skipped, butstate()styles can't -
Include multiple state pairs within the same
transition()argument:transition( 'on => off, off => void' )
Triggering the animation link
An animation requires a
trigger
, so that it knows when to start.
The
trigger()
function collects the states and transitions, and gives the animation a name, so that you can attach it to the triggering element in the HTML template.
The
trigger()
function describes the property name to watch for changes.
When a change occurs, the trigger initiates the actions included in its definition.
These actions can be transitions or other functions, as we'll see later on.
In this example, we'll name the trigger
openClose
, and attach it to the
button
element.
The trigger describes the open and closed states, and the timings for the two transitions.
NOTE
:
Within each
trigger()
function call, an element can only be in one state at any given time.
However, it's possible for multiple triggers to be active at once.
Defining animations and attaching them to the HTML template link
Animations are defined in the metadata of the component that controls the HTML element to be animated.
Put the code that defines your animations under the
animations:
property within the
@Component()
decorator.
@Component({
selector: 'app-open-close',
animations: [
trigger('openClose', [
// ...
state('open', style({
height: '200px',
opacity: 1,
backgroundColor: 'yellow'
})),
state('closed', style({
height: '100px',
opacity: 0.8,
backgroundColor: 'blue'
})),
transition('open => closed', [
animate('1s')
]),
transition('closed => open', [
animate('0.5s')
]),
]),
],
templateUrl: 'open-close.component.html',
styleUrls: ['open-close.component.css']
})
export class OpenCloseComponent {
isOpen = true;
toggle() {
this.isOpen = !this.isOpen;
}
}
When you've defined an animation trigger for a component, attach it to an element in that component's template by wrapping the trigger name in brackets and preceding it with an
@
symbol.
Then, you can bind the trigger to a template expression using standard Angular property binding syntax as shown below, where
triggerName
is the name of the trigger, and
expression
evaluates to a defined animation state.
<div [@triggerName]="expression">…</div>;
The animation is executed or triggered when the expression value changes to a new state.
The following code snippet binds the trigger to the value of the
isOpen
property.
<nav>
<button type="button" (click)="toggle()">Toggle Open/Close</button>
</nav>
<div [@openClose]="isOpen ? 'open' : 'closed'" class="open-close-container">
<p>The box is now {{ isOpen ? 'Open' : 'Closed' }}!</p>
</div>
In this example, when the
isOpen
expression evaluates to a defined state of
open
or
closed
, it notifies the trigger
openClose
of a state change.
Then it's up to the
openClose
code to handle the state change and kick off a state change animation.
For elements entering or leaving a page (inserted or removed from the DOM), you can make the animations conditional.
For example, use
*ngIf
with the animation trigger in the HTML template.
NOTE
:
In the component file, set the trigger that defines the animations as the value of the
animations:
property in the
@Component()
decorator.
In the HTML template file, use the trigger name to attach the defined animations to the HTML element to be animated.
Code review link
Here are the code files discussed in the transition example.
@Component({
selector: 'app-open-close',
animations: [
trigger('openClose', [
// ...
state('open', style({
height: '200px',
opacity: 1,
backgroundColor: 'yellow'
})),
state('closed', style({
height: '100px',
opacity: 0.8,
backgroundColor: 'blue'
})),
transition('open => closed', [
animate('1s')
]),
transition('closed => open', [
animate('0.5s')
]),
]),
],
templateUrl: 'open-close.component.html',
styleUrls: ['open-close.component.css']
})
export class OpenCloseComponent {
isOpen = true;
toggle() {
this.isOpen = !this.isOpen;
}
}
Summary link
You learned to add animation to a transition between two states, using
style()
and
state()
along with
animate()
for the timing.
Learn about more advanced features in Angular animations under the Animation section, beginning with advanced techniques in transition and triggers.
Animations API summary link
The functional API provided by the
@angular/animations
module provides a domain-specific language (DSL) for creating and controlling animations in Angular applications.
See the API reference for a complete listing and syntax details of the core functions and related data structures.
| Function name | What it does |
|---|---|
trigger()
|
Kicks off the animation and serves as a container for all other animation function calls. HTML template binds to
triggerName
. Use the first argument to declare a unique trigger name. Uses array syntax.
|
style()
|
Defines one or more CSS styles to use in animations. Controls the visual appearance of HTML elements during animations. Uses object syntax. |
state()
|
Creates a named set of CSS styles that should be applied on successful transition to a given state. The state can then be referenced by name within other animation functions. |
animate()
|
Specifies the timing information for a transition. Optional values for
delay
and
easing
. Can contain
style()
calls within.
|
transition()
|
Defines the animation sequence between two named states. Uses array syntax. |
keyframes()
|
Allows a sequential change between styles within a specified time interval. Use within
animate()
. Can include multiple
style()
calls within each
keyframe()
. Uses array syntax.
|
group()
|
Specifies a group of animation steps (
inner animations
) to be run in parallel. Animation continues only after all inner animation steps have completed. Used within
sequence()
or
transition()
.
|
query()
|
Finds one or more inner HTML elements within the current element. |
sequence()
|
Specifies a list of animation steps that are run sequentially, one by one. |
stagger()
|
Staggers the starting time for animations for multiple elements. |
animation()
|
Produces a reusable animation that can be invoked from elsewhere. Used together with
useAnimation()
.
|
useAnimation()
|
Activates a reusable animation. Used with
animation()
.
|
animateChild()
|
Allows animations on child components to be run within the same timeframe as the parent. |
More on Angular animations link
You might also be interested in the following:
- Transition and triggers
- Complex animation sequences
- Reusable animations
- Route transition animations
Check out this presentation, shown at the AngularConnect conference in November 2017, and the accompanying source code.
