iOS JSON數組和MapKit

Question

我正在嘗試使用MapKit映射JSON數組。 使用下面的代碼，我可以在地圖上得到一個點，但是我需要標記很多針，並且准備了一個JSON數組。 我的單點代碼如下。

在我的.h文件中：

#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>

@interface MapViewController : UIViewController {

MKMapView *mapView;
NSData *data;

}

@property (nonatomic, retain) IBOutlet MKMapView *mapView;

@end

在我的.m文件中：

NSData *data = @"[{"id":"1","name":"Jiffy Lube","lat":"21.306","lon":"-157.861"},    
{"id":"2","name":"Bills
Oil","lat":"21.301","lon":"-157.863"},{"id":"3","name":"Auto Zone","lat":"21.307","lon":"-
157.862"}]";

// parse the JSON into a NSArray

NSError *error;
NSArray *array = [NSJSONSerialization JSONObjectWithData:data
                                                 options:0
                                                   error:&error];

Answer 1

您的JSON是一個字典項數組。 因此，您可以通過NSJSONSerialization檢索完整數組，然后遍歷生成的數組中的字典條目。

首先，你最初說你有JSON，如下所示：

[{"id":"1","name":"Jiffy Lube","lat":"21.306","lon":"-157.861"},    
{"id":"2","name":"Bills Oil","lat":"21.301","lon":"-157.863"},
{"id":"3","name":"Auto Zone","lat":"21.307","lon":"-157.862"}]

因此，如果它位於您已包含在捆綁包中的文件“test.json”中，則可以將其加載為：

// load the data from local file

NSString *path = [[NSBundle mainBundle] pathForResource:@"test" ofType:@"json"];
NSData *data = [NSData dataWithContentsOfFile:path];

如果你在Web服務器上有這個，你可以像這樣檢索它：

// load the data from web server

NSURL *url = [NSURL URLWithString:@"http://insert.your.server/and/url/here/test.json"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
    // use NSData here
}];

假設您將JSON供稿加載到名為data的NSData對象中，則可以執行以下操作：

// parse the JSON into a NSArray

NSError *error;
NSArray *array = [NSJSONSerialization JSONObjectWithData:data 
                                                 options:0
                                                   error:&error];
if (error != nil)
{
    // handle the error as you want
}

// a few variables to be used as we iterate through the array of results

CLLocationCoordinate2D location;                         // coordinates of the annotation
NSMutableArray *newAnnotations = [NSMutableArray array]; // an array in which we'll save our annotations temporarily
MKPointAnnotation *newAnnotation;                        // the pointer to the annotation we're adding

// iterate through the array, adding an annotation to our our array of new annotations

for (NSDictionary *dictionary in array)
{
    // retrieve latitude and longitude from the dictionary entry

    location.latitude = [dictionary[@"lat"] doubleValue];
    location.longitude = [dictionary[@"lon"] doubleValue];

    // create the annotation

    newAnnotation = [[MKPointAnnotation alloc] init];
    newAnnotation.title = dictionary[@"name"];
    newAnnotation.coordinate = location;

    // add it to our array
    //
    // incidentally, generally I just add it to the mapview directly, but
    // given that you have a didAddAnnotationViews, we'll just build up 
    // an array and add them all to the map view in one step after we're 
    // done iterating through the JSON results

    [newAnnotations addObject:newAnnotation];

    // clean up

    [newAnnotation release];
}

// when done, add the annotations

[self.mapView addAnnotations:newAnnotations];