Use support dir instead of document dir

hive_flutter/lib/hive_flutter.dart

@@ -1,6 +1,7 @@
 library hive_flutter;
 
 import 'dart:async';
+import 'dart:io';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

hive_flutter/lib/src/hive_extensions.dart

@@ -2,14 +2,77 @@ part of hive_flutter;
 
 /// Flutter extensions for Hive.
 extension HiveX on HiveInterface {
-  /// Initializes Hive with the path from [getApplicationDocumentsDirectory].
+  /// Initializes Hive with the path from either
+  /// [getApplicationDocumentsDirectory] (default) or
+  /// [getApplicationSupportDirectory] ([useSupportDir] = true).
   ///
-  /// You can provide a [subDir] where the boxes should be stored.
-  Future<void> initFlutter([String? subDir]) async {
+  /// You can provide a [subDir] where the boxes should be stored. if
+  /// [migrateFromDocuments] is set to true, Boxes in (documents dir + subdir)
+  /// will be copied over to (support dir + subdir)
+  ///
+  /// [useSupportDir] cannot be false when [migrateFromDocuments] is true, and
+  /// vice versa.
+  Future<void> initFlutter({
+    bool useSupportDir = false,
+    bool migrateFromDocuments = false,
+    String? subDir,
+  }) async {
+    // We don't want the developer to migrate from documents and then try to
+    // init Hive with the documents dir.
+    assert(useSupportDir == false && migrateFromDocuments == true);
+
     WidgetsFlutterBinding.ensureInitialized();
     if (kIsWeb) return;
 
-    var appDir = await getApplicationDocumentsDirectory();
-    init(path_helper.join(appDir.path, subDir));
+    // Get the directory that Hive uses to stor DB files (dir + subdir).
+    final supportDir = useSupportDir
+        ? await getApplicationSupportDirectory()
+        : await getApplicationDocumentsDirectory();
+
+    final appDir = path_helper.join(supportDir.path, subDir);
+
+    if (migrateFromDocuments) {
+      // If the app dir doesn't exist, create it. This is usually handled later
+      // on in Hive but the directory needs to exist to copy old DB files over.
+      if (!await Directory(appDir).exists()) {
+        await Directory(appDir).create();
+      }
+
+      // Get the old location that Hive used to store files.
+      final documentsDir = await getApplicationDocumentsDirectory();
+      final oldLocationDir =
+          Directory(path_helper.join(documentsDir.path, subDir));
+
+      // If the old location exists, we start looking for old DB files to copy.
+      if (await oldLocationDir.exists()) {
+        // Make an array to store files to copy.
+        final filesToCopy = <File>[];
+
+        await oldLocationDir.list().forEach((event) {
+          final extension = path_helper.extension(event.path);
+
+          // If the item is a file and has an extension of .hive, add it and the
+          // matching .lock file to the copy array.
+          if (event is File && extension == '.hive') {
+            filesToCopy.add(File(event.path));
+
+            // We do this instead of just copying all .lock files since .lock
+            // can commonly be used for non-Hive purposes.
+            filesToCopy
+                .add(File('${path_helper.withoutExtension(event.path)}.lock'));
+          }
+        });
+
+        // Make copy/delete futures for every file and wait for them
+        // asynchronously. Files are copied to the new appDir.
+        await Future.wait(filesToCopy.map(
+          (e) => e
+              .copy(path_helper.join(appDir, path_helper.basename(e.path)))
+              .then((_) => e.delete()),
+        ));
+      }
+    }
+
+    init(appDir);
   }
 }