計算行車距離到一個特定的座標

Question

有沒有一種方法，我可以得到特定的駕駛距離geo-cordinate？我知道我必須使用http://maps.googleapis.com/maps/api/directions/output?parameters並獲得JSON輸出以獲得結果。

是否有教程解釋如何完成此任務？或者我開始的任何示例代碼？

Answer 1

您可以嘗試以下操作。此代碼提取Google Directions Services返回的所有路線（甚至是替代路線）。你可以在第2步（解析響應）

第1步的距離：輸入起始和結束位置

NSMutableString *googleURL = [[NSMutableString alloc] initWithString:[NSString stringWithFormat:@"http://maps.googleapis.com/maps/api/directions/json?origin=%@&destination=%@&sensor=true&alternatives=true", searchFrom.text, searchTo.text]]; 
NSURL *url = [NSURL URLWithString:googleURL]; 
[googleURL release]; 
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];   
[NSURLConnection connectionWithRequest:request delegate:self]; 
request = nil; 
responseData = [[NSMutableData alloc] init]; 

第2步：當你進行的查詢的響應，解析結果

- (id)parseResponseWithDictionary:(NSDictionary *)dictResponse { 
    if ([[dictResponse objectForKey:@"status"] isEqualToString:kGoogleDirectionsStatusOK]) { 
     NSArray *listRoutes = (NSArray *)[dictResponse objectForKey:@"routes"]; 
     NSMutableString *result = nil; 
     NSMutableArray *listPolylines = nil; 
     for (NSDictionary *dictRouteValues in listRoutes) { 
      NSDictionary *dictPolyline = [dictRouteValues objectForKey:@"overview_polyline"]; 
      if (!result) { 
       result = [[NSMutableString alloc] init]; 
      } 
      [result appendString:[dictPolyline objectForKey:@"points"]]; 
      if (!listPolylines) { 
       listPolylines = [[NSMutableArray alloc] init]; 
      } 
      [listPolylines addObject:result]; 
      [result release]; 
      result = nil; 
     } 
     return [listPolylines autorelease]; 
    } 
    else { 
     NSString *error = @"No result found. Please check start and end location again!"; 
     return error; 
    } 
    return nil; 
} 

第3步：解碼多段線列表中的每條多段線。這將給出路徑座標。

-(NSMutableArray *)decodePolyLine:(NSMutableString *)encoded { 
    [encoded replaceOccurrencesOfString:@"\\\\" withString:@"\\" 
           options:NSLiteralSearch 
            range:NSMakeRange(0, [encoded length])]; 
    NSInteger len = [encoded length]; 
    NSInteger index = 0; 
    NSMutableArray *listCoordinates = [[[NSMutableArray alloc] init] autorelease]; 
    NSInteger lat=0; 
    NSInteger lng=0; 
    while (index < len) { 
     NSInteger b; 
     NSInteger shift = 0; 
     NSInteger result = 0; 
     do { 
      b = [encoded characterAtIndex:index++] - 63; 
      result |= (b & 0x1f) << shift; 
      shift += 5; 
     } while (b >= 0x20); 
     NSInteger dlat = ((result & 1) ? ~(result >> 1) : (result >> 1)); 
     lat += dlat; 
     shift = 0; 
     result = 0; 
     do { 
      b = [encoded characterAtIndex:index++] - 63; 
      result |= (b & 0x1f) << shift; 
      shift += 5; 
     } while (b >= 0x20); 
     NSInteger dlng = ((result & 1) ? ~(result >> 1) : (result >> 1)); 
     lng += dlng; 
     NSNumber *latitude = [[NSNumber alloc] initWithFloat:lat * 1e-5]; 
     NSNumber *longitude = [[NSNumber alloc] initWithFloat:lng * 1e-5]; 
     //CLLocation *loc = [[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]]; 
     [listCoordinates addObject:[NSString stringWithFormat:@"%f,%f", [latitude floatValue], [longitude floatValue]]]; 
     //[loc release]; 
     [latitude release]; 
     [longitude release]; 
    } 

    return listCoordinates; 
} 

Answer 2

這個更新的tutorial/sample code使用CoreLocation和MapKit幫助了我一堆。