Xamarin 中的 UserDefault

Question

我正在尝试在 SettingViewController 关闭之前分配文本字段条目，并在 URLViewController 出现时检查它们。

然而，一旦我检查它 returns null 即使用户输入了所有必需的信息；

//设置ViewController

partial class SettingViewController : UIViewController
    {
        public ServerSettings sSettings;
        public SettingViewController (IntPtr handle) : base (handle)
        {
            this.Title = "Settings";
            this.sSettings = new ServerSettings();

        }

        public override void ViewWillDisappear (bool animated)
        {
            sSettings.server=serverTF.Text;
            sSettings.port = portTF.Text;
            sSettings.password = passwordTF.Text;
            sSettings.userid = inboxuserTF.Text;
            sSettings.username = usernameTF.Text;
        }
    }

//URLViewController

public override void ViewWillAppear(bool animated)
        {
        base.ViewWillAppear (animated);
        SettingViewController callSetting = this.Storyboard.InstantiateViewController ("SettingViewController") as SettingViewController;

        if (callSetting == null)
            throw new Exception("callSetting is null"); // Or if you can handle having a null callSetting then correct for it, but realistically this is a problem, so I'd throw an Exception

        if (callSetting.sSettings == null)
            throw new Exception("sSetting is null"); // Or if you can handle having a null callSetting.sSetting then correct it (such as using a default value).

        if (string.IsNullOrEmpty(callSetting.sSettings.password)==true) 
            Console.WriteLine("is null or empty");
        else 
            Console.WriteLine (callSetting.sSettings.password);

    }

即使用户填写了所有文本字段条目，它 returns 为空。 //设置视图控制器

//URLViewController

Answer 1

我会通过使用 dictionary& userdefaults 来解决这个问题，如下所示：

在B Viewcontroller中，将用户条目保存在字典中，将其映射并分配给userdefault。

partial class BViewController : UIViewController
{
    const string server = "server";
    const string port = "port";
    const string password = "password";
    const string username = "username";
    const string inboxuserid = "inboxuserid";
    .............
    .............



  public override void ViewWillDisappear (bool animated)
  {
    var appDefaults = new NSDictionary (server, serverTF.Text, port, portTF.Text, password, passwordTF.Text,username,usernameTF.Text, inboxuserid,inboxuserTF.Text);
    NSUserDefaults.StandardUserDefaults.RegisterDefaults (appDefaults);
    NSUserDefaults.StandardUserDefaults.Synchronize ();
  }

}

并在 A ViewController 中检索它们，如下所示：

partial class AViewController : UIViewController
 {



  public override void ViewWillAppear(bool animated)
   {
    NSUserDefaults.StandardUserDefaults.RegisterDefaults (appDefaults);
    NSUserDefaults.StandardUserDefaults.Synchronize ();
    var username = NSUserDefaults.StandardUserDefaults.StringForKey ("username");
    Console.WriteLine (username);
    }
}

以下链接中也有很好的示例：

https://github.com/xamarin/monotouch-samples/blob/master/AppPrefs/Settings.cs http://forums.xamarin.com/discussion/9089/nsuserdefaults-standarduserdefaults-returns-null-first-time

Xamarin 中的 UserDefault

UserDefault in Xamarin

c#

xamarin