在MKMapView中设置区域显示所有注释
原问题来自于CSDN问答频道，更多解决方案见：http://ask.csdn.net/questions/2005
问题描述：
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？
解决方案：
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;}@endImplementation 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