iphone - iPhone：相机自动对焦观察者？

Question

我想知道是否可以在 iPhone 应用程序中接收有关自动对焦的通知？

IE，是否存在一种在自动对焦开始，结束时通知它是否成功或失败的方式......？

如果是这样，这个通知名称是什么？

Answer 1

我找到了适合我的案例的解决方案，以找到自动对焦何时开始/结束。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 编程指南
• NSKeyValueObserving 协议

Answer 2

斯威夫特 3

AVCaptureDevice在您的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

您可以使用现代 Swift 键值观察 api 在通过观察AVCaptureDeviceInput.device.isAdjustingFocus属性开始和结束聚焦时获取回调。在下面的示例中，AVCaptureDeviceInput调用了 的实例captureDeviceInput。

例子：

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

    print("isAdjustingFocus = \(isAdjustingFocus)")

}