我知道要从应用程序委托获取当前视图控制器，我可以使用为应用程序设置的 navigationController 属性。但是，在我的应用程序中的许多地方都可能出现模式导航控制器。有没有办法从应用委托中检测到这一点，因为当前导航控制器将与应用委托持有引用的导航控制器不同？
根据此处的要点，我创建了一个类别来获取最顶层的视图控制器，这样调用[[UIApplication sharedApplication] topMostViewController]将为您提供应用中最顶层的视图控制器。
这在iOS 8中特别有用，其中UIAlertView和UIActionSheet已被弃用，取而代之的是UIAlertController，这需要在最顶部的视图控制器上显示。
UIViewController+TopMostViewController.h
#import <UIKit/UIKit.h>
@interface UIViewController (TopMostViewController)
- (UIViewController *)topMostViewController;
@end
@interface UIApplication (TopMostViewController)
- (UIViewController *)topMostViewController;
@end
UIViewController+TopMostViewController.m
#import "UIViewController+TopMostViewController.h"
@implementation UIViewController (TopMostViewController)
- (UIViewController *)topMostViewController
{
if (self.presentedViewController == nil)
{
return self;
}
else if ([self.presentedViewController isKindOfClass:[UINavigationController class]])
{
UINavigationController *navigationController = (UINavigationController *)self.presentedViewController;
UIViewController *lastViewController = [[navigationController viewControllers] lastObject];
return [lastViewController topMostViewController];
}
UIViewController *presentedViewController = (UIViewController *)self.presentedViewController;
return [presentedViewController topMostViewController];
}
@end
#pragma mark -
@implementation UIApplication (TopMostViewController)
- (UIViewController *)topMostViewController
{
return [self.keyWindow.rootViewController topMostViewController];
}
@end
我建议你使用NSNofiticationCenter。
//in AppDelegate:
@interface AppDelegate()
{
...
id lastViewController;
...
}
@implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
...
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleCurrentViewController) name:@"CurrentViewController" object:nil];
...
}
- (void)handleCurrentViewController:(NSNotification *)notification {
if([[notification userInfo] objectForKey:@"lastViewController"]) {
lastViewController = [[notification userInfo] objectForKey:@"lastViewController"];
}
}
- (void)applicationDidEnterBackground:(UIApplication *)application
{
NSLog(@"last view controller is %@", [(UIViewController *)lastViewController class]);
}
@end
//in every ViewController you want to detect
@implementation SomeViewController
...
- (void) viewWillDisappear:(BOOL)animated {
[super viewWillDisappear:animated];
[[NSNotificationCenter defaultCenter] postNotificationName:@"CurrentViewController" object:nil userInfo:[NSDictionary dictionaryWithObjectsAndKeys:self, @"lastViewController", nil]];
}
...
@end
Swift 中的出色解决方案，在 AppDelegate 中实现
func getTopViewController()->UIViewController{
return topViewControllerWithRootViewController(UIApplication.sharedApplication().keyWindow!.rootViewController!)
}
func topViewControllerWithRootViewController(rootViewController:UIViewController)->UIViewController{
if rootViewController is UITabBarController{
let tabBarController = rootViewController as! UITabBarController
return topViewControllerWithRootViewController(tabBarController.selectedViewController!)
}
if rootViewController is UINavigationController{
let navBarController = rootViewController as! UINavigationController
return topViewControllerWithRootViewController(navBarController.visibleViewController)
}
if let presentedViewController = rootViewController.presentedViewController {
return topViewControllerWithRootViewController(presentedViewController)
}
return rootViewController
}
目标 - C
- (UIViewController*)topViewController {
return [self topViewControllerWithRootViewController:[UIApplication sharedApplication].keyWindow.rootViewController];
}
- (UIViewController*)topViewControllerWithRootViewController:(UIViewController*)rootViewController {
if ([rootViewController isKindOfClass:[UITabBarController class]]) {
UITabBarController* tabBarController = (UITabBarController*)rootViewController;
return [self topViewControllerWithRootViewController:tabBarController.selectedViewController];
} else if ([rootViewController isKindOfClass:[UINavigationController class]]) {
UINavigationController* navigationController = (UINavigationController*)rootViewController;
return [self topViewControllerWithRootViewController:navigationController.visibleViewController];
} else if (rootViewController.presentedViewController) {
UIViewController* presentedViewController = rootViewController.presentedViewController;
return [self topViewControllerWithRootViewController:presentedViewController];
} else {
return rootViewController;
}
}
这对
我有用。我有很多目标有不同的控制器，所以以前的答案似乎不起作用。
首先，您希望在 AppDelegate 类中实现此内容：
var window: UIWindow?
然后，在您的函数中
let navigationController = window?.rootViewController as? UINavigationController
if let activeController = navigationController!.visibleViewController {
if activeController.isKindOfClass( MyViewController ) {
println("I have found my controller!")
}
}
您可以尝试通过以下方式获取最顶层的视图：
[[[[UIApplication sharedApplication] keyWindow] subviews] lastObject];
尽管此视图可能不可见，甚至被其某些子视图所覆盖......
这取决于您的 UI，但可能会有所帮助。
如果在应用委托中有导航控制器，只需使用 visibleViewController 属性。它会给你可见的控制器，即使它是一个模态。
在 swift 中，你可以像这样获得活动的 ViewController：
let navigationController = application.windows[0].rootViewController as UINavigationController
let activeViewCont = navigationController.visibleViewController
上述其他解决方案仅部分工作，因为无法处理复杂的视图层次结构(集成在选项卡栏控制器中的导航控制器、拆分视图控制器、视图容器以及警报控制器可能会搞砸事情(。
我通过在当前视图控制器的引用中保留对当前视图控制器的引用来解决此问题 应用委托。每次视图出现时，我都会利用
viewDidAppear(animated:)并在应用委托中设置引用。
我知道问题是关于 Objective-C 的，但我只能提供 Swift 代码，我相信它对这两种类型的用户都很有用。
首先：我已经实现了一个协议来保持事物的清洁和可重用：
protocol UpdatableViewController {
func updateUI()
}
第二：我添加了对 AppDelegate 的引用：
var currentViewController: UpdatableViewController?
第三：我在viewDidAppear((：
override func viewDidAppear(animated: Bool) {
super.viewDidAppear(animated)
let appDelegate = UIApplication.sharedApplication().delegate as? AppDelegate
appDelegate?.currentViewController = self
}
第四：
extension ViewController1: UpdatableViewController {
func updateUI() {
print("Implement updating here")
}
}
最好的解决方案，也适用于UITabBarController中的moreNavigationController：
extension UIApplication {
class func topViewController(base: UIViewController? = UIApplication.sharedApplication().keyWindow?.rootViewController) -> UIViewController? {
if let nav = base as? UINavigationController {
return topViewController(nav.visibleViewController)
}
if let tab = base as? UITabBarController {
let moreNavigationController = tab.moreNavigationController
if let top = moreNavigationController.topViewController where top.view.window != nil {
return topViewController(top)
} else if let selected = tab.selectedViewController {
return topViewController(selected)
}
}
if let presented = base?.presentedViewController {
return topViewController(presented)
}
return base
}
}
下面的代码运行良好。
+(UIViewController*( findBestViewController：(UIViewController*(vc {
if (vc.presentedViewController) {
// Return presented view controller
return [AppDelegate findBestViewController:vc.presentedViewController];
} else if ([vc isKindOfClass:[UISplitViewController class]]) {
// Return right hand side
UISplitViewController* svc = (UISplitViewController*) vc;
if (svc.viewControllers.count > 0)
return [AppDelegate findBestViewController:svc.viewControllers.lastObject];
else
return vc;
} else if ([vc isKindOfClass:[UINavigationController class]]) {
// Return top view
UINavigationController* svc = (UINavigationController*) vc;
if (svc.viewControllers.count > 0)
return [AppDelegate findBestViewController:svc.topViewController];
else
return vc;
} else if ([vc isKindOfClass:[UITabBarController class]]) {
// Return visible view
UITabBarController* svc = (UITabBarController*) vc;
if (svc.viewControllers.count > 0)
return [AppDelegate findBestViewController:svc.selectedViewController];
else
return vc;
} else {
// Unknown view controller type, return last child view controller
return vc;
}
}
+(UIViewController*( currentViewController {
// Find best view controller
UIViewController* viewController = [UIApplication sharedApplication].keyWindow.rootViewController;
return [AppDelegate findBestViewController:viewController];
}