UISearchController中的UITextField BecomeFirstResponder

我有一个UITextField，它在UISearchController中，当显示视图控制器时需要成为FirstResponder。UISearchController中的UITextField BecomeFirstResponder

在ViewDidLoad上构建了UISearchController。

在ViewDidAppear我从UISearchController得到的UITextField，并告诉它BecomeFirstResponder

public override void ViewDidLoad(bool animated) 
    { 
     base.ViewDidLoad(); 
     BuildSearchController(); 

     SearchController.SearchBar.BecomeFirstResponder(); 
    } 

private void BuildSearchController() 
    { 
     UIFont MyFont = UIFont.FromName("Helvetica", 20f); 

     SearchController = new UISearchController(ResultsTableController) 
     { 
      WeakDelegate = this, 
      DimsBackgroundDuringPresentation = false, 
      WeakSearchResultsUpdater = this, 
     }; 

     SearchController.SearchBar.ScopeButtonTitles = new string[5] { "Account", "Name", "Service Address", "Phone", "SSN" }; 
     UITextField SearchField = (UITextField)SearchController.SearchBar.Subviews[0].Subviews[2]; 

     SearchField.Font = MyFont; 
     SearchController.SearchBar.ShowsCancelButton = false; 
     SearchController.SearchBar.SetScopeBarButtonTitle(new UITextAttributes() { Font = MyFont }, UIControlState.Normal); 
     SearchController.SearchBar.SizeToFit(); 
     SearchController.SearchBar.SelectedScopeButtonIndex = 1; 
     SearchController.SearchBar.SetShowsCancelButton(false, false); 

     UISegmentedControl TempSegControl = SearchController.SearchBar.Subviews[0].Subviews[0].Subviews[1] as UISegmentedControl; 
     TempSegControl.BackgroundColor = UIColor.FromRGBA(0, 122, 255, 255); 
     TempSegControl.TintColor = UIColor.White; 
     TempSegControl.Layer.BorderWidth = 1; 
     TempSegControl.Layer.CornerRadius = 6; 
     TempSegControl.Layer.BorderColor = UIColor.White.CGColor; 
     SearchController.SearchBar.BarTintColor = UIColor.FromRGBA(232, 232, 232, 255); 


     SearchController.HidesNavigationBarDuringPresentation = false; 

     SearchField.BecomeFirstResponder(); 
     TableView.TableHeaderView = SearchController.SearchBar; 

     SearchController.SearchBar.WeakDelegate = this; 
    } 

public override void ViewDidAppear(bool animated) 
    { 
     UITextField SearchBox = SearchController.SearchBar.Subviews[0].Subviews[2] as UITextField; 

     if (SearchBox.CanBecomeFirstResponder) 
     { 
      SearchBox.BecomeFirstResponder(); 
     } 
     base.ViewWillAppear(animated); 
    }

的UITextField永远不会成为第一个响应者，因为它是不能够成为第一个响应者。为什么UITextField不能成为第一个转型者？

来源

2016-05-19 Reid Williams

ViewDidLoad在视图控制器已将其视图层次结构加载到内存中但未呈现给用户之后调用。您无法在该阶段与对象进行UI交互。

UISearchController有一个委托方法，当它自动出现时被调用。用它来调出键盘。

optional func didPresentSearchController(searchController: UISearchController){ 
     searchController.searchBar.becomeFirstResponder(); 
    }

来源

2016-05-19 14:44:37 ArunGJ

我将该调用移至ViewDidAppear方法。我的UISearchController中的UITextField仍然没有焦点。当显示控制器时，我希望用户能够在无需触摸UITextField内部的情况下开始输入 –

感谢您的工作。这是它的C＃版本。 [Export（“didPresentSearchController：”）] public virtual void DidPresentSearchController（UISearchController searchController） { SearchController.SearchBar.Subviews [0] .Subviews [2] .BecomeFirstResponder（）; } –

UISearchController中的UITextField BecomeFirstResponder

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