在MKMapView中设置范围

Question

有10-15个经纬度需要同时显示在地图上，怎么设置区域这样可以在地图中看到所有的注释？

Answer 1

create class as below. create two class: ViewController is class of UIViewController and MapViewAnnotation is class of NSObject. I have created that two class as  below. bind mapview in XIB of ViewController and set delegate.

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

@interface ViewController : UIViewController<MKMapViewDelegate>{
    IBOutlet  MKMapView* mapView;
     NSMutableArray *arrayLocation;
}
@end
#import "ViewController.h"
@implementation ViewController
- (void)viewDidLoad
{
    [super viewDidLoad];

    arrayLocation = [[NSMutableArray alloc]init];
    NSMutableArray *arrAnnotations  = [[NSMutableArray alloc]init];
    NSMutableDictionary *dict = [[NSMutableDictionary alloc]init];
    [dict setValue:@"32.774125" forKey:@"latitude"];
    [dict setValue:@"-117.240658" forKey:@"longitude"];
    [dict setValue:@"Bars & Restaurants 1" forKey:@"title"];
    [arrayLocation addObject:dict];
    dict = nil;

    dict = [[NSMutableDictionary alloc]init];
    [dict setValue:@"32.784526" forKey:@"latitude"];
    [dict setValue:@"-117.240985" forKey:@"longitude"];
    [dict setValue:@"Bars & Restaurants 2" forKey:@"title"];
    [arrayLocation addObject:dict];
    dict = nil;

    dict = [[NSMutableDictionary alloc]init];
    [dict setValue:@"32.773477" forKey:@"latitude"];
    [dict setValue:@"-117.241144" forKey:@"longitude"];
    [dict setValue:@"Bars & Restaurants 3" forKey:@"title"];
    [arrayLocation addObject:dict];
    dict = nil;

    dict = [[NSMutableDictionary alloc]init];
    [dict setValue:@"32.775301" forKey:@"latitude"];
    [dict setValue:@"-117.238893" forKey:@"longitude"];
    [dict setValue:@"Bars & Restaurants 4" forKey:@"title"];
    [arrayLocation addObject:dict];
    dict = nil;

    for(int i=0;i<[arrayLocation count];i++)
    {
        CLLocationCoordinate2D location;
        location.latitude = [[[arrayLocation objectAtIndex:i] objectForKey:@"latitude"] doubleValue];
        location.longitude = [[[arrayLocation objectAtIndex:i] objectForKey:@"longitude"] doubleValue];

        MapViewAnnotation *newAnnotation = [[MapViewAnnotation alloc] initWithTitle:[[arrayLocation objectAtIndex:i] objectForKey:@"title"] Coordinate:location andIndex:i];
        [arrAnnotations addObject:newAnnotation]; 
    }
    [mapView addAnnotations:arrAnnotations];
    mapView.region = [MapViewAnnotation regionForAnnotations:arrAnnotations];
}
- (MKAnnotationView *)mapView:(MKMapView *)map viewForAnnotation:(id <MKAnnotation>)annotation 
{
    if (annotation == mapView.userLocation)
    {
        return nil;
    }
    MKPinAnnotationView *pin = (MKPinAnnotationView *) [mapView dequeueReusableAnnotationViewWithIdentifier: @"restMap"];
    if (pin == nil) 
    {
        pin = [[MKPinAnnotationView alloc] initWithAnnotation: annotation reuseIdentifier: @"restMap"];
    }
    else 
    {
        pin.annotation = annotation;
    }
    pin.pinColor = MKPinAnnotationColorRed;
    pin.animatesDrop = NO;
    pin.canShowCallout=TRUE;
    UIButton *btn=[UIButton buttonWithType:UIButtonTypeDetailDisclosure];
    MapViewAnnotation *temp = (MapViewAnnotation *)pin.annotation;
    btn.tag=temp.index;
    pin.rightCalloutAccessoryView=btn;
    [btn addTarget:self action:@selector(openDetail:) forControlEvents:UIControlEventTouchUpInside];

    return pin;
}
@end
Implementation of MapViewAnnotation class

#import <MapKit/MapKit.h>

@interface MapViewAnnotation : NSObject <MKAnnotation , MKMapViewDelegate>{
    NSString *title;
    int index;
    CLLocationCoordinate2D coordinate;

}
@property (nonatomic, copy) NSString *title;
@property (nonatomic, readwrite) int index;
@property (nonatomic, readonly) CLLocationCoordinate2D coordinate;

- (id)initWithTitle:(NSString *)ttl andCoordinate:(CLLocationCoordinate2D)c2d;
- (id)initWithTitle:(NSString *)ttl Coordinate:(CLLocationCoordinate2D)c2d andIndex:(int)intIndex;

+(MKCoordinateRegion) regionForAnnotations:(NSArray*) annotations ;
@end

#import "MapViewAnnotation.h"
@implementation MapViewAnnotation
@synthesize title, coordinate,index;

- (id)initWithTitle:(NSString *)ttl andCoordinate:(CLLocationCoordinate2D)c2d {
    self = [super init];
    title = ttl;
    coordinate = c2d;
    return self;
}
- (id)initWithTitle:(NSString *)ttl Coordinate:(CLLocationCoordinate2D)c2d andIndex:(int)intIndex
{
    self = [super init];
    title = ttl;
    coordinate = c2d;
    index = intIndex;
    return self;
}

+(MKCoordinateRegion) regionForAnnotations:(NSArray*) annotations 
{
    NSAssert(annotations!=nil, @"annotations was nil");
    NSAssert([annotations count]!=0, @"annotations was empty");

    double minLat=360.0f, maxLat=-360.0f;
    double minLon=360.0f, maxLon=-360.0f;

    for (id<MKAnnotation> vu in annotations) {
        if ( vu.coordinate.latitude  < minLat ) minLat = vu.coordinate.latitude;
        if ( vu.coordinate.latitude  > maxLat ) maxLat = vu.coordinate.latitude;
        if ( vu.coordinate.longitude < minLon ) minLon = vu.coordinate.longitude;
        if ( vu.coordinate.longitude > maxLon ) maxLon = vu.coordinate.longitude;
    }
    CLLocationCoordinate2D center = CLLocationCoordinate2DMake((minLat+maxLat)/2.0, (minLon+maxLon)/2.0);
    MKCoordinateSpan span = MKCoordinateSpanMake(maxLat-minLat, maxLon-minLon);
    MKCoordinateRegion region = MKCoordinateRegionMake (center, span);
    return region;
}
@end