我的代码： -

后台课程： -

BackGroundClass.h

#import <UIKit/UIKit.h>

@protocol buttonprotocol<NSObject>
@required
- (void) buttonTapped;
@end

@interface BackGroundClass : UIViewController

@property (nonatomic, weak) id<buttonprotocol> delegate;

@end

BackGroundClass.m

#import＆＃34; BackGroundClass.h＆＃34;

@interface BackGroundClass ()

@end

@implementation BackGroundClass
@synthesize delegate;

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
}

- (void)backbutton: (UINavigationItem *)navigationitem
{
        UIImage* image3 = [UIImage imageNamed:@"back.png"];
        CGRect frameimg = CGRectMake(15,5,25,25);

        UIButton *someButton = [[UIButton alloc] initWithFrame:frameimg];
        [someButton setBackgroundImage:image3 forState:UIControlStateNormal];
        [someButton addTarget:self action:@selector(Back_btn:)
             forControlEvents:UIControlEventTouchUpInside];
        [someButton setShowsTouchWhenHighlighted:YES];

        UIBarButtonItem *mailbutton =[[UIBarButtonItem alloc] initWithCustomView:someButton];
        navigationitem.leftBarButtonItem = mailbutton;
}

- (void)Back_btn :(id)sender
{
   [delegate buttonTapped];
}

@end

主要班级： -

mainclass.h

#import <UIKit/UIKit.h>
#import "BackGroundClass.h"

@interface mainclass : UIViewController<buttonprotocol>

mainclass.m

#import "mainclass.h"
#import "BackGroundClass.h"

@interface mainclass ()
{
 BackGroundClass * bg;
}

@end

@implementation mainclass

- (void)viewDidLoad {
    [super viewDidLoad];

    bg = [[BackGroundClass alloc]init];
    [bg backbutton:self.navigationItem];
}

- (void)buttonTapped
{
    NSLog(@"ok it's 2");
}

但是上面的按钮点击了一个方法并没有被称为我做错了什么？

Answer 1

当你创建BackGroundClass类的对象时，你没有将类的委托设置为self，这就是你的委托方法没有调用的原因，请尝试这样做

bg = [[BackGroundClass alloc]init];
bg.delegate = self;

Answer 2

首先，在类名中使用 Class 是不好的做法。对于视图控制器，您应该使用ViewController或VC postfix作为类名。

例如，Objective-C类的专有名称是： BackgroundViewController，MainViewController

其次，ViewController实例用于响应用户与附加到此ViewController的视图的交互，并基于 MVC 工作的数据组件提供可见更改。因此，没有理由使用第二个，在您的情况下 BackgroundViewController（BackgroundClass）。

有关MVC模式的更多信息，请参阅此链接： Apple's MVC articles

由于在外部ViewController中没有必要，我们也应该删除委托，并将所有逻辑放在这个主视图控制器中。

第三，如Apple's Mobile HIG中所述，按钮的高度应为44px左右，因此后退按钮的大小为25x25会使大多数用户在尝试点击它时遇到困难。

最后，您应该收到类似于它的类：

<强> MainViewController.h

#import <UIKit/UIKit.h>

@interface MainViewController : UIViewController


@end

<强> MainViewController.m

#import "MainViewController.h"

@implementation MainViewController

- (void)viewDidLoad {
    [super viewDidLoad];

    UIImage *icon = [UIImage imageNamed:@"back.png"];

    static CGFloat defaultButtonSize = 44.; // Default button's tap area size

    CGSize buttonSize = CGSizeMake(defaultButtonSize, defaultButtonSize);
    // The size image should take inside the button
    CGSize imageSizeInsideButton = CGSizeMake(25., 25.); 

    CGRect frameimg = CGRectMake(15., 5., defaultButtonSize, defaultButtonSize);

    UIButton *someButton = [[UIButton alloc] initWithFrame:frameimg];
    [someButton setImage:icon forState:UIControlStateNormal];
    [someButton addTarget:self
                   // No need to put colon after method name,
                   // since you have no use of control that triggered action
                   action:@selector(backButtonClicked)                                      
         forControlEvents:UIControlEventTouchUpInside];

    someButton.showsTouchWhenHighlighted = YES;

    // Calculate edge insets so image will take the size 
    // you specified dozen of lines before
    CGFloat imageVerticalPaddingInButton = (buttonSize.height - imageSizeInsideButton.height) / 2.;
    CGFloat imageHorizontalPaddingInButton = (buttonSize.height - imageSizeInsideButton.height) / 2.;

    // Apply it to button
    someButton.imageEdgeInsets = UIEdgeInsetsMake(imageVerticalPaddingInButton,
             imageHorizontalPaddingInButton, 
             imageVerticalPaddingInButton, 
             imageHorizontalPaddingInButton);

    UIBarButtonItem *mailbutton =[[UIBarButtonItem alloc] initWithCustomView:someButton];
    self.navigationItem.leftBarButtonItem = mailbutton;
}

// As stated in "addTarget", there is no "sender" since you don't really need it
// If you ever would need the use of it, 
// don't forget to put colon in "addTarget" UIButton's method
// and place something like :(UIButton *)buttonThatClicked
// after methodName
- (void)backButtonClicked {
    // Get back to your previous view controller or do whatever you like there
    [self.navigationController popViewControllerAnimated:YES];
}

@end

但是如果你想在尽可能多的View Controllers中使用这个东西，那么你应该创建类别：

<强>的UIViewController + CustomBackButton.h

#import <UIKit/UIKit.h>

@interface UIViewController (CustomBackButton)

- (void)setBackButtonImage:(UIImage *)image withSize:(CGSize)size target:(id)target selector:(SEL)selector;

@end

<强>的UIViewController + CustomBackButton.m

#import "UIViewController+CustomBackButton.h"

@implementation UIViewController (CustomBackButton)

- (void)setBackButtonImage:(UIImage *)image withSize:(CGSize)size target:(id)target selector:(SEL)selector {
    static CGFloat defaultButtonSize = 44.;

    CGSize buttonSize = CGSizeMake(defaultButtonSize, defaultButtonSize);

    CGRect frameimg = CGRectMake(15., 5., defaultButtonSize, defaultButtonSize);

    UIButton *someButton = [[UIButton alloc] initWithFrame:frameimg];
    [someButton setImage:image forState:UIControlStateNormal];
    [someButton addTarget:target
                   action:selector
         forControlEvents:UIControlEventTouchUpInside];

    someButton.showsTouchWhenHighlighted = YES;

    CGFloat imageVerticalPaddingInButton = (buttonSize.height - size.height) / 2.;
    CGFloat imageHorizontalPaddingInButton = (buttonSize.height - size.height) / 2.;

    someButton.imageEdgeInsets = UIEdgeInsetsMake(imageVerticalPaddingInButton,
                                                  imageHorizontalPaddingInButton,
                                                  imageVerticalPaddingInButton,
                                                  imageHorizontalPaddingInButton);

    UIBarButtonItem *backButton = [[UIBarButtonItem alloc] initWithCustomView:someButton];
    self.navigationItem.leftBarButtonItem = backButton;
}

@end

然后你的View Controller的实现文件会更清晰。