ios - beginGeneratingDeviceOrientationNotifications 如何工作

Question

    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
    [notificationCenter addObserver:self selector:@selector(deviceOrientationDidChange) name:UIDeviceOrientationDidChangeNotification object:nil];
    orientation = AVCaptureVideoOrientationPortrait;

我想知道 beginGeneratingDeviceOrientationNotifications 意味着什么以及如何工作？

Answer 1

当你写这行时:

 [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];

你对设备说:“每次方向改变时请通知应用程序”

通过这样写:

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(deviceOrientationDidChange) name:UIDeviceOrientationDidChangeNotification object:nil];

您对应用程序说:“每次收到方向更改通知时，请调用 deviceOrientationDidChange 方法”。

现在在 deviceOrientationDidChange 中，您可以执行以下操作:

UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];
if (orientation == UIDeviceOrientationPortrait)
     [self doSomething];
else
     [self doSomethingElse];