How to extend application class in xamarin android

Question

I want to extend the Android application and I want to override onCreate method. But for some reason it's been very terrible...Only if I remove [Application] am I able to run it but according to this link we have to add [Application]

[Application]
public class MainApp : Application
{
    public MainApp(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)
    {
    }

    public override void OnCreate()
    {
        base.OnCreate();
        //app init ...
    }
}

Can anybody clarify me what is the right way to extend application class in Xamarin android

Update

If I don't remove [application] I am exactly getting the below error

/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets:
 Error: Error executing task GenerateJavaStubs: Application cannot have both a type with an [Application] attribute and an [assembly:Application] attribute. (myapp.Droid)

If I add Application then it compiles but it throws following runtime error

[AndroidRuntime] Shutting down VM [AndroidRuntime] FATAL EXCEPTION:
main [AndroidRuntime] Process: com.test.myapp, PID: 6524
[AndroidRuntime] java.lang.RuntimeException: Unable to instantiate
application com.test.myapp.MainApp: java.lang.ClassNotFoundException:
Didn't find class "com.test.myapp.MainApp" on path: DexPathList[[zip
file "/data/app/com.test.myapp-1/base.apk"],nativeLibraryDirectories=[/data/app/com.test.myapp-1/lib/arm,
/data/app/com.test.myapp-1/base.apk!/lib/armeabi-v7a, /system/lib,
/vendor/lib]] [AndroidRuntime]  at
android.app.LoadedApk.makeApplication(LoadedApk.java:802)
[AndroidRuntime]    at
android.app.ActivityThread.handleBindApplication(ActivityThread.java:5377)
[AndroidRuntime]    at
android.app.ActivityThread.-wrap2(ActivityThread.java)
[AndroidRuntime]    at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1545)
[AndroidRuntime]    at
android.os.Handler.dispatchMessage(Handler.java:102) [AndroidRuntime]
    at android.os.Looper.loop(Looper.java:154) [AndroidRuntime]     at
android.app.ActivityThread.main(ActivityThread.java:6119)
[AndroidRuntime]    at java.lang.reflect.Method.invoke(Native Method)
[AndroidRuntime]    at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
[AndroidRuntime]    at
com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
[AndroidRuntime] Caused by: java.lang.ClassNotFoundException: Didn't
find class "com.test.myapp.MainApp" on path: DexPathList[[zip file
"/data/app/com.test.myapp-1/base.apk"],nativeLibraryDirectories=[/data/app/com.test.myapp-1/lib/arm,
/data/app/com.test.myapp-1/base.apk!/lib/armeabi-v7a, /system/lib,
/vendor/lib]] [AndroidRuntime]  at
dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
[AndroidRuntime]    at
java.lang.ClassLoader.loadClass(ClassLoader.java:380) [AndroidRuntime]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
[AndroidRuntime]    at
android.app.Instrumentation.newApplication(Instrumentation.java:992)
[AndroidRuntime]    at
android.app.LoadedApk.makeApplication(LoadedApk.java:796)
[AndroidRuntime]    ... 9 more

Here is my manifest file

Recitative

Answer 1

In AssemblyInfo.cs

comment out

    #if DEBUG
    [Application(Debuggable=true)]
    #else
    [Application(Debuggable = false)]
    #endif

and move that on top of your application

#if DEBUG
[Application(Debuggable=true)]
#else
[Application(Debuggable = false)]
#endif
public class MainApp : Application
{
    public MainApp(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)
    {
    }

    public override void OnCreate()
    {
        base.OnCreate();
        //app init ...
    }
}

Basically you have defined it two places that's why this problem occurs. Commenting out in AssemblyInfo.cs and adding in the extended class will work out

FYI:

Manifest is ok

Octahedron

Answer 2

1. Apply the ApplicationAttribute, [Application], to your Application subclass to register this class in the manifest

   • https://developer.xamarin.com/api/type/Android.App.ApplicationAttribute/

2. Add the Java/JNI constructor

   • .ctor(System.IntPtr, Android.Runtime.JniHandleOwnership)
   • You will receive a fault when the runtime tries to instance the Java wrapper if you do not add this....

3. Override the OnCreate method

   • This avoids: [art] JNI RegisterNativeMethods: attempt to register 0 native methods and thus your application subclass is not instanced.

Example:

[Application]
public class MainApplication : Application
{
    public MainApplication(IntPtr javaReference, Android.Runtime.JniHandleOwnership transfer) : base(javaReference, transfer)
    {
    }

    public override void OnCreate()
    {
        base.OnCreate();
    }
}

Milestone

I am getting compilation error .... it says the file couldn't be found .. I added android:name with application – Recitative

@Recitative android:name?, Like: [Application(LargeHeap = true, Name = "com.sushihangover.application")] – Milestone

I entered =".application" ... it says .. it couldn't find com.test.myapp.applcation ... here com.test.myapp is my package – Recitative

You have to fully qualify the "Name", xamarin does support the dot notation like andriod Java or gradle – Milestone

you mean to say I have to enter com.test.myapp.application in android:name – Recitative

What is the full application attribute line that you are using? – Milestone

Hey guys how can i add Xamarin.Forms.Init() in class extending Application – Bin

@LutaayaHuzaifahIdris You are looking at the wrong type of Application, in Android you call Forms' Init in the first/main activity, on iOS you call it in the AppDelegate. – Milestone