NSTimer change repeat time

step1 
static NSTimer *timer;

step2
[timer invalidate];

step3
timer = [NSTimer scheduledTimerWithTimeInterval:newtime 
                                              target:self 
                                            selector:@selector(myMethod:)
                                            userInfo:nil 
                                             repeats:YES];

Upload an UIImage to the dropbox 相關討論

http://stackoverflow.com/questions/5933674/how-to-upload-files-to-dropbox-ios

http://stackoverflow.com/questions/5409023/upload-an-in-memory-uiimage-to-dropbox-ios-dev

Upload a UIImage from iPhone to Facebook 相關討論

http://stackoverflow.com/questions/4885471/upload-a-uiimage-from-iphone-to-facebook

http://stackoverflow.com/questions/750328/documented-process-for-using-facebook-connect-for-the-iphone-to-upload-photos

https://github.com/facebook/facebook-ios-sdk

Converting a CGPoint to NSValue

+ (NSValue *)valueWithCGPoint:(CGPoint)point

See iPhone doc

Creating a left-arrow button (like UINavigationBar's “back” style) on a UIToolbar

// create button
UIButton* backButton = [UIButton buttonWithType:101]; // left-pointing shape!
[backButton addTarget:self action:@selector(backAction) forControlEvents:UIControlEventTouchUpInside];
[backButton setTitle:@"Back" forState:UIControlStateNormal];
// create button item -- possible because UIButton subclasses UIView!
UIBarButtonItem* backItem = [[UIBarButtonItem alloc] initWithCustomView:backButton];
// add to toolbar, or to a navbar (you should only have one of these!)
[toolbar setItems:[NSArray arrayWithObject:backItem]];
navItem.leftBarButtonItem = backItem;