當引腳在地圖上丟棄時，在註釋中顯示地址

Question

目前我可以在地圖上放置引腳。現在我想讓註解標題顯示引腳被丟棄的地址。

我看了一下這一點，但不能讓我的工作：
Set annotation's title as current address

代碼在我ViewController.m

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，addressLocation調用與currentLocation但currentLocation永遠不會設置。它宣佈了幾行，但沒有設置任何值。

因此改變：

CLLocation *currentLocation; 

到：

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

二，甚至與此修復程序，它仍然會無法正常工作。註釋的title不會被設置，因爲reverseGeocodeLocation方法的完成處理程序塊將在註釋添加完成後完成（該塊是異步的 - addPinToMap:中的代碼不會等待它完成）。

當您確實擁有地理編碼器結果（無論成功還是失敗）時，您需要稍微更改代碼並在內添加批註。

移動reverseGeocodeLocation調用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]; 
}];