Angular：从文件导入bootstrap.css时，bootstrap轮播不起作用

我有一个名为"image-slider"的简单组件 . 当我从互联网上导入bootstrap.css时 <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.css" /> 轮播工作正常 .

但是当我删除这一行并从image-slider.html中的本地文件导入bootstrap.css时，如下所示：

@Component({
selector: 'app-image-slider',
templateUrl: './image-slider.component.html',
styleUrls: ['../../../node_modules/bootstrap/dist/css/bootstrap.min.css']
})
export class ImageSliderComponent implements OnInit { ... }

滑块不起作用，图像出现在另一个下面：

文件的路径是正确的 . Bootstrap工作正常，因为当我添加简单的引导按钮 <button type="button" class="btn btn-primary btn-sm">Small button</button> 它正确显示 .

为什么旋转木马表现得如此奇怪？

图像slider.component.html：

<div class="container-fluid">
      <ngb-carousel *ngIf="images">
        <ng-template ngbSlide>
          <img [src]="images[0]" alt="Random first slide">
          <div class="carousel-caption">
            <h3>First slide label</h3>
            <p>Nulla vitae elit libero, a pharetra augue mollis interdum.</p>
          </div>
        </ng-template>
        <ng-template ngbSlide>
          <img [src]="images[1]" alt="Random second slide">
          <div class="carousel-caption">
            <h3>Second slide label</h3>
            <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
          </div>
        </ng-template>
        <ng-template ngbSlide>
          <img [src]="images[2]" alt="Random third slide">
          <div class="carousel-caption">
            <h3>Third slide label</h3>
            <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
          </div>
        </ng-template>
      </ngb-carousel>
    </div>

“

package.json依赖项：

"dependencies": {
    "@angular/animations": "^6.0.3",
    "@angular/cdk": "^6.4.0",
    "@angular/common": "^6.0.3",
    "@angular/compiler": "^6.0.3",
    "@angular/core": "^6.1.4",
    "@angular/forms": "^6.0.3",
    "@angular/http": "^6.0.3",
    "@angular/material": "^6.4.0",
    "@angular/platform-browser": "^6.0.3",
    "@angular/platform-browser-dynamic": "^6.1.4",
    "@angular/router": "^6.0.3",
    "@ng-bootstrap/ng-bootstrap": "^3.1.0",
    "angular-bootstrap-md": "^6.2.2",
    "bootstrap": "^4.1.3",
    "bootstrap-loader": "^3.0.1",
    "chart.js": "^2.7.2",
    "core-js": "^2.5.4",
    "exports-loader": "^0.7.0",
    "imports-loader": "^0.8.0",
    "ng-bootstrap": "^1.6.3",
    "ngx-bootstrap": "^3.0.1",
    "postcss-loader": "^3.0.0",
    "rxjs": "^6.0.0",
    "util.js": "^0.0.0",
    "zone.js": "^0.8.26"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "~0.6.8",
    "@angular/cli": "~6.0.8",
    "@angular/compiler-cli": "^6.0.3",
    "@angular/language-service": "^6.0.3",
    "@types/jasmine": "~2.8.6",
    "@types/jasminewd2": "~2.0.3",
    "@types/node": "~8.9.4",
    "codelyzer": "~4.2.1",
    "jasmine-core": "~2.99.1",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~1.7.1",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "~2.0.0",
    "karma-jasmine": "~1.1.1",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.3.0",
    "ts-node": "~5.0.1",
    "tslint": "~5.9.1",
    "typescript": "~2.7.2"
  }