截取iOS系统自带返回按钮事件

当用户点的不是保存而是系统自带的返回，我就弹出一个提示框问是否保存后再返回。相信大家开发过程中也经常会遇到这样的需求，我这里讲一下如何简单的解决这个问题吧~

下面分两种情况处理这件事

第一种：返回键采用的是系统的返回键

通过建立类别来实现
UIViewController.h中

@protocol BackButtonHandlerProtocol <NSObject>
@optional
// Override this method in UIViewController derived class to handle 'Back' button click
-(BOOL)navigationShouldPopOnBackButton;
@end

@interface UIViewController (BackButtonHandler) <BackButtonHandlerProtocol>

@end

UIViewController.m中

#import "UIViewController+BackButtonHandler.h"

@implementation UIViewController (BackButtonHandler)

@end

@implementation UINavigationController (ShouldPopOnBackButton)

- (BOOL)navigationBar:(UINavigationBar *)navigationBar shouldPopItem:(UINavigationItem *)item {

    if([self.viewControllers count] < [navigationBar.items count]) {
        return YES;
    }

    BOOL shouldPop = YES;
    UIViewController* vc = [self topViewController];
    if([vc respondsToSelector:@selector(navigationShouldPopOnBackButton)]) {
        shouldPop = [vc navigationShouldPopOnBackButton];
    }

    if(shouldPop) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [self popViewControllerAnimated:YES];
        });
    } else {
        // Workaround for iOS7.1. Thanks to @boliva - http://stackoverflow.com/posts/comments/34452906
        for(UIView *subview in [navigationBar subviews]) {
            if(0. < subview.alpha && subview.alpha < 1.) {
                [UIView animateWithDuration:.25 animations:^{
                    subview.alpha = 1.;
                }];
            }
        }
    }

    return NO;
}

@end

controller里面的具体使用方法：

//实现方法
-(BOOL)navigationShouldPopOnBackButton{
    
    
    
    
    return YES;
}

代码下载地址：https://github.com/xiaoshunliang/OverrideBackButtonDemo

第二种：对于自定义的返回按钮

BaseViewController.h中

@protocol BackButtonHandlerProtocol <NSObject>
@optional
//点击返回按钮时做特殊处理的时候 实现这个协议方法
-(BOOL)navigationShouldPopOnBackButton;
@end

@interface BaseViewController : UIViewController<UITableViewDataSource,UITableViewDelegate,UIGestureRecognizerDelegate>
@property (assign, nonatomic) id<BackButtonHandlerProtocol> backButtonDelegate;

@end

BaseViewController.m中

    UIBarButtonItem *leftbtn = [[UIBarButtonItem alloc] initWithImage:[UIImage locatilyImage:@"arrow--return"]
                                                                style:UIBarButtonItemStylePlain
                                                               target:self action:@selector(dismiss)];
    self.navigationItem.leftBarButtonItem = leftbtn;

- (void)dismiss{
    BOOL shouldPop = YES;
    //实现返回按钮做特殊处理
    if([self respondsToSelector:@selector(navigationShouldPopOnBackButton)]) {
        shouldPop = [self.backButtonDelegate navigationShouldPopOnBackButton];
    }
    
    if(shouldPop) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.navigationController popViewControllerAnimated:YES];
        });
    }
}

实际使用：
继承于BaseViewController
实现协议方法 BackButtonHandlerProtocol
self.backButtonDelegate = self;
实现协议方法

-(BOOL)navigationShouldPopOnBackButton{
  
    return YES;
}

代码下载地址：https://github.com/xiaoshunliang/CustomBackButtonDemo