NKMapView 显示标注，并放大到标注位置

- (IBAction)FindUs:(id)sender {
    self.UsMap.hidden = NO;
    CLLocationCoordinate2D coord;
    coord.latitude = 34.7993;
    coord.longitude = 113.6939;
    POI *poi = [[POI alloc]initWithCoords:coord];
   [UsMap addAnnotation:poi]; 
    MKCoordinateRegion theRegion = { {0.0, 0.0 }, { 0.0, 0.0 } };
    theRegion.center=coord;
    [UsMap setZoomEnabled:YES];
    [UsMap setScrollEnabled:YES];
    theRegion.span.longitudeDelta = 0.01f;
    theRegion.span.latitudeDelta = 0.01f;
    [UsMap setRegion:theRegion animated:YES];
}