使用Google Map API(GMSMapView)无法获取当前位置 [英] Could not get current location using Google Map API (GMSMapView)

问题描述

我尝试使用Google Map API获取从当前位置到其他地点的路线.当我手动输入起点和终点时，一切都OK.但是，当我尝试将原点设置为当前位置时，该位置为null，如下所示:

  mainMap = [[GMSMapView alloc] initWithFrame:CGRectMake(0，0，self.view.bounds.size.width，self.view.bounds.size.height)]；GMSCameraPosition * camera = [GMSCameraPosition cameraWithTarget:[mainMap.myLocation坐标] zoom:13];mainMap.camera = camera;mainMap.myLocationEnabled = YES;//< ----蓝点出现在地图上:这正是我的位置[self.view addSubview:mainMap];//获取我的位置CLLocation * myLocation = mainMap.myLocation;//< ----- NULL 

有没有人知道我的问题在这里?非常感谢

解决方案

问题是:获取位置是异步的，您如何执行该操作，希望它一直阻塞到该位置为止……这不是它的工作原理

您必须在地图中添加KVO观察员，并在myLocation中添加观察员.
然后，当您的observe方法被调用时，您将获得myLocation.

(蓝点也是如此:))

 -(void)viewDidLoad {//...[self.mapView addObserver:self forKeyPath:"myLocation"选项:0上下文:无]；}-(void)dealloc {[_mapView removeObserver:self forKeyPath:@"myLocation"]；}-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {if([keyPath isEqualToString:@"myLocation"]){CLLocation * l = [对象myLocation]；//...}} 

I try to get the direction from current location to other point using Google Map API. Everything is OK when i input the origin point and destination point manually. But, when i try to set the origin point as current location, the location is null as the following code:

mainMap=[[GMSMapView alloc] initWithFrame:CGRectMake(0, 0, self.view.bounds.size.width, self.view.bounds.size.height)];
GMSCameraPosition *camera = [GMSCameraPosition cameraWithTarget:[mainMap.myLocation coordinate] zoom:13];
mainMap.camera=camera;
mainMap.myLocationEnabled=YES; // <---- The blue point appear on map: it's exactly my location

[self.view addSubview:mainMap];

//Get mylocation
CLLocation *myLocation = mainMap.myLocation; // <----- NULL

Is there any body know what is my problem here? Tks a lot

解决方案

The thing is: Getting a location is asynchronous and how you do it is expect it to block till its there... which is not how it works

you have to add a KVO observer inn the map and observer myLocation.
Then when your observe method gets called, you get the myLocation.

(that's how the blue dot works too :))

- (void)viewDidLoad {
    //...
    [self.mapView addObserver:self forKeyPath:"myLocation" options:0 context:nil];
}
- (void)dealloc {
    [_mapView removeObserver:self forKeyPath:@"myLocation"];
}

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if([keyPath isEqualToString:@"myLocation"]) {
        CLLocation *l = [object myLocation];
        //...
    }
}

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