Programmatically check whether GPS is enabled or not on iPhone

How can I check whether GPS is enabl开发者_如何学JAVAed or not on the iPhone?

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http://developer.apple.com/library/ios/#documentation/CoreLocation/Reference/CLLocationManager_Class/CLLocationManager/CLLocationManager.html

[CLLocationManager locationServicesEnabled]

Returns a Boolean value indicating whether location services are enabled on the device.