iPhone Landscape FAQ and Solutions_问答_开发者

There has been a lot of confusion and a set of corresponding set of questions here on SO how iPhone applications with proper handling for Landscape/Portrait mode autorotation can be implemented. It is especially difficult to implement such an application when starting in landscape mode is desired. The most common observed effect are scrambled layouts and areas of the screen where touches are no longer recognized.

A simple search for questions tagged iphone and landscape reveals these issues, which occur under certain scenarios:

Landscape only iPhone app with multiple nibs: App started in Landscape mode, view from first nib is rendered fine, everything view loaded from a different nib is not displayed correctly.
Iphone Landscape mode switching to Portraite mode on loading new controller: Self explanatory
iPhone: In landscape-only, after first addSubview, UITableViewController doesn’t rotate properly: Same issue as above.
iPhone Landscape-Only Utility-Template Application: Layout errors, controller does not seem to recognize the view should be rotated but displays a clipped portrait view in landscape mode, causing half of the screen to stay blank.
presentModalViewController in landscape after portrait viewController: Modal views are not correctly rendered either.

A set of different solutions have been presented, some of them including completely custom animation via CoreGraphics, while others build on the observation that the first view controller loaded from the main nib is always displayed correct.

I have spent a significant amount of time investigating this issue and finall开发者_开发技巧y found a solution that is not only a partial solution but should work under all these circumstances. It is my intend with this CW post to provide sort of a FAQ for others having issues with UIViewControllers in Landscape mode.

Please provide feedback and help improve the quality of this Post by incorporating any related observations. Feel free to edit and post other/better answers if you know of any.

What's in the documentation:

In your view controller, override shouldAutorotateToInterfaceOrientation: to declare your supported interface orientations. This property will/should be checked by the controller infrastructure everytime the device orientation changes.

- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)orientation
{
   return  (orientation == UIInterfaceOrientationLandscapeRight);
}

This is the absolute minimum your view controller needs to do. If you want to launch your application in landscape mode, you need to add the following key to your .plist file:

<key>UIInterfaceOrientation</key>
<string>UIInterfaceOrientationLandscapeRight</string>

Apple recommends starting landscape only applications in Landscape Right mode (see the HIG under User Experience Guidelines > Start Instantly).

What's not in the documentation:

A little background:

Everytime you try to load a different view controller other than that loaded from the main nib, your view controller is neither interrogated about it's supported interface orientations nor is its frame set correctly. Only the first view controller bound to the window will be layed out correctly.

Other people have suggested using a "MasterViewController" hooked up to the main window to which other controllers add their views as subviews instead of hooking directly into the window. While I have found this solutions is a viable option, it does not work correctly in the case of modal view controllers added to those said subviews. There's also a problem if you have some subviews that should be able to autorotate (what the master controller will prevent).

The usage of undocumented API's to force a certain interface orientation is not an option either.

The solution:

The best solution I have found so far is a modification of the "MasterViewController" workaround. Instead of using a custom "MasterViewController", a UINavigationController with hidden Navigation Bar and hidden Tab Bar is used. If all other views are pushed/popped from the navigation stack of this controller, auto-rotations of controllers on that stack will be managed correctly.

Modal controllers presented via presentModalViewController:animated: from any of the view controllers on the UINavigationController's navigation stack will be rotated and rendered with correct layout. If you want your modal view controller to be rotatable to a different orientation than that of the parent view controller, you need to return the desired orientation from the shouldAutorotateToInterfaceOrientation method of the parent controller while the modal view is presented. In order to properly restore the interface orientation when the modal controller is dismissed, you need to make sure shouldAutorotateToInterfaceOrientation returns the desired orientation for the parent controller before you call dismissModalViewController:animated:. You can use a private BOOL on your view controller to manage that (e.g. BOOL isModalMailControllerActive_).

I'll add a piece of sample code soon, It's just to late now. Please let me know if any unresolved issues remain or anything is unclear about this post. Feel free to edit and improve.

I had an interesting requirement for ios application:

main viewController should be only landscape, but all others (which can be pushed from main) can be landscape and portrait.

Problem occours - when I push to a new viewController, which then is rotated to portraited - and the pop back - main view is no longer landscape. Also - opening application, it is not in landscape.

In order to keep main viewcontroller landscape, no matter from what orientation it was popped/pushed, I did the following thing: (in viewWillAppear:)

//set statusbar to the desired rotation position
[[UIApplication sharedApplication] setStatusBarOrientation:UIDeviceOrientationLandscapeLeft animated:NO];

//present/dismiss viewcontroller in order to activate rotating.
UIViewController *mVC = [[[UIViewController alloc] init] autorelease];
[self presentModalViewController:mVC animated:NO];
[self dismissModalViewControllerAnimated:NO];

Hopefully it will help someone!

P.S.Tested on sdk 3.2.5 ios 5.0.1.

P.S. Thanks for all the info in this FAQ!

For the second bullet point, if you want to use pushViewController to go from Portrait-only to Landscape-only view, one simple hack I found is to put the following code into your pushed controller's viewDidLoad:

UIViewController *viewController = [[UIViewController alloc] init];
[self presentModalViewController:viewController animated:NO];
[self dismissModalViewControllerAnimated:NO];
[viewController release];

I'd like to add to Johannes' answer (using the UINavigationController as MasterViewController).

The disadvantage I have found is that ViewControllers that are newly pushed onto the master VC's navigation stack do not adjust to any prior orientation changes. In short, VCs already on the stack are rotated, modal view controllers presented from them are also rotated, but newly added VCs are not rotated.

I have tried many tricks to fix this before finding one that works. Most only work for pushViewController: with animated set to YES.

To fix the issue entirely, I have subclassed UINagivationController and overriden pushViewController:animated: as follows:

- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    // Correctly autoOrient the given view controller
    [self presentModalViewController:viewController animated:NO];
    [self dismissModalViewControllerAnimated:NO];

    // Push it as normal (now in its correct orientation)
    [super pushViewController:viewController animated:animated];
}

Temporarily (and quite invisibly) presenting the view controller allows it to receive its orientation update. It can then be pushed onto the navigation stack in its correct orientation.

Please let me know if this works for you. All updates and improvements are very welcome!

Finally, I highly recommend Johannes' approach to rotation management.

EDIT: Update on popping view controllers from the stack

It seems that all the popViewController-related selectors go crazy when performed with animated:YES. Specifically, the view controller is animated out in the wrong direction. You can use animated:NO and restrict the use of such animations to other UINavigationControllers deeper down in your hierarchy (i.e. the ones that you push onto the root navigation controller's stack).

Any input is greatly appreciated.

I'm developing an iPad app that displays vertically scrolling gallery view of an array of items upon startup. In landscape mode there are 4 items across. In portrait there are three. When turning the iPad orientation it is supposed to refresh the gallery to have the items fit neatly across the screen. Then I double tap on an item to drill down to a modal view of that item. Then I do stuff with that item. Finally I dismiss the modal view.

During the refresh or orientation change the gallery view calculates the number of items to display based on the screen width (or height) and the current orientation from UIViewController.interfaceOrientation.

I was having a problem getting this to work correctly. Sometimes it would display only two items in landscape orientation after I dismissed the modal dialog.

At first I was using the UIViewController.view.frame.size values to calculate the number of gallery items. When the modal view was dismissed this frame size was incorrect e.g. the width and height had been reversed even though the orientation had not changed while the modal dialog was displayed.

I switched to using the application delegate ([[UIApplication sharedApplication] delegate]] and taking the window.frame.size to calculate the number of gallery items to display across. The window.frame.size stays correct under orientation changes and modal dialogs. The gallery items display correctly now.

This will work...

UIWindow *window = [[UIApplication sharedApplication] keyWindow];
    UIView *view = [window.subviews objectAtIndex:0];
    [view removeFromSuperview];
    [window addSubview:view];