CODEWITHSUNDEEP
objective-ciosios5uikit
Sri Kadimisetty
Sri Kadimisetty

Reputation: 1982

How to update UILabel

I have a UILabel that I would like to update. It has been added to the class by ctrl-cicking and adding through the XIB file. Im trying to update the label text after waiting for a short delay. As of now, there is nothing else going on except for the code below. Howver when I run this, the simulator blanks out for a moment and takes me straight to the last updated text. It doesnt show me the 100 just the 200.

How do I get the label to update like I want it to. Ultimately Im trying to have a timer of sorts decrement inside the label.

Label linked from the XIB to header file:

@property (strong, nonatomic) IBOutlet UILabel *timeRemainingLabel;

In Implmentation:

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.timeRemainingLabel.text = @"100";
    sleep(1);
    self.timeRemainingLabel.text = @"200";    
}

Upvotes: 2

Views: 887

Answers (3)

saadnib
saadnib

Reputation: 11145

It will never show you 100 like this because you are using sleep here which is stopping the execution of your program and just after 1 sec of sleep you are updating the text. If you want to do this then you can use an NSTimer for this.

Change your above code like this:

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.timeRemainingLabel.text = @"100";

    [NSTimer scheduledTimerWithTimeInterval:2.0 target:self selector:@selector(updateLabel) userInfo:nil repeats:NO];

}

- (void) updateLabel
{
    self.timeRemainingLabel.text = @"200"; 
}

Upvotes: 3

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726987

The problem with your implementation is that the execution sequence does not leave the method while in the sleep. This is the problem, because the UI subsystem never gets a chance to update the label to the "100" value before it gets a command to set it to "200".

To do this correctly, first you need to create a timer in your init method, like this:

timer = [NSTimer scheduledTimerWithTimeInterval: 1.0 target:self selector:@selector(updateLabel) userInfo:nil repeats: YES];

Then you need to write the code for your updateLabel method:

-(void) updateLabel {
    NSInteger next = [timeRemainingLabel.text integerValue]-1;
    timeRemainingLabel.text = [NSString stringWithFormat:@"%d", next];
}

Upvotes: 3

tipycalFlow
tipycalFlow

Reputation: 7644

Your view doesn't appear till the view hasn't loaded and the text of the label timeRemainingLabel is @"200" when that happens. So you do not see the text changing. Use an NSTimer to do this instead and assign the text to the label in the selector:

timer = [NSTimer scheduledTimerWithTimeInterval:timeInSeconds target:self selector:@selector(updateText) userInfo:nil repeats: YES/NO];

and in your update method, set the latest text as per your requirement:

-(void) updateText {
    self.timeRemainingLabel.text = latestTextForLabel;
}

Upvotes: 1

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