在横向打开应用程序时，新创建的UIWindow处于横向

据我了解，当方向改变时，新创建的UIWindow不会自动旋转。我不知道这是iOS 8的新功能还是错误，但是我可以通过以下代码克服问题：

UIWindow *window=[UIApplication sharedApplication].keyWindow;
self.progressWindow = [[UIWindow alloc] initWithFrame:window.frame];
self.progressWindow.backgroundColor = [UIColor colorWithRed:0.0f green:0.0f blue:0.0f alpha:0.5f];
self.progressWindow.windowLevel = UIWindowLevelAlert;

/* some other code to create the subviews */

[self handleOrientationChange];
[self.progressWindow makeKeyAndVisible];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(handleOrientationChange) name:UIApplicationDidChangeStatusBarFrameNotification object:nil];

handleOrientationChange的实现如下：

#define DegreesToRadians(degrees) (degrees * M_PI / 180)

- (void)handleOrientationChange
{
    if (self.progressWindow)
    {
        // rotate the UIWindow manually
        UIInterfaceOrientation orientation = [[UIApplication sharedApplication] statusBarOrientation];
        [self.progressWindow setTransform:[self transformForOrientation:orientation]];

        // resize the UIWindow according to the new screen size
        if ([[UIScreen mainScreen] respondsToSelector:@selector(nativeBounds)])
        {
            // iOS 8
            CGRect screenRect = [UIScreen mainScreen].nativeBounds;
            CGRect progressWindowFrame = self.progressWindow.frame;
            progressWindowFrame.origin.x = 0;
            progressWindowFrame.origin.y = 0;
            progressWindowFrame.size.width = screenRect.size.width / [UIScreen mainScreen].nativeScale;
            progressWindowFrame.size.height = screenRect.size.height / [UIScreen mainScreen].nativeScale;
            self.progressWindow.frame = progressWindowFrame;
        }
        else
        {
            // iOs 7 or below
            CGRect screenRect = [UIScreen mainScreen].bounds;
            CGRect progressWindowFrame = self.progressWindow.frame;
            progressWindowFrame.origin.x = 0;
            progressWindowFrame.origin.y = 0;
            progressWindowFrame.size.width = screenRect.size.width;
            progressWindowFrame.size.height = screenRect.size.height;
            self.progressWindow.frame = progressWindowFrame;
        }
    }
}

- (CGAffineTransform)transformForOrientation:(UIInterfaceOrientation)orientation {

    switch (orientation) {

        case UIInterfaceOrientationLandscapeLeft:
            return CGAffineTransformMakeRotation(-DegreesToRadians(90));

        case UIInterfaceOrientationLandscapeRight:
            return CGAffineTransformMakeRotation(DegreesToRadians(90));

        case UIInterfaceOrientationPortraitUpsideDown:
            return CGAffineTransformMakeRotation(DegreesToRadians(180));

        case UIInterfaceOrientationPortrait:
        default:
            return CGAffineTransformMakeRotation(DegreesToRadians(0));
    }
}

我从这个问题的公认答案中得到了这个主意。