在地图上绘制两点间的线路图

原理：用google找到两个经纬度之间的路线点，然后在地图上把点用线连起来，就成了线路图

下面看代码：

  currLocation = [[CLLocation alloc] initWithLatitude:34.82373560 longitude:113.67290260];    MKCoordinateRegion region;    region.center = currLocation.coordinate;    region.span = MKCoordinateSpanMake(0.1, 0.1);    MKCoordinateRegion adjustedRegion = [self.myMapView regionThatFits:region];    [self.myMapView setRegion:adjustedRegion animated:YES];        anno = [[BasicMapAnnotation alloc] initWithLatitude:currLocation.coordinate.latitude                                           andLongitude:currLocation.coordinate.longitude];    anno.title = @"当前位置";    [self.myMapView addAnnotation:anno];        annoDes = [[DestAnnotionView alloc] initWithLatitude:34.774621 andLongitude:113.700673];    annoDes.title = @"广播大学";    [self.myMapView addAnnotation:annoDes];           CLLocationCoordinate2D coordinates[2] = {{currLocation.coordinate.latitude, currLocation.coordinate.longitude}, {34.774621, 113.700673}};    locations1 = [self getPointsFrom:coordinates[0] toEnd:coordinates[1]];    NSLog(@"locations = %@",locations1);    [self drawLineWithLocationArray:locations1];

- (void)drawLineWithLocationArray:(NSArray *)locationArray{    int pointCount = [locationArray count];    CLLocationCoordinate2D *coordinateArray = (CLLocationCoordinate2D *)malloc(pointCount * sizeof(CLLocationCoordinate2D));        for (int i = 0; i < pointCount; ++i) {        CLLocation *location = [locationArray objectAtIndex:i];        coordinateArray[i] = location.coordinate;    }        MKPolyline *routeLine = [MKPolyline polylineWithCoordinates:coordinateArray count:pointCount];    [self.myMapView setVisibleMapRect:[routeLine boundingMapRect]];    [self.myMapView addOverlay:routeLine];        free(coordinateArray);    coordinateArray = NULL;}#pragma mark mapView delegate functions-(void) mapView:(MKMapView *)mapView regionWillChangeAnimated:(BOOL)animated{    routeimageView.hidden = YES;}- (void)mapView:(MKMapView *)mapView regionDidChangeAnimated:(BOOL)animated{    [self updateRouteView:locations1];    routeimageView.hidden = NO;    [routeimageView setNeedsDisplay];}-(NSArray *)getPointsFrom:(CLLocationCoordinate2D)startPoint toEnd:(CLLocationCoordinate2D)destionPoint{    NSString * start = [NSString stringWithFormat:@"%f,%f",startPoint.latitude,startPoint.longitude];    NSString * end = [NSString stringWithFormat:@"%f,%f",destionPoint.latitude,destionPoint.longitude];    NSString * path = [NSString stringWithFormat:@"http://maps.google.com/maps/api/directions/json?origin=%@&destination=%@&sensor=true",start,end];    ASIHTTPRequest * request1 = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:path]];    [request1 startSynchronous];    NSString * data1 = [request1 responseString];    NSDictionary * dic = [data1 objectFromJSONString];    NSArray * dicRouts = [dic valueForKey:@"routes"];    NSDictionary * legs = [dicRouts objectAtIndex:0];    NSDictionary * temp = [legs objectForKey:@"overview_polyline"];    NSMutableString * endpoints = (NSMutableString *)[temp objectForKey:@"points"];    NSArray * arr = (NSArray *)[self decodePolyLine:endpoints];    return arr;}-(NSMutableArray *)decodePolyLine:(NSMutableString *)encoded{    NSInteger len = [encoded length];    NSInteger index = 0;    NSMutableArray * array1 = [[NSMutableArray alloc] init];    NSInteger lat = 0;    NSInteger lng = 0;    while (index<len)    {        NSInteger b;        NSInteger shift = 0;        NSInteger result = 0;        do {            b = [encoded characterAtIndex:index++]-63;            result |= (b & 0x1f)<<shift;            shift += 5;        } while (b>=0x20);        NSInteger dlat = ((result & 1)?~(result>>1):(result>>1));        lat += dlat;        shift = 0;        result = 0;        do {            b=[encoded characterAtIndex:index++]-63;            result |= (b & 0x1f)<<shift;            shift += 5;        } while (b>=0x20);        NSInteger dlng = ((result & 1)?~(result>>1):(result>>1));        lng += dlng;        NSNumber * latitude = [[NSNumber alloc] initWithFloat:lat*1e-5];        NSNumber * longitude = [[NSNumber alloc] initWithFloat:lng*1e-5];        CLLocation * loc = [[CLLocation alloc] initWithLatitude:[latitude floatValue] longitude:[longitude floatValue]];        [array1 addObject:loc];    }    NSLog(@"array1 = %@",array1);    return array1;}-(void)updateRouteView:(NSArray *)routs{    CGContextRef context = CGBitmapContextCreate(nil, routeimageView.frame.size.width, routeimageView.frame.size.height, 8, 4*routeimageView.frame.size.width, CGColorSpaceCreateDeviceRGB(), kCGImageAlphaPremultipliedLast);    CGContextSetStrokeColorWithColor(context, [UIColor redColor].CGColor);    CGContextSetRGBFillColor(context, 0.0, 1.0, 0.0, 0.0);    CGContextSetLineWidth(context, 6.0);    for (int i=0; i<routs.count; i++)    {        CLLocation * location = [routs objectAtIndex:i];        CGPoint point = [self.myMapView convertCoordinate:location.coordinate toPointToView:routeimageView];        if (i==0)        {            CGContextMoveToPoint(context, point.x, routeimageView.frame.size.height-point.y);        }        else        {            CGContextAddLineToPoint(context, point.x, routeimageView.frame.size.height-point.y);        }        CGContextStrokePath(context);                CGImageRef image = CGBitmapContextCreateImage(context);        UIImage * image1 = [UIImage imageWithCGImage:image];                routeimageView.image = image1;    }}- (MKAnnotationView *)mapView:(MKMapView *)mapView viewForAnnotation:(id <MKAnnotation>)annotation{    if ([annotation isKindOfClass:[BasicMapAnnotation class]])    {        MKAnnotationView * annocationView = [self.myMapView dequeueReusableAnnotationViewWithIdentifier:@"callAnno"];        if (annocationView == nil)        {            annocationView = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"callAnno"];        }        annocationView.image = [UIImage imageNamed:@"pin.png"];               annocationView.selected = YES;        annocationView.canShowCallout = YES;        return annocationView;    }    if ([annotation isKindOfClass:[DestAnnotionView class]])    {        MKAnnotationView * annocationView1 = [self.myMapView dequeueReusableAnnotationViewWithIdentifier:@"callAnno1"];        if (annocationView1 == nil)        {            annocationView1 = [[MKAnnotationView alloc] initWithAnnotation:annotation reuseIdentifier:@"callAnno1"];        }        annocationView1.image = [UIImage imageNamed:@"pin.png"];                annocationView1.selected = YES;        annocationView1.canShowCallout = YES;        return annocationView1;    }        return nil;}-(MKOverlayView *)mapView:(MKMapView *)mapView viewForOverlay:(id<MKOverlay>)overlay{    MKPolylineView *view = [[MKPolylineView alloc] initWithOverlay:overlay];    view.strokeColor = [[UIColor blackColor] colorWithAlphaComponent:0.5];    NSArray *pattern = [NSArray arrayWithObjects:[NSNumber numberWithInt:20], [NSNumber numberWithInt: 10], nil];    view.lineDashPattern = pattern;    view.lineWidth = 3;    return view;}

有心人 慢慢看代码啊，不做过多的解释。