我们在写代码时，有时会遇到：需要知道某个controller是否已经存在，或着，要拿到已存在的某个controller对象，这里提供一种可以获取到你想要的controller对象，只需要传入类名即可，废话不多说直接上代码：
- (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;
}
如果当前存在的同一类名的controller有多个，你要拿到最新的一个可以用下面这种方法：
- (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;
}
当然这两个方法的前提是，你如果是 present 出来的congtroller，并且导航控制器是 UINavigationController 类型，如果导航控制器是自定义的，那么在判断 if ([[topVC.class description] isEqualToString:@"UINavigationController"]) 时@"UINavigationController" 要替换成你自定义的类名即可。