Improvements

.gitignore

@@ -1,3 +1,4 @@
 .idea/
 obj/
-bin/
+bin/
+/.DS_Store

DemoAndroid/Activities/WakeOnLanActivity.cs

@@ -1,11 +1,21 @@
 using System.Net;
 using System.Net.Sockets;
+using Android.Content;
+using Android.Hardware.Biometrics;
+using Android.OS;
+using Java.Lang;
 
 namespace DemoAndroid;
 
-[Activity(Label = "WakeOnLanActivity")]
+[Activity(Label = "@string/app_name", MainLauncher = true, Theme = "@style/Default")]
 public class WakeOnLanActivity : Activity
 {
+    private const int BiometricStrong = 0x0000000f;
+    private const int BiometricWeak = 0x000000ff;
+    private const int DeviceCredential = 0x00008000;
+
+    private bool _authenticated = false;
+    
     protected override void OnCreate(Bundle? savedInstanceState)
     {
         base.OnCreate(savedInstanceState);
@@ -16,25 +26,51 @@ public class WakeOnLanActivity : Activity
         var button = FindViewById<Button>(Resource.Id.btnWakeOnLan);
         button.Click += (sender, args) =>
         {
-            WakePc();
+            OnlyAuthenticated(WakePc);
         };
     }
 
+    private void OnlyAuthenticated(Action action)
+    {
+        if (!_authenticated)
+        {
+            var callback = new BiometricCallback(this, () =>
+            {
+                _authenticated = true;
+                action();
+            });
+
+            var prompt = new BiometricPrompt.Builder(this)
+                .SetNegativeButton("Annuleren", MainExecutor, callback)
+                .SetTitle("Bewijs jezelf met je vingerafdruk")
+                .SetSubtitle("We willen zeker weten dat je niet Colinde bent")
+                .SetAllowedAuthenticators(BiometricStrong)
+                .Build();
+
+            var cancellation = new CancellationSignal();
+
+            prompt.Authenticate(cancellation, MainExecutor, callback);
+            return;
+        }
+
+        action();
+    }
+
     private void WakePc()
     {
-        byte[] macAddress = { 0x2c, 0x4d, 0x54, 0x4d, 0x10, 0x0f };
-        byte[] magicPacket = new byte[102];
+        byte[] macAddress = [0x2c, 0x4d, 0x54, 0x4d, 0x10, 0x0f];
+        var magicPacket = new byte[102];
 
         // Fill first 6 bytes with 0xFF
-        for (int i = 0; i < 6; i++)
+        for (var i = 0; i < 6; i++)
         {
             magicPacket[i] = 0xFF;
         }
 
         // Repeat MAC address 16 times
-        for (int i = 1; i <= 16; i++)
+        for (var i = 1; i <= 16; i++)
         {
-            for (int j = 0; j < 6; j++)
+            for (var j = 0; j < 6; j++)
             {
                 magicPacket[i * 6 + j] = macAddress[j];
             }
@@ -44,10 +80,49 @@ public class WakeOnLanActivity : Activity
         client.EnableBroadcast = true;
         var endpoint = new IPEndPoint(IPAddress.Broadcast, 9); // 255.255.255.255 port 9
 
-        for (int i = 0; i < 5; i++)
+        for (var i = 0; i < 5; i++)
         {
             // Try 5 times
             client.Send(magicPacket, magicPacket.Length, endpoint);
         }
+        
+        Toast.MakeText(this, "Computer started!", ToastLength.Long)!.Show();
+    }
+}
+
+/// <summary>
+/// Biometric authentication callbacks
+/// https://developer.android.com/identity/sign-in/biometric-auth#java
+/// </summary>
+class BiometricCallback : BiometricPrompt.AuthenticationCallback, IDialogInterfaceOnClickListener
+{
+    private Context _context;
+    private readonly Action _onSuccess;
+
+    public BiometricCallback(Context context, Action onSuccess)
+    {
+        _context = context;
+        _onSuccess = onSuccess;
+    }
+    
+    public override void OnAuthenticationError(BiometricErrorCode errorCode, ICharSequence? errString)
+    {
+        Toast.MakeText(_context, $"Authenticatie mislukt: {errorCode}, {errString?.ToString()}", ToastLength.Long)!.Show();
+    }
+
+    public override void OnAuthenticationSucceeded(BiometricPrompt.AuthenticationResult? result)
+    {
+        Toast.MakeText(_context, "Authentication succeeded!", ToastLength.Short)!.Show();
+        _onSuccess();
+    }
+
+    public override void OnAuthenticationFailed()
+    {
+        Toast.MakeText(_context, "Authenticatie mislukt!", ToastLength.Long)!.Show();
+    }
+
+    public void OnClick(IDialogInterface? dialog, int which)
+    {
+        Toast.MakeText(_context, "Geannuleerd!", ToastLength.Long)!.Show();
     }
 }

DemoAndroid/AndroidManifest.xml

@@ -3,4 +3,6 @@
   <application android:allowBackup="true" android:icon="@mipmap/appicon" android:label="@string/app_name" android:roundIcon="@mipmap/appicon_round" android:supportsRtl="true">
   </application>
   <uses-permission android:name="android.permission.INTERNET" />
+  <uses-permission android:name="android.permission.USE_BIOMETRIC" />
+  <uses-permission android:name="android.permission.USE_FINGERPRINT" />
 </manifest>

DemoAndroid/DemoAndroid.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <TargetFramework>net8.0-android</TargetFramework>
-        <SupportedOSPlatformVersion>21</SupportedOSPlatformVersion>
+        <SupportedOSPlatformVersion>30</SupportedOSPlatformVersion>
         <OutputType>Exe</OutputType>
         <Nullable>enable</Nullable>
         <ImplicitUsings>enable</ImplicitUsings>
@@ -12,11 +12,10 @@
         <!-- With AOT, our app is crashing in Release mode -->
         <RunAOTCompilation>False</RunAOTCompilation>
         <PublishAot>False</PublishAot>
+        <TargetFrameworkVersion>v13.0</TargetFrameworkVersion>
     </PropertyGroup>
+    
     <ItemGroup>
       <PackageReference Include="QRCoder-ImageSharp" Version="0.10.0" />
     </ItemGroup>
-    <ItemGroup>
-      <Folder Include="Activities\" />
-    </ItemGroup>
 </Project>

DemoAndroid/MainActivity.cs

@@ -4,7 +4,7 @@ using QRCoder; // QRCoder-ImageSharp else it crashes
 
 namespace DemoAndroid;
 
-[Activity(Label = "@string/app_name", MainLauncher = true)]
+[Activity(Label = "@string/app_name", MainLauncher = false)]
 public class MainActivity : Activity
 {
     private string _text = "";

DemoAndroid/README.md

@@ -0,0 +1,15 @@
+# Android Native C# readme
+
+1. AOT makes release versions crash sometimes, so it is disabled
+2. Project created with
+```bash
+dotnet new android
+```
+3. New activities can be created with
+```bash
+dotnet new android-activity -n MyNewActivity
+```
+4. Avoid NuGet packages that are not built for non-Windows environments (e.g. depend on System.Drawing)
+
+If the app crashes directly in Release, before reverting all your changes try to clean /bin and /obj
+Also, if you reverted some changes, clean /bin and /obj again before thinking it still doesn't work

DemoAndroid/Resources/layout/activity_wakeonlan.xml

@@ -2,18 +2,19 @@
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
               android:orientation="vertical"
               android:layout_width="match_parent"
-              android:layout_height="match_parent">
+              android:layout_height="match_parent"
+              android:layout_margin="5pt">
 
     <TextView android:layout_width="match_parent"
               android:layout_height="wrap_content"
-              android:text="Start PC by tapping button below" />
+              android:text="Start de computer met Wake-On-Lan door op de knop hieronder te klikken" />
 
     <Button android:id="@+id/btnWakeOnLan"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
-            android:text="Start PC"
+            android:text="Start de computer"
             android:textColor="@color/white"
-            android:background="@color/blue"
-            android:height="15pt"
+            android:background="@color/green"
+            android:height="20pt"
             android:layout_margin="10pt"/>
 </LinearLayout>

DemoAndroid/Resources/values/colors.xml

@@ -2,4 +2,5 @@
 <resources>
     <color name="blue">#4287f5</color>
     <color name="white">#FFFFFF</color>
+    <color name="green">#2abf39</color>
 </resources>

DemoAndroid/Resources/values/strings.xml

@@ -1,4 +1,4 @@
 <resources>
-    <string name="app_name">DemoAndroid</string>
+    <string name="app_name">Goofjes</string>
     <string name="app_text">Hello, Android!</string>
 </resources>

DemoAndroid/Resources/values/style.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <style name="Default" parent="@android:style/Theme.Material.Light.DarkActionBar">
+        
+    </style>
+    <style name="NoActionBar" parent="@android:style/Theme.Material.Light.DarkActionBar">
+        <item name="android:windowActionBar">false</item>
+        <item name="android:windowNoTitle">true</item>
+        <item name="android:windowFullscreen">true</item>
+    </style>
+</resources>