How to bind a command to Entry "Unfocused" event in Xamarin Forms

Question

I have a command (or a piece of code) which I want to run when a specific entry loses its focus.

I'm using MVVM so I want to do it using the binding way instead of writing code in my Form.xaml.cs.

How can I make my command (or my piece of code) run when my entry loses its focus within XAML file?

Answer 1

There is an example of an EventToCommandBehavior in the Xamarin.Forms samples (see here). Using this you could bind your control

<Entry>
    <Entry.Behaviors>
        <behaviors:EventToCommandBehavior 
            EventName="Unfocused" 
            Command="{Binding EntryUnfocused}" />
    </Entry.Behaviors>
</Entry>

Then define EntryUnfocused in your class of viewmodel.cs file of your particular view, like below:

public class LoginViewModel : XamarinViewModel
{
    public ICommand EntryUnfocused{ get; protected set; } 
    public LoginViewModel()
    {
        EntryUnfocused= new Command(CompletedCommandExecutedAsync);
    }

    private void CompletedCommandExecutedAsync(object param)
    {
     //yourcode...
    }
}

If you are using the Prism library, you can use their implementation, which is a bit more mature (allowing you to map the event arguments by specifying, which parameter shall be passed), see here.

(Please note that you'll have to add the respective namespace the behavior lives in to your XAML file).

Answer 2

If you use Xamarin Community Toolkit, you can use EventToCommandBehavior which is already there.

Using this will be the same as in the Paul Kertscher answer.

Add to your control header:

xmlns:toolkit="http://xamarin.com/schemas/2020/toolkit"

In your Entry bind to the command:

<Entry.Behaviors>
    <toolkit:EventToCommandBehavior
        EventName="Unfocused"
        Command="{Binding EntryUnfocused}" />
</Entry.Behaviors>