iOS用户位置不断回升 [英] iOS User location keeps snapping back

问题描述

我有一张地图，当按下一个按钮时，它会显示用户的位置并放大.但是，一旦按下该按钮，您将无法在地图上滚动，它会一直返回到用户的位置.我需要添加/更改什么?谢谢.

I have a map that when a button is pushed, it displays the user's location and zooms in. However, once that button is pushed, you cannot scroll on the map, it keeps snapping back to the user's location. What do I need to add/change? Thanks.

// Set action for when the refreh button is pressed

-(IBAction)refreshMapView:(id)sender {

[self refreshMap];
}

// Set action for when the show user location button is pressed

-(IBAction)getlocation {

mapView.showsUserLocation = YES;
[self.mapView.userLocation addObserver:self forKeyPath:@"location" options:(NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld) context:nil];

}

// Display segment button to change map views

-(IBAction)changeSeg:(id)sender {

if (segment.selectedSegmentIndex == 0) {
    mapView.mapType = MKMapTypeStandard;
}
if (segment.selectedSegmentIndex == 1) {
    mapView.mapType = MKMapTypeSatellite;
}
if (segment.selectedSegmentIndex == 2) {
    mapView.mapType = MKMapTypeHybrid;
}
}

// Listen to change in the userLocation

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{

MKCoordinateRegion region;
region.center = self.mapView.userLocation.coordinate;

MKCoordinateSpan span;
span.latitudeDelta  = 0.2; // Change these values to change the zoom
span.longitudeDelta = 0.2;
region.span = span;

[self.mapView setRegion:region animated:YES];
}   

// Load everying when map tab is accessed

-(void)viewDidLoad {

// Load mapView from MKMapKit

[super viewDidLoad];

mapView = [[MKMapView alloc] initWithFrame:self.view.bounds];
[self.view insertSubview:mapView atIndex:0];

[mapView setMapType:MKMapTypeStandard];
[mapView setZoomEnabled:YES];
[mapView setScrollEnabled:YES];
[mapView setDelegate:self];

// Display WCCCA HQ annotation pin.

MKCoordinateRegion WCCCA = { {0.0, 0.0} , {0.0, 0.0} };
WCCCA.center.latitude = 45.53540820864449;
WCCCA.center.longitude = -122.86178648471832;
WCCCA.span.longitudeDelta = 0.02f;
WCCCA.span.latitudeDelta = 0.02f;
[mapView setRegion:WCCCA animated:YES];

Annotation *ann1 = [[Annotation alloc] init];
ann1.title = @"WCCCA";
ann1.subtitle = @"Washington County Consolidated Communications Agency";
ann1.coordinate = WCCCA.center;
[mapView addAnnotation: ann1];

// Display call annotations based on xml parser data.

NSArray *callsArray = [xmlParser calls];

for (JointCAD *call in callsArray) {
    NSString *callnumber = [call.callnumber stringByAppendingFormat:@". "];
    NSString *callandnumber = [callnumber stringByAppendingString:call.currentCallType];
    Annotation *ann = [[Annotation alloc] init];
    ann.title = callandnumber;
    ann.subtitle = [call location];
    ann.coordinate = CLLocationCoordinate2DMake([call.latitude doubleValue], [call.longitude doubleValue]);
    [mapView addAnnotation:ann]; }

}

// Annotation details.

-(MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation {

// Set user location annotation to blue point instead of red pin

if ([annotation isKindOfClass:[MKUserLocation class]])
    return nil;

MKPinAnnotationView *MyPin=[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"current"];
MyPin.pinColor = MKPinAnnotationColorRed;

UIButton *advertButton = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
[advertButton addTarget:self action:@selector(button:) forControlEvents:UIControlEventTouchUpInside];

// MyPin.rightCalloutAccessoryView = advertButton;
MyPin.draggable = NO;
MyPin.highlighted = YES;
MyPin.animatesDrop= TRUE;
MyPin.canShowCallout = YES;

return MyPin;
}

 // Set default view when accessing Maps tab.

- (void)viewWillAppear:(BOOL)animated {

[super viewWillAppear:animated];

CLLocationCoordinate2D coord = {.latitude =  45.422424, .longitude =  -122.76};
MKCoordinateSpan span = {.latitudeDelta =  0.60, .longitudeDelta =  0.60};
MKCoordinateRegion region = {coord, span};
[mapView setRegion:region];
}

@end

推荐答案

在getlocation方法中，将showsUserLocation设置为YES，然后开始使用addObserver观察用户位置的更改.

In the getlocation method you set showsUserLocation to YES and start observing changes to the user location using addObserver.

因此，每当用户位置更改时(无论设备移动还是获得更新的位置)，都会触发observeValueForKeyPath方法.通过这种方法，您可以将地图区域重置为以用户位置为中心.

So whenever the user location changes (either when the device moves or an updated position is obtained), the observeValueForKeyPath method fires. In that method, you are resetting the map's region to center on the user location.

用户平移或缩放到其他位置后，如果发生另一个用户位置更改，该方法将再次触发，地图将返回到该用户位置.

After the user pans or zooms somewhere else, if another user location change happens, that method will fire again and the map will go back to the user location.

您遇到的最简单的解决方法是在第一次缩放到用户位置后立即停止观察.在observeValueForKeyPath方法的setRegion行之后，添加:

The simplest fix in your case is to stop observing right after you zoom to the user location the first time. In the observeValueForKeyPath method, after the setRegion line, add:

[self.mapView.userLocation removeObserver:self forKeyPath:@"location"];

请注意，自iOS 4.0起，您无需使用KVO(所有addObserver的东西)来观察用户位置的变化.相反，您可以使用

Note that since iOS 4.0, you don't need to use KVO (all that addObserver stuff) to observe user location changes. Instead, you could use the didUpdateUserLocation delegate method.

从iOS 5.0开始，缩放到用户位置的另一种方法是设置地图视图的

Since iOS 5.0, another option to zoom to the user location is to set the map view's userTrackingMode to MKUserTrackingModeFollow or MKUserTrackingModeFollowWithHeading. This way, you don't have to manually set the region. The map will zoom to and follow the user but still let the user then pan or zoom freely.

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