使用Angular-material2时发生错误

Question

I just begin to use Anuglar-material2 in my project, however, I just cannot import any component correctly. After I import some material modules in my app.module.ts, I'm getting errors like following:

uncaught Error: Unexpected value 'MdButtonModule' imported by the module 'AppModule'. Please add a @NgModule annotation.
    at syntaxError (compiler.es5.js:1690)
    at compiler.es5.js:15383
    at Array.forEach (<anonymous>)
    at CompileMetadataResolver.webpackJsonp.../../../compiler/@angular/compiler.es5.js.CompileMetadataResolver.getNgModuleMetadata (compiler.es5.js:15366)
    at JitCompiler.webpackJsonp.../../../compiler/@angular/compiler.es5.js.JitCompiler._loadModules (compiler.es5.js:26796)
    at JitCompiler.webpackJsonp.../../../compiler/@angular/compiler.es5.js.JitCompiler._compileModuleAndComponents (compiler.es5.js:26769)
    at JitCompiler.webpackJsonp.../../../compiler/@angular/compiler.es5.js.JitCompiler.compileModuleAsync (compiler.es5.js:26698)
    at PlatformRef_.webpackJsonp.../../../core/@angular/core.es5.js.PlatformRef_._bootstrapModuleWithZone (core.es5.js:4535)
    at PlatformRef_.webpackJsonp.../../../core/@angular/core.es5.js.PlatformRef_.bootstrapModule (core.es5.js:4521)
    at Object.../../../../../src/main.ts (main.ts:11)

here's my app.module.ts

import 'hammerjs';

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';

import { AppRoutingModule } from './app-routing.module';
import { SearchModule } from './search/search.module';
import { PostModule } from './post/post.module';
import { UserModule } from './user/user.module';

import { BsDropdownModule } from 'ngx-bootstrap/dropdown';
import {MdButtonModule, MdCheckboxModule} from '@angular/material';

import { AppComponent } from './app.component';
import { HomeComponent } from './home/home.component';
import { NavTopComponent } from './nav-top/nav-top.component';

import { AuthService } from './core/auth.service';

@NgModule({
  declarations: [
    AppComponent,
    HomeComponent,
    NavTopComponent,
  ],
  imports: [
    BrowserModule,
    BrowserAnimationsModule,
    MdButtonModule,
    MdCheckboxModule,
    BsDropdownModule.forRoot(),
    SearchModule,
    PostModule,
    UserModule,
    AppRoutingModule
  ],
  exports: [
  ],
  providers: [AuthService],
  bootstrap: [AppComponent]
})
export class AppModule { }

I did exactly every steps that included in official documentations of Material2.

Answer 1

Thanks a lots for your kind advice!

But I just solve this problem by deleting the whole node_modules folder and reinstall all packages using npm install .

When I run ng serve again, such error just disappeared. I don't know the reason, but hope this can help others who may have the same problem!

BTW, my Angular version is 4.0, Angular-cli version is 1.2.1 and Angular-material version is 2.0.0

Thanks again!