为什么 Angular 5 会抛出这个错误?
AppComponent.html:2 ERROR TypeError: Cannot read property 'forEach' of undefined
我正在研究 Angular 动画的概念验证,我直接使用网站上的代码。我的组件如下所示:
import { Component, OnInit } from '@angular/core';
import { trigger, state, style, transition, animate, keyframes } from '@angular/animations';
@Component({
selector: 'app-obj-list',
templateUrl: './obj-list.component.html',
styleUrls: ['./obj-list.component.css'],
animations: [
trigger('myAwesomeAnimation', [
state('small', style({
transform: 'scale(1)',
})),
state('large', style({
transform: 'scale(1.2)',
})),
]),
transition('small => large', animate('100ms ease-in'))
]
})
export class ObjListComponent implements OnInit {
state = 'small';
constructor() { }
animateMe() {
this.state = (this.state === 'small' ? 'large' : 'small');
}
ngOnInit() {
}
}
错误引用的代码行只是包含我的组件的标记:<app-obj-list></app-obj-list>
我已将其缩小到上述文件中的行:transition('small => large', animate('100ms ease-in'))
当我删除该行时,错误消失了。当我把它留在里面时,我得到了错误:
AppComponent.html:2 ERROR TypeError: Cannot read property 'forEach' of undefined
at new AnimationTrigger (browser.js:3017)
at buildTrigger (browser.js:3005)
at InjectableAnimationEngine.AnimationEngine.registerTrigger (browser.js:5504)
at eval (animations.js:291)
at Array.forEach (<anonymous>)
at AnimationRendererFactory.createRenderer (animations.js:290)
at DebugRendererFactory2.createRenderer (core.js:15075)
at createComponentView (core.js:13633)
at callWithDebugContext (core.js:15041)
at Object.debugCreateComponentView [as createComponentView] (core.js:14370)
我的 app.module 有 BrowserAnimationsModule 所以这不应该是问题:
import { BrowserModule } from '@angular/platform-browser';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { NgModule } from '@angular/core';
import { AppComponent } from './app.component';
import { ObjListComponent } from './obj-list/obj-list.component';
@NgModule({
declarations: [
AppComponent,
ObjListComponent
],
imports: [
BrowserModule,
BrowserAnimationsModule
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }
我正在尝试遵循 angular site 上的代码尽我所能。有人可以告诉我我忘记了什么吗?有没有我忘记的进口? 有我需要下载的包吗?我是 Angular 和 Angular 动画的新手,我似乎无法弄清楚这一点。
最佳答案
如果你仔细看教程,动画的“transition”属性需要在“trigger”数组中:
animations: [
trigger('myAwesomeAnimation', [
state('small', style({
transform: 'scale(1)',
})),
state('large', style({
transform: 'scale(1.2)',
})),
transition('small => large', animate('100ms ease-in'))
]) // close the array after the transition
]
关于javascript - 为什么 Angular 5 Transition 抛出 AppComponent.html :2 ERROR TypeError: Cannot read property 'forEach' of undefined,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/48214511/