ios - MKAnnotation 在点击时没有响应

Question

我在 map 上显示了几个图钉，就像这样:

for (int i = 0; i < points.count; i++) {
    if([[[points objectAtIndex:i] objectForKey:@"lat"] class] != [NSNull class]) {
        southWest.latitude = MAX(southWest.latitude , [[[points objectAtIndex:i] objectForKey:@"lat"] doubleValue]);
        southWest.longitude = MIN(southWest.longitude, [[[points objectAtIndex:i] objectForKey:@"lon"] doubleValue]);
        northEast.latitude = MIN(northEast.latitude, [[[points objectAtIndex:i] objectForKey:@"lat"] doubleValue]);
        northEast.longitude = MAX(northEast.longitude, [[[points objectAtIndex:i] objectForKey:@"lon"] doubleValue]);

        pin.latitude = [[[points objectAtIndex:i] objectForKey:@"lat"] doubleValue];
        pin.longitude = [[[points objectAtIndex:i] objectForKey:@"lon"] doubleValue];
        CarPin *cPin = [[CarPin alloc] initWithName:[[self.brain.cars objectAtIndex:i] objectForKey:@"name"] state:[self getStateStringFor:[[[points objectAtIndex:i] objectForKey:@"state"] intValue]] coordinate:pin];
        cPin.state = [[[points objectAtIndex:i] objectForKey:@"state"] intValue];
        cPin.carID = [[points objectAtIndex:i] objectForKey:@"objekt_id"];
        [self.mapView addAnnotation:cPin];
    }
}

CLLocation *locSouthWest = [[CLLocation alloc] initWithLatitude:southWest.latitude longitude:southWest.longitude];
CLLocation *locNorthEast = [[CLLocation alloc] initWithLatitude:northEast.latitude longitude:northEast.longitude];
CLLocationDistance meters = [locSouthWest distanceFromLocation:locNorthEast];

MKCoordinateRegion region;
region.center.latitude = (southWest.latitude + northEast.latitude) / 2.0;
region.center.longitude = (southWest.longitude + northEast.longitude) / 2.0;
region.span.latitudeDelta = meters / 111319.5;
region.span.longitudeDelta = 0.0;

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

然后我像这样选择每个图钉的“外观”:

- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation {
static NSString *identifier = @"CarPin";
if ([annotation isKindOfClass:[CarPin class]]) {
    MKPinAnnotationView *annotationView = (MKPinAnnotationView *) [self.mapView dequeueReusableAnnotationViewWithIdentifier:identifier];
    if (annotationView == nil) {
        annotationView = [[MKPinAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:identifier];
    } else {
        annotationView.annotation = annotation;
    }
    annotationView.enabled = YES;
    annotationView.canShowCallout = YES;
    annotationView.rightCalloutAccessoryView = [UIButton buttonWithType:UIButtonTypeDetailDisclosure];
    if (((CarPin *)annotation).state == 1) {
        annotationView.pinColor = MKPinAnnotationColorGreen;
    } else {
        annotationView.pinColor = MKPinAnnotationColorRed;
    }
    return annotationView;
}
return nil;
}

我也设置了委托(delegate)

[self.mapView setDelegate:self];

但是，当我点击每个图钉时，屏幕上没有显示任何带有详细信息的气泡!有人有同样的经历吗？

Answer 1

仅仅实现 title 属性是不够的。
您必须确保 title 没有返回 nil 或空白。
如果是，即使 canShowCallout 设置为 YES，注释 View 也不会显示标注。

与您的问题无关，但关于这一行:

region.span.latitudeDelta = meters / 111319.5;

至少出于以下三个原因，不推荐也不需要这样做:

• 计算两个角之间的米距(您有以度为单位的纬度和经度，然后将这些米转换回度)是不必要的因为 latitudeDelta 和 longitudeDelta 只是上/下或左/右之间的度数差。所以你所要做的就是:

  region.span.latitudeDelta = fabs(southWest.latitude - northEast.latitude);
  

  这是我建议您进行的更改。

• 将米转换为度的除法值 (111319.5) 仅在赤道处准确。

• 如果您想根据米指定一个区域，而不是手动计算以度为单位的跨度，使用内置的 MKCoordinateRegionMakeWithDistance 会更好也更容易功能:

  CLLocationCoordinate2D center = CLLocationCoordinate2DMake (lat, long);
  CLLocationDistance latMeters = 5000;  //5 km
  CLLocationDistance lonMeters = 5000;  //5 km
  MKCoordinateRegion region 
      = MKCoordinateRegionMakeWithDistance (center, latMeters, lonMeters);
  

此外，在您的情况下，调用 regionThatFits 是不必要的，因为 setRegion 已经对您传递给它的任何区域进行了此操作。 regionThatFits 方法用于当您想知道(无需实际更改区域) map View 会将区域调整为给定特定区域时的内容。