Passing an Android translatable string to ValueConverter

Question

I'm trying to pass a @string/something to a value converter so I can use it to format the output, so say I have a DateTime value, I want to pass something like "Signup Date: {0}" to the ValueConverter.

The problem is, the text above is translatable, so it came from the strings.xml file of any given language. So far, I tried this:

<TextView
   local:MvxBind="Text SignupDate, Converter=FriendlyDate, ConverterParameter=@string/release_date"
   android:layout_width="match_parent"
   android:layout_height="wrap_content"
   android:ellipsize="end"
   android:maxLines="5"
   android:paddingTop="8dp"
   style="@style/WhiteParagraphText" />

Note the ConverterParameter=@string/release_date . How can I do it?

Answer 1

You can do this with a value converter that takes the string resource name as parameter, looks its id up in the resources and gets the value from the resources by this id.

public class FriendlyDateValueConverter : MvxValueConverter<DateTime, string>
{
    protected override string Convert(DateTime value, Type targetType, object parameter, CultureInfo culture)
    {
        var param = parameter as string;
        if (string.IsNullOrEmpty(param))
        {
            return string.Empty;
        }

        var globals = MvvmCross.Platform.Mvx.Resolve<IMvxAndroidGlobals>();
        var res = globals.ApplicationContext.Resources;
        var id = res.GetIdentifier(param, "string", globals.ApplicationContext.PackageName);
        // id=0, if the resource could not be found -> add some error handling

        var format = res.GetString(id);
        return string.Format(format, value);
    }
}

Usage

<TextView 
    local:MvxBind="Text SignupDate, Converter=FriendlyDate, ConverterParameter='release_date'"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:ellipsize="end"
    android:maxLines="5"
    android:paddingTop="8dp" />

Note: pass 'release_date' instead of @string/release_date as parameter.