检测是否因为后退按钮被按下而加载视图

Question

是否有可能通过按下后退按钮来检测视图是否正在出现。例如对于这个层次结构，VC1 -> webViewController -> VC3，如果在VC3我按下后退按钮我想检测，当webViewController出现。我的目标是在shouldStartLoadWith方法中使用此方法，以避免在按下后退按钮时刷新页面。

Answer 1

请webViewController

- (void)webViewDidFinishLoad:(UIWebView *)webView 
    { 
     //This Check is for if still webview is Loading the page or content 
     if (webView.isLoading) { 
     NSLog(@"your webview is still loading"); 
     return; 
} 
    else { 
     //this is for when its finish loading 
     NSLog(@"your webview is loaded completely"); 
} 
    } 

Answer 2

使用此您可以使用closure这样的回调。

例：

class WebViewController: UIViewController 
{ 
    @IBAction func onTapButton(_ sender: UIButton) 
    { 
     let controller = UIStoryboard.init(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "VC3") as! VC3 
     controller.completionHandler = { 
      //Code to execute after back button is pressed. 
     } 
     self.navigationController?.pushViewController(controller, animated: true) 
    } 
} 

class VC3: UIViewController 
{ 
    var completionHandler : (()->())? 

    override func viewWillDisappear(_ animated: Bool) 
    { 
     if self.navigationController?.viewControllers.index(of: self) == nil 
     { 
      //Back Button pressed 
      self.completionHandler?() 
     } 
     super.viewWillDisappear(animated) 
    } 
}