Getting “Using two-stage rotation animation” warni

问题:

I wrote simple code to test UIImagePickerController:

@implementation ProfileEditViewController

- (void)viewDidLoad {
  [super viewDidLoad];

  photoTaker_ = [[UIImagePickerController alloc] init];
  photoTaker_.delegate = self;
  photoTaker_.sourceType = UIImagePickerControllerSourceTypeCamera;
  photoTaker_.showsCameraControls = NO;
}

- (void)viewDidAppear: (BOOL)animated {
  [self presentModalViewController: photoTaker_ animated: NO];
}

@end

And I'm getting strange warnings like the following:

2010-05-20 17:53:13.838 TestProj[2814:307] Using two-stage rotation animation. To use the smoother single-stage animation, this application must remove two-stage method implementations. 2010-05-20 17:53:13.849 TestProj[2814:307] Using two-stage rotation animation is not supported when rotating more than one view controller or view controllers not the window delegate

Got any idea what this is about? Thanks a lot in advance!

回答1:

This message will appear if you are presenting the UIImagePickerController within another UIViewController. Because it isn't pushed like a UINavigationController stack, there is confusion at the UIWindow level. I don't know if the warning is a problem, but to eliminate the warning you can do the following:

// self = a UIViewController  
//  

- (void) showCamera  
{  
    cameraView = [[UIImagePickerController alloc] init];  
    [[[UIApplication sharedApplication] keyWindow] setRootViewController:cameraView];  
    [self presentModalViewController:cameraView animated:NO];  
}   

- (void) removeCamera  
{  
    [[[UIApplication sharedApplication] keyWindow] setRootViewController:self];  
    [self dismissModalViewControllerAnimated:NO];  
    [cameraView release];  
}  

回答2:

Perhaps you are adding the root UIViewController's view as a subview of the window instead of assigning the view controller to the window's rootController property?

回答3:

IT ALL FALLS BACK ON THE UI

This warning can be implemented for several different objects: Pickers, keyboard, etc.

I have found that it is related to the UI taking two steps to complete a transition or other animation. Or for any instance where the UI is trying to finish one thing and is being asked to execute another before it has finished. (therefore it covers a wide range of possible triggers)

I have seen the warning appear on 4.0 & 4.2. In my case I was working with rotating the device and catching whether the keyboard was still up-(i.e. text field was still first responder). If so, the keyboard needed to stay up for between the views, but this presented other complications with other views.

Therefore, I implemented a BOOL tracker to keep track if keybaordIsPresent, and if so I was {textfield resignFirstResponder]; when detecting the orientation change and the reset the textfield to becomeFristResponder after the transition that was wrapped in an Animation Block. My BOOL tracker worked better, I still use the NSNotifications for the Keyboard, but there were overlaps of notifications during rotations because the keyboard was being dismissed without requesting such. The BOOL is set to NO on Load, and when the [textfield resignFirstResponder]; is implemented. *not when "-(void)keyboardWillhide is trigger by the NSNotifications, which gives me both working triggers that never conflict. The BOOL is set to YES, only when the user touches textfield which automatically triggers becomeFirstResponder.

I removed the warning by taking the [textfild resignFirstResponder]; out of the

-(void)willAnimateFirstHalfOfRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
//if (keyboardIsPresent == YES) {[self.entryTextField resignFirstResponder];}

} and placing it back at the top of the code for the:

- (void)didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation {

if (keyboardIsPresent == YES) {
    [self.entryTextField resignFirstResponder];
}

//Determine Which Orientation is Present:
if((fromInterfaceOrientation == UIInterfaceOrientationPortrait) || (fromInterfaceOrientation == UIInterfaceOrientationPortraitUpsideDown)){
    //LANDSCAPE VIEW:
    [self configureLandscapeView];
}else {
    //PORTRAIT VIEW:
    [self configurePortraitView];
}

}

---

**Even though I had no code inside the -(void)willAnimatFirstHalfOfRotationToInterface:, the warning was still popping up. I think the warning was still popping up because the compiler still has to attempt the method while it is trying to execute the first animation and therefore gets the double animation call or overlap of resources. It doesn't know that there is no executable code with the method until after it runs through it. And by that time it already set aside resource in preparation for handling possible actions within the method.

---

**To ellimiate the warning I had to remove or nil out the code for the willAnimateFirstHalfOfRotation, so that the compiler does not have to even check to see if there is a possible 2nd animation or action that may need to be executed at the same time.

/*-(void)willAnimateFirstHalfOfRotationToInterfaceOrientation:(UIInterfaceOrientation)toInterfaceOrientation duration:(NSTimeInterval)duration {
//if (keyboardIsPresent == YES) {[self.entryTextField resignFirstResponder];}}*/

After the transition is completed, within the original animation block I check to see if the "keyboardIsPresent" was YES prior to the rotation, and if so, I resign the First Responder once again. I use setAnimationDuration:0.3which comes out pretty clean and not jumpy.

回答4:

Well, you are presenting UIImagePickerController modally inside viewDidAppear of ProfileEditViewController.

Think about this. That means when ProfileEditViewController view appears, the UIImagePickerController appears, say later you dismiss UIImagePickerController and it goes back to ProfileEditViewController, then viewDidAppear is called again and UIImagePickerController appears, say later you dismiss UIImagePickerController and it goes back to ProfileEditViewController, then viewDidAppear is called again and.... you get the idea.

That warning is rather cryptic though, not sure if that is what it's trying to tell you. I would suggest making a button somewhere on the ProfileEditViewController that calls presentModalViewController and also make sure you have a way to dismiss the UIImagePickerController (I've never used it not sure if it has one automatically).

回答5:

You may be trying to present two modal view controllers at the same time, and they are fighting for animation resources.

1) There is rarely any UI reason to do this. You could instead just go directly to the second view controller (the image picker); and, after dismissing it, then present the first view or view controller.

2) If you do want two stacked view controllers or a view controller on top of a view, then set a timer in viewDidAppear to present the second view controller after the first one has finished it's animation. (You could display a dummy png image of a blank picker in the first one to prevent too much display flashing until the second view controller goes live.)

EDIT - Added a random code example:

I might try substituting this as an experiment:

- (void)foo {
    [self presentModalViewController: photoTaker_ animated: NO];
}

- (void)viewDidAppear: (BOOL)animated {
    NSTimer *bar = [ NSTimer scheduledTimerWithTimeInterval: (2.0f)
                             target: self  
                             selector: @selector(foo)
                             userInfo: nil
                             repeats:NO ];
}

A shorter time delay may work as well.

回答6:

I just had the same problem. In my case was a silly mistake that I'm putting here just in case anyone else falls into that same issue.

In my tabbed app I remove one of the original ViewControllers and added a new one with Storyboard to create a "Settings" section.

This new VC had to be a table view VC and even I designed, compiled and run it without a problem, when I changed the orientation of the app I kept getting this “Using two-stage rotation animation” error.

My problem was that I forgot to change in the original .h file interface "UIViewController" for "UITableViewController".

Once this was done I changed on the Storyboard identity badge the class from the general value to my SettingsViewController and that was the end of it.

I hope it can help someone else. It took me a while to get to bottom of this.

Cheers,

回答7:

I think the warning here is about Core Animation performance. As a test, I loaded the image picker without any action sheet or other animations going on and the warnings are still there. I think these are warnings coming from the image picker class itself and not from any misuse of the API.