Binded TappedCommand is not triggering

2022-05-04 10:23 Funky Sloth imported from Stackoverflow

Can anyone point out why my Command is not triggering? This is my custom control

public partial class RateControl : Grid
    {
        public static readonly BindableProperty RateProperty = BindableProperty.Create(nameof(Rating), typeof(int), typeof(RateControl), 1, propertyChanged: OnRatePropertyChanged);

        private static void OnRatePropertyChanged(BindableObject bindable, object oldValue, object newValue)
        {
            if(bindable is RateControl && bindable != null && newValue is int)
            {
                (bindable as RateControl).OnRateClicked((int)newValue);
            }
        }

        public int Rating
        {
            set => SetValue(RateProperty, value);
            get => (int)GetValue(RateProperty);
        }

        public ICommand OnRateSelectedCommand { get; set; }

        public RateControl()
        {
            InitializeComponent();
            OnRateSelectedCommand = new Command<int>(OnRateClicked);
        }

        private void OnRateClicked(int rating)
        {
            Rating = rating;
            ChangeStar(Rating);
        }

        private void ChangeStar(int starcount)
        {
            for (int i = 1; i <= starcount; i++)
            {
                (FindByName($"star{i}") as Label).Text = RsrIcon.StarFull;
            }

            for (int i = starcount + 1; i <= 5; i++)
            {
                (FindByName($"star{i}") as Label).Text = RsrIcon.StarEmpty;
            }
        }
    }

And this is my Xaml

<Grid xmlns="http://xamarin.com/schemas/2014/forms" 
      xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
      x:Class="Mobile.Controls.RateControl"
      xmlns:common="clr-namespace:Mobile.Common"
      xmlns:control="clr-namespace:Mobile.Controls"
      RowDefinitions="Auto"
      x:Name="component"
      ColumnDefinitions="30,30,30,30,30"
      ColumnSpacing="10">
    
    <control:TappableLabel FontSize="Large"
                           x:Name="star1"
                           TappedCommand="{x:Binding OnRateSelectedCommand, Source={x:Reference component}}"
                           TappedCommandParameter="1"
                           Text="{Static common:RsrIcon.StarEmpty}"
                           TextColor="{StaticResource RsrYellow}"
                           VerticalOptions="Center"/>

.....

So the TappableLabel is just a custom TappedGesture, The thing is upon clicking the RateControl either be StarFull or StarEmpty. The initialization of the command is working, but upon clicking nothing is happening.

2 answers

answered 2022-05-04 13:41 ToolmakerSteve
I've never seen {x:Binding ... used with Xamarin Forms.
Change it to {Binding ...:
```
... TappedCommand="{Binding OnRateSelectedCommand, Source={x:Reference component}}"
```
Optionally, add as last line in constructor:
```
    BindingContext = this;
```
Then you can do binding simply with {Binding OnRateSelectedCommand}:
```
... TappedCommand="{Binding OnRateSelectedCommand}"
```

answered 2022-05-05 03:13 ColeX - MSFT

The generic type of Command should be string not int.

Modify your code as below

//xaml
TappedCommand="{Binding OnRateSelectedCommand}"

public RateControl()
{
   InitializeComponent();
   OnRateSelectedCommand = new Command<string>(OnRateClicked);
   BindingContext = this;
}

private void OnRateClicked(string rating)
{

}

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