Question

我是棱角分明的新人。我使用vs2015和最新的角度包创建了一个web应用程序。当我尝试从按钮单击事件上的组件调用我的服务时，我在浏览器控制台窗口中收到以下错误。

错误： -

ERROR Error: Uncaught (in promise): Error: StaticInjectorError[ViewCountService]: 
  StaticInjectorError[ViewCountService]: 
    NullInjectorError: No provider for ViewCountService!
Error: StaticInjectorError[ViewCountService]: 
  StaticInjectorError[ViewCountService]: 
    NullInjectorError: No provider for ViewCountService!
    at _NullInjector.get (injector.js:31)
    at resolveToken (injector.js:387)
    at tryResolveToken (injector.js:330)
    at StaticInjector.get (injector.js:170)
    at resolveToken (injector.js:387)
    at tryResolveToken (injector.js:330)
    at StaticInjector.get (injector.js:170)
    at resolveNgModuleDep (ng_module.js:103)
    at NgModuleRef_.get (refs.js:1037)
    at resolveDep (provider.js:455)
    at _NullInjector.get (injector.js:31)
    at resolveToken (injector.js:387)
    at tryResolveToken (injector.js:330)
    at StaticInjector.get (injector.js:170)
    at resolveToken (injector.js:387)
    at tryResolveToken (injector.js:330)
    at StaticInjector.get (injector.js:170)
    at resolveNgModuleDep (ng_module.js:103)
    at NgModuleRef_.get (refs.js:1037)
    at resolveDep (provider.js:455)
    at resolvePromise (zone.js:824)
    at resolvePromise (zone.js:795)
    at zone.js:873
    at ZoneDelegate.invokeTask (zone.js:425)
    at Object.onInvokeTask (ng_zone.js:575)
    at ZoneDelegate.invokeTask (zone.js:424)
    at Zone.runTask (zone.js:192)
    at drainMicroTaskQueue (zone.js:602)
    at ZoneTask.invokeTask [as invoke] (zone.js:503)
    at invokeTask (zone.js:1540)
defaultErrorLogger @ errors.js:48
ErrorHandler.handleError @ error_handler.js:90
next @ application_ref.js:311
schedulerFn @ event_emitter.js:156
SafeSubscriber.__tryOrUnsub @ Subscriber.ts:254
SafeSubscriber.next @ Subscriber.ts:204
Subscriber._next @ Subscriber.ts:135
Subscriber.next @ Subscriber.ts:95
Subject.next @ Subject.ts:61
EventEmitter.emit @ event_emitter.js:131
(anonymous) @ ng_zone.js:605
ZoneDelegate.invoke @ zone.js:392
Zone.run @ zone.js:142
NgZone.runOutsideAngular @ ng_zone.js:404
onHandleError @ ng_zone.js:605
ZoneDelegate.handleError @ zone.js:396
Zone.runGuarded @ zone.js:158
_loop_1 @ zone.js:702
api.microtaskDrainDone @ zone.js:711
drainMicroTaskQueue @ zone.js:610
ZoneTask.invokeTask @ zone.js:503
invokeTask @ zone.js:1540
globalZoneAwareCallback @ zone.js:1566

我的app.module.ts： -

import { NgModule, Injectable } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { FormsModule } from '@angular/forms';
import { RouterModule, Routes } from '@angular/router';
import { HttpModule } from '@angular/http';


import { ModalModule } from 'ngx-modialog';
import { BootstrapModalModule, Modal, bootstrap4Mode } from 'ngx-modialog/plugins/bootstrap';

import { AppComponent } from './app.component';
import { ExportToPdfComponent } from './exportTopdf/exportTopdf.component';
import { InvalidPageComponent } from './invalidPage/invalidPage.component';

import { ViewCountService } from './Service/viewsCount.component';

const appRoutes: Routes = [
    { path: 'home', component: AppComponent },
    { path: '', redirectTo: '/home', pathMatch: 'full' },
    { path: 'export', component: ExportToPdfComponent },
    { path: '**', component: InvalidPageComponent }
];

@NgModule({
    imports: [
        BrowserModule,
        HttpModule,
        RouterModule.forRoot(appRoutes),
        ModalModule.forRoot(),
        BootstrapModalModule
    ],
    declarations: [
        AppComponent,
        ExportToPdfComponent,
        InvalidPageComponent
    ],
    bootstrap: [
        AppComponent
    ],
    providers: [
        ViewCountService
    ]
})



export class AppModule { }

exportTopdf.component.ts文件： -

import { Component, ViewContainerRef, ViewEncapsulation } from '@angular/core';
import { ViewCountService } from '../Service/ViewsCount.component';

import { Overlay } from 'ngx-modialog';
import { Modal } from 'ngx-modialog/plugins/bootstrap';

@Component({
    selector: 'export-to-pdf',
    templateUrl: 'app/exportTopdf/exportTopdf.component.html',
})
export class ExportToPdfComponent {
    name: string;
    fields: any;

    constructor(public modal: Modal, private ViewCountService: ViewCountService) {
        debugger;
        this.fields = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }];
    }


    getViewCount(): void {
        debugger;
        this.ViewCountService.getViewCount()
            .then(data => {
                this.name = data;
                console.log("I CANT SEE DATA HERE: ", this.name)
            });
    }

}

我的服务代码： -

import { Injectable } from '@angular/core';
import { Http } from '@angular/http';
import { Observable } from 'rxjs/Rx';

@Injectable()
export class ViewCountService {
    constructor(private http: Http) {
    }

    getViewCount() {
        return this.http.get('api/Tableau/GetViewsCount')
            .map(response => response.json() as string).toPromise();
    }

    getDataObservable(url: string) {
        return this.http.get('api/Tableau/GetViewsCount')
            .map(data => {
                data.json();
                console.log("I CAN SEE DATA HERE: ", data.json());
            });
    }

}

system.config.js： -

/**
 * System configuration for Angular samples
 * Adjust as necessary for your application needs.
 */
(function (global) {
    System.config({
        transpiler: 'typescript',
        //typescript compiler options
        typescriptOptions: {
            emitDecoratorMetadata: true
        },
        paths: {
            // paths serve as alias
            'npm:': '/node_modules/'
        },
        // map tells the System loader where to look for things
        map: {
            // our app is within the app folder
            'app': 'app',

            // angular bundles
            '@angular/core': 'npm:@angular/core/bundles/core.umd.js',
            '@angular/common': 'npm:@angular/common/bundles/common.umd.js',
            '@angular/compiler': 'npm:@angular/compiler/bundles/compiler.umd.js',
            '@angular/platform-browser': 'npm:@angular/platform-browser/bundles/platform-browser.umd.js',
            '@angular/platform-browser-dynamic': 'npm:@angular/platform-browser-dynamic/bundles/platform-browser-dynamic.umd.js',
            '@angular/http': 'npm:@angular/http/bundles/http.umd.js',
            '@angular/router': 'npm:@angular/router/bundles/router.umd.js',
            '@angular/forms': 'npm:@angular/forms/bundles/forms.umd.js',

            // other libraries
            'rxjs': 'npm:rxjs',
            'angular-in-memory-web-api': 'npm:angular-in-memory-web-api/bundles/in-memory-web-api.umd.js',

            'ngx-modialog': 'npm:ngx-modialog/bundle/ngx-modialog.umd.min.js',
            'ngx-modialog/plugins/bootstrap': 'npm:ngx-modialog/plugins/bootstrap/bundle/ngx-modialog-bootstrap.umd.min.js'


        },
        // packages tells the System loader how to load when no filename and/or no extension
        packages: {
            app: {
                defaultExtension: 'js',
                meta: {
                    './*.js': {
                        loader: 'systemjs-angular-loader.js'
                    }
                }
            },
            rxjs: {
                defaultExtension: 'js'
            }
        }
    });
})(this);

package.json： -

{
  "name": "angular-quickstart",
  "version": "1.0.0",
  "description": "QuickStart package.json from the documentation, supplemented with testing support",
  "scripts": {
    "build": "tsc -p src/",
    "build:watch": "tsc -p src/ -w",
    "build:e2e": "tsc -p e2e/",
    "serve": "lite-server -c=bs-config.json",
    "serve:e2e": "lite-server -c=bs-config.e2e.json",
    "prestart": "npm run build",
    "start": "concurrently \"npm run build:watch\" \"npm run serve\"",
    "pree2e": "npm run build:e2e",
    "e2e": "concurrently \"npm run serve:e2e\" \"npm run protractor\" --kill-others --success first",
    "preprotractor": "webdriver-manager update",
    "protractor": "protractor protractor.config.js",
    "pretest": "npm run build",
    "test": "concurrently \"npm run build:watch\" \"karma start karma.conf.js\"",
    "pretest:once": "npm run build",
    "test:once": "karma start karma.conf.js --single-run",
    "lint": "tslint ./src/**/*.ts -t verbose"
  },
  "keywords": [],
  "author": "",
  "license": "MIT",
  "dependencies": {
    "@angular/common": "~5.0.3",
    "@angular/compiler": "~5.0.3",
    "@angular/core": "~5.0.3",
    "@angular/forms": "~5.0.3",
    "@angular/http": "~5.0.3",
    "@angular/platform-browser": "~5.0.3",
    "@angular/platform-browser-dynamic": "~5.0.3",
    "@angular/router": "~5.0.3",
    "angular-in-memory-web-api": "~0.5.1",
    "bootstrap": "^3.3.7",
    "core-js": "^2.4.1",
    "ngx-modialog": "^5.0.0",
    "rxjs": "5.5.2",
    "systemjs": "0.20.19",
    "zone.js": "^0.8.4"
  },
  "devDependencies": {
    "concurrently": "^3.2.0",
    "lite-server": "^2.2.2",
    "typescript": "~2.6.1",
    "canonical-path": "0.0.2",
    "tslint": "^5.8.0",
    "lodash": "^4.16.4",
    "jasmine-core": "~2.8.0",
    "karma": "^1.3.0",
    "karma-chrome-launcher": "^2.0.0",
    "karma-cli": "^1.0.1",
    "karma-jasmine": "^1.0.2",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.2.0",
    "rimraf": "^2.5.4",
    "@types/node": "^8.0.53",
    "@types/jasmine": "2.8.2"
  },
  "repository": {}
}

提前感谢您提供有价值的反馈和意见。

Answer 1

看看你的影响

<强> app.module.ts

import { ViewCountService } from  './Service/viewsCount.component';

<强> exportTopdf.component.ts

import { ViewCountService } from '../Service/ViewsCount.component';

由于Systemjs区分大小写（请参阅Service instance is not available for child component in angular2）

看起来你正在导入不同的模块

ViewsCount 
|
viewsCount

因此，只选择一个选项来导入您的服务

<强> app.module.ts

import { ViewCountService } from  './Service/viewsCount.component';

<强> exportTopdf.component.ts

import { ViewCountService } from '../Service/viewsCount.component';
                                             ^
                                         instead of V

另请阅读style guide以更好地了解如何命名文件

Answer 2

如果您使用Angular 4.3+直到5，则需要从新库中导入app.module中的HttpClient

> import { HttpClientModule } from '@angular/common/http';

  imports: [
    YModule,
    XModule,
    HttpClientModule
  ],

在您的服务中：

 import { Injectable } from '@angular/core';
    import { HttpClient } from '@angular/common/http';
    import { Observable } from 'rxjs/Rx';

    @Injectable()
    export class ViewCountService {
        constructor(private http: HttpClient ) {
        }

        getViewCount() {
            return this.http.get('api/Tableau/GetViewsCount');
        }

       ...
    }

在您的组件中：

 getViewCount(): void {
    this.ViewCountService.getViewCount()
        .subscribe(
           data =>{console.log(data);//your data},
           err=>{console.log(err);},
           () => {console.log("Done loading");}
);
}

Answer 3

它看起来还没有解决： https://github.com/angular/angular/issues/20339

作为一种解决方法，尝试通过提取as属性来创建没有参数的所有import { Component, ViewContainerRef, ViewEncapsulation } from '@angular/core'; import { ViewCountService } from '../Service/ViewsCount.component'; import { Overlay } from 'ngx-modialog'; import { Modal } from 'ngx-modialog/plugins/bootstrap'; @Component({ selector: 'export-to-pdf', templateUrl: 'app/exportTopdf/exportTopdf.component.html', }) export class ExportToPdfComponent { name: string; fields: any; modal: Modal; ViewCountService: ViewCountService; constructor() { debugger; this.fields = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }]; } getViewCount(): void { debugger; this.ViewCountService.getViewCount() .then(data => { this.name = data; console.log("I CANT SEE DATA HERE: ", this.name) }); } }函数。

ExportToPdfComponent：

import { Injectable } from '@angular/core';
import { Http } from '@angular/http';
import { Observable } from 'rxjs/Rx';

@Injectable()
export class ViewCountService {
    private http: Http;
    constructor() {
    }

    getViewCount() {
        return this.http.get('api/Tableau/GetViewsCount')
            .map(response => response.json() as string).toPromise();
    }

    getDataObservable(url: string) {
        return this.http.get('api/Tableau/GetViewsCount')
            .map(data => {
                data.json();
                console.log("I CAN SEE DATA HERE: ", data.json());
            });
    }

}

ViewCountService：

var uname = "";
var pword = "";

function validateMe(e) {
  e.preventDefault();
  uname = document.forms['signIn']['username'].value;
  pword = document.forms['signIn']['password'].value;
  if (uname.length || pword.length < 1 || '') {
    var container = document.getElementById('error-container');
    var errorMsg = document.createElement('div');
    errorMsg.className = 'error-message';
    errorMsg.innerHTML = '<span class="heading-large">Please enter a valid username or password</span>';
    container.appendChild(errorMsg);
    console.log('An error occured');
    return false;
  }
return true;
}

Answer 4

import { HttpClientModule, HTTP_INTERCEPTORS } from '@angular/common/http';

imports: [
        BrowserModule,
        FormsModule,
        HttpClientModule,
        routing
    ],

将此添加到 app.module.ts 文件

中

Answer 5

我也遇到了同样的问题，然后在app.module中添加了以下内容，它对我有用。

import { HttpClientModule } from ‘@angular/common/http’;

并将其添加到

@NgModule({ imports: [ ...,   HttpClientModule,... ]

未捕获（承诺）：错误：StaticInjectorError [Service]

5 个答案: