ios4

问题 NSDate *currentDate = [NSDate date]; NSDateFormatter *format = [[NSDateFormatter alloc] init]; [format setDateFormat:@"MM/dd/yyyy,h,mm,a"]; NSString *dateString = [format stringFromDate:currentDate]; [format release]; NSLog(dateString); Output in: Device iPhone4 [240:707] 10/25/2011,22,23, Current language: auto; currently objective-c warning: Unable to read symbols for /SDK4.2/Platforms/iPhoneOS.platform/DeviceSupport/4.3.3 (8J2)/Symbols/Developer/usr/lib/libXcodeDebuggerSupport.dylib Output

问题 Is there a formula to convert a quaternion to an angle? Looking to do something on the iPhone using the Core Motion API and the gyro so that based on data I receive from it (in the form of quaternions) I can project a UIView on the screen. Thanks 回答1: Yes, see Quaternions and spatial rotation. The unit quaternion (w, x, y, z) represents a rotation about the axis (x, y, z) of an angle of 2*cos -1 (w). Note that this is only true of unit quaternions. Non-unit quaternions do not represent

来源： https://stackoverflow.com/questions/4440420/store-a-custom-value-in-a-ekevent-iphone-calendar

问题 What is the best way to keep my UI constants in seperate class accesible from all controllers? UIView, UIImage and UIColour all these images and colours create a such mess of allocations and releases in my controllers and most of them are even same. Instead of alloc/relase the same images and views, CAlayers over and over again in different classes, I want to create them once, cache them (or something like that) and easily access when needed. I want to keep memory and my code clean. 回答1: yes

问题 What is the best way to keep my UI constants in seperate class accesible from all controllers? UIView, UIImage and UIColour all these images and colours create a such mess of allocations and releases in my controllers and most of them are even same. Instead of alloc/relase the same images and views, CAlayers over and over again in different classes, I want to create them once, cache them (or something like that) and easily access when needed. I want to keep memory and my code clean. 回答1: yes

问题 The documentation is rather poorly written when talking about playing audio in the background. It gives the impression that all you have to do to continue playing the audio that you are currently playing is to just add a key/value pair to the info.plist file and wallah, it's magic. However, this is not the case. For instance, if I play an mp3 that is 2 minutes long, obviously the audio is long enough to be able to play after I hit the home button to send my app to the background. The thing is

问题 I've found on Apple documentation pages an example in which they deallocate the memory as follows: - (void)viewDidUnload { self.mapAnnotations = nil; [super viewDidUnload]; // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand. // For example: self.myOutlet = nil; } - (void)dealloc { [mapAnnotations release]; [super dealloc]; } I was wondering why they first set mapAnnotation to nil in viewDidUnload and then they release in dealloc method and why they refer

问题 I've found on Apple documentation pages an example in which they deallocate the memory as follows: - (void)viewDidUnload { self.mapAnnotations = nil; [super viewDidUnload]; // Relinquish ownership of anything that can be recreated in viewDidLoad or on demand. // For example: self.myOutlet = nil; } - (void)dealloc { [mapAnnotations release]; [super dealloc]; } I was wondering why they first set mapAnnotation to nil in viewDidUnload and then they release in dealloc method and why they refer

问题 I complete all step to provisional but i faced " Xcode cannot run using the selected device ." and below of this line is " No provisioned iOS devices are available with a compatible iOS version. Connect an iOS device with a recent enough version of iOS to run your application or choose an iOS simulator as the destination ." when i am going to organizer its show the Yellow status please some one help me he version of iOS on “KashodhaniPhone” does not match any of the versions of iOS supported

问题 I want to add image and some text on another image and create a single image. I have got to add text but not able to figure out that how to add image. Any help? 回答1: This snippet assumes you have UIImage's named bottomImage for the base image to be drawn upon, and topImage that will be drawn ON (above) the bottomImage. xpos,ypos are floats to describe the target x,y (top left) position where topImage will be drawn, and targetSize the size in which topImage will be drawn on bottomImage. ...