Xamarin.ios: Detail command is null because it shows before function - ios

Question

I'm building an iOS app with Xamarin.ios MvvmCross. And I have a function that puts a random id in a text file every day. So I get a recipe of the day.
The problem is that the code for the Detail command function (for the button) runs before the function that stores everything in the text file. So the detail command returns null and nothing happens when I push the button. The second time I run the code it does what it should do because there's already an id stored in the text file.
The view:
public override void ViewDidLoad()
{
base.ViewDidLoad();
MvxFluentBindingDescriptionSet<TabHomeView, TabHomeViewModel> set = new MvxFluentBindingDescriptionSet<TabHomeView, TabHomeViewModel>(this);
set.Bind(MorningImage).For(img => img.Image).To(res => res.MorningContent.picture).WithConversion<StringToImageConverter>();
set.Bind(MorningJuiceName).To(vm => vm.MorningContent.name);
set.Bind(MorningBtn)
.To(vm => vm.NavigateToMorningJuice);
set.Apply();
}
The function to put a random id in the text file:
public async void GetAfternoonJuice()
{
Recipes = await _recipeService.GetRecipes();
int counter = Recipes.Count;
Random rnd = new Random();
int RandomNumber = rnd.Next(1, counter);
string rndNumToStr = RandomNumber.ToString();
DateTime dateAndTime = DateTime.Now;
string day = dateAndTime.ToString("dd/MM/yyyy");
string folderValue = (day + "," + rndNumToStr);
var _folderName = "TextFilesFolder2";
var _fileName = "AfternoonJuice";
if (!_fileStore.FolderExists(_folderName))
_fileStore.EnsureFolderExists(_folderName);
//Content van de file uitlezen
string value = string.Empty;
_fileStore.TryReadTextFile(_folderName + "/" + _fileName, out (value));
string CheckFileContent = value;
string[] TextFileList;
//Als er niets in zit, default data in steken
if (CheckFileContent == null)
{
_fileStore.WriteFile(_folderName + "/" + _fileName, "00/00/00,0");
string d = "00/00/00,0";
TextFileList = d.Split(',');
}
else
{
TextFileList = CheckFileContent.Split(',');
}
if (TextFileList[0] != day)
{
//File verwijderen om overbodige data te verwijderen.
_fileStore.DeleteFile(_folderName + "/" + _fileName);
//File aanmaken.
if (!_fileStore.FolderExists(_folderName))
_fileStore.EnsureFolderExists(_folderName);
_fileStore.WriteFile(_folderName + "/" + _fileName, folderValue);
string NewValue = string.Empty;
_fileStore.TryReadTextFile(_folderName + "/" + _fileName, out (NewValue));
string NValue = NewValue;
List<string> NewTextFileList = new List<string>(
NValue.Split(new string[] { "," }, StringSplitOptions.None));
int numVall = Int32.Parse(NewTextFileList[1]);
int NewRandomValue = numVall;
AfternoonContent = await _recipeService.GetRecipeById(NewRandomValue);
RaisePropertyChanged(() => AfternoonContent);
}
else
{
int numVall = Int32.Parse(TextFileList[1]);
int NewRandomValue = numVall;
AfternoonContent = await _recipeService.GetRecipeById(NewRandomValue);
RaisePropertyChanged(() => AfternoonContent);
}
}
The detail command:
public MvxCommand<Recipe> NavigateToAfternoonJuice
{
get
{
var _folderName = "TextFilesFolder2";
var _fileName = "AfternoonJuice";
string value = string.Empty;
_fileStore.TryReadTextFile(_folderName + "/" + _fileName, out (value));
string fV = value;
List<string> TextFileList = new List<string>(
fV.Split(new string[] { "," }, StringSplitOptions.None));
int numVall = Int32.Parse(TextFileList[1]);
int NewRandomValue = numVall;
return new MvxCommand<Recipe>(SelectedRecipe =>
{
ShowViewModel<DetailJuiceListViewModel>(new { RecipeId = NewRandomValue });
});
}
}

Answer 1

Some of code in your public property NavigateToAfternoonJuice runs before your command is executed. It will be run, when the binding occurs and not when the command actually executes the body.
You probably want to modify your command to something as follows instead.
private MvxCommand<Recipe> _navigateToAfternoonJuice;
public MvxCommand<Recipe> NavigateToAfternoonJuice
{
get
{
if (_navigateToAfternoonJuice == null)
_navigateToAfternoonJuice = new MvxCommand<Recipe>(DoNavigateToAfternoonJuice);
return _navigateToAfternoonJuice;
}
}
private void DoNavigateToAfternoonJuice(Reciepe selectedRecipe)
{
var _folderName = "TextFilesFolder2";
var _fileName = "AfternoonJuice";
string value = string.Empty;
_fileStore.TryReadTextFile(_folderName + "/" + _fileName, out (value));
string fV = value;
List<string> TextFileList = new List<string>(
fV.Split(new string[] { "," }, StringSplitOptions.None));
int numVall = Int32.Parse(TextFileList[1]);
int NewRandomValue = numVall;
ShowViewModel<DetailJuiceListViewModel>(new { RecipeId = NewRandomValue });
}
This will make the text file to be read when the command executes.