Question

我正在地图上显示几个图钉：

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];

那么我选择每个引脚的“外观”如下：

- (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;
}

我还设置了委托

[self.mapView setDelegate:self];

但是，当我点击每个引脚时，我的屏幕上没有显示带有细节的气泡！有没有人经历过同样的事情？

Answer 1

仅仅实施title财产是不够的您必须确保title未返回nil或空白如果是，即使canShowCallout设置为YES，注释视图也不会显示标注。

与您的问题无关，但关于这一行：

region.span.latitudeDelta = meters / 111319.5;

至少有三个原因不建议这样做，不需要这样做：

计算两个角之间的仪表距离（您有度的纬度和经度，然后将这些米转换回度）是不必要的因为latitudeDelta和longitudeDelta只是顶部/底部或左/右之间的度数差异。所以你要做的就是：
```
region.span.latitudeDelta = fabs(southWest.latitude - northEast.latitude);
```
这是我建议你做的改变。
除以将米转换为度数（111319.5）的值只能在赤道上准确。

如果要根据米数指定区域，而不是手动计算度数范围，则使用内置MKCoordinateRegionMakeWithDistance函数会更好更容易：

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已经在您传递它的任何区域自己执行此操作。如果您想知道（不实际更改区域）地图视图将区域调整为给定某个区域的内容，则使用regionThatFits方法。

MKAnnotation没有响应

1 个答案: