//html file
<ion-input type="tel" #forgetSendCodeInput></ion-input>

//1. import componet
import { ElementRef, ViewChild } from '@angular/core';
//2. statement
export class xxPage {
@ViewChild('forgetSendCodeInput') forgetSendCodeInput;
}
//3. configure config.xml file
<preference name="KeyboardDisplayRequiresUserAction" value="false" />

//ts file focus
this.forgetSendCodeInput._native.nativeElement.focus();
//ts file blur
this.forgetSendCodeInput._native.nativeElement.focus();