HostListener on document

I follow this article (using HostListener) and got the “keyup” event fired on desktop web, ios safari, android app, but NOT ios app.

I am connect my android / ios device with a hardware BT barcode scanner.
Is it focus in a input field is a must for iOS to get keyup event?

Just found renderer2 have a simple method to get keyup event.
But ios still need a on focus input field before the event will fire.

this.keyUpListener = this.renderer.listen('document', 'keyup', (event) => {
      console.log('event', event);