ios - 由于光线不足，如何在自动闪光模式下打开或关闭闪光灯时收到通知

Question

我正在使用 UIImagePickerController 来呈现相机并最初将闪光灯模式设置为自动。

videoCapturer.sourceType = UIImagePickerControllerSourceType.Camera
videoCapturer.mediaTypes = [kUTTypeMovie as String]
videoCapturer.cameraFlashMode = UIImagePickerControllerCameraFlashMode.Auto
[self .presentViewController(videoCapturer, animated: true, completion: nil)]

我想在闪光灯根据光线设置为打开或关闭时收到通知。

Answer 1

只需使用 KVO。

let capture = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo)
capture.addObserver(self, forKeyPath: "torchActive", options: NSKeyValueObservingOptions.New.union(.Initial), context: nil)

并实现这个方法:

public override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
    if keyPath == "torchActive" {
        // do something when torchActive changed
    } else {
        super.observeValueForKeyPath(keyPath, ofObject: object, change: change, context: context)
    }
}

这是 Apple 对 torchActive 的描述:

 @property torchActive
 @abstract
     Indicates whether the receiver's torch is currently active.

 @discussion
     The value of this property is a BOOL indicating whether the receiver's torch is 
     currently active. If the current torchMode is AVCaptureTorchModeAuto and isTorchActive
     is YES, the torch will illuminate once a recording starts (see AVCaptureOutput.h 
     -startRecordingToOutputFileURL:recordingDelegate:). This property is key-value observable.