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

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

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
],
})

Answer 2

Try this,
<button ion-button color="primary">Primary</button>

Answer 3

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]
})

Answer 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.

Answer 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

Answer 6

Import your custom component in the parent module. for example in your app.module.ts:
declarations: [MyComponent],
exports: [
PopoverComponent,
]

Answer 7

yes try this
<button ion-button color="primary">Primary</button>

Answer 8

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 { }

Answer 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';

Answer 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
})

Answer 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

Answer 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]

Answer 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**