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/Angular 7

trigger

function

Creates a named animation trigger, containing a list of state() and transition() entries to be evaluated when the expression bound to the trigger changes.

trigger(name: string, definitions: AnimationMetadata[]): AnimationTriggerMetadata

Parameters
name string

An identifying string.

definitions AnimationMetadata[]

An animation definition object, containing an array of state() and transition() declarations.

Returns

AnimationTriggerMetadata: An object that encapsulates the trigger data.

Usage notes

Define an animation trigger in the animations section of @Component metadata. In the template, reference the trigger by name and bind it to a trigger expression that evaluates to a defined animation state, using the following format:

[@triggerName]="expression"

Animation trigger bindings convert all values to strings, and then match the previous and current values against any linked transitions. Booleans can be specified as 1 or true and 0 or false.

Usage Example

The following example creates an animation trigger reference based on the provided name value. The provided animation value is expected to be an array consisting of state and transition declarations.

@Component({
  selector: "my-component",
  templateUrl: "my-component-tpl.html",
  animations: [
    trigger("myAnimationTrigger", [
      state(...),
      state(...),
      transition(...),
      transition(...)
    ])
  ]
})
class MyComponent {
  myStatusExp = "something";
}

The template associated with this component makes use of the defined trigger by binding to an element within its template code.

<!-- somewhere inside of my-component-tpl.html -->
<div [@myAnimationTrigger]="myStatusExp">...</div>

Using an inline function

The transition animation method also supports reading an inline function which can decide if its associated animation should be run.

// this method is run each time the `myAnimationTrigger` trigger value changes.
function myInlineMatcherFn(fromState: string, toState: string, element: any, params: {[key:
 string]: any}): boolean {
  // notice that `element` and `params` are also available here
  return toState == 'yes-please-animate';
}

@Component({
  selector: 'my-component',
  templateUrl: 'my-component-tpl.html',
  animations: [
    trigger('myAnimationTrigger', [
      transition(myInlineMatcherFn, [
        // the animation sequence code
      ]),
    ])
  ]
})
class MyComponent {
  myStatusExp = "yes-please-animate";
}

Disabling Animations

When true, the special animation control binding @.disabled binding prevents all animations from rendering. Place the @.disabled binding on an element to disable animations on the element itself, as well as any inner animation triggers within the element.

The following example shows how to use this feature:

@Component({
  selector: 'my-component',
  template: `
    <div [@.disabled]="isDisabled">
      <div [@childAnimation]="exp"></div>
    </div>
  `,
  animations: [
    trigger("childAnimation", [
      // ...
    ])
  ]
})
class MyComponent {
  isDisabled = true;
  exp = '...';
}

When @.disabled is true, it prevents the @childAnimation trigger from animating, along with any inner animations.

Disable animations application-wide

When an area of the template is set to have animations disabled, all inner components have their animations disabled as well. This means that you can disable all animations for an app by placing a host binding set on @.disabled on the topmost Angular component.

import {Component, HostBinding} from '@angular/core';

@Component({
  selector: 'app-component',
  templateUrl: 'app.component.html',
})
class AppComponent {
  @HostBinding('@.disabled')
  public animationsDisabled = true;
}

Overriding disablement of inner animations

Despite inner animations being disabled, a parent animation can query() for inner elements located in disabled areas of the template and still animate them if needed. This is also the case for when a sub animation is queried by a parent and then later animated using animateChild().

Detecting when an animation is disabled

If a region of the DOM (or the entire application) has its animations disabled, the animation trigger callbacks still fire, but for zero seconds. When the callback fires, it provides an instance of an AnimationEvent. If animations are disabled, the .disabled flag on the event is true.

© 2010–2019 Google, Inc.
Licensed under the Creative Commons Attribution License 4.0.
https://v7.angular.io/api/animations/trigger