iPhone：相机自动对焦观察器？

Question

我想知道是否可以在iPhone应用程序中收到有关自动对焦的通知？

I.E，它是否存在自动对焦开始，结束，如果成功或失败时被通知的方式......？

如果是这样，这个通知名称是什么？

Answer 1

我发现自动对焦开始/结束时我的案例的解决方案。它只是处理KVO（键值观察）。

在我的UIViewController中：

// callback
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if( [keyPath isEqualToString:@"adjustingFocus"] ){
        BOOL adjustingFocus = [ [change objectForKey:NSKeyValueChangeNewKey] isEqualToNumber:[NSNumber numberWithInt:1] ];
        NSLog(@"Is adjusting focus? %@", adjustingFocus ? @"YES" : @"NO" );
        NSLog(@"Change dictionary: %@", change);
    }
}

// register observer
- (void)viewWillAppear:(BOOL)animated{
    AVCaptureDevice *camDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    int flags = NSKeyValueObservingOptionNew; 
    [camDevice addObserver:self forKeyPath:@"adjustingFocus" options:flags context:nil];

    (...)   
}

// unregister observer
- (void)viewWillDisappear:(BOOL)animated{
    AVCaptureDevice *camDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    [camDevice removeObserver:self forKeyPath:@"adjustingFocus"];

    (...)
}

文档：

• Key-Value Observing programming guide
• NSKeyValueObserving protocol

Answer 2

斯威夫特3

在AVCaptureDevice实例上设置焦点模式：

do {
     try videoCaptureDevice.lockForConfiguration()
     videoCaptureDevice.focusMode = .continuousAutoFocus
     videoCaptureDevice.unlockForConfiguration()
} catch {}

添加观察者：

videoCaptureDevice.addObserver(self, forKeyPath: "adjustingFocus", options: [.new], context: nil)

覆盖observeValue：

override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {

    guard let key = keyPath, let changes = change else { 
        return
    }

    if key == "adjustingFocus" {

        let newValue = changes[.newKey]
        print("adjustingFocus \(newValue)")
    }
}

Answer 3

通过观察AVCaptureDeviceInput.device.isAdjustingFocus属性，您可以使用现代Swift键值观察api来获得回调开始和结束时的回调。在下面的示例中，AVCaptureDeviceInput的实例称为captureDeviceInput。

例：

self.focusObservation = observe(\.captureDeviceInput.device.isAdjustingFocus, options: .new) { _, change in
    guard let isAdjustingFocus = change.newValue else { return }

    print("isAdjustingFocus = \(isAdjustingFocus)")

}