显示拖动的MKAnnotationPin的位置

Question

我正在尝试为拖拽的MKAnnotationPin的位置添加某种指示器。

到目前为止，我想出了以下不可行的解决方案：

- (void) showDragLoc{


UIView *cross = [[UIView alloc] initWithFrame:CGRectMake(dragPin.center.x, dragPin.center.y, 10, 10)];
[self.mapView addSubview:cross];
while(dragPin.dragState  == MKAnnotationViewDragStateDragging){

    [UIView beginAnimations:nil context:NULL]; // animate the following:
    cross.frame = CGRectMake(dragPin.center.x, dragPin.center.y, 10, 10); // move to new location
    [UIView setAnimationDuration:0.3];
    [UIView commitAnimations];
}
}

ere dragPin是在标题中声明的MKAnnotationView。当引脚的dragState转到MKAnnotationViewDragStateDragging (从委托方法)时，调用此函数。

我的目标是添加某种类型的指示器，指示被拖拽的引脚当前所在的位置。

Answer 1

如果要向标准MKPinAnnotationView添加十字准线，则应将其子类化为子类，然后在setDragState:animated:实现中添加十字准线。

因此，要创建子类，请创建一个新类，例如PinWithCrosshairAnnotationView。.h公共接口不需要太多：

@interface PinWithCrosshairAnnotationView : MKPinAnnotationView

@end

.m实现只是实现了一个添加十字准线的setDragState:animated:，然后调用super实现来获得引脚拖放功能。如果animated标志处于打开状态，我也会对其进行动画处理，但您不必这样做。您的frame坐标无疑会与我的不同，但我从上面的代码示例中了解到，您已经为您的十字准线图像找到了正确的值：

#import "PinWithCrosshairAnnotationView.h"

@interface PinWithCrosshairAnnotationView ()
@property (nonatomic, weak) UIImageView *crosshairImageView;
@end

@implementation PinWithCrosshairAnnotationView

- (void)setDragState:(MKAnnotationViewDragState)newDragState animated:(BOOL)animated
{
    if (newDragState == MKAnnotationViewDragStateStarting)
    {
        // create the crosshair imageview and add it as a subview

        UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(-1.5, 30, 17.5, 17.5)];
        imageView.image = [UIImage imageNamed:@"Crosshairs.png"];
        [self addSubview:imageView];

        // if the animated flag is on, we'll fade it to visible state

        if (animated)
        {
            imageView.alpha = 0.0;
            [UIView animateWithDuration:0.2
                             animations:^{
                                 imageView.alpha = 1.0;
                             }];
        }

        // save a reference to that imageview in a class property

        self.crosshairImageView = imageView;
    }
    else if (newDragState == MKAnnotationViewDragStateEnding || newDragState == MKAnnotationViewDragStateCanceling)
    {
        if (animated)
        {
            // if we're animating, let's quickly fade it to invisible
            // and in the completion block, we'll remove it

            [UIView animateWithDuration:0.2
                             animations:^{
                                 self.crosshairImageView.alpha = 0.0;
                             }
                             completion:^(BOOL finished) {
                                 [self.crosshairImageView removeFromSuperview];
                                 self.crosshairImageView = nil;
                             }];
        }
        else
        {
            // if we're not animating, just remove it

            [self.crosshairImageView removeFromSuperview];
            self.crosshairImageView = nil;
        }
    }

    // remember to call super so we get all the other wonderful superclass behavior

    [super setDragState:newDragState animated:animated];
}
@end

显然，您需要在MKMapView委托中相应地定制viewForAnnotation。这是一个极简主义版本，但您显然会根据您的需要(标注、标题、副标题等)来调整您的版本：

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id<MKAnnotation>)annotation
{
    if ([annotation isKindOfClass:[MKUserLocation class]])
        return nil;

    MKAnnotationView *view = [[PinWithCrosshairAnnotationView alloc] initWithAnnotation:annotation
                                                                        reuseIdentifier:@"pinwithcrosshairannotation"];
    view.draggable = YES;
    view.canShowCallout = NO;

    return view;
}