How to stop NSTimer

问题

Hey so i am just making an example application and i am having a little trouble, So i have a table view and then i have a few rows and when a user clicks a row it takes them to a new view. On this view i have a button to play music. I am using a timer to make a slider bar increase based on music duration and remaining time.

Now my problem is, what do i have to put so that when i go back to the table view via the top left button, that the NSTimer stops?

this is what i have so far, i cannot get a repeat: YES timer to stop.

#import "SecondViewController.h"

@implementation SecondViewController
@synthesize lbl1;
@synthesize timer;

-(IBAction) slide {
 myMusic.currentTime = slider.value;
}

-(IBAction)play
{
timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:@selector(updateTime) userInfo:nil repeats:YES];
 slider.maximumValue = [myMusic duration];
 myMusic.volume = 0.2;
 [myMusic prepareToPlay];
 [myMusic play];
}

-(IBAction)pause
{
 [myMusic pause];
}

-(IBAction)stop
{
 slider.value = 0;
 myMusic.currentTime = 0;
 [myMusic stop];
}

- (void)updateTime{
  slider.value = myMusic.currentTime;
}

// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad {

  //This plays music, we must give it a path to find the file and then u can change it. 
 NSString * pathToMusicFile = [[NSBundle mainBundle] pathForResource:@"Katy" ofType:@"mp3"];
     myMusic = [[ AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:pathToMusicFile] error:NULL];
     myMusic.delegate = self;
     myMusic.numberOfLoops = -1;

 slider.value = 0;
 //[myMusic play];

    [super viewDidLoad];
}


- (void)viewDidUnload {

 [timer invalidate];
 timer = nil;
 //myMusic.currentTime = 0;
 [myMusic stop];
 [super viewDidUnload];

 // Release any retained subviews of the main view.
 // e.g. self.myOutlet = nil;
}

-(IBAction) TxtChange;{

 lbl1.text = @" test2! I CHNAGED TEXT FROM ANOTHER XIB";
}

- (void)dealloc {
 [timer invalidate];
 timer = nil; 
 [myMusic release];
    [super dealloc];
}

@end

回答1:

Use the below code. It will work But keep in mind that it must only be called if our timer is in running mode else the application will get crashed.

- (void)viewWillDisappear:(BOOL)animated {
    //BEFORE DOING SO CHECK THAT TIMER MUST NOT BE ALREADY INVALIDATED
    //Always nil your timer after invalidating so that 
    //it does not cause crash due to duplicate invalidate
       if(timer)
       {
         [timer invalidate];
         timer = nil;
       }
    [super viewWillDisappear:animated];
}

回答2:

like this:

[yourtimername invalidate];

But be careful, you cant stop the timer if it's already stopped because your app will crash.

回答3:

As iCoder says it has to be invalidated in viewWillDisappear.

I added the following just to make sure. it works for me. Hope it helps (and adds to icoders answer do not intent to copy)

- (void) startTimer
{
[self stopTimer];
timer = [NSTimer scheduledTimerWithTimeInterval: 5.0
                                                     target: self
                                                   selector:@selector(onTick)
                                                   userInfo: nil repeats:YES];

}

- (void) stopTimer
{
    if (timer) {
        [timer invalidate];
        timer = nil;
    }

}

回答4:

4 year old post, I know but maybe I can save the NEXT guy from wasting time trying invalidate a NSTimer. Apples documentation explains it and it works for me.

in .h

@property(nonatomic, retain) NSTimer *yourTimer;
@property(weak) NSTimer *repeatingTimer;

in .m

@synthesize yourTimer, repeatingTimer;

in viewDidLoad

yourTimer = [NSTimer scheduledTimerWithTimeInterval:(NSTimerInterval)(40.0/60.0)
                                             target:self
                                           selector:@selector(blink)
                                           userInfo:nil
                                            repeats:TRUE];

  self.repeatingTimer = yourTimer;

in my viewDidDisappear

   [repeatingTimer invalidate];
   repeatingTimer = nil;

the trick is in the assignment of the first NSTimer to (weak) NStimer object and killing THAT object.

回答5:

You Could Use Two Different Things

    [timername invalidate];

Or You Could Use

    timername = nil;

回答6:

Trick is to use a singleton class, google myGlobals class which is mostly used as a singleton Although if u do wish to use NSTimer, then

lets say the view 1 is which u go into and view 2 is the one which u go back 2.

So in case of view 2, write the NSTimer to invalidate the timer in the viewDidLoad(Assuming you have two separate classes for both views).Problem will occur because when u go to view 1, the view 2 Timers will be dealloc. So, make a Singleton class and save the NSTimer pointer like this

//to be done in viewDidLoad function
theGlobals *globals = [theGlobals alloc] init];// for the singleton class to initiate,
[globals.myTimer invalidate];


//to be done in viewDidUnload
theGlobals *globals = [theGlobals alloc] init];// for the singleton class to initiate,
globals.myTimer = [NSTimer scheduledTimerWithTimeInterval: 5.0
                                                 target: self
                                               selector:@selector(onTick)
                                               userInfo: nil repeats:YES];

oh , and here is the myGlobals class code that u will need

//theglobals.h file

#import <Foundation/Foundation.h>


@interface theGlobals : NSObject 
{
    NSTimer *myTimer;
}

@property (nonatomic, copy) NSString *changeyes;



+(theGlobals*)sharedInstance;
@end

//implementaton .m file

#import "theGlobals.h"
@implementation theGlobals

@synthesize myTimer;



static theGlobals *sharedInstance;

- (id) init
{
return self;
}

+(theGlobals*)sharedInstance
{
if (!sharedInstance)
{
    sharedInstance = [[theGlobals alloc] init];
}
return sharedInstance;
}
@end

回答7:

Just invalidate the timer

[timer invalidate];

来源：https://stackoverflow.com/questions/3509012/how-to-stop-nstimer