NativeScript/apps/ui/app/events/layout-changed-event-page.ts

import { StackLayout } from '@nativescript/core/ui/layouts/stack-layout';
import { Button } from '@nativescript/core/ui/button';
import { TextView } from '@nativescript/core/ui/text-view';
let buttonsCount = 1;

export function onLayoutChanged(args) {
	let msg = 'StackLayout layout changed - width:' + args.object.getActualSize().width;
	(<TextView>args.object.page.getViewById('output')).text += msg + '\n';
}

export function addChild(args) {
	let button = new Button();
	button.text = 'Button' + buttonsCount;
	button.margin = 10;
	button.backgroundColor = 'lightgreen';

	(<StackLayout>args.object.page.getViewById('target')).addChild(button);
	buttonsCount++;
}

export function clear(args) {
	(<StackLayout>args.object.page.getViewById('target')).removeChildren();
	args.object.page.getViewById('output').text = '';
}