Ngx- IONIC 4中的翻译构建产品问题

"projects": {
  "your-project-name": {
    "i18n": {
      "sourceLocale": "en-US",
      "locales": {
        "fr-FR": "src/locale/messages.fr.xlf"
      }
    }
  }
}

ng build --prod --i18n-locale fr-FR --i18n-format xlf --i18n-file src/locale/messages.fr.xlf

import { HttpClientModule, HttpClient } from '@angular/common/http';
import { TranslateModule, TranslateLoader } from '@ngx-translate/core';
import { TranslateHttpLoader } from '@ngx-translate/http-loader';

export function HttpLoaderFactory(http: HttpClient) {
  return new TranslateHttpLoader(http);
}

@NgModule({
  imports: [
    HttpClientModule,
    TranslateModule.forRoot({
      loader: {
        provide: TranslateLoader,
        useFactory: HttpLoaderFactory,
        deps: [HttpClient]
      }
    })
  ]
})
export class AppModule { }

<p>{{ 'HELLO' | translate }}</p>

<trans-unit id="HELLO">
  <source>HELLO</source>
  <target>BONJOUR</target>
</trans-unit>

import { Component } from '@angular/core';
import { TranslateService } from '@ngx-translate/core';

@Component({
  selector: 'app-root',
  template: `<p>{{ 'HELLO' | translate }}</p>`
})
export class AppComponent {
  constructor(private translate: TranslateService) {
    translate.setDefaultLang('en');
    translate.use('fr');
  }
}