给任务之间的时间 - iOS

Question

我从iPhone的GPS获取我的位置位置。我想从同一点获得15次坐标（以获得最佳水平精度）。

有没有办法在一个坐标和另一个坐标之间等待2秒？

我使用一个称为坐标的对象，以纬度和经度为属性。

.... Exemple code 
Coordinate * coord = [[Coordinate alloc] init]; 
NSMutableArray *coordinates = [[NSMutableArray alloc] init]; 

for (i=0 ; i<=14; i++) 
{ 
    coord = newlocation; 
    [coordinates addObject:coord]; 
    .... some code to wait 2 seconds before add a new object to the array.... 
} 

我试图使用NSThread sleepfortimeinterval，但视图冻结。

感谢

Answer 1

不是有for循环这样，理论上可以使用重复NSTimer即每两秒钟发射，然后invalidate计时器后15次迭代。

但我不会建议这样做，而是转而采用事件驱动模式，等待拨打didUpdateLocations。如果didUpdateLocations尚未更新，则在两秒内检查没有意义。同样，在30秒内重复检查15次也没有意义，例如，5秒后您是否获得了非常准确的位置。

我建议开始监控的位置，观看的位置，因为他们进来，随后调用didUpdateLocations，并检查CLLocation的horizontalAccuracy（它告诉你位置的精确程度）。一旦你到达期望的horizontalAccuracy，你可以声明成功（例如停止监控位置或其他）。如果您愿意，也可以建立一个NSTimer，在30秒后自动关闭位置监控。

---

例如：

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    NSLog(@"%s", __PRETTY_FUNCTION__); 

    [self startStandardUpdates]; 

    // after 30 seconds, if we haven't found a location, declare success with whatever we got (if anything) 

    dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(30.0 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{ 
     [self stopStandardUpdates]; // stop monitoring location if you want 

     if (!self.foundLocation) { 
      if (self.bestLocation) { 
       NSLog(@"Didn't find perfect location, but location has accuracy of %.1f meters", self.bestLocation.horizontalAccuracy); 
      } else { 
       NSLog(@"Even after 30 seconds, did not find any locations!"); 
      } 
     } 
    }); 
} 

#pragma mark - Location Services 

- (void)startStandardUpdates 
{ 
    // Create the location manager if this object does not 
    // already have one. 
    if (nil == self.locationManager) 
     self.locationManager = [[CLLocationManager alloc] init]; 

    self.locationManager.delegate = self; 
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest; 

    // Set a movement threshold for new events. 
    self.locationManager.distanceFilter = 5; 

    [self.locationManager startUpdatingLocation]; 
} 

- (void)stopStandardUpdates 
{ 
    [self.locationManager stopUpdatingLocation]; 
    self.locationManager = nil; 
} 

#pragma mark - CLLocationManagerDelegate 

- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations 
{ 
    CLLocation* location = [locations lastObject]; 

    NSLog(@"%s: horizontalAccuracy = %.1f", __FUNCTION__, location.horizontalAccuracy); 

    if (location.horizontalAccuracy < 0) // not a valid location 
     return; 

    // this checks to see if the location is more accurate than the last; 
    // or you might just want to eliminate this `if` clause, because if 
    // you get updated location, you can probably assume it's better than 
    // the last one (esp if the user might be moving) 

    if (!self.bestLocation || location.horizontalAccuracy <= self.bestLocation.horizontalAccuracy) { 
     self.bestLocation = location; 
    } 

    if (location.horizontalAccuracy <= 5) { // use whatever you want here 
     NSLog(@"Found location %@", location); 
     self.foundLocation = YES; 
     [self stopStandardUpdates]; // stop it if you want 
    } 
} 

它使用以下属性：

@property (nonatomic, strong) CLLocationManager *locationManager; 
@property (nonatomic, strong) CLLocation *bestLocation; 
@property (nonatomic) BOOL foundLocation;