How to uncheck a checkbox after returning to a page - xamarin.forms

Question

i have a checkboxes that i am setting in View Model and i am collecting user decision on a list, however once i filter my items and then go bakc on the page the checkbox is still checked even thought the list is empty so if i press again button to show filtered items i get nothing. I am clearing my list but i am not sure how to get the checkboxes unchecked once i come back. I have Mode = two way
private bool _filterBeginnerItems = false;
private bool _filterIntermediateItems = false;
private bool _filterAdvancedItems = false;
private bool _filterUpperIntermediateItems = false;
public bool FilterBeginnerItems
{
set
{
NotifyPropertyChanged();
_filterBeginnerItems = value;
if (_filterBeginnerItems)
{
FilterAllItems = false;
UserDecision.Add(_parentCategoryId = 1);
}
}
get => _filterBeginnerItems;
}
public bool FilterIntermediateItems
{
set
{
NotifyPropertyChanged();
_filterIntermediateItems = value;
if (_filterIntermediateItems)
{
FilterAllItems = false;
UserDecision.Add(_parentCategoryId = 2);
}
}
get => _filterIntermediateItems;
}
public bool FilterUpperIntermediateItems
{
set
{
NotifyPropertyChanged();
_filterUpperIntermediateItems = value;
if (_filterUpperIntermediateItems)
{
FilterAllItems = false;
UserDecision.Add(_parentCategoryId = 3);
}
}
get => _filterUpperIntermediateItems;
}
public FilterArticlesForPurchaseViewModel(INavigation navigation)
: base()
{
Task.Run(async () => await LoadAllDataForArticlesAndCategories()).Wait();
FilterItemsCommand = new Command(async () => navigation.PushAsync(new ArticlesForPurchaseFiltered()));
UserDecision.Clear();
//FilterAdvancedItems = false;
// FilterBeginnerItems = false;
}
Have tried to set their value to false but it doesnt help.

Answer 1

I write a demo about clear the CheckBox
Here is running gif.
Here is FilterArticlesForPurchaseViewModel.cs to achieve the INotifyPropertyChanged interface. I used a Command to clear these checkbox.
public class FilterArticlesForPurchaseViewModel: INotifyPropertyChanged
{
private bool _filterBeginnerItems = true;
private bool _filterIntermediateItems = false;
private bool _filterAdvancedItems = false;
private bool _filterUpperIntermediateItems = false;
public bool FilterBeginnerItems
{
set
{
// NotifyPropertyChanged();
_filterBeginnerItems = value;
OnPropertyChanged("FilterBeginnerItems");
//if (_filterBeginnerItems)
//{
// FilterAllItems = false;
// UserDecision.Add(_parentCategoryId = 1);
//}
}
get => _filterBeginnerItems;
}
public bool FilterIntermediateItems
{
set
{
// NotifyPropertyChanged();
_filterIntermediateItems = value;
OnPropertyChanged("FilterIntermediateItems");
//if (_filterIntermediateItems)
//{
// FilterAllItems = false;
// UserDecision.Add(_parentCategoryId = 2);
//}
}
get => _filterIntermediateItems;
}
public bool FilterUpperIntermediateItems
{
set
{
// NotifyPropertyChanged();
_filterUpperIntermediateItems = value;
OnPropertyChanged("FilterUpperIntermediateItems");
//if (_filterUpperIntermediateItems)
//{
// FilterAllItems = false;
// UserDecision.Add(_parentCategoryId = 3);
//}
}
get => _filterUpperIntermediateItems;
}
public ICommand ClearCommand { protected set; get; }
public FilterArticlesForPurchaseViewModel(INavigation navigation)
{
ClearCommand = new Command(async () =>
{
FilterBeginnerItems = false;
FilterIntermediateItems = false;
FilterUpperIntermediateItems = false;
});
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged(string propertyName)
{
PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
}
}
}
Here is layout.xaml
<StackLayout>
<!-- Place new controls here -->
<CheckBox IsChecked="{Binding FilterBeginnerItems,Mode=TwoWay}"></CheckBox>
<CheckBox IsChecked="{Binding FilterIntermediateItems,Mode=TwoWay}"></CheckBox>
<CheckBox IsChecked="{Binding FilterUpperIntermediateItems,Mode=TwoWay}"></CheckBox>
<Button Text="clear" Command="{Binding ClearCommand}"></Button>
</StackLayout>
Here is background code.
public MainPage()
{
InitializeComponent();
this.BindingContext = new FilterArticlesForPurchaseViewModel(Navigation);
}
=================update===================
I make edit your viewmodel. Here is code, I achieve the remove data from the List<int> UserDecision
public class FilterViewModel : BaseViewModel
{
private bool _filterAllItems = true;
private bool _filterBeginnerItems = false;
private bool _filterIntermediateItems = false;
private bool _filterAdvancedItems = false;
private bool _filterUpperIntermediateItems = false;
private static List<Article> _allArticlesForPurchase;
private static List<Category> _allCategories;
private static List<CategoryGroup> _allUserCategoryGroups;
public static List<int> UserDecisionResult { get; set; }
private static int _parentCategoryId;
public ICommand FilterItemsCommand { get; private set; }
public static List<int> UserDecision { get; set; } = new List<int>();
public bool FilterAllItems
{
set
{
_filterAllItems = value;
OnPropertyChanged();
if (FilterAllItems == false)
{
if (UserDecision.Contains(_parentCategoryId = -1))
{
UserDecision.Remove(_parentCategoryId = -1);
}
}
if (FilterAllItems == true)
{
FilterBeginnerItems = false;
FilterIntermediateItems = false;
FilterUpperIntermediateItems = false;
FilterAdvancedItems = false;
if (!UserDecision.Contains(_parentCategoryId = -1))
{
UserDecision.Add(_parentCategoryId = -1);
}
if (UserDecision.Contains(_parentCategoryId=1))
{
UserDecision.Remove(_parentCategoryId = 1);
}
if (UserDecision.Contains(_parentCategoryId = 2))
{
UserDecision.Remove(_parentCategoryId = 2);
}
if (UserDecision.Contains(_parentCategoryId = 3))
{
UserDecision.Remove(_parentCategoryId = 3);
}
if (UserDecision.Contains(_parentCategoryId = 4))
{
UserDecision.Remove(_parentCategoryId = 4);
}
}
}
get => _filterAllItems;
}
public bool FilterBeginnerItems
{
set
{
_filterBeginnerItems = value;
OnPropertyChanged();
if (_filterBeginnerItems)
{
FilterAllItems = false;
UserDecision.Add(_parentCategoryId = 1);
if (UserDecision.Contains(_parentCategoryId = -1))
{
UserDecision.Remove(_parentCategoryId = -1);
}
}
}
get => _filterBeginnerItems;
}
public bool FilterIntermediateItems
{
set
{
_filterIntermediateItems = value;
OnPropertyChanged();
if (_filterIntermediateItems)
{
FilterAllItems = false;
UserDecision.Add(_parentCategoryId = 2);
if (UserDecision.Contains(_parentCategoryId = -1))
{
UserDecision.Remove(_parentCategoryId = -1);
}
}
}
get => _filterIntermediateItems;
}
public bool FilterUpperIntermediateItems
{
set
{
_filterUpperIntermediateItems = value;
OnPropertyChanged();
if (_filterUpperIntermediateItems)
{
FilterAllItems = false;
UserDecision.Add(_parentCategoryId = 3);
if (UserDecision.Contains(_parentCategoryId = -1))
{
UserDecision.Remove(_parentCategoryId = -1);
}
}
}
get => _filterUpperIntermediateItems;
}
public bool FilterAdvancedItems
{
set
{
_filterAdvancedItems = value;
OnPropertyChanged();
if (_filterAdvancedItems)
{
FilterAllItems = false;
UserDecision.Add(_parentCategoryId = 4);
if (UserDecision.Contains(_parentCategoryId = -1))
{
UserDecision.Remove(_parentCategoryId = -1);
}
}
}
get => _filterAdvancedItems;
}
public FilterViewModel()
{
FilterItemsCommand = new Command(async () => await FilterItems());
FindAllArticlesForPurchase();
}
public ObservableCollection<Article> FilterArticlesForPurchase { get; } = new ObservableCollection<Article>();
private static void FindAllArticlesForPurchase()
{
foreach (var userDecision in UserDecision)
{
if (userDecision != -1)
{
if (UserDecision.Count > 1)
{
Console.WriteLine("more than one item");
}
else
{
Console.WriteLine("one item");
}
}
else
{
Console.WriteLine("not minus one");
}
}
}
private async Task FilterItems()
{
await Application.Current.MainPage.Navigation.PushAsync(new Filter());
}
}
If you want to binding same FilterViewModel in MainPage and Filter page.
You should use static FilterViewModel in the MainPage.xaml.cs
public partial class MainPage : ContentPage
{
public static FilterViewModel filterViewModel ;
public MainPage()
{
InitializeComponent();
filterViewModel= new FilterViewModel();
BindingContext = filterViewModel;
}
}
In Filter page.You can binding same FilterViewModel in MainPage.xaml.cs
public partial class Filter: ContentPage
{
public Filter()
{
InitializeComponent();
BindingContext = MainPage.filterViewModel;
//If this FilterAllItems is empty, you want AllItems the checkbox to unselect, just set the value to false, the checkbox will update in the MainPage
MainPage.filterViewModel.FilterAllItems = false;
}
}