iOS的JSON數組和MapKit

Question

我想映射一個JSON數組使用MapKit。我可以用下面的代碼在地圖上得到一個點，但我有幾十個我需要標記的引腳，並且準備了一個JSON數組。我的單點代碼如下。

在我的.h文件：

#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：

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

你JSON是字典項的數組。所以你可以通過NSJSONSerialization來檢索完整的數組，然後迭代結果數組中的字典條目。

首先，你原來說你有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，如果這是坐在一個文件，「test.json」你已經包含在你的包，你可以加載它像這樣：

// load the data from local file 

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

如果你有這樣的一個Web服務器上，你會找回它像這樣：

// 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ÿ歐加載你的JSON飼料到名爲data一個NSData對象，你可能只是這樣做：

// 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];