无法在Angular 7中执行另一个组件的方法

Question

我正在尝试调用headerComponent槽的sidebarcomponent的方法togglesidebar（）方法calltogglesidebarontogglesidebarbtn（），但我得到了一些我不了解的错误。如何使用另一个组件的方法？

我在headerComponent中导入sidebarcomponent;在HeaderComponent中，我在构造函数中添加sidebarcomponent以使用她的一种方法。我试图删除header.component.ts的方法callToggleSideBarontoggleSideBarbtn（），但我得到了相同的输出。

sinebar.component.html：

<div id="sidebar" class="bg-gray">
<a href="" class="nav-link"><i class="fa fa-calendar"></i> Event</a>
<a href="" class="nav-link"><i class="fa fa-user-circle-o"></i> Profile</a>
<a href="" class="nav-link"><i class="fa fa-commenting-o"></i> Chat</a>
<a href="" class="nav-link"><i class="fa fa-gear"></i> Setting</a>
<a href="" class="nav-link"><i class="fa fa-question-circle-o"></i> Help</a>
<a href="" class="nav-link"><i class="fa fa-sign-out"></i> Log out</a>

sidebar.component.ts：

import { Component, OnInit } from '@angular/core';
import * as $ from 'jquery';
@Component({
  selector: 'app-sidebar',
  templateUrl: './sidebar.component.html',
  styleUrls: ['./sidebar.component.css']
})
export class SidebarComponent implements OnInit {
  constructor() { }
  ngOnInit() {
  }
  // Display the sidebar if it's not visible and otherwise if else.
  toggleSidebar() {
    $("#sidebar").animate({width: 'toggle'});
  }
}

header.component.html：

<div>
  <nav class="navbar navbar-expand-lg d-flex justify-content-between fixed-top">
    <button class="btn" (click)="callToggleSidebarOnToggleSidebarBtn()"><i class="fa fa-reorder"></i></button>
    <div class="d-flex p-0 m-0">
      <a href="#" class="nav-link d-none d-lg-block">Event</a>
      <a href="#" class="nav-link d-none d-lg-block">Contact Us</a>
      <a href="#" class="nav-link d-none d-lg-block">About Us</a>
      <a href="#" class="nav-link d-none d-lg-block"><i class="fa fa-user-circle"></i></a>
    </div>
    <div class="d-flex">
      <a href="#" class="nav-link"><i class="fa fa-bell"></i></a>
      <a href="#" class="nav-link"><i class="fa fa-globe"></i></a>
    </div>
  </nav>
  <div class="d-sm-flex align-items-center justify-content-between" id="secondMenu">
    <div id="logoContainer">
      <img src="../assets/images/logo.png" alt="" id="logo">
    </div>
    <div class="input-group">
      <div class="input-group-prepend">
        <button class="input-group-text btn dropdown-toggle" data-toggle="dropdown">Meeting</button>
        <div class="dropdown-menu">
          <a class="dropdown-item" class="dropdown-item">Action</a>
          <a class="dropdown-item" class="dropdown-item">Another action</a>
          <a class="dropdown-item" class="dropdown-item">Something else here</a>
        </div>
      </div>
      <input type="text" class="form-control" placeholder="What are you looking for ?" aria-label="Search">
      <div class="input-group-append">
        <button class="btn" type="submit"><i class="fa fa-search"></i></button>
      </div>
    </div>
  </div>
<div>

header.component.ts：

import { Component, OnInit } from '@angular/core';
import { SidebarComponent } from '../sidebar/sidebar.component';
@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {
  constructor(private sidebarComponent : SidebarComponent) { }
  ngOnInit() {
  }
  callToggleSidebarOnToggleSidebarBtn() {
    this.sidebarComponent.toggleSidebar();
  }
}

我希望能够通过单击标头左上方的按钮来切换sidebar.component.html的内容，但实际输出为：

ERROR Error: Uncaught (in promise): Error: StaticInjectorError(AppModule) 
[HeaderComponent -> SidebarComponent]: 
  StaticInjectorError(Platform: core)[HeaderComponent -> SidebarComponent]: 
    NullInjectorError: No provider for SidebarComponent!
Error: StaticInjectorError(AppModule)[HeaderComponent -> SidebarComponent]: 
  StaticInjectorError(Platform: core)[HeaderComponent -> SidebarComponent]: 
    NullInjectorError: No provider for SidebarComponent!
    at NullInjector.push../node_modules/@angular/core/fesm5/core.js.NullInjector.get (core.js:3228)
at resolveToken (core.js:3473)
at tryResolveToken (core.js:3417)
at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:3314)
at resolveToken (core.js:3473)
at tryResolveToken (core.js:3417)
at StaticInjector.push../node_modules/@angular/core/fesm5/core.js.StaticInjector.get (core.js:3314)
at resolveNgModuleDep (core.js:19784)
at NgModuleRef_.push../node_modules/@angular/core/fesm5/core.js.NgModuleRef_.get (core.js:20473)
at resolveDep (core.js:20844)
at resolvePromise (zone.js:831)
at resolvePromise (zone.js:788)
at zone.js:892
at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:423)
at Object.onInvokeTask (core.js:16147)
at ZoneDelegate.push../node_modules/zone.js/dist/zone.js.ZoneDelegate.invokeTask (zone.js:422)
at Zone.push../node_modules/zone.js/dist/zone.js.Zone.runTask (zone.js:195)
at drainMicroTaskQueue (zone.js:601)

Answer 1

组件不是依赖项，无法注入它们。

要做您想做的事，在标题中找到侧边栏，并给它一个参考：

<app-sidebar #sidebarReference></app-sidebar>

您现在可以在模板中使用它：

<button (click)="sidebarReference.toggleSidebar()">...</button>

或组件中：

@ViewChild(SidebarComponent) sidebar: SidebarComponent;
// or, if several sidebars are in the template,
@ViewChild('sidebarReference') sidebar: SidebarComponent;
this.sidebar.toggleSidebar();

Answer 2

，而不是创建标头组件中的侧栏组件实例，而是使用以下命令创建服务， appService.ts，

ng generate service app

在该服务中写下以下代码

import { Injectable } from '@angular/core';
import { Subject } from 'rxjs';
@Injectable({
  providedIn: 'root'
})
export class AppService {
  flagChange:Subject<boolean> = new Subject<boolean>();
  constructor() { }
  setFlag(flagValue){
    this.flagChange.next(flagValue);
  }
}

然后在我们的 header.component.ts中以

注入该服务实例

import { Component, OnInit } from '@angular/core';
import { AppService } from './app.service';
@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {
   flag:boolean = false;
  constructor(private appService :  AppService) { }
  ngOnInit() {
  }
  callToggleSidebarOnToggleSidebarBtn() {
    this.appService.setFlag(!this.flag);
  }
}

然后在我们的sidebar.component.ts中，更新代码如下，

import { Component, OnInit } from '@angular/core';
import * as $ from 'jquery';
import { AppService } from './app.service';
@Component({
  selector: 'app-sidebar',
  templateUrl: './sidebar.component.html',
  styleUrls: ['./sidebar.component.css']
})
export class SidebarComponent implements OnInit {
  constructor(private appService: AppService) { }
  ngOnInit() {
   this.appService.flagChange.subscribe((flag) => {
      $("#sidebar").animate({width: 'toggle'});
    })
  }
}

因此，当用户单击图标上时，使用Next（）函数在AppService中的flagChange变量注册/给出了标题组件中的标志值，并且使用sidebar组件中的订阅方法观察了此更改。

Answer 3

为了解决此问题，我首先删除header.component.ts和构造函数中侧栏的导入。这是我的最终header.component.ts：

import { Component, OnInit } from '@angular/core';
@Component({
  selector: 'app-header',
  templateUrl: './header.component.html',
  styleUrls: ['./header.component.css']
})
export class HeaderComponent implements OnInit {
  constructor() { }
  ngOnInit() {
  }
}

您可以看到我所做的所有更改。

然后，我在标题中添加以下代码以引用sidebarcomponent：

<app-sidebar #sidebarReference></app-sidebar>

现在，您可以在header.component.ts

中使用模板中使用它

<button class="btn" (click)="sidebarReference.toggleSidebar()"><i class="fa fa-reorder"></i></button>

Answer 4

afaik，您无法将组件注入另一个组件。如果您想要组件间交流，您要么：1.使用服务2.或根据组件之间的关系使用@Input或@output构造。