add DonateFragment

app/src/main/java/net/vonforst/evmap/fragment/AboutFragment.kt

@@ -51,6 +51,10 @@ class AboutFragment : PreferenceFragmentCompat() {
                     .start(requireActivity())
                 true
             }
+            "donate" -> {
+                findNavController().navigate(R.id.action_about_to_donateFragment)
+                true
+            }
             else -> super.onPreferenceTreeClick(preference)
         }
     }

app/src/main/java/net/vonforst/evmap/fragment/DonateFragment.kt

@@ -0,0 +1,44 @@
+package net.vonforst.evmap.fragment
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.appcompat.app.AppCompatActivity
+import androidx.appcompat.widget.Toolbar
+import androidx.databinding.DataBindingUtil
+import androidx.fragment.app.Fragment
+import androidx.fragment.app.viewModels
+import androidx.navigation.fragment.findNavController
+import androidx.navigation.ui.setupWithNavController
+import net.vonforst.evmap.MapsActivity
+import net.vonforst.evmap.R
+import net.vonforst.evmap.databinding.FragmentDonateBinding
+import net.vonforst.evmap.viewmodel.DonateViewModel
+
+class DonateFragment : Fragment() {
+    private lateinit var binding: FragmentDonateBinding
+    private val vm: DonateViewModel by viewModels()
+
+    override fun onCreateView(
+        inflater: LayoutInflater,
+        container: ViewGroup?,
+        savedInstanceState: Bundle?
+    ): View? {
+        binding = DataBindingUtil.inflate(inflater, R.layout.fragment_donate, container, false)
+        binding.lifecycleOwner = this
+        binding.vm = vm
+        return binding.root
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        val toolbar = view.findViewById(R.id.toolbar) as Toolbar
+        (requireActivity() as AppCompatActivity).setSupportActionBar(toolbar)
+
+        val navController = findNavController()
+        toolbar.setupWithNavController(
+            navController,
+            (requireActivity() as MapsActivity).appBarConfiguration
+        )
+    }
+}

app/src/main/java/net/vonforst/evmap/viewmodel/DonateViewModel.kt

@@ -0,0 +1,29 @@
+package net.vonforst.evmap.viewmodel
+
+import android.app.Application
+import androidx.lifecycle.AndroidViewModel
+import androidx.lifecycle.MutableLiveData
+import com.android.billingclient.api.*
+
+class DonateViewModel(application: Application) : AndroidViewModel(application),
+    PurchasesUpdatedListener {
+    private var billingClient = BillingClient.newBuilder(application)
+        .setListener(this)
+        .enablePendingPurchases()
+        .build()
+
+    val products: MutableLiveData<List<SkuDetails>> by lazy {
+        MutableLiveData<List<SkuDetails>>().apply {
+            value = null
+
+            val params = SkuDetailsParams.newBuilder().setType(BillingClient.SkuType.INAPP).build()
+            billingClient.querySkuDetailsAsync(params) { result, details ->
+                value = details
+            }
+        }
+    }
+
+    override fun onPurchasesUpdated(result: BillingResult, purchases: List<Purchase>?) {
+        TODO("Not yet implemented")
+    }
+}