Understanding iOS 6 Interface orientation change

问题:

ADDED: I see that my question is viewed often without upvotes so I decided that you guys do not get what you search. Redirecting you to question that has really nice answer about How to handle orientation changes in iOS6

Specific demands to orientation changes: Restricted rotation

Upvotes are welcome :)

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I've created a new project from Master Detail template and trying to start it with landscape orientation. As you know the

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation

method is deprecated and we must use

- (NSUInteger)supportedInterfaceOrientations

and/or

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation

Here's my code:

- (NSUInteger)supportedInterfaceOrientations {
    NSLog(@"supported called");
    return UIInterfaceOrientationMaskAll;//Which is actually a default value
}

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation {
    NSLog(@" preferred called");//This method is never called. WHY?
    return UIInterfaceOrientationLandscapeRight;
}

As you can see I'm trying to return landscape orientation in preferred method but it is never called. p.s. documentation states:

Discussion The system calls this method when presenting the view controller full screen. You implement this method when your view controller supports two or more orientations but the content appears best in one of those orientations.

If your view controller implements this method, then when presented, its view is shown in the preferred orientation (although it can later be rotated to another supported rotation). If you do not implement this method, the system presents the view controller using the current orientation of the status bar.

So, the question is: Why the prefferredOrientation method is never get called? And how should we handle different orientations in different controllers?. Thanks! P.S don't mark the question as duplicate. I've investigated all similar questions and they do not have answer for mine.

回答1:

About preferredInterfaceOrientationForPresentation

preferredInterfaceOrientationForPresentation is never called because this is not a "presented" view controller. There is no "presentation" involved here.

"Presented" and "presentation" are not some vague terms meaning "appears". These are precise, technical terms meaning that this view controller is brought into play with the call presentViewController:animated:completion:. In other words, this event arrives only if this is what we used to call a "modal" view controller.

Well, your view controller is not a modal view controller; it is not brought into play with presentViewController:animated:completion:. So there is no "presentation" involved, and therefore preferredInterfaceOrientationForPresentation is irrelevant here.

I'm being very explicit about this because I'm thinking that many folks will be confused or misled in the same way you were. So perhaps this note will help them.

Launch into Landscape

In iOS 6, the "Supported Interface Orientations" key in your Info.plist is taken much more seriously than previously. The solution to your overall problem of launching into a desired orientation is:

1. Make sure that "Supported Interface Orientations" in your Info.plist lists all orientations your app will ever be allowed to assume.

2. Make sure that the desired launch orientation is first within the "Supported Interface Orientations".

That's all there is to it. You should not in fact have to put any code into the root view controller to manage the initial orientation.

回答2:

If you would like launch modal view in Landscape Mode, just put this code in presented view controller

- (UIInterfaceOrientation)preferredInterfaceOrientationForPresentation
{
    UIInterfaceOrientation orient = [[UIApplication sharedApplication] statusBarOrientation];
    if (UIInterfaceOrientationIsLandscape(orient)) {
        return orient;
    }

    return UIInterfaceOrientationLandscapeLeft;
}

Then, present this controller as usual

UIViewController *vc = [[UIViewController alloc] initWithNibName:nil bundle:nil];
[vc setModalTransitionStyle:UIModalTransitionStyleCrossDissolve];
[vc setModalPresentationStyle:UIModalPresentationFullScreen];
[self.navigationController presentViewController:vc animated:YES completion:^{}];

回答3:

There is a very simple answer: You can only change or fix the interface orientation of a modal presented view controller. If you do so i.e. with a Present Modally segue in Interface builder (or the navigation controller method) you can define the allowed orientations with

- (NSUInteger)supportedInterfaceOrientations {
    return UIInterfaceOrientationMaskPortrait; // for example else an addition of all allowed
}

This event doesn't fire up when you only push a view controller on the navigation Controller ... so : You don't have a BACK button and need a

[self dismissViewControllerAnimated:YES completion: ^(void) {

    }];

to close it.