Question

我正在对NSNotification做一个简单的教程，并在正确执行它时面临一些问题。当我单击第一个视图上的按钮时，第二个视图中的文本字段不会更新。当我在NSLog中放置receiveNotification进行调试时，没有回复。不确定为什么没有调用receiveNotification。

代码如下所示：

ViewController.h

#import <UIKit/UIKit.h>

@interface ViewController : UIViewController{

}
-(IBAction)one:(id)sender;
-(IBAction)two:(id)sender;
-(IBAction)secondview:(id)sender;
@end

ViewController.m

#import "ViewController.h"
#import "SecondViewController.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.
}
-(IBAction)one:(id)sender{
    [[NSNotificationCenter defaultCenter] postNotificationName:@"Test1" object:self];
    NSLog(@"Hello");
}
-(IBAction)two:(id)sender{
    [[NSNotificationCenter defaultCenter] postNotificationName:@"Test2" object:self];
     NSLog(@"Hello");
}
-(IBAction)secondview:(id)sender{
    SecondViewController *secondview = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil];
    [self presentViewController:secondview animated:YES completion:nil];
}

@end

SecondViewController.h

#import <UIKit/UIKit.h>

@interface SecondViewController : UIViewController{
    IBOutlet UITextField *counterOneText;
    IBOutlet UITextField *counterTwoText;
    int counterOne;
    int counterTwo;
}

-(IBAction)back:(id)sender;
@end

SecondViewController.m

#import "SecondViewController.h"

@interface SecondViewController ()

@end

@implementation SecondViewController

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

        counterOne = 0;
        counterTwo = 0;

        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveNotification) name:@"Test1" object:nil];
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveNotification) name:@"Test2" object:nil];
    }
    return self;
}

-(void)receiveNotification:(NSNotification *)notification{
    if([[notification name] isEqualToString:@"Test1"])  {
        counterOne++;
        counterOneText.text = [NSString stringWithFormat:@"%d",counterOne];
        NSLog(@"%@",counterOneText.text);
        NSLog(@"Hello");
    }else
    {
        counterTwo++;
        counterTwoText.text = [NSString stringWithFormat:@"%d",counterTwo];
    }
}

- (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.
}
-(IBAction)back:(id)sender{
    [self dismissViewControllerAnimated:YES completion:nil];
}

@end

需要一些指导......

Answer 1

receiveNotification未被调用，因为您的SecondViewController从未实例化过。当对象不存在时，无法调用它。如果您按secondView，back，然后点击one或two，则会触发receiveNotification。

修改我复制并粘贴了你的代码来测试它，我得到了你想要的大部分内容。您仍然需要先按secondview，然后按back。

在ViewController.m中

@interface ViewController (){ SecondViewController *secondview; } @end @implementation ViewController -(id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil{ self = [super initWithNibName: nibNameOrNil bundle:nibBundleOrNil]; if(self){ secondview = [[SecondViewController alloc] initWithNibName:@"SecondViewController" bundle:nil]; } return self; } - (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. } -(IBAction)one:(id)sender{ [[NSNotificationCenter defaultCenter] postNotificationName:@"Test1" object:self]; } -(IBAction)two:(id)sender{ [[NSNotificationCenter defaultCenter] postNotificationName:@"Test2" object:self]; } -(IBAction)secondview:(id)sender{ [self presentViewController:secondview animated:YES completion:nil]; }

在SecondViewController.h中

@interface SecondViewController : UIViewController{ int counterOne; int counterTwo; } @property (nonatomic,retain)UITextField *counterOneText; @property (nonatomic,retain)UITextField *counterTwoText; -(IBAction)back:(id)sender; @end

在SecondViewController.m中

@interface SecondViewController（）

@end

@implementation SecondViewController @synthesize counterOneText, counterTwoText; - (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil { self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil]; if (self) { counterOne = 0; counterTwo = 0; self.counterOneText = [[UITextField alloc]initWithFrame:CGRectMake(100, 50, 150, 30)]; self.counterOneText.borderStyle = UITextBorderStyleRoundedRect; self.counterOneText.text = [NSString stringWithFormat:@"%@", [NSNumber numberWithInt:counterOne]]; self.counterTwoText = [[UITextField alloc]initWithFrame:CGRectMake(100, 100, 150, 30)]; self.counterTwoText.borderStyle = UITextBorderStyleRoundedRect; self.counterTwoText.text = [NSString stringWithFormat:@"%@", [NSNumber numberWithInt:counterTwo]]; //self.counterOneText.text = [NSString stringWithFormat:@"%d",counterOne]; //self.counterTwoText.text = [NSString stringWithFormat:@"%d",counterTwo]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveNotification:) name:@"Test1" object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(receiveNotification:) name:@"Test2" object:nil]; } return self; } -(void)receiveNotification:(NSNotification *)notification{ if([[notification name] isEqualToString:@"Test1"]) { counterOne++; NSLog(@"counterOne: %d", counterOne); counterOneText.text = [NSString stringWithFormat:@"%@", [NSNumber numberWithInt:counterOne]]; NSLog(@"counterOneText.text: %@",counterOneText.text); NSLog(@"Test1"); }else { counterTwo++; NSLog(@"counterTwo: %d", counterTwo); counterTwoText.text = [NSString stringWithFormat:@"%@",[NSNumber numberWithInt:counterTwo]]; NSLog(@"counterTwoText.text: %@",counterTwoText.text); NSLog(@"Test2"); } } - (void)viewDidLoad { [self.view addSubview:self.counterOneText]; [self.view addSubview:self.counterTwoText]; [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. } -(IBAction)back:(id)sender{ [self dismissViewControllerAnimated:YES completion:nil]; }

Answer 2

不是@selector(receiveNotification)，应为@selector(receiveNotification:)

文本字段未在NSNotification中更新

2 个答案: