Taoffi's blog

As XF documentations say, your platform-application (Droid, iOS or WP) should call Forms.Init() at startup.

That should be done:

• In iOS: in the AppDelegate.FinishedLaunching method
  • global::Xamarin.Forms.Forms.Init();
• In Droid: in the MainActivity. OnCreate (Bundle bundle)
  • global::Xamarin.Forms.Forms.Init(this, bundle);
• In Win Phone: in your application's MainPage constructor
  • global::Xamarin.Forms.Forms.Init();

What does Forms.Init do?

On droid

Here is an example of what Forms.Init method does on Android:

public static void Init(Activity activity, Bundle bundle)
{
    // get the calling assembly 
    Assembly callingAssembly = Assembly.GetCallingAssembly(); 

    // Call SetupInit 
    SetupInit(activity, callingAssembly); 
}

Let us continue following the call to SetupInit():

private static void SetupInit(Activity activity, Assembly resourceAssembly) 
{
    // set the Context to current activity 
    Context = activity; 

    // initialize resources for this assembly 
    ResourceManager.Init(resourceAssembly); 

    // set the AccentColor according to OS version 
    if (Build.VERSION.SdkInt <=    BuildVersionCodes.GingerbreadMr1) 
    { 
       Color.Accent = Color.FromHex("#fffeaa0c"); 
    } 
    else 
    { 
       Color.Accent = Color.FromHex("#ff33b5e5"); 
    } 

    // log (if not initialized) 
    if (!IsInitialized) 
    { 
       Log.get_Listeners().Add(new DelegateLogListener( 
 (c, m) => Trace.WriteLine(m, c))); 
    } 

    // set the Device.OS version and platform services (here android) 
       Device.OS = TargetPlatform.Android; 
       Device.PlatformServices = new AndroidPlatformServices(); 

    // recreate the device info from this activity 
    if (Device.info != null) 
    { 
       ((AndroidDeviceInfo) Device.info).Dispose(); 
       Device.info = null; 
    } 

    IDeviceInfoProvider formsActivity = activity as IDeviceInfoProvider; 

    if (formsActivity != null) 
    { 
       Device.Info = new AndroidDeviceInfo(formsActivity); 
    } 

    // recreate the ticker 
    AndroidTicker ticker = Ticker.Default as AndroidTicker; 

    if (ticker != null) 
    { 
       ticker.Dispose(); 
   } 

   Ticker.Default = new AndroidTicker(); 

    // initialize renderers (if not initialized (again)) 
    if (!IsInitialized) 
    { 
       // register renderers for attributes export / cell / image source 
       Type[] typeArray1 = new Type[] 
                   { typeof(ExportRendererAttribute), 
                   typeof(ExportCellAttribute), 
                   typeof(ExportImageSourceHandlerAttribute) 
                   }; 

       // registrer the handlers of these types 
       Registrar.RegisterAll(typeArray1); 
    } 

    // set the device idiom according to screen width dpi 
    Device.Idiom = (Context.Resources.Configuration.SmallestScreenWidthDp >= 600) 
             ? TargetIdiom.Tablet : TargetIdiom.Phone; 
 
    // set search expression default (if not already set) 
    if (ExpressionSearch.Default == null) 
    { 
       ExpressionSearch.Default = new AndroidExpressionSearch(); 
    } 

    // set initialzed flag 
    IsInitialized = true; 
} 

On iOS

public static void Init() 
{ 
    if (!IsInitialized) 
    { 
       // set initialized flag 
       IsInitialized = true; 

       // set the AccentColor 
       Color.Accent = Color.FromRgba(50, 0x4f, 0x85, 0xff); 

       Log.get_Listeners().Add(new DelegateLogListener( 
             // obscure decompilation of an anonymous methodJ 
          <>c.<>9__9_0 
             ?? (<>c.<>9__9_0 = new Action<string, string>      (<>c.<>9.<Init>b__9_0)))); 

       // device os and platform services 
       Device.OS = TargetPlatform.iOS; 
       Device.PlatformServices = new IOSPlatformServices(); 

       Device.Info = new IOSDeviceInfo(); 

       // set the ticker 
       Ticker.Default = new CADisplayLinkTicker(); 

       // register renderers for attributes export / cell / image source 
       Type[] typeArray1 = new Type[] 
                      { typeof(ExportRendererAttribute), 
                      typeof(ExportCellAttribute), 
                      typeof(ExportImageSourceHandlerAttribute) 
                      }; 

       Registrar.RegisterAll(typeArray1); 

       // set device idiom 
       Device.Idiom = (UIDevice.get_CurrentDevice  ().get_UserInterfaceIdiom() == 1L) 
             ? TargetIdiom.Tablet : TargetIdiom.Phone; 

       // set search expression default 
       ExpressionSearch.Default = new iOSExpressionSearch(); 
    } 
}

On Win Phone

public static void Init()
{
    if (!isInitialized)
    {
        // create an event trigger object (why?) 
        // note: constructor initializes an EventNameProperty DependencyProperty 
        new EventTrigger();

        string name = Assembly.GetExecutingAssembly().GetName().Name;
        ResourceDictionary dictionary1 = new ResourceDictionary();

        // load xaml resources 
        dictionary1.set_Source(
                new Uri(string.Format("/{0};component/WPResources.xaml", name),
                UriKind.Relative));

        // add resources to merged dictionaries 
        Application.get_Current().get_Resources().get_MergedDictionaries().Add(dictionary1);

        // set accent( color from resources 
        Color color = (Application.get_Current().get_Resources().get_Item("PhoneAccentBrush") as SolidColorBrush).get_Color();

        byte introduced3 = color.get_R();
        byte introduced4 = color.get_G();
        byte introduced5 = color.get_B();

        Color.Accent = Color.FromRgba((int)introduced3,
                                (int)introduced4,
                                (int)introduced5,
                                (int)color.get_A());

        // log 
        Log.get_Listeners().Add(new DelegateLogListener(<> c.<> 9__3_0
                    ?? (<> c.<> 9__3_0 = new Action<string,
                    string>(<> c.<> 9.< Init > b__3_0))));

        // set device os and platform services 
        Device.OS = TargetPlatform.WinPhone;
        Device.PlatformServices = new WP8PlatformServices();
        Device.Info = new WP8DeviceInfo();

        // register renderers for attributes export / cell / image source 
        Type[] typeArray1 = new Type[]
                    { typeof(ExportRendererAttribute),
                            typeof(ExportCellAttribute),
                            typeof(ExportImageSourceHandlerAttribute)
                    };

        Registrar.RegisterAll(typeArray1);

        // set ticker default 
        Ticker.Default = new WinPhoneTicker();

        // set device idiom 
        Device.Idiom = TargetIdiom.Phone;

        // set search expression default 
        ExpressionSearch.Default = new WinPhoneExpressionSearch();

        // set initialzed flag 
        isInitialized = true;
    }
}