成为第一响应者未触发
我有一个视图控制器，其 viewDidLoad 方法在其关联视图中包含的文本字段（电子邮件）上调用成为FirstResponder：
-(void) viewDidLoad {
[email becomeFirstResponder];
}
该视图控制器通过将其推入导航控制器的堆栈来加载。上面的代码第一次运行效果很好。
但是，稍后在应用程序中，当我想返回到此视图控制器时，键盘不会自动出现（这是在使用 popToViewController:animated 时）。相反，用户必须手动将焦点设置到文本字段才能显示键盘...我的猜测是 popToViewController:animated 加载相关视图控制器后不会调用 viewDidLoad ？
我该如何解决这个问题？
I have a view controller whose viewDidLoad method invokes becomeFirstResponder on a textfield (email) contained within its associated view:
-(void) viewDidLoad {
[email becomeFirstResponder];
}
This view controller is loaded by pushing it onto the navigation controller's stack. The above code works great for the first time round.
However, later on in the application when I want to return to this view controller the keyboard doesn't appear automatically (this is when using popToViewController:animated). Instead the user has to manually set the focus to a textfield for the keyboard to appear...My guess is viewDidLoad isn't invoked after popToViewController:animated has loaded the relevant view controller?
How do I resolve this issue?
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viewDidLoad仅在第一次调用。当您希望每次出现视图时都运行某些内容时，请使用 viewWillAppear 。viewDidLoadis only invoked the first time. UseviewWillAppearwhen you want something to run every time a view appears.尝试将其放入 viewWillAppear 中。 viewDidLoad 通常只会运行一次，除非您特别告诉它。
Try putting it in viewWillAppear. viewDidLoad will usually only run once unless you specifically tell it otherwise.