截取iOS系統(tǒng)自帶返回按鈕事件

當用戶點的不是保存而是系統(tǒng)自帶的返回，我就彈出一個提示框問是否保存后再返回。相信大家開發(fā)過程中也經(jīng)常會遇到這樣的需求，我這里講一下如何簡單的解決這個問題吧~

下面分兩種情況處理這件事

第一種：返回鍵采用的是系統(tǒng)的返回鍵

通過建立類別來實現(xiàn)
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里面的具體使用方法：

//實現(xiàn)方法
-(BOOL)navigationShouldPopOnBackButton{
    
    
    
    
    return YES;
}

代碼下載地址：https://github.com/xiaoshunliang/OverrideBackButtonDemo

第二種：對于自定義的返回按鈕

BaseViewController.h中

@protocol BackButtonHandlerProtocol <NSObject>
@optional
//點擊返回按鈕時做特殊處理的時候 實現(xiàn)這個協(xié)議方法
-(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;
    //實現(xiàn)返回按鈕做特殊處理
    if([self respondsToSelector:@selector(navigationShouldPopOnBackButton)]) {
        shouldPop = [self.backButtonDelegate navigationShouldPopOnBackButton];
    }
    
    if(shouldPop) {
        dispatch_async(dispatch_get_main_queue(), ^{
            [self.navigationController popViewControllerAnimated:YES];
        });
    }
}

實際使用：
繼承于BaseViewController
實現(xiàn)協(xié)議方法 BackButtonHandlerProtocol
self.backButtonDelegate = self;
實現(xiàn)協(xié)議方法

-(BOOL)navigationShouldPopOnBackButton{
  
    return YES;
}

代碼下載地址：https://github.com/xiaoshunliang/CustomBackButtonDemo