MKMapView

how to trigger map view to show callout annotations?

- (void)mapView:(MKMapView *)mapView didAddAnnotationViews:(NSArray *)views
{
    //Here
    [mapView selectAnnotation:[[mapView annotations] lastObject] animated:YES];
}

reference

how to remove all annotations in mapview?

[mapView removeAnnotations:mapView.annotations]

mapview examples?

apple developer map search

how to open address with ios map?

-(void)actionSheet:(UIActionSheet *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex{

    NSString *btnTitle = [actionSheet buttonTitleAtIndex:buttonIndex];
    if (buttonIndex == 0) {
        if (!ISIOS6) {//ios6 调用goole网页地图
            NSString *urlString = [[NSString alloc]
                                   initWithFormat:@"http://maps.google.com/maps?saddr=&daddr=%.8f,%.8f&dirfl=d",self.naviCoordsGd.latitude,self.naviCoordsGd.longitude];

            NSURL *aURL = [NSURL URLWithString:urlString];
            [[UIApplication sharedApplication] openURL:aURL];
        }else{//ios7 跳转apple map
            CLLocationCoordinate2D to;

            to.latitude = naviCoordsGd.latitude;
            to.longitude = naviCoordsGd.longitude;
            MKMapItem *currentLocation = [MKMapItem mapItemForCurrentLocation];
            MKMapItem *toLocation = [[MKMapItem alloc] initWithPlacemark:[[MKPlacemark alloc] initWithCoordinate:to addressDictionary:nil]];

            toLocation.name = addressStr;
            [MKMapItem openMapsWithItems:[NSArray arrayWithObjects:currentLocation, toLocation, nil] launchOptions:[NSDictionary dictionaryWithObjects:[NSArray arrayWithObjects:MKLaunchOptionsDirectionsModeDriving, [NSNumber numberWithBool:YES], nil] forKeys:[NSArray arrayWithObjects:MKLaunchOptionsDirectionsModeKey, MKLaunchOptionsShowsTrafficKey, nil]]];
        }
    }
    if ([btnTitle isEqualToString:@"google地图"]) {
        NSString *urlStr = [NSString stringWithFormat:@"comgooglemaps://?saddr=%.8f,%.8f&daddr=%.8f,%.8f&directionsmode=transit",self.nowCoords.latitude,self.nowCoords.longitude,self.naviCoordsGd.latitude,self.naviCoordsGd.longitude];
        [[UIApplication sharedApplication] openURL:[NSURL URLWithString:urlStr]];
    }else if ([btnTitle isEqualToString:@"高德地图"]){
        NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:@"iosamap://navi?sourceApplication=broker&backScheme=openbroker2&poiname=%@&poiid=BGVIS&lat=%.8f&lon=%.8f&dev=1&style=2",self.addressStr,self.naviCoordsGd.latitude,self.naviCoordsGd.longitude]];
        [[UIApplication sharedApplication] openURL:url];

    }else if ([btnTitle isEqualToString:@"百度地图"]){
        double bdNowLat,bdNowLon;
        bd_encrypt(self.nowCoords.latitude, self.nowCoords.longitude, &bdNowLat, &bdNowLon);

        NSString *stringURL = [NSString stringWithFormat:@"baidumap://map/direction?origin=%.8f,%.8f&destination=%.8f,%.8f&&mode=driving",bdNowLat,bdNowLon,self.naviCoordsBd.latitude,self.naviCoordsBd.longitude];
        NSURL *url = [NSURL URLWithString:stringURL];
        [[UIApplication sharedApplication] openURL:url];
    }else if ([btnTitle isEqualToString:@"显示路线"]){
        [self drawRout];
    }
}

Or using the URL reference