GH-130 & GH-129: Android support for safe shareable file URI’s

DeviceTests/DeviceTests.Android/Properties/AndroidManifest.xml

@@ -9,5 +9,6 @@
 	<uses-permission android:name="android.permission.FLASHLIGHT" />
 	<uses-permission android:name="android.permission.INTERNET" />
 	<uses-permission android:name="android.permission.VIBRATE" />
+	<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
 	<application android:label="@string/app_name" android:icon="@mipmap/ic_launcher" android:roundIcon="@mipmap/ic_launcher_round" android:theme="@style/MainTheme"></application>
 </manifest>

DeviceTests/DeviceTests.Shared/Android_FileProvider_Tests.cs

@@ -0,0 +1,39 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using Xamarin.Essentials;
+using Xunit;
+
+namespace DeviceTests.Shared
+{
+#if __ANDROID__
+    public class Android_FileProvider_Tests
+    {
+        [Fact]
+        [Trait(Traits.InteractionType, Traits.InteractionTypes.Human)]
+        public void Share_Simple_Text_File_Test()
+        {
+            const string TestStr = "Test Text File";
+
+            // Save a local cache data directory file
+            var file = Path.Combine(FileSystem.CacheDirectory, "test.txt");
+            File.WriteAllText(file, TestStr);
+
+            // Actually get a safe shareable file uri
+            var shareableUri = Platform.GetShareableFileUri(file);
+
+            // Launch an intent to let tye user pick where to open this content
+            var intent = new Android.Content.Intent(Android.Content.Intent.ActionSend);
+            intent.SetType("text/plain");
+            intent.PutExtra(Android.Content.Intent.ExtraStream, shareableUri);
+            intent.PutExtra(Android.Content.Intent.ExtraTitle, TestStr);
+            intent.SetFlags(Android.Content.ActivityFlags.GrantReadUriPermission);
+
+            var intentChooser = Android.Content.Intent.CreateChooser(intent, TestStr);
+
+            Platform.AppContext.StartActivity(intentChooser);
+        }
+    }
+#endif
+}

Xamarin.Essentials/Permissions/Permissions.android.cs

@@ -161,6 +161,9 @@ internal static IEnumerable<string> ToAndroidPermissions(this PermissionType per
                 case PermissionType.Vibrate:
                     permissions.Add((Manifest.Permission.Vibrate, true));
                     break;
+                case PermissionType.ExternalStorage:
+                    permissions.Add((Manifest.Permission.WriteExternalStorage, false));
+                    break;
             }
 
             if (onlyRuntimePermissions)

Xamarin.Essentials/Permissions/Permissions.shared.enums.cs

@@ -27,5 +27,6 @@ enum PermissionType
         LocationWhenInUse,
         NetworkState,
         Vibrate,
+        ExternalStorage,
     }
 }

Xamarin.Essentials/Platform/Platform.android.cs

@@ -9,6 +9,8 @@
 using Android.Net;
 using Android.Net.Wifi;
 using Android.OS;
+using Android.Support.V4.Content;
+using AndroidUri = Android.Net.Uri;
 
 namespace Xamarin.Essentials
 {
@@ -61,6 +63,45 @@ internal static bool IsIntentSupported(Intent intent)
             return activities.Any();
         }
 
+        internal static AndroidUri GetShareableFileUri(string filename)
+        {
+            // We require external storage permissions for this API
+            Permissions.EnsureDeclared(PermissionType.ExternalStorage);
+
+            var extDir = AppContext.GetExternalFilesDir("2203693cc04e0be7f4f024d5f9499e13");
+            var fileInfo = new System.IO.FileInfo(filename);
+            var tmpDir = System.IO.Path.Combine(extDir.AbsolutePath, Guid.NewGuid().ToString("N"));
+            var tmpFile = System.IO.Path.Combine(tmpDir, fileInfo.Name);
+
+            // Create inner temp dir if we need to
+            // We create a subdirectory so we can still have a unique path
+            // but keep the original filename the same
+            System.IO.Directory.CreateDirectory(tmpDir);
+
+            // Copy the original file to a known externals dir that we can share
+            System.IO.File.Copy(filename, tmpFile);
+
+            // Mark the file and directory for deletion on exit
+            var javaFile = new Java.IO.File(tmpFile);
+            javaFile.DeleteOnExit();
+            var javaDir = new Java.IO.File(tmpDir);
+            javaDir.DeleteOnExit();
+
+            var providerAuthority = AppContext.PackageName + ".fileProvider";
+
+            if (HasApiLevel(BuildVersionCodes.N))
+            {
+                return FileProvider.GetUriForFile(
+                    AppContext.ApplicationContext,
+                    providerAuthority,
+                    javaFile);
+            }
+            else
+            {
+                return AndroidUri.FromFile(new Java.IO.File(filename));
+            }
+        }
+
         internal static bool HasApiLevel(BuildVersionCodes versionCode) =>
             (int)Build.VERSION.SdkInt >= (int)versionCode;
 

Xamarin.Essentials/Resources/xml/xamarin_essentials_fileprovider_file_paths.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<paths>
+  <external-path name="2203693cc04e0be7f4f024d5f9499e13" path="" />
+</paths>

Xamarin.Essentials/Types/FileProvider.android.cs

@@ -0,0 +1,20 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Android.App;
+using Android.Content;
+
+namespace Xamarin.Essentials.Types
+{
+    [ContentProvider(
+        new[] { "${applicationId}.fileProvider" },
+        Name = "xamarin.essentials.fileProvider",
+        Exported = false,
+        GrantUriPermissions = true)]
+    [MetaData(
+        "android.support.FILE_PROVIDER_PATHS",
+        Resource = "@xml/xamarin_essentials_fileprovider_file_paths")]
+    public class FileProvider : global::Android.Support.V4.Content.FileProvider
+    {
+    }
+}

Xamarin.Essentials/Xamarin.Essentials.csproj

@@ -68,17 +68,21 @@
     <Compile Include="**\*.android.*.cs" />
     <Reference Include="System.Numerics" />
     <Reference Include="System.Numerics.Vectors" />
+    <AndroidResource Include="Resources\xml\*.xml" />
   </ItemGroup>
   <ItemGroup Condition=" $(TargetFramework.StartsWith('MonoAndroid81')) ">
     <PackageReference Include="Xamarin.Android.Support.CustomTabs" Version="27.0.2" />
+    <PackageReference Include="Xamarin.Android.Support.Compat" Version="27.0.2" />
     <PackageReference Include="Xamarin.Android.Support.Core.Utils" Version="27.0.2" />
   </ItemGroup>
   <ItemGroup Condition=" $(TargetFramework.StartsWith('MonoAndroid80')) ">
     <PackageReference Include="Xamarin.Android.Support.CustomTabs" Version="26.1.0.1" />
+    <PackageReference Include="Xamarin.Android.Support.Compat" Version="26.1.0.1" />
     <PackageReference Include="Xamarin.Android.Support.Core.Utils" Version="26.1.0.1" />
   </ItemGroup>
   <ItemGroup Condition=" $(TargetFramework.StartsWith('MonoAndroid71')) ">
     <PackageReference Include="Xamarin.Android.Support.CustomTabs" Version="25.4.0.2" />
+    <PackageReference Include="Xamarin.Android.Support.Compat" Version="25.4.0.2" />
     <PackageReference Include="Xamarin.Android.Support.Core.Utils" Version="25.4.0.2" />
   </ItemGroup>
   <ItemGroup Condition=" $(TargetFramework.StartsWith('Xamarin.iOS')) ">