[Xamarin.Forms] Behaviors for Xamarin.Forms @ 小賢的部落格

Nuget:

Behaviors for Xamarin.Forms 1.1.0

Install-Package Behaviors.Forms

Xaml

<?xml version="1.0" encoding="utf-8" ?>
<local:BasePage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:MilitaryCountdown"
             xmlns:behaviors="clr-namespace:Behaviors;assembly=Behaviors" 
             x:Class="MilitaryCountdown.SafeReportPage"
             Title="安全回報"
	>

    <local:BasePage.BindingContext>
        <local:SafeReportViewModel />
	</local:BasePage.BindingContext>

    <Button Text="傳送安全回報" 
               >

        <Button.Behaviors>
            <behaviors:EventHandlerBehavior EventName="Clicked">
                <behaviors:InvokeMethodAction TargetObject="{Binding}" MethodName="SendReport_Click" />
            </behaviors:EventHandlerBehavior>
        </Button.Behaviors>

    </Button>
</local:BasePage>

C# ViewModel

namespace MilitaryCountdown
{
    public class SafeReportViewModel : BaseViewModel
    {
        public void SendReport_Click(object sender, EventArgs e)
        {
            var smsMessenger = MessagingPlugin.SmsMessenger;
            if (!smsMessenger.CanSendSms)
            {
                return;
            }

            smsMessenger.SendSms("", "報告班長，我是二兵OOO，目前在家做安全回報。");
        }
    }
}

iOS 的問題:

Unhandled Exception: Xamarin.Forms.Xaml.XamlParseException: Position 47:22. Type behaviors:InvokeMethodAction not found in xmlns clr-namespace:Behaviors;assembly=Behaviors

iOS解法

namespace MilitaryCountdown.iOS
{
	// The UIApplicationDelegate for the application. This class is responsible for launching the 
	// User Interface of the application, as well as listening (and optionally responding) to 
	// application events from iOS.
	[Register("AppDelegate")]
	public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
	{
		//
		// This method is invoked when the application has loaded and is ready to run. In this 
		// method you should instantiate the window, load the UI into it and then make the window
		// visible.
		//
		// You have 17 seconds to return from this method, or iOS will terminate your application.
		//
		public override bool FinishedLaunching(UIApplication app, NSDictionary options)
		{
			global::Xamarin.Forms.Forms.Init ();
			LoadApplication (new MilitaryCountdown.App ());

            var x = typeof(Behaviors.EventHandlerBehavior);

            return base.FinishedLaunching (app, options);
		}
    }
}

Android 解法

namespace MilitaryCountdown.Droid
{
	[Activity (Label = "國軍Online倒數計時器", Icon = "@drawable/icon", Theme="@style/MainTheme", MainLauncher = true, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
	public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
	{
		protected override void OnCreate (Bundle bundle)
		{
			TabLayoutResource = Resource.Layout.Tabbar;
			ToolbarResource = Resource.Layout.Toolbar; 

			base.OnCreate (bundle);

			global::Xamarin.Forms.Forms.Init (this, bundle);
			LoadApplication (new MilitaryCountdown.App ());

            var x = typeof(Behaviors.EventHandlerBehavior);
        }
    }
}

結論：

透過Behavior SDK就能夠將原本必須寫在Page的C# Code，轉移到ViewModel中，讓商業邏輯更集中於ViewModel。

4/10更新：

在包版後上傳到TestFlight，再用內部測試下載回來測試，發現會Crash...，上傳幾版之後，發現Release Mode也能重現Crash。