尝试获取距用户位置的距离以固定在地图上时 mkmap 崩溃

Question

由于某种原因，每当我点击我的图钉时，应用程序就会崩溃。我的代码中没有错误或警告。仅当我尝试获取从 userLocation 到 pin 的距离时才会发生这种情况。发现我的错误了吗？

@implementation FirstViewController
// Implement viewDidLoad to do additional setup after loading the view, typically from a nib.
- (void)viewDidLoad
{   
mapView.showsUserLocation = YES;

[super viewDidLoad];
}
-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)userLocation   { 

[self showPin];
[self updateLocation];
}
-(IBAction) updateLocation{
mapView.showsUserLocation = YES;
}
 - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
// Return YES for supported orientations
return (interfaceOrientation == UIInterfaceOrientationPortrait);
}  


- (void)didReceiveMemoryWarning
{
// Releases the view if it doesn't have a superview.
[super didReceiveMemoryWarning];

// Release any cached data, images, etc. that aren't in use.
}


- (void)viewDidUnload
{
[super viewDidUnload];

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


-(IBAction)setMap:(id)sender{
switch(((UISegmentedControl *)sender).selectedSegmentIndex){
case 0:
{
    mapView.mapType = MKMapTypeStandard;
     break;
}
case 1:
{
    mapView.mapType = MKMapTypeSatellite;
    break;
}
case 2:
{
mapView.mapType = MKMapTypeHybrid;
break;
}

}}
- (void)dealloc
{
[super dealloc];
}
- (MKAnnotationView *)mapView:(MKMapView *)mv viewForAnnotation:(id <MKAnnotation>)annotation {
MKPinAnnotationView *pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:@"pinView"];
if (!pinView) {
    pinView = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"pinView"] autorelease];
    pinView.pinColor = MKPinAnnotationColorRed;
    pinView.animatesDrop = YES;
    pinView.canShowCallout = YES;


    UIButton *rightButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
    pinView.rightCalloutAccessoryView = rightButton;
} else {
    pinView.annotation = annotation;
}
if (annotation == mapView.userLocation){
    return nil; //default to blue dot
}
return pinView;
}
-(IBAction) showPin{
//MOST CODE WILL BE INSERTED HERE!
//instructions

CLLocation *usersLocation = [[CLLocation alloc]initWithLatitude:mapView.userLocation.coordinate.latitude longitude:mapView.userLocation.coordinate.longitude];
MKCoordinateRegion region;
MKCoordinateSpan span;
span.latitudeDelta=0.2;
span.longitudeDelta=0.2;
//ignore above
//always declare location as companyCity 
//if more than one in one city then add a number i.e. companyCity2
//chili in mobile alabama
CLLocationCoordinate2D chiliAuburn = mapView.userLocation.coordinate;

chiliAuburn.latitude = 32.606434 ;
chiliAuburn.longitude = -85.484025;
region.span=span;
region.center=chiliAuburn;
CLLocation *chiliAuburnLocation = [[CLLocation alloc] initWithLatitude:chiliAuburn.latitude longitude:chiliAuburn.longitude];
if(chiliAuburnAlabama != nil) {
    [mapView removeAnnotation:chiliAuburnAlabama];
    [chiliAuburnAlabama release];
    chiliAuburnAlabama = nil;
}

chiliAuburnAlabama = [[AddressAnnotation alloc] initWithCoordinate:chiliAuburn];
[chiliAuburnAlabama setTitle:@"Chili Yogurt Café"];
double distanceMiles = ([usersLocation distanceFromLocation:chiliAuburnLocation]/1609.334);
[chiliAuburnAlabama setSubTitle:[NSString stringWithFormat:@"%.2fm", distanceMiles]];
//[chiliAuburnAlabama setSubTitle:@"TEST"];
[mapView addAnnotation:chiliAuburnAlabama];
[chiliAuburnAlabama release];
//tutti frutti homewood alabama
CLLocationCoordinate2D tuttifruttiHomewood = mapView.userLocation.coordinate;

tuttifruttiHomewood.latitude = 33.479775 ;
tuttifruttiHomewood.longitude = -86.790977;
region.span=span;
region.center=tuttifruttiHomewood;

if(tuttifruttiHomewoodAlabama != nil) {
    [mapView removeAnnotation:tuttifruttiHomewoodAlabama];
    [tuttifruttiHomewoodAlabama release];
    tuttifruttiHomewoodAlabama = nil;
}

tuttifruttiHomewoodAlabama = [[AddressAnnotation alloc] initWithCoordinate:tuttifruttiHomewood];
[tuttifruttiHomewoodAlabama setTitle:@"Tutti Frutti"];
[tuttifruttiHomewoodAlabama setSubTitle:@"YOUR RATING HERE"];
[mapView addAnnotation:tuttifruttiHomewoodAlabama];


//ignore below
[mapView setRegion:region animated:TRUE];
[mapView regionThatFits:region];

}
- (void)mapView:(MKMapView *)mv didAddAnnotationViews:(NSArray *)views {
for(MKAnnotationView *annotationView in views) {
    if(annotationView.annotation == mv.userLocation) {
        MKCoordinateRegion region;
        MKCoordinateSpan span;

        span.latitudeDelta=0.1;
        span.longitudeDelta=0.1; 

        CLLocationCoordinate2D location=mv.userLocation.coordinate;

        region.span=span;
        region.center=location;

        [mv setRegion:region animated:TRUE];
        [mv regionThatFits:region];
    }

}
}



@end

GNU gdb 6.3.50-20050815（Apple 版本 gdb-1518）（UTC 2011 年 2 月 12 日星期六 02:52:12） 版权所有 2004 自由软件基金会，Inc. GDB 是免费软件，受 GNU 通用公共许可证保护，您可以 欢迎在某些条件下对其进行更改和/或分发其副本。 输入“显示复制”以查看条件。 GDB 绝对没有任何保证。输入“显示保修”以了解详细信息。 该 GDB 被配置为“x86_64-apple-darwin”。附加到进程 23386。 2011-06-02 00:39:46.146 YogurtStoreLocator[23386:207] 32.606434，-85.484025 2011-06-02 00:39:46.148 YogurtStoreLocator[23386:207] 33.479775，-86.790977 2011-06-02 00:39:53.121 YogurtStoreLocator[23386:207] -[NSCFNumber stringByStandardizingWhitespace]：无法识别的选择器发送到实例 0x587b2d0 2011-06-02 00:39:53.123 YogurtStoreLocator[23386:207] * 由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“-[NSCFNumber stringByStandardizingWhitespace]：无法识别的选择器发送到实例 0x587b2d0” *第一次抛出时的调用堆栈： （ 0 CoreFoundation 0x00fca5a9 异常预处理 + 185 1 libobjc.A.dylib 0x0111e313 objc_异常_抛出 + 44 2 CoreFoundation 0x00fcc0bb -[NSObject(NSObject) doesNotRecognizeSelector:] + 187 3 CoreFoundation 0x00f3b966 __转发 + 966 4 核心基础 0x00f3b522 _CF_forwarding_prep_0 + 50 5 UIKit 0x0034c340 -[UICalloutView setSubtitle：动画：] + 88 6 UIKit 0x0034c010 -[UICalloutView setSubtitle:] + 49 7 MapKit 0x000bb0ac -[MKAnnotationContainerView _showBubbleForAnnotationView:bounce:scrollToFit:userInitiated:avoid:] + 537 8 MapKit 0x000bc3ed -[MKAnnotationContainerView _setSelectedAnnotationView:bounce:pressed:scrollToFit:userInitiated:avoid:] + 653 9 MapKit 0x000b54bc -[MKAnnotationContainerView _setSelectedAnnotationView:bounce:pressed:scrollToFit:userInitiated:] + 144 10 MapKit 0x0008cab3 -[MKMapView 句柄Tap:] + 459 11 UIKit 0x004ad4f2-[UIGestureRecognizer_updateGestureWithEvent:] + 730 12 UIKit 0x004a94fe -[UIGestureRecognizer _delayedUpdateGesture] + 47 13 UIKit 0x004afafc_UIGestureRecognizerUpdateObserver + 584 14 CoreFoundation 0x00fab89b CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 27 15 核心基础 0x00f406e7 __CFRunLoopDoObservers + 295 16 核心基础 0x00f091d7 __CFRunLoopRun + 1575 17 核心基础 0x00f08840 CFRunLoopRunSpecific + 208 18 核心基础 0x00f08761 CFRunLoopRunInMode + 97 19 图形服务 0x01f071c4 GSEventRunModal + 217 20 图形服务 0x01f07289 GSEventRun + 115 21 UIKit 0x0022ac93 UIApplicationMain + 1160 22 酸奶店定位器 0x00002099 主 + 121 23 酸奶商店定位器 0x00002015 开始 + 53 ） 抛出“NSException”实例后调用终止 共享库应用加载规则全部 当前语言：自动；目前objective-c （gdb）

Answer 1

仅将 showsUserLocation 设置为 YES 是不够的。地图视图需要获取该数据。这是一个异步过程，数据只会在一段时间后更新。通过 mapView:didUpdateUseLocation: 方法向委托通知此更新。您应该实现该方法，并仅在获得用户位置后才调用 showPin。