拦截UIViewController的popViewController事件

实现拦截UIViewController的pop操作有两种方式：

• 自定义实现返回按钮，即设置UIBarButtonItem来实现自定义的返回操作。
• 创建UINavigatonController的Category，来定制navigationBar: shouldPopItem:的逻辑。

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：

#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;
}

使用：

• 在UIViewController当中引入头文件

#import "UIViewController+BackButtonHandler.h"

• 在UIViewController中实现navigationShouldPopOnBackButton方法。

- (BOOL)navigationShouldPopOnBackButton{
    [[[UIAlertView alloc] initWithTitle:@"提示" message:@"确定返回上一界面?"
                               delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"确定", nil] show];
    //renturn no 拦截pop事件
    return NO;
}

参考：

• iOS拦截导航栏返回按钮事件的正确方式

• UIViewController-BackButtonHandler

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