Update

ios/Runner/AppDelegate.swift

@@ -1,12 +1,122 @@
 import UIKit
 import Flutter
+import Foundation
+
+func extFromMimetype(mimeType: String) -> String? {
+  switch (mimeType) {
+  case "image/jpeg":
+    return ".jpg"
+  case "image/png":
+    return ".png"
+  case "image/webp":
+    return ".webp"
+  case "application/zip":
+    return ".zip"
+  default:
+    return nil
+  }
+}
+
+class FilePickerDelegate: NSObject, UIDocumentPickerDelegate {
+  let readOnly: Bool
+  let writeOnly: Bool
+  let append: Bool
+  let url: URL
+  let result: FlutterResult
+  init(readOnly: Bool, writeOnly: Bool, append: Bool, url: URL, result: @escaping FlutterResult) {
+    self.readOnly = readOnly
+    self.writeOnly = writeOnly
+    self.append = append
+    self.url = url
+    self.result = result
+  }
+
+  func pickFile() {
+    guard let viewController = UIApplication.shared.keyWindow?.rootViewController else {
+      result(FlutterError(code: "fatal",
+                          message: "Getting rootViewController failed",
+                          details: nil))
+      return
+    }
+    let con = if #available(iOS 14.0, *) {
+      UIDocumentPickerViewController(forExporting: [self.url])
+    } else {
+      UIDocumentPickerViewController(url: self.url, in: UIDocumentPickerMode.exportToService)
+    }
+    con.delegate = self
+    viewController.present(con, animated: true, completion: nil)
+    print("pickFile")
+  }
+
+  func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentsAt urls: [URL]) {
+  }
+
+  func documentPicker(_ controller: UIDocumentPickerViewController, didPickDocumentAt url: URL) {
+  }
+  
+  func documentPickerWasCancelled(_ controller: UIDocumentPickerViewController) {
+    result(FlutterError(code: "USER_CANCELLED", message: nil, details: nil))
+    controller.dismiss(animated: true, completion: nil)
+    print("documentPickerWasCancelled")
+    try? FileManager.default.removeItem(at: url);
+  }
+}
 
 @UIApplicationMain
 @objc class AppDelegate: FlutterAppDelegate {
+  var filePickerDelegate: FilePickerDelegate?
   override func application(
     _ application: UIApplication,
     didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?
   ) -> Bool {
+    let controller : FlutterViewController = window?.rootViewController as! FlutterViewController
+    let safChannel = FlutterMethodChannel(name: "lifegpc.eh_downloader_flutter/saf",
+                                          binaryMessenger: controller.binaryMessenger)
+    safChannel.setMethodCallHandler{(call, result) in
+      switch call.method {
+      case "openFile":
+        if let args = call.arguments as? Array<Any>,
+           let fileName = args[0] as? String,
+           let dir = args[1] as? String,
+           let mimeType = args[2] as? String,
+           let readOnly = args[3] as? NSNumber,
+           let writeOnly = args[4] as? NSNumber,
+           let append = args[5] as? NSNumber,
+           let saveAs = args[6] as? NSNumber {
+            let ext = extFromMimetype(mimeType: mimeType)
+            if saveAs.boolValue {
+              let path = NSSearchPathForDirectoriesInDomains(FileManager.SearchPathDirectory.cachesDirectory, FileManager.SearchPathDomainMask.userDomainMask, true).last
+              if path == nil {
+                result(FlutterError(code: "FAILED_TO_GET_CACHE_DIRERCTORY", message: nil, details: nil))
+                return
+              }
+              let dUrl = if #available(iOS 16.0, *) {
+                URL.init(filePath: path!)
+              } else {
+                URL.init(fileURLWithPath: path!)
+              }
+              let url = dUrl.appendingPathComponent(fileName + (ext ?? ""))
+              let uPath = if #available(iOS 16.0, *) {
+                url.path(percentEncoded: false)
+              } else {
+                url.path
+              }
+              if !FileManager.default.createFile(atPath: uPath, contents: nil) {
+                result(FlutterError(code: "FAILED_TO_CREATE_FILE", message: nil, details: nil))
+                return
+              }
+              self.filePickerDelegate = FilePickerDelegate(readOnly: readOnly.boolValue, writeOnly: writeOnly.boolValue, append: append.boolValue, url: url, result: result)
+              self.filePickerDelegate!.pickFile()
+            } else {
+              result(FlutterMethodNotImplemented)
+            }
+           } else {
+            result(FlutterError(code: "INVALID_ARGUMENTS", message: nil, details: nil))
+           }
+      default:
+        result(FlutterMethodNotImplemented)
+      }
+    }
     GeneratedPluginRegistrant.register(with: self)
     return super.application(application, didFinishLaunchingWithOptions: launchOptions)
   }