Using a Custom Application Class in Xamarin.Android

Question

I have several variables that I want to share across all classes in my app (Activity(s), Adapter(s), ViewHolder(s), etc.). I am trying to use a custom Application by inheriting from Android.App.Application. Here is the declaration for my custom Application class:

public class ScorePadApplication : Application
{
    public static readonly int[] NameColors = new[] {  };
    public static readonly int[] ScoreColors = new[] {  };
    public static PlayerData[] Players { get; set; }
}

And here is the application line from my AndroidManifest.xml file (the only change I made is the name attribute):

<application android:name="ScorePadApplication" android:allowBackup="false" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:roundIcon="@mipmap/ic_launcher_round" android:supportsRtl="true" android:theme="@style/AppTheme"></application>

However, my app now refuses to do anything (it doesn't start). The only output to the Output window is the following:

am start -a "android.intent.action.MAIN" -c "android.intent.category.LAUNCHER" -n "com.companyname.scorepad/crc6420a578ac0cde9c07.MainActivity"
Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=com.companyname.scorepad/crc6420a578ac0cde9c07.MainActivity }

Is there something else I need to do to use a custom Application class? Am I doing this wrong? Thanks.

Answer 1

Hello,​

Welcome to our Microsoft Q&A platform!

Xamarin.Android permits writing Android apps with C# instead of Java. To create a custom Application/View class, we need to add the Java/JNI constructor.

   [Application]  
   public class CustomApplication : Application  
   {  
       protected CustomApplication(System.IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)  
       {  
       }  
       public override void OnCreate()  
       {  
           base.OnCreate();  
       }  
   }  

Best Regards,

Jarvan Zhang

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Answer 2

You need to add the additional protected ctor. See the Application class

protected Application(IntPtr javaReference, JniHandleOwnership transfer);