how to resume timer when poping to view2

问题

my application has 3 views

in view1 only one button (play level 1) that pushes to veiw2 and updates titlelabel in view2

when view2 loads and appears a timer starts to count down and update another label in view2 itself, also view2 has button that pauses the timer and pushes to view3

in view3 only one button that pop back to view2 and resumes thee timer

my problem is that when i pop from view3 to view2 the timer is still paused

any help please?

Thanks & kind regards.

view1.h

#import <UIKit/UIKit.h>

@interface view1 : UIViewController





-(IBAction)nextpage;

@end

view1.m

#import "view1.h"
#import "view2.h"
@interface view1 ()

@end

@implementation view1




-(IBAction)nextpage{

    view2 *obj = [[view2 alloc] init];
    [self.navigationController pushViewController:obj animated:YES];
    [obj.leveltitle setText:@"Level"];
    obj.time=10;  

}




- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [self.navigationController setNavigationBarHidden:YES];
    [super viewDidLoad];
    // Do any additional setup after loading the view from its nib.
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
     return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

view2.h

#import <UIKit/UIKit.h>

@interface view2 : UIViewController



{
    int time;
    NSTimer *timer;
    BOOL paused;
}

@property (nonatomic, retain) NSTimer *timer;
@property (readwrite, nonatomic) int time;
@property (nonatomic) BOOL paused;


@property (readwrite, retain) IBOutlet UILabel *leveltitle;
@property (nonatomic, readwrite) IBOutlet UILabel *label;



-(IBAction)back;
-(IBAction)pause;


@end

view2.m

#import "view2.h"
#import "view3.h"
@interface view2 ()

@end

@implementation view2

@synthesize leveltitle, label;
@synthesize time, timer;
@synthesize paused;

-(void)countDown2
{
    if (paused == NO && time>0) 
 {
        time = time -1 ;
     view3 *obj = [[view3 alloc] init];
     obj.sss = time;
    if (time == 0)
 {
            [timer invalidate];    

 }

        [label setText:[NSString stringWithFormat:@"%i",time]];
 }


}


-(IBAction)back{

    [self.navigationController popViewControllerAnimated:YES];

}


-(IBAction)pause{

     view3 *obj = [[view3 alloc] init];
    [self.navigationController pushViewController:obj animated:YES];
     paused = YES;   
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization
    }
    return self;
}



- (void)viewDidLoad
{
    paused = NO;
    timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self     selector:@selector(countDown2) userInfo:nil repeats:YES];



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

- (void)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:    (UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

view3.h

#import <UIKit/UIKit.h>

@interface view3 : UIViewController

{

    int sss;
}

@property (nonatomic) int sss;
-(IBAction)back;


@end

view3.m

#import "view3.h"
#import "view2.h"
@interface view3 ()

@end

@implementation view3
@synthesize sss;

-(IBAction)back{

    view2 *obj = [[view2 alloc] init];
    obj.paused=NO;
    obj.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self     selector:@selector(cont) userInfo:nil repeats:YES];
     //[obj.timer fire];
    [self.navigationController popViewControllerAnimated:YES];

}



 -(void)cont{
     view2 *obj = [[view2 alloc] init];
     obj.time = sss;
     if (obj.paused == NO && time>0) 
     {
         obj.time = obj.time -1 ;

         if (obj.time == 0)
         {
             [obj.timer invalidate];    

         }

         [obj.label setText:[NSString stringWithFormat:@"%i",obj.time]];
     }



 }


- (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)viewDidUnload
{
    [super viewDidUnload];
    // Release any retained subviews of the main view.
    // e.g. self.myOutlet = nil;
}

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
    return (interfaceOrientation == UIInterfaceOrientationPortrait);
}

@end

回答1:

It is because in view3's back method, you created a new instant of view2 name obj and set paused=NO. But that obj was not the same instant of view2 when you pop back. What you need to do is to use a delegate method pattern, so that view3 will have a callback method in view2 to set the paused to NO.

For an example of delegate method pattern, check out an example from this SO.

Edit: sample callback code:

Make these addition/changes to your code:

In view2.h:

#import "view3.h"

@interface view2 : UIViewController <view3Delegate>

In view2.m:

-(IBAction)pause{

    view3 *obj = [[view3 alloc] init];
    obj.delegate = self;  //adding this line
    [self.navigationController pushViewController:obj animated:YES];
    paused = YES;   
}

-(void)setPausedValue:(BOOL)value   //this is the new method callback from view3 to set paused value
{
    paused = value;
}

In view3.h:

#import <UIKit/UIKit.h>
@protocol view3Delegate <NSObject>
-(void) setPausedValue:(BOOL)value;
@end
@interface view3 : UIViewController
{
    int sss;
}
@property (assign) id <view3Delegate> delegate;
@property (nonatomic) int sss;
-(IBAction)back;
@end

In view3.m:

@implementation view3
@synthesize delegate;

-(IBAction)back{

//    view2 *obj = [[view2 alloc] init];  
//    obj.paused=NO;
    [self.delegate setPausedValue:NO];  //make callback and set value
    obj.timer = [NSTimer scheduledTimerWithTimeInterval:1 target:self     selector:@selector(cont) userInfo:nil repeats:YES];
    //[obj.timer fire];
    [self.navigationController popViewControllerAnimated:YES];

}

来源：https://stackoverflow.com/questions/11377133/how-to-resume-timer-when-poping-to-view2