Update for API 31

Updated UsbManagerExtenstions to support PendingIntents for API 31
Added write button to show show to send a string a text
Bumped project sdk to Xamarin.Legacy.Sdk/0.2.0-alpha4
Added .NET as a target
Updates sample app to .NET 7

Author: anotherlab

UsbSerialExampleApp/Resources/layout/serial_console.axml

@@ -23,6 +23,13 @@
       android:layout_below="@+id/demoTitle"
       android:layout_toRightOf="@+id/sleepButton"
       android:text="@string/wakeup" />
+  <Button
+      android:id="@+id/helloButton"
+      android:layout_width="wrap_content"
+      android:layout_height="wrap_content"
+      android:layout_below="@+id/demoTitle"
+      android:layout_toRightOf="@+id/wakeupButton"
+      android:text="@string/sendCaption" />
   <View
       android:id="@+id/separator"
       android:layout_width="match_parent"

UsbSerialExampleApp/Resources/values/Strings.xml

@@ -4,4 +4,5 @@
   <string name="refreshing">Refreshing...</string>
   <string name="sleep">Sleep</string>
   <string name="wakeup">Wakeup</string>
+	<string name="sendCaption">hello</string>
 </resources>

UsbSerialExampleApp/SerialConsoleActivity.cs

@@ -44,6 +44,7 @@ public class SerialConsoleActivity : Activity
         ScrollView scrollView;
         Button sleepButton;
         Button wakeButton;
+        Button sendHelloButton;
 
         SerialInputOutputManager serialIoManager;
 
@@ -62,6 +63,7 @@ protected override void OnCreate(Bundle savedInstanceState)
 
             sleepButton = FindViewById<Button>(Resource.Id.sleepButton);
             wakeButton = FindViewById<Button>(Resource.Id.wakeupButton);
+            sendHelloButton = FindViewById<Button>(Resource.Id.helloButton);
 
             // The following arrays contain data that is used for a custom firmware for
             // the Elatec TWN4 RFID reader. This code is included here to show how to
@@ -78,6 +80,14 @@ protected override void OnCreate(Bundle savedInstanceState)
             {
                 WriteData(wakedata);
             };
+
+            // The following shows one way to write ASCII text to the serial port
+            sendHelloButton.Click += delegate
+            {
+                byte[] byteArray = Encoding.ASCII.GetBytes("Hello");
+
+                WriteData(byteArray);
+            };
         }
 
         protected override void OnPause()

UsbSerialExampleApp/UsbSerialExampleApp.csproj

@@ -1,6 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFramework>net7.0-android</TargetFramework>
+    <TargetFramework>net6.0-android</TargetFramework>
     <SupportedOSPlatformVersion>21</SupportedOSPlatformVersion>
     <OutputType>Exe</OutputType>
     <Nullable>disable</Nullable>

UsbSerialForAndroid.sln

@@ -1,11 +1,11 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio 14
-VisualStudioVersion = 14.0.25420.1
+# Visual Studio Version 17
+VisualStudioVersion = 17.6.33620.401
 MinimumVisualStudioVersion = 10.0.40219.1
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "UsbSerialForAndroid", "UsbSerialForAndroid\UsbSerialForAndroid.csproj", "{A64567BC-548A-4CB7-9F2C-ECE75EE1A868}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "UsbSerialForAndroid", "UsbSerialForAndroid\UsbSerialForAndroid.csproj", "{A64567BC-548A-4CB7-9F2C-ECE75EE1A868}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "UsbSerialExampleApp", "UsbSerialExampleApp\UsbSerialExampleApp.csproj", "{59C7DFF3-4E5E-42D7-BB77-E6C4F4E74512}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "UsbSerialExampleApp", "UsbSerialExampleApp\UsbSerialExampleApp.csproj", "{59C7DFF3-4E5E-42D7-BB77-E6C4F4E74512}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -27,4 +27,7 @@ Global
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
+	GlobalSection(ExtensibilityGlobals) = postSolution
+		SolutionGuid = {5A3F5991-F724-4D65-B724-3EC768A7304E}
+	EndGlobalSection
 EndGlobal

UsbSerialForAndroid/Extensions/UsbManagerExtensions.cs

@@ -10,6 +10,7 @@
 using Android.Hardware.Usb;
 using Android.App;
 using Android.Content;
+using Android.OS;
 using System.Collections.Generic;
 
 namespace Hoho.Android.UsbSerial.Util
@@ -28,7 +29,15 @@ public static Task<bool> RequestPermissionAsync(this UsbManager manager, UsbDevi
             var usbPermissionReceiver = new UsbPermissionReceiver(completionSource);
             context.RegisterReceiver(usbPermissionReceiver, new IntentFilter(ACTION_USB_PERMISSION));
 
-            var intent = PendingIntent.GetBroadcast(context, 0, new Intent(ACTION_USB_PERMISSION), 0);
+            // Targeting S+ (version 31 and above) requires that one of FLAG_IMMUTABLE or FLAG_MUTABLE be specified when creating a PendingIntent.
+#if NET6_0_OR_GREATER
+            PendingIntentFlags pendingIntentFlags = Build.VERSION.SdkInt >= BuildVersionCodes.S ? PendingIntentFlags.Mutable : 0;
+#else
+            PendingIntentFlags pendingIntentFlags = Build.VERSION.SdkInt >= (BuildVersionCodes)31 ? (PendingIntentFlags).33554432 : 0;
+#endif
+
+            var intent = PendingIntent.GetBroadcast(context, 0, new Intent(ACTION_USB_PERMISSION), pendingIntentFlags);
+
             manager.RequestPermission(device, intent);
 
             return completionSource.Task;

UsbSerialForAndroid/UsbSerialForAndroid.csproj

@@ -1,6 +1,6 @@
-<Project Sdk="Xamarin.Legacy.Sdk/0.2.0-alpha3">
+<Project Sdk="Xamarin.Legacy.Sdk/0.2.0-alpha4">
   <PropertyGroup>
-    <TargetFrameworks>net6.0-android;monoandroid5.0</TargetFrameworks>
+    <TargetFrameworks>net6.0-android;net7.0-android;monoandroid5.0</TargetFrameworks>
     <SupportedOSPlatformVersion>21</SupportedOSPlatformVersion>
     <Nullable>disable</Nullable>
     <ImplicitUsings>disable</ImplicitUsings>