我有一个 Xamarin 形式的 MultiTrigger，对于一个按钮，它不起作用

Question

I have a create-account page in my PCL, with a button that depends on several entry fields.

I want to enable the Create button only when the fields have the proper input. Here's my markup:

<Button Text="Create Account" Clicked="CreateAccountButton_Clicked" IsEnabled="False">
     <Button.Triggers>
          <MultiTrigger TargetType="Button">
               <MultiTrigger.Conditions>
                    <BindingCondition Binding="{Binding Source={x:Reference EmailValidator}, Path=IsValid}" Value="True" />
                    <BindingCondition Binding="{Binding Source={x:Reference PasswordValidator}, Path=IsValid}" Value="True" />
               </MultiTrigger.Conditions>
               <Setter Property="IsEnabled" Value="True" />
          </MultiTrigger>
     </Button.Triggers>
</Button>

I have verified that the validators are setting their IsValid properties to True, yet the button is NOT being enabled. I am using an Android emulator and Visual Studio 2019.

The code above is identical to several examples I found online.

Am I missing something?

Answer 1

In your Xaml :

<ResourceDictionary>
   <local:MultiTriggerConverter x:Key="DataHasBeenEnteredTrigger" />
</ResourceDictionary>

My Example :

<Button IsEnabled="False" Text="{localization:Translate login}" Margin="25,0" TextColor="{StaticResource color-fourth}" BackgroundColor="Yellow" Opacity="0.5" FontAttributes="Bold" Command="{Binding GoConnexionCommand}" >
                <Button.Triggers>
                    <MultiTrigger TargetType="Button">
                        <MultiTrigger.Conditions>
                            <BindingCondition Binding="{Binding Source={x:Reference user},
                                      Path=Text.Length,
                                      Converter={StaticResource DataHasBeenEnteredTrigger}}"
                                      Value="true" />
                            <BindingCondition Binding="{Binding Source={x:Reference password},
                                      Path=Text.Length, 
                                      Converter={StaticResource DataHasBeenEnteredTrigger}}"
                                      Value="true" />
                </MultiTrigger.Conditions>
            <Setter Property="IsEnabled" Value="True" />
        <Setter Property="Opacity" Value="1" />
    </MultiTrigger>
</Button.Triggers>

Convert Class:

public class MultiTriggerConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        if (value == null) return false;

        if ((int)value > 0) return true;            
         else return false;   // Input is empty
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

Test this and tell me what it looks like!

Best regrads