viewdidappear在将子视图添加到导航控制器时未调用

问题描述：

func showCustomViewController(vc : UIViewController,dummy : UIView,fromView1:UIViewController){ 
    datePickerShown = true 
    let fromView = fromView1.navigationController?.view 
    var navTopConstraint : NSLayoutConstraint! 
    vc.view.translatesAutoresizingMaskIntoConstraints=false 

    self.navigationController?.addChildViewController(vc) 
    dummy.addSubview(vc.view) 
    vc.didMove(toParentViewController: self.navigationController) 

    dummy.addConstraint(NSLayoutConstraint(item: vc.view, attribute: .top, relatedBy: .equal, toItem: dummy, attribute: .top, multiplier: 1, constant: 0)) 
    dummy.addConstraint(NSLayoutConstraint(item: vc.view, attribute: .left, relatedBy: .equal, toItem: dummy, attribute: .left, multiplier: 1, constant: 0)) 
    dummy.addConstraint(NSLayoutConstraint(item: vc.view, attribute: .width, relatedBy: .equal, toItem: dummy, attribute: .width, multiplier: 1, constant: 0)) 
    dummy.addConstraint(NSLayoutConstraint(item: vc.view, attribute: .height, relatedBy: .equal, toItem: dummy, attribute: .height, multiplier: 1, constant: 0)) 
    dummy.backgroundColor=UIColor.clear 

    if dummy.superview == nil{ 
     fromView?.addSubview(dummy) 
    } 

    for constraints in dummy.constraints{ 
     if constraints.firstAttribute == .top{ 
      navTopConstraint = constraints 
     } 
    } 

    fromView?.addConstraint(NSLayoutConstraint(item: dummy, attribute: .width, relatedBy: .equal, toItem: fromView, attribute: .width, multiplier: 1, constant:0)) 
    fromView?.addConstraint(NSLayoutConstraint(item: dummy, attribute: .top, relatedBy: .equal, toItem: fromView, attribute: .top, multiplier: 1, constant: -60)) 
    fromView?.addConstraint(NSLayoutConstraint(item: dummy, attribute: .bottom, relatedBy: .equal, toItem: fromView, attribute: .bottom, multiplier: 1, constant: 0)) 
    fromView?.addConstraint(NSLayoutConstraint(item: dummy, attribute: .left, relatedBy: .equal, toItem: fromView, attribute: .left, multiplier: 1, constant: 0)) 

    navTopConstraint.constant = (fromView?.frame.maxY)! 
    fromView?.layoutIfNeeded() 

    UIView.animate(withDuration: 0.33, delay: 0, options:.curveEaseInOut, animations: { 
     dummy.backgroundColor=UIColor.init(white: 0.0, alpha: 0.4) 
     navTopConstraint.constant=0 
     fromView?.layoutIfNeeded() 
    }, completion: nil) 
}

哑视图是添加到当前导航控制器视图的uiview。 vc是要添加到导航控制器视图的视图控制器。在vc viewcontroller中，调用了viewdidload。但是viewdidappear和viewwillappear从未被称为。为什么呢？以及如何调用相同的。提前感谢viewdidappear在将子视图添加到导航控制器时未调用

答

根据Apple's documentation您添加视图控制器和视图的顺序是正确的，但是，有时似乎有一个bug添加视图控制器之前添加视图（可能某种竞争条件）。

尝试添加控制器作为子视图控制器

dummy.addSubview(vc.view) 
self.navigationController?.addChildViewController(vc)

也许你可以也尝试着换一个defer块内的addChildViewController()方法之前，首先添加视图。

viewdidappear在将子视图添加到导航控制器时未调用

相关推荐