位置服务，如何在一段时间（30秒）后更新纬度、经度？

Question

我从位置服务获取纬度、经度、海拔高度、精度、速度。

我想每 30 秒更新一次所有这些信息。为此，我使用了 NSTimer：

[NSTimer scheduledTimerWithTimeInterval:30 target:self selector:@selector(locationUpdate:) userInfo:nil repeats:YES];

将其放入 viewDidLoad 方法中。它第一次显示输出，但第二次，当计时器调用它时，它显示此错误：

2011-08-02 13:17:00.141 CoreLocationAssign[1120:207] This is location   <__NSCFTimer: 0x4b200a0>
2011-08-02 13:17:00.142 CoreLocationAssign[1120:207] -[__NSCFTimer coordinate]: unrecognized selector sent to instance 0x4b200a0
2011-08-02 13:17:00.144 CoreLocationAssign[1120:207] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFTimer coordinate]: unrecognized selector sent to instance 0x4b200a0'
*** Call stack at first throw:

代码如下：

MyCLController.h

@implementation MyCLController
@synthesize locationManager;
@synthesize delegate;

- (id) init{
    if (self!=nil) {
        self.locationManager  = [[[CLLocationManager alloc] init] autorelease];
        self.locationManager.delegate = self;
        self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
        self.locationManager.distanceFilter = kCLDistanceFilterNone;
        [self.locationManager startUpdatingLocation];
    }
    return self;
}

- (void)locationManager:(CLLocationManager *)manager
    didUpdateToLocation:(CLLocation *)newLocation
           fromLocation:(CLLocation *)oldLocation
{
    //NSLog(@"Location: %@", [newLocation description]);
    [self.delegate locationUpdate:newLocation];
}

- (void)locationManager:(CLLocationManager *)manager
       didFailWithError:(NSError *)error
{
//  NSLog(@"Error: %@", [error description]);
    [self.delegate locationError:error];
}

- (void)dealloc {
    [self.locationManager release];
    [super dealloc];
}

---

CoreLoactionController.h
- (void)viewDidLoad {
    locationController = [[MyCLController alloc] init];
    locationController.delegate = self;
    [locationController.locationManager startUpdatingLocation];
    [NSTimer scheduledTimerWithTimeInterval:30 target:self selector:@selector(locationUpdate:) userInfo:nil repeats:YES];
    [super viewDidLoad];
}


- (void)locationUpdate:(CLLocation *)location {
    locationLable.text = [location description];
    CLLocationCoordinate2D coordinate = [location coordinate];
    NSLog(@"This is location   %@",[location description]);
    NSLog(@"Lattitude          =   %@",[NSString stringWithFormat:@"%f", coordinate.latitude]);
    NSLog(@"Langitude          =   %@",[NSString stringWithFormat:@"%f", coordinate.longitude]);
    NSLog(@"Altitude           =   %@",[NSString stringWithFormat:@"%gm", location.altitude]);
    NSLog(@"horizontalAccuracy =   %@",[NSString stringWithFormat:@"%gm", location.horizontalAccuracy]);
    NSLog(@"verticalAccuracy   =   %@",[NSString stringWithFormat:@"%gm", location.verticalAccuracy]);
    NSLog(@"Speed   =   %@",[NSString stringWithFormat:@"%gm", location.speed]);

}

我如何解决这个问题？我想每 30 秒更新一次位置。

Answer 1

有比使用计时器更好的解决方案。 CoreLocation 内置了延迟更新功能，并且计时器与普通 CoreLocation 相结合会损坏手机电池。尝试allowDeferredLocationUpdatesUntilDistanceTraveled：超时：

https://developer.apple.com/library/ios/documentation/CoreLocation/Reference/CLLocationManager_Class/CLLocationManager/CLLocationManager.html#//apple_ref/occ/instm/CLLocationManager/allowDeferredLocationUpdatesUntilTraveled:timeout：

Answer 2

事实上在这里：

- (void)locationUpdate:(CLLocation *)location

您收到的不是 CLLocation * 而是 NSTimer。
您应该使用 userInfo 来传输对象：

[NSTimer scheduledTimerWithTimeInterval:30 target:self selector:@selector(locationUpdate:) userInfo:location repeats:YES];

和

-(void)locationUpdate:(NSTimer*) timer{
    //probably
    CLLocation *location = (CLLocation*)[timer userInfo];
    //...
}

Answer 3

基于计时器的位置更新非常耗电。

CoreLocation 可以告诉您位置何时发生变化，无需轮询。如果我正在走路，30 秒就太慢了，而且如果我的手机在床边放置几个小时一动不动，它也会不必要地损坏电池。