Question

我正在通过JSON获得价值观：

{
        id = 1;
        latitude = "-23.0002";
        longitude = "-43.2438";
        name = Vips;
}

{
        id = 2;
        latitude = "-22.9283";
        longitude = "-43.1746";
        name = Elegance;
}

...

我需要在tableview中显示这些值，按距离到用户位置排序。并且必须始终更新此值。我怎么能这样做？

displayObject是一个NSMutableArray，我从WS中获取值。在viewWillappear中，我正在尝试：

NSArray *rawData = [NSArray arrayWithArray:displayObject];

rawData = [rawData sortedArrayUsingComparator: ^(id a, id b) {

    CLLocationDistance dist_a= [[a objectForKey:@"coordinate"] distanceFromLocation: locAtual];
    CLLocationDistance dist_b= [[b objectForKey:@"coordinate"] distanceFromLocation: locAtual];
    if ( dist_a < dist_b ) {
        return (NSComparisonResult)NSOrderedDescending;
    } else if ( dist_a > dist_b) {
        return (NSComparisonResult)NSOrderedDescending;
    } else {
        return (NSComparisonResult)NSOrderedSame;
    }
}];

但它不起作用。我只有纬度和经度。我没有“坐标”。有人？

谢谢!!

Answer 1

如果您正在计算距离，请将其与存储在数组中的数据一起添加，然后根据距离进行排序。

for (int idx = 0; idx<[displayObject count];idx++) {

    NSMutableDictionary *dict = [displayObject[idx] mutableCopy];
    CLLocationDegrees latitude = [dict[@"latitude"] doubleValue];
    CLLocationDegrees longitude = [dict[@"longitude"] doubleValue];
    CLLocation *location = [[CLLocation alloc]initWithLatitude:latitude longitude:longitude];
    CLLocationDistance distance = [userLocation distanceFromLocation:location];
    //Storing as string since latitude and longitude is also string values
    //Since its a dictionary storing as NSNumber is better
    dict[@"distance"] = [@(distance) stringValue];

    displayObject[idx] = dict;

}

//sorting based on distance
NSSortDescriptor *descriptor = [NSSortDescriptor sortDescriptorWithKey:@"distance" ascending:YES];
[displayObject sortUsingDescriptors:@[descriptor]];

Answer 2

首先创建具有纬度和经度的位置对象：

CLLocation *location = [[CLLocation alloc] initWithLatitude:-23.0002 longitude:-43.2438];
CLLocation *userLocation = [[CLLocation alloc] initWithLatitude:-23.0002 longitude:-43.2438];

使用这两个对象，可以使用以下方法检查距离：

 -(CLLocationDistance)distanceFromLocation:(const CLLocation *)location

例如：

CLLocationDistance dist_a = [locationUser distanceFromLocation:location];

Answer 3

你的比较器错了。试试这个：

rawData = [rawData sortedArrayUsingComparator: ^(id a, id b) 
{
    CLLocation *locationA = [[CLLocation alloc] initWithLatitude:[[a objectForKey:@"latitude"] doubleValue] longitude:[[a objectForKey:@"longitude"] doubleValue]];
    CLLocation *locationB = [[CLLocation alloc] initWithLatitude:[[b objectForKey:@"latitude"] doubleValue] longitude:[[b objectForKey:@"longitude"] doubleValue]];

    CLLocationDistance dist_a = [locationA distanceFromLocation:currentLocation];
    CLLocationDistance dist_b = [locationB distanceFromLocation:currentLocation];

    if ( dist_a < dist_b ) {
        return (NSComparisonResult)NSOrderedAscending;
    } else if ( dist_a > dist_b) {
        return (NSComparisonResult)NSOrderedDescending;
    } else {
        return (NSComparisonResult)NSOrderedSame;
    }
}];

按距离排序表（经度和纬度）

3 个答案: