ios - 获取 "Directions Not Available"使用 URLWithString 调用谷歌地图

Question

我有一个非常成功地使用 Apple Maps 的应用程序:我有一个包含一些兴趣点的列表，如果我首先点击其中一个，应用程序会在 map 上显示它，然后，如果我点击它，它会打开 Apple Maps用于导航的应用程序。

问题是，在第一次点击/启动应用程序时，它会打开 Apple map ，但无论是请求使用用户位置的许可还是不请求，Apple map 都不起作用并返回:“方向不可用. 在这些位置之间找不到方向。”但在常规设置中，我的应用程序的位置服务设置为开启。

我想我必须使用一种超时，因为我的应用程序需要很长时间来解析导航数据(我从 xml 检索数据)但是在第二次点击时一切正常，即使我从 Mac 运行它 Debug模式(它甚至第二次解析 xml)...

希望我解释得很好。有什么提示吗？

   -(MKAnnotationView *)mapView:(MKMapView *)mV viewForAnnotation:(id <MKAnnotation>)annotation 
{
    MKPinAnnotationView *pinView = nil; 
    if(annotation != mapView.userLocation) 
    {
    static NSString *defaultPinID = @"com.invasivecode.pin";
    pinView = (MKPinAnnotationView *)[mapView dequeueReusableAnnotationViewWithIdentifier:defaultPinID];
    if ( pinView == nil ) pinView = [[[MKPinAnnotationView alloc]
                                      initWithAnnotation:annotation reuseIdentifier:defaultPinID] autorelease];

    pinView.pinColor = MKPinAnnotationColorRed; 


    UIButton *myAccessoryButton = [[UIButton alloc] initWithFrame:CGRectMake(0, 0, 24, 24)];
    [myAccessoryButton setBackgroundColor:[UIColor clearColor]];
    [myAccessoryButton setImage:[UIImage imageNamed:@"flag.png"] forState:UIControlStateNormal];
    pinView.rightCalloutAccessoryView = myAccessoryButton;
    pinView.canShowCallout = YES;
    pinView.animatesDrop = YES;
    [myAccessoryButton release];
} 
else {
    [mapView.userLocation setTitle:@"You're here"];
}
return pinView;
}

-(void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control{

locationManager = [[CLLocationManager alloc] init];
locationManager.delegate = self; 
locationManager.desiredAccuracy = kCLLocationAccuracyBest; 
locationManager.distanceFilter = kCLDistanceFilterNone; 
[locationManager startUpdatingLocation];

CLLocation *location = [locationManager location];

// Configure the new event with information from the location
CLLocationCoordinate2D coordinate = [location coordinate];

NSString *latitude = [NSString stringWithFormat:@"%f", coordinate.latitude]; 
NSString *longitude = [NSString stringWithFormat:@"%f", coordinate.longitude];


CLLocationCoordinate2D start = { [latitude floatValue], [longitude floatValue] };
CLLocationCoordinate2D end = {[posto.latitude floatValue], [posto.longitude floatValue]};

NSString *googleMapsURLString = [NSString stringWithFormat:@"http://maps.google.com/?saddr=%1.6f,%1.6f&daddr=%1.6f,%1.6f", start.latitude, start.longitude, end.latitude, end.longitude];

[[UIApplication sharedApplication] openURL:[NSURL URLWithString:googleMapsURLString]];
}

Answer 1

在 calloutAccessoryControlTapped 中，您在调用 startUpdatingLocation 后立即使用 [locationManager location]。

location 通常在开始查找当前位置后立即不可用(如果可用，它可能不可靠或已过时)。

当 location 可用时，位置管理器将调用其 didUpdateToLocation 委托(delegate)方法，这就是您应该将 startUpdatingLocation 之后的所有代码移动到的地方>.

(即使在那个委托(delegate)方法中，在使用它之前检查 newLocation 是否为 nil 可能是个好主意。它有时会在 map View 等待时发生供用户授予定位服务权限(参见 this question ))。

-(void)mapView:(MKMapView *)mapView annotationView:(MKAnnotationView *)view calloutAccessoryControlTapped:(UIControl *)control
{
    locationManager = [[CLLocationManager alloc] init];
    locationManager.delegate = self; 
    locationManager.desiredAccuracy = kCLLocationAccuracyBest; 
    locationManager.distanceFilter = kCLDistanceFilterNone; 
    [locationManager startUpdatingLocation];
}

-(void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    if (newLocation == nil)
    {
        NSLog(@"didUpdateToLocation: newLocation is nil");
        return;
    }

    //May want to check newLocation.horizontalAccuracy and 
    //newLocation.timestamp to see if the location is accurate 
    //enough for you.  If not, return and wait for a more 
    //accurate location (which may never come).

    //all the code currently after "startUpdatingLocation" goes here...
    CLLocation *location = [locationManager location];
    ...
}

-(void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error
{
    NSLog(@"locationManager:didFailWithError: %@", error);
}

您可能还想实现 didFailWithError 来处理获取位置的任何问题，或者至少要知道它。