攔截UIViewController的popViewController事件

實現攔截UIViewController的pop操做有兩種方式：

• 自定義實現返回按鈕，即設置UIBarButtonItem來實現自定義的返回操做。
• 建立UINavigatonController的Category，來定製navigationBar: shouldPopItem:的邏輯。

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當中引入頭文件

#import "UIViewController+BackButtonHandler.h"

• 在UIViewController中實現navigationShouldPopOnBackButton方法。

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

參考：

• iOS攔截導航欄返回按鈕事件的正確方式

• UIViewController-BackButtonHandler