在地图上放置图钉时在注释中显示地址

Question

目前我可以在地图周围放置图钉。现在我希望注释标题显示图钉放置的地址。

我看过这个，但无法让我的工作：
Set annotation's title as current address

我的 ViewController.m 中的代码

已更新。

- (void)addPinToMap:(UIGestureRecognizer *)gestureRecognizer
{
    if (gestureRecognizer.state != UIGestureRecognizerStateBegan)
        return;

    CGPoint touchPoint = [gestureRecognizer locationInView:self.map];
    CLLocationCoordinate2D touchMapCoordinate =
    [self.map convertPoint:touchPoint toCoordinateFromView:self.map];

    CLLocation *currentLocation = [[CLLocation alloc]
                                   initWithLatitude:touchMapCoordinate.latitude
                                   longitude:touchMapCoordinate.longitude];

    [self.geocoder reverseGeocodeLocation:currentLocation completionHandler:^(NSArray *placemark, NSError *error) {

        //initialize the title to "unknown" in case geocode has failed...
        NSString *annTitle = @"Address unknown";

        //set the title if we got any placemarks...
        if (placemark.count > 0)
        {
            CLPlacemark *topResult = [placemark objectAtIndex:0];
            annTitle = [NSString stringWithFormat:@"%@ %@ %@ %@", topResult.country, topResult.locality, topResult.subLocality, topResult.thoroughfare];
        }

        //now create the annotation...
        MapAnnotation *toAdd = [[MapAnnotation alloc]init];

        toAdd.coordinate = touchMapCoordinate;
        toAdd.title = annTitle;
        //toAdd.title = @"Title";
        toAdd.subtitle = @"Subtitle";

        [self.map addAnnotation:toAdd];
    }];
}

Answer 1

首先，在addPinToMap: 方法中，addressLocation 使用currentLocation 调用，但从未设置currentLocation。它声明了几行，但没有设置任何值。

所以改变：

CLLocation *currentLocation;

到：

CLLocation *currentLocation = [[CLLocation alloc] 
                                initWithLatitude:touchMapCoordinate.latitude 
                                longitude:touchMapCoordinate.longitude];

第二，即使有了这个修复，它仍然无法正常工作。注释的title 不会被设置，因为reverseGeocodeLocation 方法的完成处理程序块将在注释已经添加后完成（该块是异步的——addPinToMap: 中的代码不会等待它完成）。

当您实际获得地理编码器结果（无论是成功还是失败）时，您需要稍微更改代码并在完成块中添加注释。

将reverseGeocodeLocation 调用移至addPinToMap: 方法：

CLLocation *currentLocation = [[CLLocation alloc] 
                                initWithLatitude:touchMapCoordinate.latitude 
                                longitude:touchMapCoordinate.longitude];

[self.geocoder reverseGeocodeLocation:currentLocation completionHandler:^(NSArray *placemark, NSError *error) {

    //initialize the title to "unknown" in case geocode has failed...
    NSString *annTitle = @"Address unknown";

    //set the title if we got any placemarks...
    if (placemark.count > 0)
    {
        CLPlacemark *topResult = [placemark objectAtIndex:0];
        annTitle = [NSString stringWithFormat:@"%@ %@ %@ %@", topResult.country, topResult.locality, topResult.subLocality, topResult.thoroughfare];
    }

    //now create the annotation...
    MapAnnotation *toAdd = [[MapAnnotation alloc]init];

    toAdd.coordinate = touchMapCoordinate;
    toAdd.title = annTitle;
    toAdd.subtitle = @"Subtitle";

    [self.map addAnnotation:toAdd];
}];