我编写了一个简单的应用程序，它在 MapKit 上的两个位置之间绘制路线。我正在使用谷歌地图 API。我使用了在网上找到的资源，这是我用来向 Google 发出请求的代码：
_httpClient = [AFHTTPClient clientWithBaseURL:[NSURL URLWithString:@"http://maps.googleapis.com/"]];
[_httpClient registerHTTPOperationClass: [AFJSONRequestOperation class]];
[_httpClient setDefaultHeader:@"Accept" value:@"application/json"];
NSMutableDictionary *parameters = [[NSMutableDictionary alloc] init];
[parameters setObject:[NSString stringWithFormat:@"%f,%f", coordinate.latitude, coordinate.longitude] forKey:@"origin"];
[parameters setObject:[NSString stringWithFormat:@"%f,%f", endCoordinate.latitude, endCoordinate.longitude] forKey:@"destination"];
[parameters setObject:@"true" forKey:@"sensor"];
NSMutableURLRequest *request = [_httpClient requestWithMethod:@"GET" path: @"maps/api/directions/json" parameters:parameters];
request.cachePolicy = NSURLRequestReloadIgnoringLocalCacheData;
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc]initWithRequest:request];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject){
NSInteger statusCode = operation.response.statusCode;
if (statusCode == 200)
{
NSLog(@"Success: %@", operation.responseString);
}
else
{
NSLog(@"Status code = %d", statusCode);
}
}
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(@"Error: %@", operation.responseString);
}
];
[_httpClient enqueueHTTPRequestOperation:operation];
这完美无缺。当我运行它并尝试显示洛杉矶和芝加哥之间的路线时，它是这样的：
但。当我将地图缩放到街道级别时，路线如下所示：
有谁知道我怎样才能在地图放大时实现我正在绘制的沿着街道的路线？我想路线显示穿过街道的确切路径。我不知道是否需要在我对 Google 的请求中添加一些额外的参数。
任何帮助或建议都会很棒。提前谢谢了！
[编辑#1：添加请求 URL 和来自 Google 的响应]
从上面的代码创建操作对象后，我的请求 URL 如下所示：
http://maps.googleapis.com/maps/api/directions/json?sensor=true&destination=34%2E052360,-118%2E243560&origin=41%2E903630,-87%2E629790
只需将该 URL 粘贴到您的浏览器，您就会看到 Google 发送的 JSON 数据作为我在代码中得到的响应。
[编辑#2：解析来自谷歌的答案并构建路径]
- (void)parseResponse:(NSData *)response
{
NSDictionary *dictResponse = [NSJSONSerialization JSONObjectWithData:response options:NSJSONReadingMutableContainers error:nil];
NSArray *routes = [dictResponse objectForKey:@"routes"];
NSDictionary *route = [routes lastObject];
if (route)
{
NSString *overviewPolyline = [[route objectForKey: @"overview_polyline"] objectForKey:@"points"];
_path = [self decodePolyLine:overviewPolyline];
}
}
- (NSMutableArray *)decodePolyLine:(NSString *)encodedStr
{
NSMutableString *encoded = [[NSMutableString alloc] initWithCapacity:[encodedStr length]];
[encoded appendString:encodedStr];
[encoded replaceOccurrencesOfString:@"\\\\" withString:@"\\"
options:NSLiteralSearch
range:NSMakeRange(0, [encoded length])];
NSInteger len = [encoded length];
NSInteger index = 0;
NSMutableArray *array = [[NSMutableArray alloc] init];
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 *location = [[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]];
[array addObject:location];
}
return array;
}