StartActivity上的Android.Content.ActivityNotFoundException

Question

I'm currently developing an Androd app in Visual Studio 2017 using Xamarin and I'm somewhat of a beginner. My main activity is "MainActivity.cs", and in this activity I navigate to another activity on a button click. I do this with the code:

var activity2 = new Intent(this, typeof(Menu2));
activity2.PutExtra("Token", Token);
StartActivity(activity2);

Everything works fine. Then, in the second activity, "Menu2.cs", I try to navigate to another activity on a button click, but I get an error. I use the same code:

var activity3 = new Intent(this, typeof(Menu3));
StartActivity(activity3);

But I get the following error:

Android.Content.ActivityNotFoundException: 
Unable to find explicit activity class {RWS.RWS/md563c841bc41fc48076b499c07864126c3.Menu3};
have you declared this activity in your AndroidManifest.xml?

Now, I tried adding the activities manully on the AndroidManifest, since Visual Studio does not add them automatically. This didn't work as well. Currently, my AndroidManifest file is like this:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
  package="RWS.RWS" android:versionCode="1" android:versionName="1.0" 
  android:installLocation="auto">
    <uses-sdk android:minSdkVersion="16" />
    <uses-permission android:name="android.permission.INTERNET" />
    <application android:label="RWS" android:icon="@drawable/rws"></application>
</manifest>

Also, if it helps, the headers of my activities (Menu2 and Menu3) are the following:

[Activity(Label = "Menu2", MainLauncher = true, Icon = "@drawable/EAD", Theme = "@android:style/Theme.Light.NoTitleBar.Fullscreen")]
public class Menu2 : Activity

[Activity(Label = "Menu3", Icon = "@drawable/EAD", Theme = "@android:style/Theme.Light.NoTitleBar.Fullscreen")]
public class Menu3 : Activity

Menu2 and Menu3 full class as per asked by @Ferdous Ahamed:

namespace RWS
{
    [Activity(Label = "Menu2", MainLauncher = true, Icon = "@drawable/EAD", Theme = "@android:style/Theme.Light.NoTitleBar.Fullscreen")]
    public class Menu2 : Activity
    {
   protected override void OnCreate(Bundle savedInstanceState)
   {
       base.OnCreate(savedInstanceState);
       string token = Intent.GetStringExtra("Token");

       // Create your application here
       SetContentView(Resource.Layout.Menu2);

       Button trabalho = FindViewById<Button>(Resource.Id.trabalho);
       trabalho.Click += delegate
       {
           Toast.MakeText(this, "Aguarde...", ToastLength.Short).Show();
       };

       Button pesquisa = FindViewById<Button>(Resource.Id.pesquisa);
       pesquisa.Click += delegate
       {
           var activity2 = new Intent(this, typeof(Menu3));
           //activity2.PutExtra("Token", Token);
           StartActivity(activity2);

       };

   }
   }
}

namespace RWS
{
     [Activity(Label = "Menu3")]
     public class Menu3 : Activity
     {

         protected override void OnCreate(Bundle savedInstanceState)
         {
             base.OnCreate(savedInstanceState);
             SetContentView(Resource.Layout.Menu3);
         }
     }
 }

Please note that Menu2 works properly while not having any difference and not being added on AndroidManifest, but Menu3 doesn't. The activities were added the same way, and one works, one doesn't.

What can I do?

Answer 1

Use:

[Activity(Label = "Menu3")]
public class Menu3 : Activity

Instead of:

[Activity(Label = "Menu3", Icon = "@drawable/EAD", Theme = "@android:style/Theme.Light.NoTitleBar.Fullscreen")]
public class Menu3 : Activity

Finally, clean and rebuild your project.

Answer 2

It seems it wasn't actually this error. I tried rebuilding the project and looking at the output logs, but I never saw an actual code error, until I created a new project, rebuilt everything and then I was able to see an error in one of my .xaml file that was bugging the project.

Quick tip: If Visual Studio is throwing an error, even if the error doesn't seem right, try to Clean the project and Rebuild. After, check Output log and you'll find if your project has errors or not.

Thanks to those who helped me.

Answer 3

I had the same problem. It was about namespaces.

I made a catalog inside my project "activities", made new activity file inside it and VS automaticly set namespace "myProject.activities" in this file. Then the problem occured.

So I changed namespace in activity to "myProject" and it worked well.

Answer 4

I did like this, it fixed my problem.

[Activity(name = "RWS.RWS.Menu3")]
public class Menu3 : Activity
{
}