import { EventData } from '@nativescript/core/data/observable' ; import { Page } from '@nativescript/core/ui/page' ; import * as observable from '@nativescript/core/data/observable' ; export function navigatingTo ( args ) { let page = < Page > args . object ; page . bindingContext = new ActionItemPostitionView ( ) ; } export class ActionItemPostitionView extends observable . Observable { private _values = [ '-i---' , '---i---' , '---i-' ] ; private _count : number ; private _text : string ; constructor ( ) { super ( ) ; this . _count = 0 ; } get text ( ) : string { return this . _text ; } set text ( value ) { if ( this . _text !== value ) { this . _text = value ; this . notifyPropertyChange ( 'text' , value ) ; } } public onTap ( ) { this . change ( ) ; } public change ( ) { let index = this . _count ++ % 3 ; this . text = this . _values [ index ] ; } }