通过 MKMapView 上的用户交互创建叠加层？

Question

我有两个问题，

1. 如何根据用户的触摸事件在 MKMapkitView 上创建叠加层？即为了简单起见，用户触地并创建一个 MKCircle 叠加层

2. 地图应用程序如何在触地时实现“掉落的图钉”？有人知道或有一些关于如何完成类似事情的代码示例吗？

任何指示将不胜感激。正如你所看到的，我一直在谷歌上搜索并阅读大量文档，但没有取得多大成功。

Answer 1

下面的示例创建了一个圆圈，并在用户触摸并按住手指 1 秒的地方放置了一个图钉。它使用 UILongPressGestureRecognizer，在地图初始化的任何地方（例如 viewDidLoad）都会将其添加到 mapView 中。

确保还设置了mapView 的委托。

// In viewDidLoad or where map is initialized...
UILongPressGestureRecognizer *lpgr = [[UILongPressGestureRecognizer alloc] initWithTarget:self action:@selector(handleLongPress:)];
lpgr.minimumPressDuration = 1.0;  //user must hold for 1 second
[mapView addGestureRecognizer:lpgr];
[lpgr release];

...

- (void)handleLongPress:(UIGestureRecognizer *)gestureRecognizer
{
    if (gestureRecognizer.state != UIGestureRecognizerStateBegan)
        return;

    CGPoint touchPoint = [gestureRecognizer locationInView:mapView];    
    CLLocationCoordinate2D touchMapCoordinate = [mapView convertPoint:touchPoint toCoordinateFromView:mapView];

    //add pin where user touched down...
    MKPointAnnotation *pa = [[MKPointAnnotation alloc] init];
    pa.coordinate = touchMapCoordinate;
    pa.title = @"Hello";
    [mapView addAnnotation:pa];
    [pa release];

    //add circle with 5km radius where user touched down...
    MKCircle *circle = [MKCircle circleWithCenterCoordinate:touchMapCoordinate radius:5000];
    [mapView addOverlay:circle];
}

-(MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id)overlay 
{
    MKCircleView* circleView = [[[MKCircleView alloc] initWithOverlay:overlay] autorelease];
    circleView.fillColor = [UIColor redColor];
    return circleView;
}

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation
{
    static NSString *AnnotationIdentifier = @"Annotation";
    MKPinAnnotationView* pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:AnnotationIdentifier];
    if (!pinView)
    {
        pinView = [[[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:AnnotationIdentifier] autorelease];
        pinView.pinColor = MKPinAnnotationColorGreen;
        pinView.animatesDrop = YES;
    }
    else
    {
        pinView.annotation = annotation;
    }
    return pinView;
}