What is the format of android:name inside the activity,inside the application tag on manifest file

Dears,

I add some code to the manifest file for launch my app by tapping a url.
My code inside application tag of manifest file:

    <activity android:icon="@drawable/icon" android:name="Packagename.MainActivity" android:label="myapp">
                    <intent-filter>
                        <data android:scheme="https" android:host="www.myapp.com" />
                        <action android:name="android.intent.action.VIEW" />
                        <category android:name="android.intent.category.DEFAULT" />
                        <category android:name="android.intent.category.BROWSABLE" />
                    </intent-filter>
                </activity> 

But when I open the app in that way app breaks with an exception Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack available.

I feel some mistakes in the android:name="Packagename.MainActivity" in activity tag. Is it correct? Maybe because of this getting class not found exception?

What is the correct format for android:name? "Packagename.MainActivity" or "Packagename.namespace.MainActivity" or "namespace.MainActivity" any other format? Also, the app is opening when direct tapping(I mean without url tap).

Thanks in advance