Xamarin ios：ABAddressbook.Create始終爲空，無法請求訪問

Question

我有一個請求訪問Addressbook的問題，因爲ABAddressbook.Create始終爲空。

那麼我該如何請求訪問？

NSError err = new NSError(); 
ABAddressBook ab = ABAddressBook.Create(out err) 
ab.RequestAccess (delegate {}); //ab always null 

感謝您的幫助。

Answer 1

如果是null那麼什麼是錯的，你NSError應該告訴你它是什麼（順便說一句有沒有需要初始化的out參數）。

一般（iOS6的+），你的代碼應該是這樣的：

NSError err; 
var ab = ABAddressBook.Create (out err); 
if (err != null) { 
    // process error 
    return; 
} 
// if the app was not authorized then we need to ask permission 
if (ABAddressBook.GetAuthorizationStatus() != ABAuthorizationStatus.Authorized) { 
    ab.RequestAccess (delegate (bool granted, NSError error) { 
     if (error != null) { 
      // process error 
     } else if (granted) { 
      // permission now granted -> use the address book 
     } 
    }); 
} else { 
    // permission already granted -> use the address book 
} 

Answer 2

這是我對付這種情況的公式。

private void RequestAddressBookAccess() 
{ 
    NSError error; 
    ABAddressBook addressBook = ABAddressBook.Create (out error); 
    if (error != null || addressBook == null) 
     ShowAddressBookAccessInstructions(); 

    else if (ABAddressBook.GetAuthorizationStatus() != ABAuthorizationStatus.Authorized) { 
     addressBook.RequestAccess (delegate(bool granted, NSError err) { 
      if (granted && err == null) 
       this.InvokeOnMainThread (() => DoStuff (addressBook)); 
      else 
       ShowAddressBookAccessInstructions(); 
     }); 
    } else 
     DoStuff (addressBook); 
} 

private void ShowAddressBookAccessInstructions() 
{ 
    UIAlertView alert = new UIAlertView ("Cannot Access Contacts", 
     "Go to Settings -> Privacy -> Contacts and allow this app to access your contacts to use this functionality", 
     null, "Ok", null); 
    alert.Show(); 
}