Invert NativeScript ListView trick to feed chat items in from bottom up (Android workaround for proper momentum scroll on API level 28)

fixAndroidScrollMomentum

export function fixAndroidScrollMomentum(listview: ListView) {
  if (android.os.Build.VERSION.SDK_INT !== 28) {
    return;
  }
  // suppress the default momentum behaviour
  listview.android.setVelocityScale(0);
  // stores the last 5 move events in this array
  let lastMoveEvents = [];
  (<any>listview).on(GestureTypes.touch, (args, b) => {
    if (args.action === 'up') {
      const eventCount = lastMoveEvents.length;
      if (eventCount < 2) {
        return;
      }
      // calculate velocity based on the fist and last recorded move events.
      const flingVelocity =
        (lastMoveEvents[eventCount - 1].y - lastMoveEvents[0].y) * (lastMoveEvents[eventCount - 1].time - lastMoveEvents[0].time) * -1;
      // apply the velocity
      listview.android.fling(flingVelocity);
    } else if (args.action === 'move') {
      // add the move event to the array and crop its length to 5.
      lastMoveEvents.unshift({
        x: args.getX(),
        y: args.getY(),
        time: Date.now()
      });
      lastMoveEvents = lastMoveEvents.slice(0, 5);
    } else if (args.action === 'down' || args.action === 'cancel') {
      lastMoveEvents = [];
    }
  });
}