我們在寫代碼時，有時會遇到：需要知道某個controller是否已經存在，或着，要拿到已存在的某個controller對象，這里提供一種可以獲取到你想要的controller對象，只需要傳入類名即可，廢話不多說直接上代碼：
- (UIViewController *)getActivityViewController:(NSString *)controllerName {
UIViewController *topVC = [UIApplication sharedApplication].keyWindow.rootViewController;
while (topVC.presentedViewController) {
topVC = topVC.presentedViewController;
if ([[topVC.class description] isEqualToString:@"UINavigationController"]) {
UINavigationController *navi = (UINavigationController *)topVC;
if (navi && navi.viewControllers && navi.viewControllers.count > 0) {
NSInteger count = navi.viewControllers.count;
for (NSInteger i=count-1; i>=0; i--) {
UIViewController *controller = [navi.viewControllers objectAtIndex:i];
if ([[controller.class description] isEqualToString:controllerName]) {
return controller;
}
}
}
}
}
return nil;
}
如果當前存在的同一類名的controller有多個，你要拿到最新的一個可以用下面這種方法：
- (UIViewController *)getActivityViewController:(NSString *)controllerName {
UIViewController *topVC = [UIApplication sharedApplication].keyWindow.rootViewController;
UIViewController *resaultVC = nil;
while (topVC.presentedViewController) {
topVC = topVC.presentedViewController;
if ([[topVC.class description] isEqualToString:@"UINavigationController"]) {
UINavigationController *navi = (UINavigationController *)topVC;
if (navi && navi.viewControllers && navi.viewControllers.count > 0) {
NSInteger count = navi.viewControllers.count;
for (NSInteger i=count-1; i>=0; i--) {
UIViewController *controller = [navi.viewControllers objectAtIndex:i];
if ([[controller.class description] isEqualToString:controllerName]) {
resaultVC = controller;
}
}
}
}
}
return resaultVC;
}
當然這兩個方法的前提是，你如果是 present 出來的congtroller，並且導航控制器是 UINavigationController 類型，如果導航控制器是自定義的，那么在判斷 if ([[topVC.class description] isEqualToString:@"UINavigationController"]) 時@"UINavigationController" 要替換成你自定義的類名即可。