iOS疯狂详解之设备前后摄像头切换

#import <AVFoundation/AVFoundation.h>
 
// Switching between front and back cameras
 
- (AVCaptureDevice *)cameraWithPosition:(AVCaptureDevicePosition)position
{
NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
for ( AVCaptureDevice *device in devices )
if ( device.position == position )
return device;
return nil;
}
 
- (void)swapFrontAndBackCameras {
// Assume the session is already running
 
NSArray *inputs = self.session.inputs;
for ( AVCaptureDeviceInput *input in inputs ) {
AVCaptureDevice *device = input.device;
if ( [device hasMediaType:AVMediaTypeVideo] ) {
AVCaptureDevicePosition position = device.position;
AVCaptureDevice *newCamera = nil;
AVCaptureDeviceInput *newInput = nil;
 
if (position == AVCaptureDevicePositionFront)
newCamera = [self cameraWithPosition:AVCaptureDevicePositionBack];
else
newCamera = [self cameraWithPosition:AVCaptureDevicePositionFront];
newInput = [AVCaptureDeviceInput deviceInputWithDevice:newCamera error:nil];
 
// beginConfiguration ensures that pending changes are not applied immediately
[self.session beginConfiguration];
 
[self.session removeInput:input];
[self.session addInput:newInput];
 
// Changes take effect once the outermost commitConfiguration is invoked.
[self.session commitConfiguration];
break;
}
}
}