experimental support for set new storage path on iOS

ios/Runner/DirectoryPicker.swift

@@ -0,0 +1,36 @@
+import UIKit
+import Flutter
+
+class DirectoryPicker: NSObject, UIDocumentPickerDelegate {
+    private var result: FlutterResult?
+
+    // 初始化选择目录方法
+    func selectDirectory(result: @escaping FlutterResult) {
+        self.result = result
+
+        // 配置 UIDocumentPicker 为目录选择模式
+        let documentPicker = UIDocumentPickerViewController(forOpeningContentTypes: [.folder])
+        documentPicker.delegate = self
+        documentPicker.allowsMultipleSelection = false
+
+        // 获取根视图控制器并显示选择器
+        if let rootViewController = UIApplication.shared.keyWindow?.rootViewController {
+            rootViewController.present(documentPicker, animated: true, completion: nil)
+        }
+    }
+
+    // 处理选择完成后的结果
+    func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
+        // 获取选中的路径
+        if let url = urls.first {
+            result?(url.path)
+        } else {
+            result?(nil)
+        }
+    }
+
+    // 处理取消选择情况
+    func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
+        result?(nil)
+    }
+}