- Change navigation bar system button event
- 自定义导航栏系统返回按钮事件
- 将QYNavBackButton文件夹导入项目中即可
- 如果遇到需要自定义事件,可在对应的viewController中
#import "UIViewController+QYCustomBackButton.h",然后复写- (void)customNavBackButtonMethod方法即可
最近遇到一个关于导航栏返回按钮的问题,因为之前项目里面都是用的系统默认的返回按钮样式所以没有想过要去更改,后来有需要将返回按钮箭头旁边的文字去掉,同时将该返回按钮的点击事件重新定义。一开始尝试自定义按钮然后设置为leftBarButtonItem,但是这样图片可能跟系统自带的不一样,还有就是返回按钮的位置跟系统自带的不一样。后来找了一些资料,发现将文字去掉比较简单,一般做法是控制器中添加如下代码,然后他的下一级控制就有一个只有箭头没有文字返回按钮:
UIBarButtonItem *backBtn = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil];
self.navigationItem.backBarButtonItem = backBtn;
也可以创建一个根控制器在其中使用上述代码然后让其他控制器继承这个根控制器实现批量操作。但是如果遇到需要自定义该返回的点击事件的时候,在上面方法中添加target与action是不可行的,同时这种做法也会产生一个问题,就是实际的返回按钮点击区域总是比按钮看到的范围大,一般是距离箭头右边30距离都可点击。接下来我就带大家一起了解这些问题产生的原因以及如何更好的解决这些问题。
首先我们看一下按照上面代码去掉返回按钮文字之后的导航栏视图的结构层次,因为导航栏的视图加载以及初始化跟viewController的view不一样,不能再veiwDidLoad中去观察(viewWillAppear中也不行)要在viewDidLoad中才可以看到完整的导航栏视图结构层次。我们可以在一个有去掉文字的返回按钮控制器的viewDidLoad中打上断点然后在控制台执行:
po [[UIWindow keyWindow] recursiveDescription]
会得到如下输出:
<UIWindow: 0x8d6f970; frame = (0 0; 320 480); autoresize = W+H; gestureRecognizers = <NSArray: 0x8d5dbf0>; layer = <UIWindowLayer: 0x8d717d0>> | <UILayoutContainerView: 0x8d7bbf0; frame = (0 0; 320 480); autoresize = W+H; gestureRecognizers = <NSArray: 0x8d78a70>; layer = <CALayer: 0x8d7bcd0>> | | <UINavigationTransitionView: 0x8d813f0; frame = (0 0; 320 480); clipsToBounds = YES; autoresize = W+H; layer = <CALayer: 0x8d814d0>> | | | <UIViewControllerWrapperView: 0x8d61050; frame = (0 0; 320 480); autoresize = W+H; userInteractionEnabled = NO; layer = <CALayer: 0x8d88f40>> | | | | <UIView: 0x8ab0dc0; frame = (0 0; 320 480); autoresize = RM+BM; layer = <CALayer: 0x8ab0610>> | | | | | <_UILayoutGuide: 0x8ab0e20; frame = (0 0; 0 64); hidden = YES; layer = <CALayer: 0x8ab0e90>> | | | | | <_UILayoutGuide: 0x8ab1080; frame = (0 480; 0 0); hidden = YES; layer = <CALayer: 0x8ab10f0>> | | <UINavigationBar: 0x8d75c40; frame = (0 20; 320 44); opaque = NO; autoresize = W; userInteractionEnabled = NO; gestureRecognizers = <NSArray: 0x8d5e750>; layer = <CALayer: 0x8d70f00>> | | | <_UINavigationBarBackground: 0x8d59af0; frame = (0 -20; 320 64); opaque = NO; autoresize = W; userInteractionEnabled = NO; layer = <CALayer: 0x8d549f0>> - (null) | | | | <_UIBackdropView: 0x8d7c440; frame = (0 0; 320 64); opaque = NO; autoresize = W+H; userInteractionEnabled = NO; layer = <_UIBackdropViewLayer: 0x8d7e7b0>> | | | | | <_UIBackdropEffectView: 0x8d7f1c0; frame = (0 0; 320 64); clipsToBounds = YES; opaque = NO; autoresize = W+H; userInteractionEnabled = NO; animations = { filters.colorMatrix.inputColorMatrix=<CABasicAnimation: 0x8ba4490>; }; layer = <CABackdropLayer: 0x8d7f480>> | | | | | <UIView: 0x8d7fc80; frame = (0 0; 320 64); hidden = YES; opaque = NO; autoresize = W+H; userInteractionEnabled = NO; layer = <CALayer: 0x8d7fce0>> | | | | <UIImageView: 0x8d67cc0; frame = (0 64; 320 0.5); userInteractionEnabled = NO; layer = <CALayer: 0x8d67d50>> - (null) | | | <UINavigationItemView: 0x8ab6400; frame = (124 8; 163 27); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x8ab6480>> | | | | <UILabel: 0x8ab64b0; frame = (0 3; 163 22); text = 'A Story About a Fish'; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x8ab6550>> | | | <UINavigationItemButtonView: 0x8ab6c80; frame = (8 6; 41 30); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x8ab6d60>> | | | | <UILabel: 0x8ab6f10; frame = (-981 -995; 91 22); text = ''; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x8ab6fb0>> | | | <_UINavigationBarBackIndicatorView: 0x8d87560; frame = (8 12; 12.5 20.5); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x8d87650>> - Back
直接看或许不容易懂,还需要结合Xcode的"Debug view Hierarchy"或者是Reveal工具看实际视图结构:
我们可以看到在UINavigationBar中包含有4个类,它们大致的作用是:
- _UINavigationBarBackground :(UIImageView)导航栏背景图(不可以直接设置图片)
- UINavigationItemView :(UIView)包含显示导航栏标题
- UINavigationItemButtonView :(UIView)包含显示导航栏左视图(不可移除、更改大小、颜色,可以隐藏,决定了我们的自定义区域是否显示)
- _UINavigationBarBackIndicatorView :(UIImageView)导航栏返回按钮箭头图片(不可以修改图片)
_UINavigationBarBackIndicatorView就是返回按钮的箭头也就是我们需要保留的,UINavigationItemButtonView就是就是决定导航栏要不要显示返回按钮的依据。再次看看这个对象在控制台的输出:
| | | <UINavigationItemButtonView: 0x8ab6c80; frame = (8 6; 41 30); opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x8ab6d60>> | | | | <UILabel: 0x8ab6f10; frame = (-981 -995; 91 22); text = ''; clipsToBounds = YES; opaque = NO; userInteractionEnabled = NO; layer = <CALayer: 0x8ab6fb0>>
这个UINavigationItemButtonView应该是系统在这个view的draw方法里就决定frame,修改frame就触发needdisplay重新改变它的frame,因此这个view只会根据其上的label(也就是返回按钮显示的文字)的内容变化而改变宽度其余基本不可变,我们虽然将label的内容设置为空但是这个UINavigationItemButtonView的大小却并没有改变同时点击区域也没有改变。从控制台里的还可看到这个veiw的userInteractionEnabled属性为NO,很明显我们的返回事件并不在这个view上,只能说明是真正响应点击事件的是这个view背后添加了某个UIGestureRecognizer。因此要想解决我之前提到的问题首先我们得覆盖这个默认的返回响应事件,然后添加我们自己的事件。同时还得想到的是当我们有需要自己定义左按钮的时候就得移除这种覆盖操作,因此我在这里创建了一个自定义的视图QYMaskView覆盖系统事件,然后通过UINavigationItemButtonView的存在与否来控制QYMaskView是否存在就可以实现以上效果
for (UIView *view in self.navigationController.navigationBar.subviews) { if ([view isKindOfClass:NSClassFromString(@"UINavigationItemButtonView")]) { nav_backView = view; } else if ([view isKindOfClass:[QYMaskView class]]) { nav_qyView = (QYMaskView *)view; } } if (nav_backView && !nav_qyView) { QYMaskView *qyButtonView = [[QYMaskView alloc] initWithFrame:CGRectMake(0, 0, 100, 44)]; qyButtonView.backButton = [UIButton buttonWithType:UIButtonTypeCustom]; qyButtonView.backButton.frame = CGRectMake(8, 6, 30, 30); [qyButtonView.backButton addTarget:self action:@selector(customNavBackButtonMethod) forControlEvents:UIControlEventTouchUpInside]; [qyButtonView addSubview:qyButtonView.backButton]; [self.navigationController.navigationBar addSubview:qyButtonView]; } else if (nav_backView && nav_qyView) { [nav_qyView.backButton removeTarget:nil action:NULL forControlEvents:UIControlEventAllEvents]; [nav_qyView.backButton addTarget:self action:@selector(customNavBackButtonMethod) forControlEvents:UIControlEventTouchUpInside]; } else if (!nav_backView && nav_qyView) { [nav_qyView removeFromSuperview]; }
通过在QYMaskView中添加按钮来替换系统返回事件。其中有一步是给按钮添加与移除按钮事件,目的是为了加入我们自定义的事件。当视图控制器显示的时候我们会去给该按钮重新添加点击事件,由于customNavBackButtonMethod事件定义到了.h中,当我们在本类中也实现了这个方法,我们在分类中调用这个方法就会执行本类中的实现(因为此时该方法的定义已经被覆盖)。因此只要在对应的viewController中复写customNavBackButtonMethod方法就可以在点击返回按钮时执行到你复写的方法中了。
注意:iOS7以后可以通过手势进行返回,由属性interactivePopGestureRecognizer来控制,而且这种方式并不会调用自定义的方法与系统的pop方法,这里通过禁用该手势来解决这问题,因此需要增加一个可以控制该手势的方法。最后总结出来的解决办法就是创建一个viewController的分类:
UIViewController+QYCustomBackButton.h文件
#import <UIKit/UIKit.h> @interface QYMaskView : UIView @property (nonatomic, strong) UIButton *backButton; @end @protocol QYNavBackButtonDelegate <NSObject> @optional /** * 自定义返回事件,在需要自定义返回事件的viewController中实现该方法 */ - (void)customNavBackButtonMethod; /** * 右滑手势返回是否可用 * * @return YES表示手势可用,NO表示不可用 */ - (BOOL)isPopGestureAvailable; @end @interface UIViewController (QYCustomBackButton) <QYNavBackButtonDelegate> /** * 重新布局返回事件 */ - (void)setQYNavNeedLayout; @end
UIViewController+QYCustomBackButton.m文件
#import "UIViewController+QYCustomBackButton.h" #import <objc/runtime.h> @implementation QYMaskView @end @implementation UIViewController (QYCustomBackButton) + (void)load { static dispatch_once_t onceToken; dispatch_once(&onceToken, ^{ Class class = [self class]; SEL originalviewDidLoad = @selector(viewDidLoad); SEL swizzledviewDidLoad = @selector(qy_viewDidLoad); SEL originalviewDidAppear = @selector(viewDidAppear:); SEL swizzledviewDidAppear = @selector(qy_viewDidAppear); Method originalMethodLoad = class_getInstanceMethod(class, originalviewDidLoad); Method swizzledMethodLoad = class_getInstanceMethod(class, swizzledviewDidLoad); Method originalMethodAppear = class_getInstanceMethod(class, originalviewDidAppear); Method swizzledMethodAppear = class_getInstanceMethod(class, swizzledviewDidAppear); BOOL didAddMethodLoad = class_addMethod(class, originalviewDidLoad, method_getImplementation(swizzledMethodLoad), method_getTypeEncoding(swizzledMethodLoad)); BOOL didAddMethodAppear = class_addMethod(class, originalviewDidAppear, method_getImplementation(swizzledMethodAppear), method_getTypeEncoding(swizzledMethodAppear)); if (didAddMethodLoad) { class_replaceMethod(class, swizzledviewDidLoad, method_getImplementation(originalMethodLoad), method_getTypeEncoding(originalMethodLoad)); } else { method_exchangeImplementations(originalMethodLoad, swizzledMethodLoad); } if (didAddMethodAppear) { class_replaceMethod(class, swizzledviewDidAppear, method_getImplementation(originalMethodAppear), method_getTypeEncoding(originalMethodAppear)); } else { method_exchangeImplementations(originalMethodAppear, swizzledMethodAppear); } }); } #pragma mark - Method Swizzling - (void)qy_viewDidLoad { [self qy_viewDidLoad]; UIBarButtonItem *backButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"" style:UIBarButtonItemStylePlain target:nil action:nil]; [self.navigationItem setBackBarButtonItem:backButtonItem]; } - (void)qy_viewDidAppear { [self qy_viewDidAppear]; [self setQYNavNeedLayout]; } - (void)setQYNavNeedLayout { UIView *nav_backView = nil; QYMaskView *nav_qyView = nil; for (UIView *view in self.navigationController.navigationBar.subviews) { if ([view isKindOfClass:NSClassFromString(@"UINavigationItemButtonView")]) { nav_backView = view; } else if ([view isKindOfClass:[QYMaskView class]]) { nav_qyView = (QYMaskView *)view; } } self.navigationController.interactivePopGestureRecognizer.enabled = [self isPopGestureAvailable]; if (nav_backView && !nav_qyView) { QYMaskView *qyButtonView = [[QYMaskView alloc] initWithFrame:CGRectMake(0, 0, 100, 44)]; qyButtonView.backButton = [UIButton buttonWithType:UIButtonTypeCustom]; qyButtonView.backButton.frame = CGRectMake(8, 6, 30, 30); [qyButtonView.backButton addTarget:self action:@selector(customNavBackButtonMethod) forControlEvents:UIControlEventTouchUpInside]; [qyButtonView addSubview:qyButtonView.backButton]; [self.navigationController.navigationBar addSubview:qyButtonView]; } else if (nav_backView && nav_qyView) { [nav_qyView.backButton removeTarget:nil action:NULL forControlEvents:UIControlEventAllEvents]; [nav_qyView.backButton addTarget:self action:@selector(customNavBackButtonMethod) forControlEvents:UIControlEventTouchUpInside]; } else if (!nav_backView && nav_qyView) { [nav_qyView removeFromSuperview]; } } - (void)customNavBackButtonMethod { [self.navigationController popViewControllerAnimated:YES]; } - (BOOL)isPopGestureAvailable { return YES; } @end
导入到项目中就可以生效了。这里所做的就是在所有的viewController执行viewDidLoad的时候将返回按钮的文字置空,在执行viewDidAppear的时候添加一个自定义的按钮去响应pop事件。好了,是不是感觉很简单呢。当然在研究这一个问题过程中还是有很多我没弄明白的地方,可能在各位同学使用的时候产生各种问题,给大家带来的不便敬请谅解,同时欢迎大家提出宝贵的建议予以改进,在此感激不尽!