iphone google maps crosshair button

I would like 开发者_如何学Cto use or emulate a button like the gps button in the bottom left corner of the standard maps application on the iphone OS. The button behaves like a toggle button where gps is enabled or disabled depending on whether it is pushed and it may hold a small spinner component while the gps is finding your position.

Does anyone know if this component can be easily constructed using default components? If no, what would be the best way to develop such a component?

Is the crosshair/target icon a generic icon that I can re-use?

The button is just an image, you should be able to recreate it.

In order to do the tracking, I would look at this sample code: http://developer.apple.com/iphone/library/samplecode/LocateMe/index.html

It shows you how to get the GPS coordinates, then you can feed that data into a MKMapView.

Apple's Spinner Button is hidden, but can be used with systemButton: 100