ios - 即使成功切换到前置摄像头，iPhone 仍然显示后置摄像头的 View

Question

我正在使用 AV Foundation，我设置了一个按钮，我想在点击时在前置和后置摄像头之间切换。

如果我运行该应用并点击按钮，控制台会告诉我我已成功将设备更改为前置摄像头，但屏幕仍然显示后置摄像头所看到的内容。

我需要更新屏幕，使其真正显示前置摄像头看到的内容，并真正捕捉到前置摄像头看到的内容。

这是连接到切换按钮的 IBAction 代码:

-(IBAction)toggleCamera {


_inputDevice = [self frontCamera];

}

下面是为“frontCamera”提供支持的方法实现:

- (AVCaptureDevice *)frontCamera {
    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    for (AVCaptureDevice *device in devices) {
        if ([device position] == AVCaptureDevicePositionFront) {
            NSLog(@"Device position during frontCamera method: %d", [device position]);
            return device;
        }
    }
    return nil;
}

Answer 1

您需要做的不仅仅是设置输入设备。你有设置 AVCaptureSession 吗？如果是这样，每次交换相机时，您都需要 (1) 重新配置 session ，(2) 删除当前输入，(3) 添加新输入，以及 (4) 提交 session 配置:

// Define a flag in your header file to keep track of the current camera input
BOOL isUsingFrontFacingCamera;


-(IBAction)toggleCamera
{
    // determine the mode to switch to
    AVCaptureDevicePosition desiredPosition;
    if (isUsingFrontFacingCamera)
    {
        desiredPosition = AVCaptureDevicePositionBack;
    }
    else
        desiredPosition = AVCaptureDevicePositionFront;
    }

    for (AVCaptureDevice *d in [AVCaptureDevice devicesWithMediaType: AVMediaTypeVideo])
    {
        if ([d position] == desiredPosition)
        {
            // configure the session
            [session beginConfiguration];

            // find and clear all the existing inputs
            for (AVCaptureInput *oldInput in [session inputs])
            {
                [session removeInput:oldInput];
            }

            // add the new input to session
            AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:d error:nil];
            [session addInput:input];

            // commit the configuration
            [session commitConfiguration];
            break;
        }
    }
    // update the flag to reflect the current mode
    isUsingFrontFacingCamera = !isUsingFrontFacingCamera;
}

改编自此 post 的答案