iOS system swipe right to return to the global control solution

Preface

Today, there is a small requirement. Before clicking the back button on the navigation bar, we need to call a certain API and pop up a UIAlertView to display it. According to the user's option, we determine whether to return or stay in the current controller. For example, when you click the back button in the upper left corner of the navigation bar, our API is called to prompt whether you know. If you click yes, you return. If you click no, you stay in the current controller.

Then the question is, the navigation's built-in right swipe back gesture will not be handled when clicking the system's back button, it is automatic, so we have to find a way to change it to leftBarButtonItem, but using leftBarButtonItem will eliminate the right swipe back gesture.

You can't have your cake and eat it too? I have a way!

The author tried to write a demo to verify what solutions there are, and tried the following four methods:

• Only if the current controller complies with UIGestureRecognizerDelegate and sets the delegate to self
• Put UIGestureRecognizerDelegate in a public base class controller and set the delegate to self, then subclasses override the delegate method
• Put UIGestureRecognizerDelegate in the public navigation class HYBNavigationController, set the delegate to the navigation class, and then rewrite all push/pop related methods
• Put UIGestureRecognizerDelegate in the public navigation class HYBNavigationController and set the delegate to the navigation class, but only follow the -gestureRecognizerShouldBegin: delegate method

Option 1 (Not feasible)

Solution 1: Only the current controller complies with UIGestureRecognizerDelegate and sets the delegate to self

Why is it not feasible? How can we know if we don't test it? It's hard to consider it comprehensively just by thinking about it. So I wrote a small demo to test it.

We write this in the controller:

 - (void)viewDidLoad { 
 
 [super viewDidLoad]; 
 
  
 
    UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; 
 
  [button setTitle:@ "return" forState:UIControlStateNormal]; 
 
  [button addTarget:self action :@selector(onBack) forControlEvents:UIControlEventTouchUpInside]; 
 
 [button sizeToFit]; 
 
  [button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal]; 
 
  UIBarButtonItem *btnItem = [[UIBarButtonItem alloc] initWithCustomView:button]; 
 
  self.navigationItem.leftBarButtonItem = btnItem; 
 
  
 
 //Key lines 
 
  self.navigationController.interactivePopGestureRecognizer.delegate = self; 
 
 }

Once the delegate is set to self, the click callback can be implemented by using leftBarButtonItem, and the right swipe gesture is still there.

However, the proxy of self.navigationController, which is the navigation controller object, is modified to a certain controller object. When this controller class is released, the proxy becomes nil, so there is no more right swipe back gesture.

Then someone might think, what if we set the proxy to self in -viewDidAppear: and set the proxy to the original proxy object in -viewDidDisappear:? This is also not possible. When A pushes to B, B pushes to C, and then returns from C, the proxy is no longer the original navigation proxy.

Therefore, this solution is not feasible.

Option 2 (Not feasible)

Solution 2: Put UIGestureRecognizerDelegate in a common base class controller and set the delegate to self, then override the delegate method in the subclass

I tried to put UIGestureRecognizerDelegate in HYBBaseViewControlle, and then implemented the proxy. By default, it returns YES, indicating that it supports right swipe back. If you want a controller not to support right swipe back or to perform some operations before returning, you can do so by overriding this proxy method.

This is possible when there is only one controller. However, when the controller is released, the proxy object becomes nil, so the proxy is for the navigation bar object, not a single controller.

Option 3 (feasible, but complicated)

Solution 3: Put UIGestureRecognizerDelegate in the public navigation class HYBNavigationController, set the delegate to the navigation class, and then rewrite all push/pop related methods.

How to implement it as follows:

 //HYBNavigationController.m 
 
 // NavRightPanGestureDemo 
 
 // 
 
 // Created by huangyibiao on 16/2/22. 
 
 // Copyright © 2016 huangyibiao. All rights reserved. 
 
 // 
 
  
 
 #import "HYBNavigationController.h"   
 
 #import "HYBBaseViewController.h"   
 
  
 
 @interface HYBNavigationController () 
 
  
 
 @property (nonatomic, assign) BOOL enableRightGesture; 
 
  
 
 @ end   
 
  
 
 @implementation HYBNavigationController 
 
  
 
 - (void)viewDidLoad { 
 
 [super viewDidLoad]; 
 
  
 
  self.enableRightGesture = YES; 
 
  self.interactivePopGestureRecognizer.delegate = self; 
 
 } 
 
  
 
 - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer { 
 
 return self.enableRightGesture; 
 
 } 
 
  
 
 - (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated { 
 
  if ([viewController isKindOfClass:[HYBBaseViewController class]]) { 
 
    if ([viewController respondsToSelector:@selector(gestureRecognizerShouldBegin)]) { 
 
      HYBBaseViewController *vc = (HYBBaseViewController *)viewController; 
 
      self.enableRightGesture = [vc gestureRecognizerShouldBegin]; 
 
 } 
 
 } 
 
  
 
  [super pushViewController:viewController animated:YES]; 
 
 } 
 
  
 
 - (NSArray *)popToRootViewControllerAnimated:(BOOL)animated { 
 
     self.enableRightGesture = YES; 
 
 return [super popToRootViewControllerAnimated:animated]; 
 
 } 
 
  
 
 - (UIViewController *)popViewControllerAnimated:(BOOL)animated { 
 
  if ( self.viewControllers.count == 1) { 
 
    self.enableRightGesture = YES; 
 
 } else { 
 
    NSUInteger index = self.viewControllers.count - 2; 
 
    UIViewController *destinationController = [self.viewControllers objectAtIndex: index ]; 
 
    if ([destinationController isKindOfClass:[HYBBaseViewController class]]) { 
 
      if ([destinationController respondsToSelector:@selector(gestureRecognizerShouldBegin)]) { 
 
        HYBBaseViewController *vc = (HYBBaseViewController *)destinationController; 
 
        self.enableRightGesture = [vc gestureRecognizerShouldBegin]; 
 
 } 
 
 } 
 
 } 
 
  
 
 return [super popViewControllerAnimated:animated]; 
 
 } 
 
  
 
 - (NSArray *)popToViewController:(UIViewController *)viewController animated:(BOOL)animated { 
 
  if ( self.viewControllers.count == 1) { 
 
    self.enableRightGesture = YES; 
 
 } else { 
 
    UIViewController *destinationController = viewController; 
 
    if ([destinationController isKindOfClass:[HYBBaseViewController class]]) { 
 
      if ([destinationController respondsToSelector:@selector(gestureRecognizerShouldBegin)]) { 
 
        HYBBaseViewController *vc = (HYBBaseViewController *)destinationController; 
 
        self.enableRightGesture = [vc gestureRecognizerShouldBegin]; 
 
 } 
 
 } 
 
 } 
 
  
 
 return [super popToViewController:viewController animated:animated]; 
 
 } 
 
  
 
 @ end  

This is done by rewriting all pop/push related methods and determining whether right swipe is required. Then, we need to make a controller class call our API to determine before swiping right or clicking back, as follows:

 #import "HYBBController.h"   
 
  
 
 @implementation HYBBController 
 
  
 
 - (void)viewDidLoad { 
 
 [super viewDidLoad]; 
 
  
 
  UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom]; 
 
  [button setTitle:@ "return" forState:UIControlStateNormal]; 
 
  [button addTarget:self action :@selector(onBack) forControlEvents:UIControlEventTouchUpInside]; 
 
 [button sizeToFit]; 
 
  [button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal]; 
 
  UIBarButtonItem *btnItem = [[UIBarButtonItem alloc] initWithCustomView:button]; 
 
  self.navigationItem.leftBarButtonItem = btnItem; 
 
 } 
 
  
 
 - (BOOL)gestureRecognizerShouldBegin { 
 
 [self onBack]; 
 
 return   NO ; 
 
 } 
 
  
 
 - (void)onBack { 
 
 UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@ "Brother Biao's Technology Blog"   
 
 message:@ "Do you know what the blog address is?"   
 
                                                     delegate:self 
 
 cancelButtonTitle:@ "Don't know"   
 
 otherButtonTitles:@ "Know" , nil]; 
 
 [alertView show]; 
 
 } 
 
  
 
 #pragma mark - UIAlertViewDelegate 
 
 - (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex { 
 
 if (buttonIndex == 0) { 
 
  
 
 } else { 
 
    if ([self.navigationItem.title isEqualToString:@ "VC6" ]) { 
 
      NSUInteger index = self.navigationController.viewControllers.count - 3; 
 
      UIViewController *vc = [self.navigationController.viewControllers objectAtIndex: index ]; 
 
      [self.navigationController popToViewController:vc animated:YES]; 
 
 } else { 
 
      [self.navigationController popViewControllerAnimated:YES]; 
 
 } 
 
 } 
 
 } 
 
  
 
 @ end  

This solution does meet our needs. But is there a simpler solution? Maybe because my eyes are a little sleepy today, I didn't realize the fourth solution when I was researching. When I was preparing to write this article, I read the logic again and found that there is a very simple solution that can meet my needs.

Option 4 (reliable, ***)

Solution 4: Put UIGestureRecognizerDelegate in the public navigation class HYBNavigationController and set the delegate to the navigation class, but only follow the -gestureRecognizerShouldBegin: delegate method.

 @interface HYBNavigationController () 
 
  
 
 @ end   
 
  
 
 @implementation HYBNavigationController 
 
  
 
 - (void)viewDidLoad { 
 
 [super viewDidLoad]; 
 
  
 
  self.interactivePopGestureRecognizer.delegate = self; 
 
 } 
 
  
 
 - (BOOL)gestureRecognizerShouldBegin:(UIGestureRecognizer *)gestureRecognizer { 
 
 BOOL ok = YES; // By default, right swipe is supported 
 
  if ([self.topViewController isKindOfClass:[HYBBaseViewController class]]) { 
 
    if ([self.topViewController respondsToSelector:@selector(gestureRecognizerShouldBegin)]) { 
 
      HYBBaseViewController *vc = (HYBBaseViewController *)self.topViewController; 
 
     ok = [vc gestureRecognizerShouldBegin]; 
 
 } 
 
 } 
 
  
 
 return ok; 
 
 } 
 
  
 
 @ end  

The usage is the same as the third solution. Isn't it very simplified? It seems that the Lantern Festival gave me a gift. I suddenly thought of this method. I have never studied the interactivePopGestureRecognizer attribute before. This attribute is only available after iOS7. Therefore, I can't directly use leftBarButtonItem to handle it in the project, unless that interface does not need to swipe right to return.

Now, everything is clear. It is very simple to use the leftBarButtonItem to call the API in the common base class controller to set it up uniformly. The right swipe back gesture can also be used normally~

What are you waiting for? Try it now!

***

If the project you are using also has such a requirement, why not give it a try! The author provides a demo, so you can download the demo first to see the effect! After many tests, the author believes that this is a feasible solution. If you encounter any problems during use, please give feedback to the author. I also want to understand what the situation is. Of course, we also need to find a solution and make progress together.