Flutter: disable screenshot capture for app

It’s only in iOS,just modify in AppDelegate.
And no more plugins

import UIKit
import Flutter
import Firebase

@UIApplicationMain
@objc class AppDelegate: FlutterAppDelegate {
    override func application(_ application: UIApplication,
    didFinishLaunchingWithOptions launchOptions[UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    FirebaseApp.configure()
    self.window.makeSecure() //Add this line 
    GeneratedPluginRegistrant.register(with: self)
    return super.application(application, didFinishLaunchingWithOptions: launchOptions)
  }

}
//And this extension
extension UIWindow {
func makeSecure() {
    let field = UITextField()
    field.isSecureTextEntry = true
    self.addSubview(field)
    field.centerYAnchor.constraint(equalTo: self.centerYAnchor).isActive = true
    field.centerXAnchor.constraint(equalTo: self.centerXAnchor).isActive = true
    self.layer.superlayer?.addSublayer(field.layer)
    field.layer.sublayers?.first?.addSublayer(self.layer)
  }
}

See image here