需求描述：
在项目开发过程中，遇到一种情况，需要自定义UIBarButtonItem，来实现分享样式，并在iPad中弹出系统分享框（UIActivityViewController），系统分享框需要指定显示位置（barButtonItem）。而自定义的UIBarButtonItem target指向的是UIButton。这与需求不符，需自定义UIBarButtonItem。
在介绍自定义UIBarButtonItem前，先介绍一下相关控件的子父类关系（也可以说继承关系）。
1、UIBarItem
NS_CLASS_AVAILABLE_IOS(2_0) @interface UIBarItem : NSObject <NSCoding, UIAppearance>UIBarButtonItem
NS_CLASS_AVAILABLE_IOS(2_0) @interface UIBarButtonItem : UIBarItem <NSCoding>UITabBarItem
NS_CLASS_AVAILABLE_IOS(2_0) @interface UITabBarItem : UIBarItem下面是在界面上的显示效果
UIBarButtonItem和UITabBarItem效果显示
从上图中看到UIBarButtonItem有三种效果显示，分别是
导航左侧返回按钮，UINavigationItem中的backBarButtonItem属性
@property(nullable,nonatomic,strong) UIBarButtonItem *backBarButtonItem纯文本的UIBarButtonItem
- (instancetype)initWithTitle:(nullable NSString *)title style:(UIBarButtonItemStyle)style target:(nullable id)target action:(nullable SEL)action;纯图片的UIBarButtonItem，其中包括自定义图片和系统样式
- (instancetype)initWithImage:(nullable UIImage *)image style:(UIBarButtonItemStyle)style target:(nullable id)target action:(nullable SEL)action;
- (instancetype)initWithBarButtonSystemItem:(UIBarButtonSystemItem)systemItem target:(nullable id)target action:(nullable SEL)action;UIToolBar使用UIBarButtonItem与导航效果一致。
关于UITabBarItem在这里就不多介绍，只是拿其显示效果与UIBarButtonItem对比。
在开发过程中，我们会使用到自定义UIBarButtonItem，来显示我们想要的界面效果。使用的方法常为：
- (instancetype)initWithCustomView:(UIView *)customView;
- (void)viewDidLoad {
[super viewDidLoad];
//自定义View
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, 60.0, 40.0)];
view.backgroundColor = [UIColor redColor];
//自定义按钮
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
btn.frame = view.bounds;
[btn addTarget:self action:@selector(clickRight:) forControlEvents:UIControlEventTouchUpInside];
[view addSubview:btn];
//自定义Item
UIBarButtonItem *barItem = [[UIBarButtonItem alloc] initWithCustomView:view];
//
self.navigationItem.leftBarButtonItem = barItem;
}
#pragma mark -
- (void)clickRight:(id)sender {
NSLog(@"sender:%@",sender);
}其中打印sender，其类型是UIButton。
2017-10-17 16:08:43.917 TestImage[5482:163865] sender:<UIButton: 0x7fb9bad12e60; frame = (0 0; 60 40); opaque = NO; layer = <CALayer: 0x61000003b940>>
通过上面描述，发现系统方法不能实现项目需求效果。当然也可以通过属性保存UIBarButtonItem方法来实现需求效果。即在点击按钮响应后，直接使用保存的UIBarButtonItem，但是我没有采用这种方法。
下面是我给出的两种解决方案:
方案一
继承UIBarButtonItem，实现子类。
定义子类
#import <UIKit/UIKit.h>
@interface LLBarButtonItem : UIBarButtonItem
@end
#import "LLBarButtonItem.h"
@implementation LLBarButtonItem
- (id)initWithCustomView:(UIView *)customView {
self = [super initWithCustomView:customView];
if (self) {
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
btn.frame = customView.bounds;
btn.backgroundColor = [UIColor clearColor];
[btn addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];
[customView addSubview:btn];
}
return self;
}
- (void)clickButton:(UIButton *)sender {
if (self.target && [self.target respondsToSelector:self.action]) {
//[self.target performSelector:self.action withObject:self];
IMP imp = [self.target methodForSelector:self.action];
void (*func)(id, SEL, id) = (void *)imp;
func(self.target, self.action, self);
}
}
@end定义子类对象，调用子类对象
- (void)viewDidLoad {
[super viewDidLoad];
//自定义View
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, 60.0, 40.0)];
view.backgroundColor = [UIColor clearColor];
//自定义Item
LLBarButtonItem *barItem = [[LLBarButtonItem alloc] initWithCustomView:view];
barItem.target = self;
barItem.action = @selector(clickRight:);
//
self.navigationItem.leftBarButtonItem = barItem;
}
#pragma mark -
- (void)clickRight:(id)sender {
NSLog(@"sender:%@",sender);
}打印target对象
2017-10-17 16:24:11.696 TestImage[5557:170144] sender:<LLBarButtonItem: 0x7fb403c16080>
方案二
UIBarButtonItem类别
定义类别
#import <UIKit/UIKit.h>
@interface UIBarButtonItem (Custom)
- (void)addCutomTarget:(id)target action:(SEL)action;
@end
#import "UIBarButtonItem+Custom.h"
@implementation UIBarButtonItem (Custom)
- (void)addCutomTarget:(id)target action:(SEL)action {
if (self.customView != nil) {
self.target = target;
self.action = action;
//
UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom];
btn.frame = self.customView.bounds;
btn.backgroundColor = [UIColor clearColor];
[btn addTarget:self action:@selector(clickButton:) forControlEvents:UIControlEventTouchUpInside];
[self.customView addSubview:btn];
}
}
- (void)clickButton:(UIButton *)sender {
if (self.target && [self.target respondsToSelector:self.action]) {
//[self.target performSelector:self.action withObject:self];
IMP imp = [self.target methodForSelector:self.action];
void (*func)(id, SEL, id) = (void *)imp;
func(self.target, self.action, self);
}
}
@end调用类别方法
- (void)viewDidLoad {
[super viewDidLoad];
//自定义View
UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0.0, 0.0, 60.0, 40.0)];
view.backgroundColor = [UIColor clearColor];
//自定义Item
UIBarButtonItem *barItem = [[UIBarButtonItem alloc] initWithCustomView:view];
[barItem addCutomTarget:self action:@selector(clickRight:)];
//
self.navigationItem.leftBarButtonItem = barItem;
}
#pragma mark -
- (void)clickRight:(id)sender {
NSLog(@"sender:%@",sender);
}打印target对象
2017-10-17 16:28:14.407 TestImage[5598:172418] sender:<UIBarButtonItem: 0x7ffeda609e20>
两种方法都使用了IMP做消息传递。
你更喜欢哪一种？！
总结
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