ListView: recycling contract, template selectors, refresh

The itemLoading recycling contract

args.view is the recycled view from a row that scrolled off. Create only when it's absent; otherwise reconfigure what you're given:

import { ItemEventData, Label, ListView } from '@nativescript/core';

listView.on(ListView.itemLoadingEvent, (args: ItemEventData) => {
  if (!args.view) {
    args.view = new Label(); // create once per on-screen slot
  }
  (<Label>args.view).text = items[args.index];
});

Unconditionally assigning args.view = new Label() defeats recycling — every scroll frame allocates native views and scrolling jank follows. The handler must be a pure function of args.index: recycled views arrive with the previous row's state, so set every property you ever set, not just the ones that changed.