Question

我正在开发一个iOS应用程序，其中一个屏幕应该显示当前的用户名和时间但我遇到了麻烦，试图将该信息分配到NSStrings：当我运行应用程序时，标签显示（null）消息。

这是我的代码：

About.h

@interface About : UIViewController

@property (weak) IBOutlet UILabel * username;
@property (weak) IBOutlet UILabel * date;

@property (strong, nonatomic) NSString * usuari;
@property (strong, nonatomic) NSString * data;
@property (strong, nonatomic) NSString * name;
@property (strong, nonatomic) NSString * currentTime;


@end

About.m

#import "About.h"

@interface About()
@end

@implementation About

- (void)viewDidLoad
{
    [super viewDidLoad];

    UILabel * username = [[UILabel alloc] initWithFrame:CGRectMake(162, 106, 150, 72)];
    [self.view addSubview: username];
    username.numberOfLines = 4;
    username.textColor = [UIColor blackColor];
    username.text = [NSString stringWithFormat:@"Usuari: %@", _usuari];

    UILabel * date = [[UILabel alloc] initWithFrame:CGRectMake(160, 261, 1488, 44)];
    [self.view addSubview: date];
    date.numberOfLines = 4;
    date.textColor = [UIColor blackColor];
    date.text = [NSString stringWithFormat:@"Hora: %@", _currentTime];

}

-(void) gettingUser
{
    [[UIDevice currentDevice] name];
   _username.text = [NSString stringWithFormat:@"Usuari: %@", _name];
}

-(void) gettingTime
{
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateStyle:NSDateFormatterMediumStyle];
    [dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
    [dateFormatter setTimeZone:[NSTimeZone localTimeZone]];
    NSString *currentTime = [dateFormatter stringFromDate:[NSDate date]];

    _date.text = [NSString stringWithFormat:@"Hora: %@", _currentTime];
    //self.date.text = [NSDate date];

    //NSTimer schedule interval
    //NSDateFormatter alloc
}


@end

你可以帮我解决这个问题吗？

Answer 1

使用＆＃34; self.＆＃34;在引用对象的属性而不是属性的基础ivars时。

E.G。改变这样的一行：

_username.text = [NSString stringWithFormat:@"Usuari: %@", _name];

到

self.username.text = [NSString stringWithFormat:@"Usuari: %@", self.name];

Answer 2

您似乎无法在任何地方呼叫[self gettingUser];或[self gettingTime];。您应该在设置文本字段后调用这些方法，正如Michael所说，在访问您的属性时使用self.name而不是_name等

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.username = [[UILabel alloc] initWithFrame:CGRectMake(162, 106, 150, 72)];
    [self.view addSubview: self.username];
    self.username.numberOfLines = 4;
    self.username.textColor = [UIColor blackColor];
    [self gettingUser];

    self.date = [[UILabel alloc] initWithFrame:CGRectMake(160, 261, 1488, 44)];
    [self.view addSubview: self.date];
    self.date.numberOfLines = 4;
    self.date.textColor = [UIColor blackColor];
    [self gettingTime];

}

-(void) gettingUser
{
    self.name=[[UIDevice currentDevice] name];
    self.username.text = [NSString stringWithFormat:@"Usuari: %@", self.name];
}

-(void) gettingTime
{
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateStyle:NSDateFormatterMediumStyle];
    [dateFormatter setTimeStyle:NSDateFormatterMediumStyle];
    [dateFormatter setTimeZone:[NSTimeZone localTimeZone]];
    self.currentTime = [dateFormatter stringFromDate:[NSDate date]];

    self.date.text = [NSString stringWithFormat:@"Hora: %@", self.currentTime];
}

Answer 3

问题是在你的方法viewDidLoad中，你声明并使用了两个名为userName和date的局部变量。当viewDidLoad完成后，这两个局部变量将永远消失。

您应该使用实例变量_userName和_date，或者更好地使用属性self.userName和self.date。

iOS获取用户名和当前时间

3 个答案: