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

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>

ionic-framework ionic4

Solution 1:^[1]

Try this,

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

Solution 2:^[2]

In order to avoid that error message:

Import CUSTOM_ELEMENTS_SCHEMA into app.modules.ts:

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

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]
    })

Solution 3:^[3]

I think the solution is importing Ionic module in the respective module imports

import { IonicModule } from '@ionic/angular';  <--add this line
@NgModule({
imports: [
    CommonModule,
    FormsModule,
    IonicModule, <-- add this line
  ],

})

Solution 4:^[4]

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.

Solution 5:^[5]

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

Solution 6:^[6]

yes try this

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

Solution 7:^[7]

In Ionic 5, I have a same problem when I build with --prod option.

Since *.module.ts file is not available in components in Ionic 5, I need to add shared module for components and then add CUSTOM_ELEMENTS_SCHEMA schema to that shared module.

ionic g module modules/shared

cat shared.module

import { NgModule, CUSTOM_ELEMENTS_SCHEMA } from '@angular/core';
import { CommonModule } from '@angular/common';
import { FooComponent } from '../../components/foo/foocomponent.component'; <== Add your components


@NgModule({
  declarations: [FooComponent], <== Add your components
  imports: [
    CommonModule
  ], 
  exports: [FooComponent], <== Add your components
  schemas: [CUSTOM_ELEMENTS_SCHEMA]
})
export class SharedModule { }

Solution 8:^[8]

Import your custom component in the parent module. for example in your app.module.ts:

declarations: [MyComponent],
exports: [
    PopoverComponent,
]

Solution 9:^[9]

I was having this problem in a library that I was building because I forgot to export the module of that was importing the IonicModule and exporting my component.

So, in my module was importing Ionic lib and exporting my component as below.

import { CommonModule } from '@angular/common';
import { NgModule } from '@angular/core';
import { IonicModule } from '@ionic/angular';

import { MyComponent } from './my.component';

@NgModule({
  declarations: [
    MyComponent,
  ],
  imports: [
    CommonModule,
    IonicModule,
  ],
  exports: [
    MyComponent,
  ],
})
export class MyModule {
}

And in the public-api.ts file of my lib, I should have something like this

export { MyModule } from './lib/my.module'; // <--- exporting my module
export { MyComponent } from './lib/my.component';

Solution 10:^[10]

My issue was that there were errors prior to this error that seemed to cascade down. The error I had was some elements in the declarations that should have been in the providers. Also, one of these was marked private in the constructor when it should have been public.

@NgModule({
    imports: [
        IonicModule,
        CommonModule,
        FormsModule,
        RouterModule.forChild([{ path: '', component: DevicesPage }]),
        DevicesPageRoutingModule,
        TranslateModule.forChild()
    ],
    declarations: [DevicesPage  --> remove BLE, LocationAccuracy, DeviceManagerService  ],
    providers: [BLE, LocationAccuracy, DeviceManagerService]  <--Add
})

Solution 11:^[11]

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

Solution 12:^[12]

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]

Solution 13:^[13]

Should add in app.module.ts

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


  providers: [
    StatusBar,
    SplashScreen,
    { provide: RouteReuseStrategy, useClass: IonicRouteStrategy }
  ],
  schemas: [CUSTOM_ELEMENTS_SCHEMA] ==> add line**

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source
Solution 1	Mangesh Daundkar
Solution 2	Gerry R
Solution 3	Raghuram Sadineni
Solution 4
Solution 5	ram12393
Solution 6	Tanzeel U Rehman
Solution 7	Bubba
Solution 8	Ghonche Yqr
Solution 9	Wesley GonÃ§alves
Solution 10	T Brown
Solution 11	Claudio Teles
Solution 12
Solution 13	Makyen

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

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