我的应用中有 MAP 视图，我想在地图视图的中心添加注释图钉（红色图钉）。
现在，当用户滚动地图视图时，应根据该图调整中心。
如何做到这一点？
谢谢
【问题讨论】：
标签： iphone annotations mkmapview center
如果您想使用实际注释而不是仅使用位于地图视图中心上方的常规视图，您可以：
MKPointAnnotation 类）。这样可以避免在中心更改时必须删除和添加注释。regionDidChangeAnimated 委托方法中更新其坐标（和标题等）（确保已设置地图视图的委托属性）例子：
@interface SomeViewController : UIViewController <MKMapViewDelegate> {
MKPointAnnotation *centerAnnotation;
}
@property (nonatomic, retain) MKPointAnnotation *centerAnnotation;
@end
@implementation SomeViewController
@synthesize centerAnnotation;
- (void)viewDidLoad {
[super viewDidLoad];
MKPointAnnotation *pa = [[MKPointAnnotation alloc] init];
pa.coordinate = mapView.centerCoordinate;
pa.title = @"Map Center";
pa.subtitle = [NSString stringWithFormat:@"%f, %f", pa.coordinate.latitude, pa.coordinate.longitude];
[mapView addAnnotation:pa];
self.centerAnnotation = pa;
[pa release];
}
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
centerAnnotation.coordinate = mapView.centerCoordinate;
centerAnnotation.subtitle = [NSString stringWithFormat:@"%f, %f", centerAnnotation.coordinate.latitude, centerAnnotation.coordinate.longitude];
}
- (void)dealloc {
[centerAnnotation release];
[super dealloc];
}
@end
现在这将移动注释，但不顺利。如果您需要注解更顺畅地移动，您可以在地图视图中添加UIPanGestureRecognizer 和UIPinchGestureRecognizer，并在手势处理程序中更新注解：
// (Also add UIGestureRecognizerDelegate to the interface.)
// In viewDidLoad:
UIPanGestureRecognizer *panGesture = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handleGesture:)];
panGesture.delegate = self;
[mapView addGestureRecognizer:panGesture];
[panGesture release];
UIPinchGestureRecognizer *pinchGesture = [[UIPinchGestureRecognizer alloc] initWithTarget:self action:@selector(handleGesture:)];
pinchGesture.delegate = self;
[mapView addGestureRecognizer:pinchGesture];
[pinchGesture release];
- (void)handleGesture:(UIGestureRecognizer *)gestureRecognizer
{
centerAnnotation.coordinate = mapView.centerCoordinate;
centerAnnotation.subtitle = [NSString stringWithFormat:@"%f, %f", centerAnnotation.coordinate.latitude, centerAnnotation.coordinate.longitude];
}
- (BOOL)gestureRecognizer:(UIGestureRecognizer *)gestureRecognizer shouldRecognizeSimultaneouslyWithGestureRecognizer:(UIGestureRecognizer *)otherGestureRecognizer {
//let the map view's and our gesture recognizers work at the same time...
return YES;
}
【讨论】：
安娜的回答是使用标准地图视图方式中的注释将注释保持在地图中心的巧妙方法。然而，正如一位评论者指出的那样，滚动和捏合虽然好得多，但仍然显示出明显的滞后，推荐的方法是将注释视图添加为地图视图的子视图。这就是它的样子。
@interface SHCenterPinMapViewController () <MKMapViewDelegate>
@property (weak, nonatomic) IBOutlet MKMapView *mapView;
@property (strong, nonatomic) MKPointAnnotation *centerAnnotaion;
@property (strong, nonatomic) MKPinAnnotationView *centerAnnotationView;
@end
@implementation SHCenterPinMapViewController
- (MKPointAnnotation *)centerAnnotaion
{
if (!_centerAnnotaion) {
_centerAnnotaion = [[MKPointAnnotation alloc] init];
}
return _centerAnnotaion;
}
- (MKPinAnnotationView *)centerAnnotationView
{
if (!_centerAnnotationView) {
_centerAnnotationView = [[MKPinAnnotationView alloc] initWithAnnotation:self.centerAnnotaion
reuseIdentifier:@"centerAnnotationView"];
}
return _centerAnnotationView;
}
- (void)viewDidLoad
{
[super viewDidLoad];
self.mapView.delegate = self;
[self.mapView addSubview:self.centerAnnotationView];
}
-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[self moveMapAnnotationToCoordinate:self.mapView.centerCoordinate];
}
// These are the constants need to offset distance between the lower left corner of
// the annotaion view and the head of the pin
#define PIN_WIDTH_OFFSET 7.75
#define PIN_HEIGHT_OFFSET 5
- (void)moveMapAnnotationToCoordinate:(CLLocationCoordinate2D) coordinate
{
CGPoint mapViewPoint = [self.mapView convertCoordinate:coordinate toPointToView:self.mapView];
// Offset the view from to account for distance from the lower left corner to the pin head
CGFloat xoffset = CGRectGetMidX(self.centerAnnotationView.bounds) - PIN_WIDTH_OFFSET;
CGFloat yoffset = -CGRectGetMidY(self.centerAnnotationView.bounds) + PIN_HEIGHT_OFFSET;
self.centerAnnotationView.center = CGPointMake(mapViewPoint.x + xoffset,
mapViewPoint.y + yoffset);
}
- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated
{
self.centerAnnotaion.coordinate = mapView.centerCoordinate;
[self moveMapAnnotationToCoordinate:mapView.centerCoordinate];
}
@end
真正唯一有趣的事情是，您必须将 MKPinAnnotationView 偏移一定量以考虑左下角和针头之间的距离。我不喜欢在代码中包含这些资产相关的常量，所以如果有人能找到更好的方法来做到这一点，我会全力以赴。
我创建了一个带有地图控制器的 github 项目，该控制器执行此操作以及与使用地图视图让用户选择位置相关的其他一些事情。在这里查看：https://github.com/scottrhoyt/CenterPinMapViewController
【讨论】：
在课堂上：
var centerAnnotation = MKPointAnnotation()
var centerAnnotationView = MKPinAnnotationView()
在 viewDidLoad 中：
if #available(iOS 9.0, *) {
centerAnnotationView.pinTintColor = customColor
} else {
// Fallback on earlier versions
centerAnnotationView.pinColor = MKPinAnnotationColor.Red
}
self.view.addSubview(centerAnnotationView)
在 viewDidAppear 中：
self.moveMapAnnotationToCoordinate(self.mapView.centerCoordinate)
然后：
func moveMapAnnotationToCoordinate(locate : CLLocationCoordinate2D ) {
let mapViewPoint : CGPoint = self.mapView.convertCoordinate(locate, toPointToView: self.mapView)
let pinWidth : CGFloat = 7.75
let pinHeight : CGFloat = 7
let xOffset : CGFloat = CGRectGetMidX(self.centerAnnotationView.bounds) - pinWidth
let yOffset : CGFloat = CGRectGetMidY(self.centerAnnotationView.bounds) - pinHeight
self.centerAnnotationView.center = CGPointMake(mapViewPoint.x - xOffset, mapViewPoint.y - yOffset)
}
要使用位置更改，请添加委托CLLocationManagerDelegate，然后：
func mapView(mapView: MKMapView, regionDidChangeAnimated animated: Bool) {
self.centerAnnotation.coordinate = self.mapView.centerCoordinate
self.moveMapAnnotationToCoordinate(self.mapView.centerCoordinate)
}
【讨论】：