重写系统中的UINavigationController返回按钮的事件

1.扩展UIviewController
UIViewController+BackButtonHandler.h

#import <UIKit/UIKit.h>
@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+BackButtonHandler.m文件

 #import "UIViewController+BackButtonHandler.h"

@implementation UIViewController (BackButtonHandler)

@end

2.扩展UINavigationController ,也可以继承 使用

@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(subview.alpha < 1.) {
[UIView animateWithDuration:.25 animations:^{
subview.alpha = 1.;
}];
}
}
}

return NO;
}

@end

3.测试使用

#import "ViewController.h
#import "UIViewController+BackButtonHandler.h"

@implementation ViewController

-(void) viewDidLoad
{
[super viewDidLoad];
self.title =  [NSString stringWithFormat:@"Screen-%d", self.navigationController.viewControllers.count];
self.navigationItem.rightBarButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Next" style:UIBarButtonItemStylePlain
 target:selfaction:@selector(onNextBtn:)];
}

-(void) onNextBtn:(id)sender
{
[self.navigationController pushViewController:[ViewController new] animated:YES];
}

-(BOOL) navigationShouldPopOnBackButton ///在这个方法里写返回按钮的事件处理
{

//这里写要处理的代码
 [self.navigationController popViewControllerAnimated:YES];
return YES;//返回NO 不会执行

}