feat(android,interface): Implement video thumbnail generation

example/lib/main.dart

@@ -4,6 +4,7 @@ import 'dart:typed_data';
 import 'package:flutter/material.dart';
 import 'package:file_picker/file_picker.dart';
 import 'package:moxplatform/moxplatform.dart';
+import 'package:path/path.dart';
 import 'package:permission_handler/permission_handler.dart';
 
 /// The id of the notification channel.
@@ -286,6 +287,43 @@ class MyHomePageState extends State<MyHomePage> {
               },
               child: const Text('Open battery optimisation page'),
             ),
+            ElevatedButton(
+              onPressed: () async {
+                final result = await FilePicker.platform.pickFiles(
+                  type: FileType.video,
+                );
+                if (result == null) return;
+
+                final path = result.files.single.path!;
+                final storagePath =
+                    await MoxplatformPlugin.platform.getPersistentDataPath();
+                final mediaPath = join(storagePath, 'media');
+                if (!Directory(mediaPath).existsSync()) {
+                  await Directory(mediaPath).create(recursive: true);
+                }
+
+                final internalPath = join(mediaPath, basename(path));
+                print('Copying file');
+                await File(path).copy(internalPath);
+
+                print('Generating thumbnail');
+                final thumbResult =
+                    await MoxplatformPlugin.platform.generateVideoThumbnail(
+                  internalPath,
+                  '$internalPath.thumbnail.jpg',
+                  720,
+                );
+                print('Success: $thumbResult');
+
+                await showDialog<void>(
+                  context: context,
+                  builder: (context) => Image.file(
+                    File('$internalPath.thumbnail.jpg'),
+                  ),
+                );
+              },
+              child: const Text('Thumbnail'),
+            )
           ],
         ),
       ),

example/pubspec.yaml

@@ -39,6 +39,8 @@ dependencies:
 
   file_picker: 5.2.0+1
 
+  path: 1.8.3
+
   permission_handler: 10.4.3
     
   # The following adds the Cupertino Icons font to your application.

packages/moxplatform_android/android/src/main/AndroidManifest.xml

@@ -10,7 +10,7 @@
     <application>
         <provider
             android:name="me.polynom.moxplatform_android.MoxplatformFileProvider"
-            android:authorities="me.polynom.moxplatform_android.fileprovider"
+            android:authorities="me.polynom.moxplatform_android.fileprovider2"
             android:exported="false"
             android:grantUriPermissions="true">
             <meta-data

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/Api.java

@@ -1097,6 +1097,9 @@ public class Api {
     void decryptFile(@NonNull String sourcePath, @NonNull String destPath, @NonNull byte[] key, @NonNull byte[] iv, @NonNull CipherAlgorithm algorithm, @NonNull String hashSpec, @NonNull Result<CryptographyResult> result);
 
     void hashFile(@NonNull String sourcePath, @NonNull String hashSpec, @NonNull Result<byte[]> result);
+    /** Media APIs */
+    @NonNull 
+    Boolean generateVideoThumbnail(@NonNull String src, @NonNull String dest, @NonNull Long maxWidth);
     /** Stubs */
     void eventStub(@NonNull NotificationEvent event);
 
@@ -1466,6 +1469,32 @@ public class Api {
           channel.setMessageHandler(null);
         }
       }
+      {
+        BasicMessageChannel<Object> channel =
+            new BasicMessageChannel<>(
+                binaryMessenger, "dev.flutter.pigeon.moxplatform_platform_interface.MoxplatformApi.generateVideoThumbnail", getCodec());
+        if (api != null) {
+          channel.setMessageHandler(
+              (message, reply) -> {
+                ArrayList<Object> wrapped = new ArrayList<Object>();
+                ArrayList<Object> args = (ArrayList<Object>) message;
+                String srcArg = (String) args.get(0);
+                String destArg = (String) args.get(1);
+                Number maxWidthArg = (Number) args.get(2);
+                try {
+                  Boolean output = api.generateVideoThumbnail(srcArg, destArg, (maxWidthArg == null) ? null : maxWidthArg.longValue());
+                  wrapped.add(0, output);
+                }
+ catch (Throwable exception) {
+                  ArrayList<Object> wrappedError = wrapError(exception);
+                  wrapped = wrappedError;
+                }
+                reply.reply(wrapped);
+              });
+        } else {
+          channel.setMessageHandler(null);
+        }
+      }
       {
         BasicMessageChannel<Object> channel =
             new BasicMessageChannel<>(

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/Constants.kt

@@ -25,7 +25,7 @@ const val NOTIFICATION_EXTRA_ID_KEY = "notification_id"
 const val NOTIFICATION_MESSAGE_EXTRA_MIME = "mime"
 const val NOTIFICATION_MESSAGE_EXTRA_PATH = "path"
 
-const val MOXPLATFORM_FILEPROVIDER_ID = "me.polynom.moxplatform_android.fileprovider"
+const val MOXPLATFORM_FILEPROVIDER_ID = "me.polynom.moxplatform_android.fileprovider2"
 
 // Shared preferences keys
 const val SHARED_PREFERENCES_KEY = "me.polynom.moxplatform_android"

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/MoxplatformAndroidPlugin.java

@@ -3,9 +3,11 @@ package me.polynom.moxplatform_android;
 import static android.provider.Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS;
 import static androidx.core.content.ContextCompat.getSystemService;
 import static androidx.core.content.ContextCompat.startActivity;
+import static me.polynom.moxplatform_android.ConstantsKt.MOXPLATFORM_FILEPROVIDER_ID;
 import static me.polynom.moxplatform_android.ConstantsKt.SHARED_PREFERENCES_KEY;
 import static me.polynom.moxplatform_android.CryptoKt.*;
 import static me.polynom.moxplatform_android.RecordSentMessageKt.*;
+import static me.polynom.moxplatform_android.ThumbnailsKt.generateVideoThumbnailImplementation;
 
 import me.polynom.moxplatform_android.Api.*;
 
@@ -13,20 +15,31 @@ import android.app.ActivityManager;
 import android.app.NotificationChannel;
 import android.app.NotificationManager;
 import android.content.BroadcastReceiver;
+import android.content.ContentResolver;
 import android.content.Context;
 import android.content.Intent;
 import android.content.IntentFilter;
 import android.content.SharedPreferences;
+import android.graphics.Bitmap;
+import android.media.MediaMetadataRetriever;
+import android.media.ThumbnailUtils;
 import android.net.Uri;
+import android.os.Build;
 import android.os.PowerManager;
+import android.provider.MediaStore;
 import android.util.Log;
+import android.util.Size;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.core.app.NotificationManagerCompat;
 import androidx.core.content.ContextCompat;
+import androidx.core.content.FileProvider;
 import androidx.localbroadcastmanager.content.LocalBroadcastManager;
 
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.FileOutputStream;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -313,6 +326,12 @@ public class MoxplatformAndroidPlugin extends BroadcastReceiver implements Flutt
         CryptoKt.hashFile(sourcePath, hashSpec, result);
     }
 
+    @NonNull
+    @Override
+    public Boolean generateVideoThumbnail(@NonNull String src, @NonNull String dest, @NonNull Long maxWidth) {
+        return generateVideoThumbnailImplementation(src, dest, maxWidth);
+    }
+
     @Override
     public void eventStub(@NonNull NotificationEvent event) {
         // Stub to trick pigeon into

packages/moxplatform_android/android/src/main/java/me/polynom/moxplatform_android/Thumbnails.kt

@@ -0,0 +1,43 @@
+package me.polynom.moxplatform_android
+
+import android.graphics.Bitmap
+import android.media.MediaMetadataRetriever
+import android.util.Log
+import java.io.FileOutputStream
+
+/*
+ * Generate a video thumbnail using the first frame of the video at @src. Afterwards, scale it
+ * down such that its width is equal to @maxWidth (while keeping the aspect ratio) and write it to
+ * @dest.
+ *
+ * If everything went well, returns true. If we're unable to generate the thumbnail, returns false.
+ * */
+fun generateVideoThumbnailImplementation(src: String, dest: String, maxWidth: Long): Boolean {
+    try {
+        val mmr = MediaMetadataRetriever().apply {
+            setDataSource(src)
+        }
+        val unscaledThumbnail = mmr.getFrameAtTime(0) ?: return false
+
+        // Scale down the thumbnail while keeping the aspect ratio
+        val scalingFactor = maxWidth.toDouble() / unscaledThumbnail.width;
+        Log.d(TAG, "Scaling to $maxWidth from ${unscaledThumbnail.width} with scalingFactor $scalingFactor");
+        val thumbnail = Bitmap.createScaledBitmap(
+            unscaledThumbnail,
+            (unscaledThumbnail.width * scalingFactor).toInt(),
+            (unscaledThumbnail.height * scalingFactor).toInt(),
+            false,
+        )
+
+        // Write it to the destination file
+        val fos = FileOutputStream(dest)
+        thumbnail.compress(Bitmap.CompressFormat.JPEG, 75, fos)
+        fos.flush()
+        fos.close()
+        return true;
+    } catch (ex: Exception) {
+        Log.e(TAG, "Failed to create thumbnail for $src: ${ex.message}")
+        ex.printStackTrace()
+        return false;
+    }
+}

packages/moxplatform_android/lib/src/platform_android.dart

@@ -1,3 +1,4 @@
+import 'package:moxplatform/moxplatform.dart';
 import 'package:moxplatform_platform_interface/moxplatform_platform_interface.dart';
 
 class AndroidPlatformImplementation extends PlatformImplementation {
@@ -20,4 +21,10 @@ class AndroidPlatformImplementation extends PlatformImplementation {
   Future<void> openBatteryOptimisationSettings() {
     return MoxplatformInterface.api.openBatteryOptimisationSettings();
   }
+
+  @override
+  Future<bool> generateVideoThumbnail(
+      String src, String dest, int width) async {
+    return MoxplatformInterface.api.generateVideoThumbnail(src, dest, width);
+  }
 }

packages/moxplatform_platform_interface/lib/src/api.g.dart

@@ -756,6 +756,36 @@ class MoxplatformApi {
     }
   }
 
+  /// Media APIs
+  Future<bool> generateVideoThumbnail(
+      String arg_src, String arg_dest, int arg_maxWidth) async {
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+        'dev.flutter.pigeon.moxplatform_platform_interface.MoxplatformApi.generateVideoThumbnail',
+        codec,
+        binaryMessenger: _binaryMessenger);
+    final List<Object?>? replyList = await channel
+        .send(<Object?>[arg_src, arg_dest, arg_maxWidth]) as List<Object?>?;
+    if (replyList == null) {
+      throw PlatformException(
+        code: 'channel-error',
+        message: 'Unable to establish connection on channel.',
+      );
+    } else if (replyList.length > 1) {
+      throw PlatformException(
+        code: replyList[0]! as String,
+        message: replyList[1] as String?,
+        details: replyList[2],
+      );
+    } else if (replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (replyList[0] as bool?)!;
+    }
+  }
+
   /// Stubs
   Future<void> eventStub(NotificationEvent arg_event) async {
     final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(

packages/moxplatform_platform_interface/lib/src/platform.dart

@@ -12,4 +12,9 @@ abstract class PlatformImplementation {
   /// Opens the page for battery optimisations. If not supported on the
   /// platform, does nothing.
   Future<void> openBatteryOptimisationSettings();
+
+  /// Attempt to generate a thumbnail for the video file at [src], scale it, while keeping the
+  /// aspect ratio in tact to [width], and write it to [dest]. If we were successful, returns true.
+  /// If no thumbnail was generated, returns false.
+  Future<bool> generateVideoThumbnail(String src, String dest, int width);
 }

packages/moxplatform_platform_interface/lib/src/platform_stub.dart

@@ -14,4 +14,9 @@ class StubPlatformImplementation extends PlatformImplementation {
 
   @override
   Future<void> openBatteryOptimisationSettings() async {}
+
+  @override
+  Future<bool> generateVideoThumbnail(
+          String src, String dest, int width) async =>
+      false;
 }

pigeons/api.dart

@@ -192,6 +192,9 @@ abstract class MoxplatformApi {
   @async CryptographyResult? decryptFile(String sourcePath, String destPath, Uint8List key, Uint8List iv, CipherAlgorithm algorithm, String hashSpec);
   @async Uint8List? hashFile(String sourcePath, String hashSpec);
 
+  /// Media APIs
+  bool generateVideoThumbnail(String src, String dest, int maxWidth);
+
   /// Stubs
   void eventStub(NotificationEvent event);
 }