ios - UIViewController animations wait until animation complete

Question

I'm using this observer: UIDeviceOrientationDidChangeNotification to detect when user is changing the device orientation. When the orientation changed to landscape I present a new UIViewController or dismiss this UIViewController when he changes it back to portrait.

My problem starts when the user start rotating the device number of times and fast, then the application goes crazy until I get this error:

Warning: Attempt to present on whose view is not in the window hierarchy!`.

What is the best possible way to wait until the animation is over and then change the rotation?

This is what I'm using on the Presenting view controller:

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self beginDeviceOrientationListener];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)beginDeviceOrientationListener
{
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification object:[UIDevice currentDevice]];
}

- (void)orientationChanged:(NSNotification *)notification
{
    UIDevice *device = notification.object;
    switch (device.orientation)
    {
        case UIDeviceOrientationLandscapeLeft:
        case UIDeviceOrientationLandscapeRight:
        {
            TheViewControllerToPresent *viewController = [[TheViewControllerToPresent alloc] init];
            [self presentViewController:viewController animated:YES completion:nil];
            [[UIDevice currentDevice] setValue:[NSNumber numberWithInteger:UIInterfaceOrientationLandscapeRight] forKey:@"orientation"];
            [[UIApplication sharedApplication] setStatusBarOrientation:[[[UIDevice currentDevice] valueForKey:@"orientation"] integerValue] animated:YES];
            [[UIApplication sharedApplication] setStatusBarHidden:NO withAnimation:UIStatusBarAnimationSlide];
        }
            break;

        default:
            break;
    }
}

This is what I'm using on the Presented view controller:

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [self beginDeviceOrientationListener];
}

- (void)viewWillDisappear:(BOOL)animated
{
    [super viewWillDisappear:animated];
    [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)beginDeviceOrientationListener
{
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(orientationChanged:) name:UIDeviceOrientationDidChangeNotification object:[UIDevice currentDevice]];
}

- (void)orientationChanged:(NSNotification *)notification
{
    UIDevice *device = notification.object;
    switch (device.orientation)
    {
        case UIDeviceOrientationPortrait:
        {
            [self dismissViewControllerAnimated:YES completion:nil];
            [[UIDevice currentDevice] setValue:[NSNumber numberWithInteger:UIInterfaceOrientationPortrait] forKey:@"orientation"];
            [[UIApplication sharedApplication] setStatusBarOrientation:[[[UIDevice currentDevice] valueForKey:@"orientation"] integerValue] animated:YES];
        }
            break;
        default:
            break;
    }
}

Answer 1

我自己使用的最简单的解决方案是在动画正在进行时阻止用户进行任何更改。

这是通过在动画开始时添加以下代码来完成的：

[[UIApplication sharedApplication] beginIgnoringInteractionEvents];
[[UIDevice currentDevice] endGeneratingDeviceOrientationNotifications];

并到完成处理程序：

[[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
[[UIApplication sharedApplication] endIgnoringInteractionEvents];

用户可以旋转设备，但在动画期间不会生成事件，因此动画不会发生碰撞。但是，当动画结束时，您应该明确检查方向：

UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];

看看你是否应该开始另一个动画。