public async Task OnNavigatedTo()
{
// initialize firebase helper
_firebaseHelper = new FirebaseHelper();
// initialize list for storing favorites cities, which will be shown on the page
_favoriteCitiesTmp = new List <CityForecastItem>(); // tmp list
FavoriteCities = new ObservableCollection <CityForecastItem>();
await RefreshFavoriteCitiesList();
}
/// <summary>
/// Checks if the city is in favorites list and sets favorite icon depending on that
/// </summary>
/// <returns></returns>
private async Task IsCityInFavorites()
{
// get the current favorites list
FirebaseHelper firebaseHelper = new FirebaseHelper();
await firebaseHelper.GetFavoritesCities();
if (await firebaseHelper.CityIsInFavorites(_weatherForecastService.CityId))
{
FavoriteIconPath = Constants.FavoriteIconPath;
}
else
{
FavoriteIconPath = Constants.FavoriteBorderIconPath;
}
}
/// <summary>
/// Adds city to the favorite cities list if the city doesn't belong to it
/// Deletes city from the favorite cities list if the city belong to it
/// </summary>
/// <returns></returns>
private async Task AddOrDeleteCityFromFavorites()
{
// get the current favorites list
FirebaseHelper firebaseHelper = new FirebaseHelper();
await firebaseHelper.GetFavoritesCities();
// Add or delete the city form favorites
if (await firebaseHelper.CityIsInFavorites(_weatherForecastService.CityId))
{
await firebaseHelper.DeleteCityFromFavorites(_weatherForecastService.CityId);
}
else
{
await firebaseHelper.PutFavoriteCity(
_weatherForecastService.CityName,
_weatherForecastService.CityId
);
}
// reload favorite icon
await IsCityInFavorites();
}