具有绑定属性的图像IsEnabled不能使用Xamarin表单

Question

Using Xamarin forms -pcl v 2.3.4.267 -Debug on Android Device

I have an Image that is being used as button

          <Image Source="loginbutton.png"           
           Aspect="AspectFit"
           HorizontalOptions="Fill"
           Margin="50,20,50,0"
           fe:TappedGestureAttached.Command="{Binding Login}"
           IsVisible ="{Binding user.IsSubmitEnabled}"<---works fine
           IsEnabled="{Binding user.IsSubmitEnabled}"<---Does nothing
           /> 

as i mentioned in the code the Is Visible Works Great But Is Enabled does nothing.

note:-if there is any workaround please share it .

Answer 1

This is a known issue in Xamarin, already reported here and should be fixed in a future version of Xamarin.Forms, more specifically version 2.4.0-pre .

As a Workaround you can use the IsSubmitEnabled as the parameter for the CanExecute parameter in your Command .

Something like this:

public MyViewModel()
{
    Login = new Command(() => OnLogin(), () => IsSubmitEnabled);
}

But you will need to add a line Login.CanExecute(null); in your Property setter too.

private bool _isSubmitEnabled;
public bool IsSubmitEnabled
{
    get { return _isSubmitEnabled; }
    set
    {
        _isSubmitEnabled= value;
        RaisePropertyChanged(nameof(IsSubmitEnabled));
        Login.CanExecute(null);
    }
}

This should work in the mean time. Till the fix is in production.

Note : just for information, this issue seems only to be happening on Android while on iOS seems to be working correctly.

Hope this helps.-

Answer 2

Are you using both statements in parallel?

IsVisible ="{Binding user.IsSubmitEnabled}"<---works fine
IsEnabled="{Binding user.IsSubmitEnabled}"<---Does nothing

Then IsEnabled=false is only active if the button is invisible, because both are binding to the same boolean property => IsSubmitEnabled.

Maybe you have to use a second boolean binding property?

Answer 3

If you want unclickable when you enable property false you do as following

As First binding property of IsVisible and IsEnable must be different.

<Image Source="loginbutton.png"           
           Aspect="AspectFit"
           HorizontalOptions="Fill"
           Margin="50,20,50,0"
           fe:TappedGestureAttached.Command="{Binding Login}"
           IsVisible ="{Binding user.IsSubmitVisible}"
           IsEnabled="{Binding user.IsSubmitEnabled}"
           />

And you change the code in ViewModel like:

 public void Login()
    {
        If(IsSubmitEnabled){
           // Put your code here
        }
    }

Answer 4

According to this post , if we bind IsEnabled property before binding commands, the properties wont' trigger. I ran in to same problem and moved IsEnabled binding after Command binding, and IsEnabled property was set correctly.

Hope that helps