Question

我想更改label.text但是当我执行此操作并使用NSLog进行检查时，它会返回(null)。

这是我的代码：

NextViewController.h

    @interface NextViewController (){
    NSTimer *timerTen;
    NSInteger countDown;
    NSString *timer;
}

@end

@implementation NextViewController
static UILabel *lblTest;
- (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.

}

-(void)startCountDown{
    countDown = 10;
    timerTen = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(dismissView) userInfo:nil repeats:YES];
}
-(void)dismissView{
    timer = [NSString stringWithFormat:@"%ld", (long)countDown];
    _lbl_countDown.text = timer;
    NSLog(@"\nCountDown: %@\n", self.lbl_countDown.text);
    countDown--;
    if (countDown <= 0) {
        SectionViewController *sectionView = [[SectionViewController alloc] init];
        [sectionView.presentedViewController dismissViewControllerAnimated:YES completion:nil];
    }
}

然后我有一个标签和更多东西的XIB文件，所以我在.h中使用了一个道具来改变其他类，但是我无法改变它。

NextViewController.h

    #import <UIKit/UIKit.h>

@interface NextViewController : UIViewController
@property (strong, nonatomic) IBOutlet UILabel *lbl_section;
@property (strong, nonatomic) IBOutlet UILabel *lbl_nextSection;
@property (strong, nonatomic) IBOutlet UILabel *lbl_countDown;

-(void)startCountDown;
@end

希望有人能帮助我，因为我不知道这里发生了什么。

感谢。

Answer 1

在ViewDidLoad或ViewWillAppear

中调用您的方法

- (void)viewDidLoad
{

    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.

     [self startCountDown]
}

或

- (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; [self startCountDown] }

Answer 2

尝试使用[self startCountDown]方法

中的ViewDidLoad首先调用该函数

如果问题仍然存在：

尝试使用此功能：[_lbl_count setText@"myText"];
在Identity Inspector中，点击标签取消选中＆＃39;静态文字＆＃39; ，然后选中＆＃39;已启用＆＃39; 和＆＃39;用户互动已启用＆＃39;
最后检查初始化后变量timer是否为空。

timer = [NSString stringWithFormat:@"%ld", (long)countDown];

希望这将有所帮助

Answer 3

我写了这段代码，用一个按钮来开始倒计时从10到segue：

在我的h：

@property (strong, nonatomic) IBOutlet UILabel *countdownCounter;
@property (strong, nonatomic) IBOutlet UIButton *countdownStarter;

在我的m：

static NSTimer *timer;
static int remainingCounts;
.
.
-(void)countDown 
{
  if (--remainingCounts == 0)
  {
    [timer invalidate];
     timer = nil;
    [self performSegueWithIdentifier:@"FromStartToBalancer" sender:self];
  }
  else
  {
    NSString * holdText = [NSString stringWithFormat:@"%d", remainingCounts];
    [self.countdownCounter setText:holdText];
  }
}

- (IBAction)goToBalancerPressed:(UIButton *)sender
{
  self.countdownStarter.userInteractionEnabled = NO;
  self.countdownStarter.alpha = .3;
  remainingCounts = 10;
  timer = [NSTimer scheduledTimerWithTimeInterval:1
                                         target:self
                                       selector:@selector(countDown)
                                       userInfo:nil
                                        repeats:YES];  
}

无法更改label.text并且不知道为什么

3 个答案: