iOS:目前有没有办法防止两个视图控制器同时被推送或弹出? [英] iOS: Is there currently a way to prevent two view controllers being pushed or popped at the same time?
问题描述
我看到的唯一解决方案是对 stackoverflow 问题的回答.我在下面发布了链接.我指的答案是第五个.然而，似乎有些用户对解决方案有一些问题.不知道有没有别的类可以防止两个控制器同时被推送.任何提示或建议表示赞赏.
The only solution I have seen was an answer to a stackoverflow question. I posted the link below. The answer I am referring is the 5th one. It seems that some users have some problems with the solution however. I don't know if there is another category to prevent two controllers from being pushed at the same time. Any tips or suggestions are appreciated.
#import "UINavigationController+Consistent.h"
#import <objc/runtime.h>
/// This char is used to add storage for the isPushingViewController property.
static char const * const ObjectTagKey = "ObjectTag";
@interface UINavigationController ()
@property (readwrite,getter = isViewTransitionInProgress) BOOL viewTransitionInProgress;
@end
@implementation UINavigationController (Consistent)
- (void)setViewTransitionInProgress:(BOOL)property {
NSNumber *number = [NSNumber numberWithBool:property];
objc_setAssociatedObject(self, ObjectTagKey, number , OBJC_ASSOCIATION_RETAIN);
}
- (BOOL)isViewTransitionInProgress {
NSNumber *number = objc_getAssociatedObject(self, ObjectTagKey);
return [number boolValue];
}
#pragma mark - Intercept Pop, Push, PopToRootVC
/// @name Intercept Pop, Push, PopToRootVC
- (NSArray *)safePopToRootViewControllerAnimated:(BOOL)animated {
if (self.viewTransitionInProgress) return nil;
if (animated) {
self.viewTransitionInProgress = YES;
}
//-- This is not a recursion, due to method swizzling the call below calls the original method.
return [self safePopToRootViewControllerAnimated:animated];
}
- (NSArray *)safePopToViewController:(UIViewController *)viewController animated:(BOOL)animated {
if (self.viewTransitionInProgress) return nil;
if (animated) {
self.viewTransitionInProgress = YES;
}
//-- This is not a recursion, due to method swizzling the call below calls the original method.
return [self safePopToViewController:viewController animated:animated];
}
- (UIViewController *)safePopViewControllerAnimated:(BOOL)animated {
if (self.viewTransitionInProgress) return nil;
if (animated) {
self.viewTransitionInProgress = YES;
}
//-- This is not a recursion, due to method swizzling the call below calls the original method.
return [self safePopViewControllerAnimated:animated];
}
- (void)safePushViewController:(UIViewController *)viewController animated:(BOOL)animated {
self.delegate = self;
//-- If we are already pushing a view controller, we dont push another one.
if (self.isViewTransitionInProgress == NO) {
//-- This is not a recursion, due to method swizzling the call below calls the original method.
[self safePushViewController:viewController animated:animated];
if (animated) {
self.viewTransitionInProgress = YES;
}
}
}
// This is confirmed to be App Store safe.
// If you feel uncomfortable to use Private API, you could also use the delegate method navigationController:didShowViewController:animated:.
- (void)safeDidShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
//-- This is not a recursion. Due to method swizzling this is calling the original method.
[self safeDidShowViewController:viewController animated:animated];
self.viewTransitionInProgress = NO;
}
// If the user doesnt complete the swipe-to-go-back gesture, we need to intercept it and set the flag to NO again.
- (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
id<UIViewControllerTransitionCoordinator> tc = navigationController.topViewController.transitionCoordinator;
[tc notifyWhenInteractionEndsUsingBlock:^(id<UIViewControllerTransitionCoordinatorContext> context) {
self.viewTransitionInProgress = NO;
//--Reenable swipe back gesture.
self.interactivePopGestureRecognizer.delegate = (id<UIGestureRecognizerDelegate>)viewController;
[self.interactivePopGestureRecognizer setEnabled:YES];
}];
//-- Method swizzling wont work in the case of a delegate so:
//-- forward this method to the original delegate if there is one different than ourselves.
if (navigationController.delegate != self) {
[navigationController.delegate navigationController:navigationController
willShowViewController:viewController
animated:animated];
}
}
+ (void)load {
//-- Exchange the original implementation with our custom one.
method_exchangeImplementations(class_getInstanceMethod(self, @selector(pushViewController:animated:)), class_getInstanceMethod(self, @selector(safePushViewController:animated:)));
method_exchangeImplementations(class_getInstanceMethod(self, @selector(didShowViewController:animated:)), class_getInstanceMethod(self, @selector(safeDidShowViewController:animated:)));
method_exchangeImplementations(class_getInstanceMethod(self, @selector(popViewControllerAnimated:)), class_getInstanceMethod(self, @selector(safePopViewControllerAnimated:)));
method_exchangeImplementations(class_getInstanceMethod(self, @selector(popToRootViewControllerAnimated:)), class_getInstanceMethod(self, @selector(safePopToRootViewControllerAnimated:)));
method_exchangeImplementations(class_getInstanceMethod(self, @selector(popToViewController:animated:)), class_getInstanceMethod(self, @selector(safePopToViewController:animated:)));
}
@end
推荐答案
更新答案:
我更喜欢 Github 上 nonamelive 的这个解决方案，而不是我最初发布的内容:https://gist.github.com/nonamelive/9334458.通过继承 UINavigationController 并利用 UINavigationControllerDelegate，您可以确定何时发生转换，防止在该转换期间发生其他转换，并在同一班级.这是 nonamelive 解决方案的更新，不包括私有 API:
I prefer this solution by nonamelive on Github to what I originally posted: https://gist.github.com/nonamelive/9334458. By subclassing the UINavigationController and taking advantage of the UINavigationControllerDelegate, you can establish when a transition is happening, prevent other transitions from happening during that transition, and do so all within the same class. Here's an update of nonamelive's solution which excludes the private API:
#import "NavController.h"
@interface NavController ()
@property (nonatomic, assign) BOOL shouldIgnorePushingViewControllers;
@end
@implementation NavController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
if (!self.shouldIgnorePushingViewControllers)
{
[super pushViewController:viewController animated:animated];
}
self.shouldIgnorePushingViewControllers = YES;
}
- (void)navigationController:(UINavigationController *)navigationController didShowViewController:(UIViewController *)viewController animated:(BOOL)animated {
self.shouldIgnorePushingViewControllers = NO;
}
@end
<小时>
上一个答案:
Previous answer:
上一个答案的问题:isBeingPresented 和 isBeingDismissed 仅适用于 viewDidLoad: 或 viewDidApper:
Problem with this Previous Answer:
isBeingPresentedandisBeingDismissedonly work inviewDidLoad:orviewDidApper:
虽然我自己没有测试过，但这里有一个建议.
Although I haven't tested this myself, here is a suggestion.
由于您使用的是 UINavigationController，因此您可以访问导航堆栈的内容，如下所示:
Since you're using a UINavigationController, you can access the contents of your navigation stack, like so:
NSArray *viewControllers = self.navigationController.viewControllers;
通过该视图控制器数组，您可以在需要时访问部分或全部相关索引.
And through that array of view controllers, you can access some or all relevant indices if need be.
幸运的是，iOS 5 中引入了两个特别方便的方法:isBeingPresented 和 isBeingDismissed 如果视图控制器分别处于呈现或关闭过程中，则返回YES"；否则为否".
Luckily, two especially convenient methods were introduced in iOS 5: isBeingPresented and isBeingDismissed which return "YES" if the view controller is in the process of being presented or being dismissed, respectively; "NO" otherwise.
因此，例如，这是一种方法:
So, for example, here's one approach:
NSArray *viewControllers = self.navigationController.viewControllers;
for (UIViewController *viewController in viewControllers) {
if (viewController.isBeingPresented || viewController.isBeingDismissed) {
// In this case when a pop or push is already in progress, don't perform
// a pop or push on the current view controller. Perhaps return to this
// method after a delay to check this conditional again.
return;
}
}
// Else if you make it through the loop uninterrupted, perform push or pop
// of the current view controller.
实际上，您可能不必遍历堆栈中的每个视图控制器，但也许这个建议会帮助您走上正轨.
In actuality, you probably won't have to loop through every view controller on the stack, but perhaps this suggestion will help set you off on the right foot.
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