摘要：
ProblemYou want to allow the users of your app to select from a list of values.SolutionUse the UIPickerView class.DiscussionA picker view is a graphic... 阅读全文
摘要：
ProblemYou want to instantiate and display a map on a viewSolutionCreate an instance of the MKMapView class and add it to a view or assign it as a sub... 阅读全文