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

}