的NSTimer無法正常暫停和恢復

Question

我有一個NSTimer，我停下來，分別與下面的方法恢復：

-(void) pauseTimer:(NSTimer *)timer { 
    self.scene.paused = YES; 

    pauseStart = [NSDate date]; 

    previousFireDate = [timer fireDate]; 

    [timer setFireDate:[NSDate distantFuture]]; 
} 

-(void) resumeTimer:(NSTimer *)timer { 
    self.scene.paused = NO; 
    NSDate *currentDate = [NSDate date]; 
    NSTimeInterval pauseTime = [currentDate timeIntervalSinceDate:pauseStart]; 
    NSDate *neededFireDate = [NSDate dateWithTimeInterval:pauseTime sinceDate:previousFireDate]; 
    [timer setFireDate:neededFireDate]; 
    NSLog(@"Fire Date: %@", timer.fireDate); //returning null 
} 

它不能正常復位火日期，因爲當我檢查timer.fireDate，它說null 。我們只需要這些方法來暫停計時器，並在繼續方法被調用時恢復停止的計時器。任何幫助是極大的讚賞。

Answer 1

我的解決方案與您的主要不同。恢復時重新創建一個計時器。下面是我如何做，它一直工作得很好：

@property (nonatomic, strong) NSTimer *timer; 
@property (nonatomic, assign) NSTimeInterval elapsedTime; 
@property (nonatomic, strong) NSDate *startDate; 

- (void)startTimer 
{ 
    NSTimeInterval timeInterval = 20.0f; 

    // Create a timer. Adjust the elapsed time. 
    _timer = [NSTimer scheduledTimerWithTimeInterval:(timeInterval - _elapsedTime) 
               target:self 
              selector:@selector(timerFireMethod:) 
              userInfo:nil 
              repeats:YES]; 
    // Save the start date. 
    _startDate = [NSDate date]; 
} 


- (void)timerFireMethod:(NSTimer *)theTimer 
{ 
    // Clean. 
    [_timer invalidate]; 
    _timer = nil; 
    _elapsedTime = 0.0; 

    [self startTimer]; 

    // Additional handling. 
} 


- (void)pauseTimer 
{ 
    // Clean. 
    [_timer invalidate]; 
    _timer = nil; 

    // Save the elapsed time. 
    _elapsedTime = [[NSDate date] timeIntervalSinceDate:_startDate]; 
} 

希望它有幫助。