iphone - 如何在 iPhone 中的 map View 中心添加注释？

Question

我的应用程序中有 map View ，我想在 map View 的中心添加注释图钉(红色图钉)。
现在，当用户滚动 map View 引脚时，应根据该情况调整中心位置。
如何做到这一点？
谢谢

Answer 1

如果您想使用实际的注释，而不仅仅是位于 map View 中心上方的常规 View ，您可以:

• 使用具有可设置坐标属性的注释类(例如预定义的MKPointAnnotation类)。这避免了在中心发生变化时必须删除和添加注释。
• 在viewDidLoad中创建注释
• 在属性中保留对其的引用，例如 centerAnnotation
• 在 map View 的 regionDidChangeAnimated 委托(delegate)方法中更新其坐标(和标题等)(确保设置了 map View 的委托(delegate)属性)

示例:

@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。如果您需要注释移动得更流畅，可以将 UIPanGestureRecognizer 和 UIPinchGestureRecognizer 添加到 map View ，并在手势处理程序中更新注释:

    // (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;
}