Implementing a Countdown Timer in Objective-c?

Question

I am new to iOS programming. I am working on words matching game. In this game I need to implement time counter which shows minutes and seconds. I want when my game is started my timer to start with 3 minutes. Now I want to decrease this timer in reverse direction with seconds. my code just work for seconds..here is my code:

  secondsLeft--;

  int seconds = (secondsLeft %3600) % 60;

  Timerlbl.text = [NSString stringWithFormat:@"%02d",seconds];


  if (seconds==0)

{


 UIAlertView *pAlert = [[UIAlertView alloc]initWithTitle:@"Sorry!!"   
 message:@"TimeOver"        delegate:self    cancelButtonTitle:@"OK"   
 otherButtonTitles:@"Cancel",nil];

 [pAlert show];

[pAlert release];

 }

 }

In Viewdidload i call it through timer..

          countDown=[NSTimer scheduledTimerWithTimeInterval:5.0 target:self 
                 selector:@selector(TimeOver) userInfo:nil repeats:YES];

pleas any one guide me how can i do it in both minutes and seconds.

Answer 1

You can do it like this(ARC Enabled):-

@interface ViewController()
{
UILabel *progress;
    NSTimer *timer;
    int currMinute;
    int currSeconds;
}
@end


@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];
    progress=[[UILabel alloc] initWithFrame:CGRectMake(80, 15, 100, 50)];
    progress.textColor=[UIColor redColor];
    [progress setText:@"Time : 3:00"];
    progress.backgroundColor=[UIColor clearColor];
    [self.view addSubview:progress];
    currMinute=3;
    currSeconds=00;

    // Do any additional setup after loading the view, typically from a nib.
}
-(void)start
{
    timer=[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerFired) userInfo:nil repeats:YES];

}
-(void)timerFired
{
if((currMinute>0 || currSeconds>=0) && currMinute>=0)
{
    if(currSeconds==0)
    {
        currMinute-=1;
        currSeconds=59;
    }
    else if(currSeconds>0)
    {
        currSeconds-=1;
    }
    if(currMinute>-1)
    [progress setText:[NSString stringWithFormat:@"%@%d%@%02d",@"Time : ",currMinute,@":",currSeconds]];
}
    else
    {
        [timer invalidate];
    }
}

Answer 2

I know this is old question, but I want to share my way to achieve this. We have method (timeIntervalSinceDate:) to calculate the interval and have fixed amount of seconds to count down. In my case 300 s.

UPDATE JULY, 2015 SWIFT

@IBAction func startTimer(sender: UIButton) {
    sender.selected = !sender.selected;
    //if selected fire timer, otherwise stop
    if (sender.selected) {
        self.timer = NSTimer.scheduledTimerWithTimeInterval(0.1, target: self, selector: Selector("updateTimer"), userInfo: nil, repeats: true);
        self.startDate = NSDate();
    } else {
        self.stopTimer();
    }

}

func stopTimer() {
    self.timer.invalidate();
}

func updateTimer() {
    // Create date from the elapsed time
    var currentDate:NSDate = NSDate();
    var timeInterval:NSTimeInterval = currentDate.timeIntervalSinceDate(self.startDate!);

    //300 seconds count down
    var timeIntervalCountDown = 300 - timeInterval;
    var timerDate:NSDate = NSDate(timeIntervalSince1970: timeIntervalCountDown);

    // Create a date formatter
    var dateFormatter = NSDateFormatter();
    dateFormatter.dateFormat = "mm:ss";
    dateFormatter.timeZone = NSTimeZone(forSecondsFromGMT: 0);

    // Format the elapsed time and set it to the label
    var timeString = dateFormatter.stringFromDate(timerDate);
    self.timerLabel?.text = timeString;
}

Working github swift sample project

Objective-C

- (void)updateTimer
{
    // Create date from the elapsed time
    NSDate *currentDate = [NSDate date];
    NSTimeInterval timeInterval = [currentDate 
                                   timeIntervalSinceDate:self.startDate];
    NSLog(@"time interval %f",timeInterval);

    //300 seconds count down
    NSTimeInterval timeIntervalCountDown = 300 - timeInterval;

    NSDate *timerDate = [NSDate 
                         dateWithTimeIntervalSince1970:timeIntervalCountDown];

    // Create a date formatter
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"mm:ss"];
    [dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0.0]];


    // Format the elapsed time and set it to the label
    NSString *timeString = [dateFormatter stringFromDate:timerDate];
    self.stopWatch.text = timeString;
}

- (void)stopTimer
{
    [self.stopWatchTimer invalidate];
    self.stopWatchTimer = nil;
    [self updateTimer];

}

- (void)startTimer
{

    if (self.stopWatchTimer) {
        [self.stopWatchTimer invalidate];
        self.stopWatchTimer = nil;
    }

    self.startDate = [NSDate date];    

    // Create the stop watch timer that fires every 100 ms
    self.stopWatchTimer = [NSTimer scheduledTimerWithTimeInterval:1.0/10.0
                                           target:self
                                         selector:@selector(updateTimer)
                                         userInfo:nil
                                          repeats:YES];
}

UPDATE:

it is extremely expensive to create a NSDateFormatter each time you pass through updateTimer. Far better to create the NSDateFormatter outside the loop and reuse it. Credits: @siburb

Answer 3

In .h file

 IBOutlet UILabel* lblTimer;
 NSTimer* gameTimer;

In .m file

-(void)viewDidLoad 
{
    [super viewDidLoad];
    [self createTimer];
}

- (void)createTimer 
{       
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
     NSRunLoop* runLoop = [NSRunLoop currentRunLoop];

   gameTimer = [[NSTimer timerWithTimeInterval:1.00 target:self selector:@selector(timerFired:) userInfo:nil repeats:YES] retain];
   [[NSRunLoop currentRunLoop] addTimer:gameTimer forMode:NSDefaultRunLoopMode];
   timeCount = 20; 
   [runLoop run];
   [pool release];
}

- (void)timerFired:(NSTimer *)timer 
{
    if(timeCount == 0)
    {
         [self timerExpired];
    } 
    else 
    {
         timeCount--;
        if(timeCount == 0) {
        [timer invalidate];
        [self timerExpired];
    }
 }
   lblTimer.text = [NSString stringWithFormat:@"%02d:%02d",timeCount/60, timeCount % 60];
   self.title = lblTimer.text;
}

Bind the above Label Outlet with Label in View.

It is working correctly with Me

Answer 4

Simple and less code in Objective-C,

in .h file create objects for Timer and totalSeconds

 NSTimer *timer;
 int totalSeconds;

.m file
//you can call this method where you want 
[self startTimer];

-(void)startOtpTimer {
     totalSeconds = 120;//your time 
     timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self 
     selector:@selector(updateCountDownTime) userInfo:nil repeats:YES];
 }

-(void)updateCountDownTime {
    [self populateLabelwithTime:totalSeconds];
        if( totalSeconds != 0) {
            totalSeconds -= 1;
        } else {
              [timer invalidate];//stop timer
              self.timeLabel.text = @"";//after reach 0 you can set empty string
         }
}

- (void)populateLabelwithTime:(int)seconds {
    self.timeLabel.text = [NSString stringWithFormat:@"%02d", totalSeconds];
}

Answer 5

OBJECTIVE-C

Here what we are going to achieve is a reverse countdown timer with circular progress.

We need to follow some steps to achieve the above result in Objective-C.

A. Create XIB Files.

B. Design the layout

C. Configure the circular progress with this library. MBCircularProgressBarView

D. Populate XIB in the UIViewController.

==============================================================

A. Create XIB Files:

• Go to Project Navigation and by right click, you will get the options to create a new file -> Cocoa Touch Class -> write Class Name: ProgressDelayView

You will get the .h & .m file named ProgressDelayView

Now we will create a User Interface for the class files.

This time you will get the .xib file named ProgressDelayView

Now, Assign the class name to the Interface file

B. Design the layout

Now design the layout according to your requirement. I have designed based on mine.

C. Configure the circular progress with this library. MBCircularProgressBarView

Assign the attribute properties based on your app theme. please check out the attributes in a screenshot.

D. Populate XIB in the UIViewController.

Let's move to the code part

Open your viewcontroller.h file

and paste this code.

#import <UIKit/UIKit.h>

@interface viewcontroller : UIViewController

@property (nonatomic) int remainingSeconds;

@end

open viewcontroller.m and paste this

#import "viewcontroller.h"
#import "ProgressDelayView.h"

@interface viewcontroller(){
    ProgressDelayView *TimerTicker;
    NSTimer *timer;
}
@implementation viewcontroller
#pragma mark - Controller Lifecycle
- (void)viewDidLoad {
    [super viewDidLoad];
    TimerTicker = [[[NSBundle mainBundle] loadNibNamed:@"ProgressDelayView" owner:self options:nil] objectAtIndex:0];
}

-(void)viewDidAppear:(BOOL)animated {
    [super viewDidAppear:animated];
    [self populateTimeTicker];
}

-(void)populateTimeTicker {
    TimerTicker.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
    [self showWithAnimation:TimerTicker];
    self.remainingSeconds = 180;
    [self startTicker];
}

-(void)startTicker {
    timer=[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:@selector(timerTicker) userInfo:nil repeats:YES];
}

- (void)timerTicker {
    self.remainingSeconds--;
    if (self.remainingSeconds == -1) {
        //dismiss alertview
        [timer invalidate];
        [TimerTicker removeFromSuperview];
        return;
    }
    [UIView animateWithDuration:1.f animations:^{
        TimerTicker.progress.value = self.remainingSeconds;
    }];
}

-(void)showWithAnimation:(UIView *)customView{
    [UIView animateWithDuration:0.5
                          delay:0.1
                        options: UIViewAnimationOptionCurveEaseIn
                     animations:^{
        customView.frame = CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height);
                     }
                     completion:^(BOOL finished){
                     }];
    [self.view addSubview:customView];
}

==============================================================

Check out these two files ProgressDelayView.h & ProgressDelayView.m

ProgressDelayView.h

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

NS_ASSUME_NONNULL_BEGIN

@interface ProgressDelayView : UIView
@property (weak, nonatomic) IBOutlet MBCircularProgressBarView *progress;

@end

NS_ASSUME_NONNULL_END

ProgressDelayView.m

#import "ProgressDelayView.h"

@implementation ProgressDelayView

@end

HURRAY hit the ⌘R

Answer 6

You can use NSTimer to achieve this.