即使成功切换到前置摄像头，iPhone 仍然显示后置摄像头的视图

Posted 2023-03-11

【中文标题】即使成功切换到前置摄像头，iPhone 仍然显示后置摄像头的视图

【英文标题】：iPhone still shows rear camera's view even after successfully switching to front camera

【发布时间】：2014-02-22 05:28:53

【问题描述】：

我正在使用 AV Foundation，并且我设置了一个按钮，当我点击该按钮时，我想在前置摄像头和后置摄像头之间切换。

如果我运行应用程序并点击按钮，控制台会告诉我已成功将设备更改为前置摄像头，但屏幕仍会显示后置摄像头所看到的内容。

我需要更新屏幕，以便它真正显示前置摄像头看到的内容，并且确实捕捉到前置摄像头看到的内容。

这是连接到我的切换按钮的 IBAction 代码：

-(IBAction)toggleCamera 


_inputDevice = [self frontCamera];

这是为“frontCamera”提供动力的方法实现：

- (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;

【参考方案1】：

您需要做的不仅仅是设置输入设备。您是否设置了 AVCaptureSession？如果是这样，每次更换相机时，您都需要 (1) 重新配置会话，(2) 删除当前输入，(3) 添加新输入并 (4) 提交会话配置：

// 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;

答案改编自此post