Question

我正在使用多个视图控制器并尝试使用委托将一个视图控制器中的UITextfield链接到另一个视图控制器中的标签。

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController <UITextFieldDelegate>
{
    IBOutlet UITextField *txtField;

}

@end

ViewController.m

#import "ViewController.h"
#import "ViewController2nd.h"


@interface ViewController ()

@end

@implementation ViewController

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

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
- (BOOL)textFieldShouldReturn:(UITextField *)textField{

    lbl.text = [NSString stringWithFormat:@"Hello, %@",txtField.text]
    [txtField resignFirstResponder];
    return YES;
}

@end

ViewController2nd.h

#import <UIKit/UIKit.h>

@interface ViewController2nd : UIViewController <UITextFieldDelegate> {

    IBOutlet UILabel *lbl;
}

@end

ViewController2nd.m

#import "ViewController2nd.h"

@interface ViewController2nd ()

@end

@implementation ViewController2nd

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

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

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

我得到的错误是：

在Viewcontroller.m中使用未声明的标识符lbl

不确定如何解决这个问题。需要一些指导..谢谢...

Answer 1

ViewController2nd中IBOutlet UILabel *lbl; ViewController的范围/超出范围，因为您需要自定义代理，ViewController代理ViewController2nd并传回数据。有关详细信息，请查看this post。

Answer 2

lbl的声明是在错误的类中完成的。发布IBOutlet UILabel *lbl; 在viewcontroller.h

的界面内

如果你想使用其他类的变量将代码更改为

#import <UIKit/UIKit.h>
#import "ViewController2.h"

@interface ViewController : UIViewController <UITextFieldDelegate>
{
    IBOutlet UITextField *txtField;
   ViewController2 *viewController2;

}
@property(nonatomic,retain)ViewController2 *viewController2;
@end

ViewController.m

#import "ViewController.h"
#import "ViewController2nd.h"


@interface ViewController ()

@end

@implementation ViewController
@synthesize viewcontroller2;
- (void)viewDidLoad
{
    viewController2 = [[ViewController2 alloc]initWithNibName:@"ViewController2" bundle:nil];
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}
- (BOOL)textFieldShouldReturn:(UITextField *)textField{

    viewController2.lbl.text = [NSString stringWithFormat:@"Hello, %@",txtField.text]
    [txtField resignFirstResponder];
    return YES;
}

@end

ViewController2nd.h

#import <UIKit/UIKit.h>

@interface ViewController2nd : UIViewController <UITextFieldDelegate> {

    IBOutlet UILabel *lbl;
}
@property(nonatomic,retain)IBOUTlet UILabel *lbl;
@end

ViewController2nd.m

#import "ViewController2nd.h"

@interface ViewController2nd ()

@end

@implementation ViewController2nd
@synthesize lbl;
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

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

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

@end

Answer 3

错误是正确的

ViewController中没有元素作为lbl：）

您必须使用ViewController2nd对象来访问其实例属性

Here is用Objective-C开始面向对象编程的地方。

Answer 4

首先，您必须初始化ViewController2nd的对象。

- (BOOL)textFieldShouldReturn:(UITextField *)textField
{
ViewController2nd *objeView2nd = [[ViewController2nd alloc]init];
objeView2nd.lbl.text = [NSString stringWithFormat:@"Hello, %@",txtField.text]
[txtField resignFirstResponder];
return YES;
}

还有一件事，lbl ViewController2nd必须是@property和@synthesize。没有它，您将无法访问lbl。

Answer 5

您始终可以使用Singleton Class来回传递数据。例如，appDelegate类是单例类。您可以使用该类的共享实例来回传递数据。

示例：

      Step 1: 

             yourAppDelegate.h

             @property (strong, nonatomic) NSString *txtLabelText;


             yourAppDelegate.m

             @synthesize txtLabelText;


      Step 2:

            viewController1.m

            #import viewController1.m
            #import yourAppDelegate.m

            -(void)viewDidLoad{

                 UILabel *txtLabel = [[UILabel alloc] initWithFrame:CGRectMake(50,50,100,20)];

                  txtLabel.text = @"Rebel Yell";

                  yourAppDelegate *appDelegate = (yourAppDelegate *)[[UIApplication sharedApplication] delegate]; 

                  appDelegate.txtLabelText = txtLabel.text;                

               }



     Step 3:

                  viewController2.m

                  #import viewController2.m
                  #import yourAppDelegate.m

                  -(void)viewDidLoad{

                      yourAppDelegate *appDelegate = (yourAppDelegate*)[[UIApplication sharedApplication] delegate];

                      NSLog(@"Passed UILabel Text from viewController 1 %@", appDelegate.txtLabelText);

                     }

我建议您创建一个自定义单例类并使用该类的共享实例，而不是仅仅依赖于appDelegate类。

希望这会帮助你澄清一些疑惑

在多个视图控制器中使用Delegates

5 个答案: