Xamarin MvvmCross交叉绑定数据作为方法

Question

I have a button, that goes back, and I'm binding it to command, that needs a parameter. Is it possible to pass command parameter as a method, that gets string?

I want to make something like that:

<ImageButton
    local:MvxBind="Click GoHomeCommand, CommandParameter='Application.Context.GetSharedPreferences('USER_INFO', FileCreationMode.Private).GetString('USER_FACEBOOK_ID', null)'"
    android:id="@+id/backButton"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:src="@drawable/ic_menu_back"
    android:background="@null"
    android:paddingLeft="30dp"
    android:paddingRight="30dp" />

As you can see I binded click and I'm trying to send command parameter which now is obviously a string, but can I send a params that is the result of method: Application.Context.GetSharedPreferences('USER_INFO', FileCreationMode.Private).GetString('USER_FACEBOOK_ID', null) ??

Answer 1

This is not possible. There are some ways to work around it. The easiest might be to set a ValueConverter which you implement in Android and do this in.

I think a better option is to add a function to the command, and call a interface through IoC which you implement in Android.

Answer 2

There are already some plugins out there, which uses SharedPreferences internally, so you could leverage those to expose this string you have in the shared prefs.

I am the author of Cheesebaron.MvxPlugin.Settings , if you provide a configuration to the plugin, with the USER_INFO path for your settings you will be able to get the same values out of the plugin.

So first add the NuGet to your Core and Droid project.

In the Setup.cs file of your Droid project override GetPluginConfiguration :

protected override IMvxPluginConfiguration GetPluginConfiguration(Type plugin)
{
    if (plugin == typeof(Cheesebaron.MvxPlugins.Settings.PluginLoader))
    {
        return new DroidCheeseSettingsConfiguration
        {
            SettingsFileName = "USER_INFO"
        };
    }

    return base.GetPluginConfiguration(plugin);
}

Then in your ViewModel you can expose any setting:

public class MyViewModel : MvxViewModel
{
    private ISettings _settings;

    public MyViewModel(ISettings settings)
    {
        _settings = settings;
    }

    public string FacebookId => _settings.GetValue("USER_FACEBOOK_ID", string.Empty);
}

Now you can use FacebookId as the parameter in your binding instead.