Ionic button showing 'ion-button' is not a known element

Question

I am new to ionic, it seems like a silly question but I need some help Using some simple button is throwing error. I am using ionic 4.0.

'ion-button' is not a known element: 1. If 'ion-button' is an Angular component, then verify that it is part of this module. 2. If 'ion-button' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the '@NgModule.schemas' of this component to suppress this message.

<ion-button color="primary">Primary</ion-button>

Answer 1

Try this,

<button ion-button color="primary">Primary</button>

Answer 2

In order to avoid that error message:

1. Import CUSTOM_ELEMENTS_SCHEMA into app.modules.ts:

    import { ErrorHandler, NgModule, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';

2. Add schema: [CUSTOM_ELEMENTS_SCHEMA] to app.modules.ts as below:

    @NgModule({
      declarations: [
        MyApp,
        HomePage
      ],
      imports: [
        BrowserModule,
        HttpClientModule,
        MomentModule,
        IonicModule.forRoot(MyApp),
      ],
      bootstrap: [IonicApp],
      entryComponents: [
        MyApp,
        HomePage
      ],
      providers: [
        StatusBar,
        SplashScreen,
        {provide: ErrorHandler, useClass: IonicErrorHandler},
      ],
      schemas: [CUSTOM_ELEMENTS_SCHEMA]
    })

Answer 3

I've run into this too. Your solution is not the best one as the new Ionic 4 way is to use <ion-button> (https://beta.ionicframework.com/docs/components/#button).

It does work for me fine in a page I have under /src/app/my-page/my-page.html, but when I put it in /src/shared/components/my-comp/my-comp.html it gives the error. The odd thing is that I have other Ionic elements in the same page <ion-grid>, <ion-row> and <ion-col>. Also, this code used to be in my-page.html where it worked without error.

FYI, MyComponent is in components.module.ts as a declaration and an export. Not sure yet what I am missing...

UPDATE 1: Neither moving the components directory under src nor under src/app made any difference.

UPDATE 2: This is my environment:

   ionic (Ionic CLI)          : 4.0.6
   Ionic Framework            : @ionic/angular 4.0.0-beta.2
   @angular-devkit/core       : 0.7.2
   @angular-devkit/schematics : 0.7.2
   @angular/cli               : 6.1.2
   @ionic/ng-toolkit          : 1.0.0
   @ionic/schematics-angular  : 1.0.1

UPDATE 3: Still broken in this environment:

   ionic (Ionic CLI)          : 4.1.0
   Ionic Framework            : @ionic/angular 4.0.0-beta.3
   @angular-devkit/core       : 0.7.2
   @angular-devkit/schematics : 0.7.2
   @angular/cli               : 6.1.2
   @ionic/ng-toolkit          : 1.0.6
   @ionic/schematics-angular  : 1.0.5

UPDATE 4: After much trial and error, I had to add schemas: [CUSTOM_ELEMENTS_SCHEMA] to my components.module.ts file. I was able to leave the directory structure as-is. I'm not sure why this is required for this scenario, though.

Answer 4

It seems you are not importing the ionicModule in the component module. So, Import the IonicModulein the module.ts, rest of the things will work fine

Answer 5

yes try this

<button ion-button color="primary">Primary</button>

Answer 6

I was stuck on this for a little while as well until I realized that the problem was I did not create the Ionic Angular project properly. you have to include --type=angular
https://github.com/ionic-team/ionic-cli

exp: ionic start myApp tabs --type=angular

Answer 7

I faced similar issue after ionic 4, So I added the CUSTOM_ELEMENTS_SCHEMA in app.modules.ts. Then it worked fine

app.module.ts

  providers: [
    StatusBar,
    SplashScreen,
    {provide: ErrorHandler, useClass: IonicErrorHandler},
    SpineRestServiceProvider,
    FingerprintAIO
      ],
  schemas: [CUSTOM_ELEMENTS_SCHEMA]