ios - 为什么我的注释中有 MKUserLocation？

Question

我想计算用户和所有注释之间的距离。
我的注释来自一个经过解析的 csv 文件。我的注释位于 Location 类中。除了距离计算，一切正常。

为了计算距离，我找到了这段代码:

-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)newLocation
{

    for (Location *annotation in self.mapView.annotations) {
    CLLocationCoordinate2D coord = [annotation coordinate];
    CLLocationCoordinate2D userCoordinate = [[[self.mapView userLocation] location] coordinate];
    CLLocation *myLoc = [[CLLocation alloc] initWithLatitude:coord.latitude longitude:coord.longitude];
    CLLocation *userLoc = [[CLLocation alloc] initWithLatitude:userCoordinate.latitude longitude:userCoordinate.longitude];

     annotation.distance = [myLoc distanceFromLocation:userLoc];


        NSLog(@"Distance is = %f", annotation.distance);
} // ! CRASH !

NSArray *sortedArray;
sortedArray = [self.mapView.annotations sortedArrayUsingComparator:^NSComparisonResult(id a, id b) {
    NSNumber *first = [NSNumber numberWithDouble:[(Location*)a distance]];
    NSNumber *second = [NSNumber numberWithDouble:[(Location*)b distance]];
    return [first compare:second];
}];

但是我的应用程序在循环结束之前崩溃了。我发现，有断点，有一个奇怪的注释(MKUserLocation* 而不是 Location*)；在这个 MKUserLocation* 之后，应用程序崩溃了:

不正常(崩溃):

确定(没有崩溃):

为什么在我的 self.mapView.annotations 中有 MKUserLocation？如何忽略它？

日志:

2014-09-22 06:01:47.965 MyFirstGPS2[472:60b] -[MKUserLocation setDistance:]: unrecognized selector sent to instance 0x9db0bb0
2014-09-22 06:01:48.030 MyFirstGPS2[472:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[MKUserLocation setDistance:]: unrecognized selector sent to instance 0x9db0bb0'
*** First throw call stack:
(
    0   CoreFoundation                      0x01d971e4 __exceptionPreprocess + 180
    1   libobjc.A.dylib                     0x01b168e5 objc_exception_throw + 44
    2   CoreFoundation                      0x01e34243 -[NSObject(NSObject) doesNotRecognizeSelector:] + 275
    3   CoreFoundation                      0x01d8750b ___forwarding___ + 1019
    4   CoreFoundation                      0x01d870ee _CF_forwarding_prep_0 + 14
    5   MyFirstGPS2                         0x00005043 -[HPViewController mapView:didUpdateUserLocation:] + 1203
    6   MapKit                              0x006825e6 -[MKMapView(MKHeadingAdditions) _stopTrackingHeading] + 469
    7   MapKit                              0x00666a92 -[MKMapView _setUserTrackingMode:animated:fromTrackingButton:] + 301
    8   MapKit                              0x00666960 -[MKMapView setUserTrackingMode:animated:] + 56
    9   MapKit                              0x00682176 -[MKMapView(MKHeadingAdditions) disableHeadingTracking:] + 65
    10  MapKit                              0x00669524 -[MKMapView _didChangeRegionMidstream:] + 672
    11  MapKit                              0x00671fbd -[MKMapView mapLayerDidChangeVisibleRegion:] + 66
    12  VectorKit                           0x0407a15e -[VKMapView mapDidChangeVisibleRegion:] + 78
    13  VectorKit                           0x040821fe -[VKMapCanvas cameraControllerDidChangeCameraState:] + 46
    14  VectorKit                           0x0409f1f7 -[VKMapCameraController updatePanWithTranslation:] + 231
    15  VectorKit                           0x0408268f -[VKMapCanvas updatePanWithTranslation:] + 63
    16  VectorKit                           0x0407aca9 -[VKMapView updatePanWithTranslation:] + 73
    17  MapKit                              0x0069e30b -[MKMapGestureController handlePan:] + 530
    18  UIKit                               0x00b724f4 _UIGestureRecognizerSendActions + 230
    19  UIKit                               0x00b71168 -[UIGestureRecognizer _updateGestureWithEvent:buttonEvent:] + 383
    20  UIKit                               0x00b72bdd -[UIGestureRecognizer _delayedUpdateGesture] + 60
    21  UIKit                               0x00b7613d ___UIGestureRecognizerUpdate_block_invoke + 57
    22  UIKit                               0x00b760be _UIGestureRecognizerRemoveObjectsFromArrayAndApplyBlocks + 317
    23  UIKit                               0x00b6c7ac _UIGestureRecognizerUpdate + 199
    24  UIKit                               0x00817a5a -[UIWindow _sendGesturesForEvent:] + 1291
    25  UIKit                               0x00818971 -[UIWindow sendEvent:] + 1021
    26  UIKit                               0x007ea5f2 -[UIApplication sendEvent:] + 242
    27  UIKit                               0x007d4353 _UIApplicationHandleEventQueue + 11455
    28  CoreFoundation                      0x01d2077f __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 15
    29  CoreFoundation                      0x01d2010b __CFRunLoopDoSources0 + 235
    30  CoreFoundation                      0x01d3d1ae __CFRunLoopRun + 910
    31  CoreFoundation                      0x01d3c9d3 CFRunLoopRunSpecific + 467
    32  CoreFoundation                      0x01d3c7eb CFRunLoopRunInMode + 123
    33  GraphicsServices                    0x03acf5ee GSEventRunModal + 192
    34  GraphicsServices                    0x03acf42b GSEventRun + 104
    35  UIKit                               0x007d6f9b UIApplicationMain + 1225
    36  MyFirstGPS2                         0x00013592 main + 130
    37  libdyld.dylib                       0x0258a701 start + 1
    38  ???                                 0x00000001 0x0 + 1
)
libc++abi.dylib: terminating with uncaught exception of type NSException
(lldb) 

注意:我正在使用此页面中的代码来解析 csv 文件，我认为这不是问题所在:http://blog.smartfrog.fr/post/32123941502/tutorial-ios-mapkit

Answer 1

MKUserLocation 不是一个“奇怪”的注解。

当您将 showsUserLocation 设置为 YES 时，它是 map View 添加的用户位置(蓝点)注释的文档类。

map View 的annotations 数组包括添加到 map 的所有 注释——无论是由您还是由 map View 添加(另请注意，这些注释不会以任何特定顺序).

为确保您只处理 Location 类型的注释，您可以在使用 isKindOfClass 方法处理之前检查注释对象的类。

如果注释不属于该类，则跳过它(继续 循环)。

排序数组的代码会遇到类似的问题，因为它会尝试访问 MKUserLocation 注释上的 distance 属性。

与其尝试从 map View 的 annotations 数组创建排序数组，我建议在 for 循环(在同时设置 distance) 然后对该数组进行排序。

在 for 循环和排序更改中使用 isKindOfClass 的示例:

-(void)mapView:(MKMapView *)mapView didUpdateUserLocation:(MKUserLocation *)newLocation
{
    if (newLocation == nil) {
        //can happen if still waiting for user permission
        return;
    }
    if (!CLLocationCoordinate2DIsValid(newLocation.coordinate)) {
        //can happen if just resumed from some time in the background
        return;
    }

    //Declare and set user location variables outside the for-loop
    //since they won't be changing during the loop...
    CLLocationCoordinate2D userCoordinate = [[[self.mapView userLocation] location] coordinate];
    CLLocation *userLoc = [[CLLocation alloc] initWithLatitude:userCoordinate.latitude longitude:userCoordinate.longitude];

    //declare array in which you will put your Location annotations for sorting later...
    NSMutableArray *locAnnArray = [NSMutableArray array];

    //Declare the loop variable as a generic id<MKAnnotation>   
    for (id<MKAnnotation> annotation in self.mapView.annotations) {
        //Before processing the annotation, check it it's of type Location...
        if (! [annotation isKindOfClass:[Location class]]) {
            continue;
        }

        //Cast annotation to Location so we can see the distance property...
        Location *locAnn = (Location *)annotation;

        CLLocationCoordinate2D coord = [locAnn coordinate];
        CLLocation *myLoc = [[CLLocation alloc] initWithLatitude:coord.latitude longitude:coord.longitude];

        locAnn.distance = [myLoc distanceFromLocation:userLoc];

        NSLog(@"Distance is = %f", locAnn.distance);

        //Add Location annotation to local array for later sorting...   
        [locAnnArray addObject:locAnn];
    }

    //Sort our array of Location annotations...
    [locAnnArray sortUsingComparator:^NSComparisonResult(id a, id b) {
        NSNumber *first = [NSNumber numberWithDouble:[(Location*)a distance]];
        NSNumber *second = [NSNumber numberWithDouble:[(Location*)b distance]];
        return [first compare:second];
    }];

    //do something with the sorted array...
    //...
}