add DonateFragment

app/build.gradle

@@ -112,6 +112,11 @@ dependencies {
     kapt "androidx.room:room-compiler:$room_version"
     implementation "androidx.room:room-ktx:$room_version"
 
+    // billing library
+    def billing_version = "2.2.0"
+    implementation "com.android.billingclient:billing:$billing_version"
+    implementation "com.android.billingclient:billing-ktx:$billing_version"
+
     // debug tools
     implementation 'com.facebook.stetho:stetho:1.5.1'
     implementation 'com.facebook.stetho:stetho-okhttp3:1.5.1'

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")
+    }
+}

app/src/main/res/layout/fragment_donate.xml

@@ -0,0 +1,38 @@
+<?xml version="1.0" encoding="utf-8"?>
+<layout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto">
+
+    <data>
+
+        <import type="net.vonforst.evmap.viewmodel.DonateViewModel" />
+
+        <variable
+            name="vm"
+            type="DonateViewModel" />
+    </data>
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:orientation="vertical">
+
+        <com.google.android.material.appbar.AppBarLayout
+            android:id="@+id/toolbar_container"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:fitsSystemWindows="true">
+
+            <androidx.appcompat.widget.Toolbar
+                android:id="@+id/toolbar"
+                android:layout_width="match_parent"
+                android:layout_height="?android:actionBarSize" />
+
+        </com.google.android.material.appbar.AppBarLayout>
+
+        <androidx.recyclerview.widget.RecyclerView
+            android:id="@+id/products_list"
+            android:layout_width="match_parent"
+            android:layout_height="match_parent"
+            app:data="@{vm.products}" />
+    </LinearLayout>
+</layout>

app/src/main/res/navigation/nav_graph.xml

@@ -29,7 +29,11 @@
         android:id="@+id/about"
         android:name="net.vonforst.evmap.fragment.AboutFragment"
         android:label="@string/about"
-        tools:layout="@layout/fragment_preference" />
+        tools:layout="@layout/fragment_preference">
+        <action
+            android:id="@+id/action_about_to_donateFragment"
+            app:destination="@id/donate" />
+    </fragment>
     <fragment
         android:id="@+id/settings"
         android:name="net.vonforst.evmap.fragment.SettingsFragment"
@@ -54,4 +58,9 @@
         android:name="net.vonforst.evmap.fragment.FilterFragment"
         android:label="@string/menu_filter"
         tools:layout="@layout/fragment_filter" />
+    <fragment
+        android:id="@+id/donate"
+        android:name="net.vonforst.evmap.fragment.DonateFragment"
+        android:label="@string/donate"
+        tools:layout="@layout/fragment_donate" />
 </navigation>

app/src/main/res/values-de/strings.xml

@@ -63,4 +63,5 @@
     <string name="show_more">mehr…</string>
     <string name="show_less">weniger…</string>
     <string name="favorites_empty_state">Wenn du Ladestationen als Favorit markierst, tauchen sie hier auf.</string>
+    <string name="donate">Spenden</string>
 </resources>

app/src/main/res/values/strings.xml

@@ -62,4 +62,5 @@
     <string name="show_more">more…</string>
     <string name="show_less">less…</string>
     <string name="favorites_empty_state">If you add chargers as favorites, they will show up here.</string>
+    <string name="donate">Donate</string>
 </resources>

app/src/main/res/xml/about.xml

@@ -14,8 +14,12 @@
             android:title="@string/copyright"
             android:summary="@string/copyright_summary" />
 
+        <Preference
+            android:key="donate"
+            android:title="@string/donate" />
 
     </PreferenceCategory>
+
     <PreferenceCategory android:title="@string/other">
         <Preference
             android:key="github_link"