舆图描线的简单示例

首先，需要将CoreLocation.framework和MapKit.framework加入到项目中。

mapLinesViewController.h

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

@interface mapLinesViewController : UIViewController {
	MKMapView *mapView;
	MapRouteLayerView *routeView;
}

@property(nonatomic, retain) MKMapView *mapView;
@property(nonatomic, retain) MapRouteLayerView *routeView;

@end

mapLinesViewController.m

#import "mapLinesViewController.h"
#import <CoreLocation/CoreLocation.h>
#import "MapRouteLayerView.h"

@implementation mapLinesViewController

@synthesize routeView;
@synthesize mapView;

- (void)viewDidLoad {
    [super viewDidLoad];
	NSString *filePath = [[NSBundle mainBundle] pathForResource:@"route" ofType:@"csv"];
	NSString *fileContents = [NSString stringWithContentsOfFile:filePath];
	NSArray *pointStrings = [fileContents componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];	
	NSMutableArray *points = [[NSMutableArray alloc] initWithCapacity:pointStrings.count];	
	for(int idx = 0; idx < pointStrings.count; idx++) {
		NSString *currentPointString = [pointStrings objectAtIndex:idx];
		NSArray *latLonArr = [currentPointString componentsSeparatedByCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@","]];		
		CLLocationDegrees latitude = [[latLonArr objectAtIndex:0] doubleValue];
		CLLocationDegrees longitude = [[latLonArr objectAtIndex:1] doubleValue];		
		CLLocation *currentLocation = [[[CLLocation alloc] initWithLatitude:latitude longitude:longitude] autorelease];
		[points addObject:currentLocation];
	}
	mapView = [[MKMapView alloc] initWithFrame:CGRectMake(0, 0, self.view.frame.size.width, self.view.frame.size.height)];
	[self.view addSubview:mapView];
	routeView = [[MapRouteLayerView alloc] initWithRoute:points mapView:mapView];	
	[points release];
}

- (void)viewDidUnload {
	self.mapView = nil;
	self.routeView = nil;
}

- (void)dealloc {	
	[mapView release];
	[routeView release];
    [super dealloc];
}

@end

MapRouteLayerView.h

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

@interface MapRouteLayerView : UIView <MKMapViewDelegate> {
	MKMapView *mapView;
	NSArray *points;
	UIColor *lineColor;
}

@property(nonatomic, retain) NSArray *points;
@property(nonatomic, retain) MKMapView *mapView;
@property(nonatomic, retain) UIColor *lineColor; 

- (id)initWithRoute:(NSArray *)routePoints mapView:(MKMapView *)mapView;

@end

MapRouteLayerView.m

#import "MapRouteLayerView.h"

@implementation MapRouteLayerView

@synthesize mapView;
@synthesize points;
@synthesize lineColor; 

- (id)initWithRoute:(NSArray *)routePoints mapView:(MKMapView *)mapView {
	self = [super initWithFrame:CGRectMake(0, 0, mapView.frame.size.width, mapView.frame.size.height)];
	[self setBackgroundColor:[UIColor clearColor]];	
	[self setMapView:mapView];
	[self setPoints:routePoints];
	
	CLLocationDegrees maxLat = -90;
	CLLocationDegrees maxLon = -180;
	CLLocationDegrees minLat = 90;
	CLLocationDegrees minLon = 180;
	
	for(int idx = 0; idx < self.points.count; idx++) {
		CLLocation *currentLocation = [self.points objectAtIndex:idx];
		if(currentLocation.coordinate.latitude > maxLat)
			maxLat = currentLocation.coordinate.latitude;
		if(currentLocation.coordinate.latitude < minLat)
			minLat = currentLocation.coordinate.latitude;
		if(currentLocation.coordinate.longitude > maxLon)
			maxLon = currentLocation.coordinate.longitude;
		if(currentLocation.coordinate.longitude < minLon)
			minLon = currentLocation.coordinate.longitude;
	}
	
	MKCoordinateRegion region;
	region.center.latitude = (maxLat + minLat) / 2;
	region.center.longitude = (maxLon + minLon) / 2;
	region.span.latitudeDelta = maxLat - minLat;
	region.span.longitudeDelta = maxLon - minLon;
	
	[self.mapView setRegion:region];
	[self.mapView setDelegate:self];
	[self.mapView addSubview:self];
	
	return self;
}

- (void)drawRect:(CGRect)rect {
	if(!self.hidden && nil != self.points && self.points.count > 0) {
		CGContextRef context = UIGraphicsGetCurrentContext(); 		
		if(nil == self.lineColor)
			self.lineColor = [UIColor blueColor];		
		CGContextSetStrokeColorWithColor(context, self.lineColor.CGColor);
		CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1.0);
		CGContextSetLineWidth(context, 2.0);		
		for(int idx = 0; idx < self.points.count; idx++) {
			CLLocation *location = [self.points objectAtIndex:idx];
			CGPoint point = [mapView convertCoordinate:location.coordinate toPointToView:self];			
			if(idx == 0) {
				CGContextMoveToPoint(context, point.x, point.y);
			} else {
				CGContextAddLineToPoint(context, point.x, point.y);
			}
		}		
		CGContextStrokePath(context);
	}
}

#pragma mark mapView delegate functions
- (void)mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated {
	self.hidden = YES;
}

- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated {
	self.hidden = NO;
	[self setNeedsDisplay];
}

- (void) dealloc {
	[points release];
	[mapView release];
	[lineColor release];
	[super dealloc];
}

@end

示例图：