IOS Toggle AVFoundation Camera - ios

Question

In my App I'm capturing images using AVFoundation
I made a button to switch between front and back cameras but it won't work.
Here's the code I used :
if (captureDevice.position == AVCaptureDevicePositionFront) {
for ( AVCaptureDevice *device in [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo] ) {
if ( device.position == AVCaptureDevicePositionBack) {
NSError * error;
AVCaptureDeviceInput * newDeviceInput = [[AVCaptureDeviceInput alloc]initWithDevice:device error:&error];
[captureSesion beginConfiguration];
for (AVCaptureDeviceInput *oldInput in [captureSesion inputs]) {
[captureSesion removeInput:oldInput];
}
if ([captureSesion canAddInput:newDeviceInput]) {
[captureSesion addInput:newDeviceInput];
}
[captureSesion commitConfiguration];
break;
}
}
}
THX.

Answer 1

If your captureSession's sessionPreset is not compatible with the camera you're switching to it will fail the canAddInput test. I always reset to AVCaptureSessionPresetHigh before toggling cameras then try to switch it to whatever preset I have preferred. Here's the code I use:
- (void)toggleCamera {
AVCaptureDevicePosition newPosition = self.currentCameraPossition == AVCaptureDevicePositionBack ? AVCaptureDevicePositionFront : AVCaptureDevicePositionBack;
AVCaptureDevice *device = [self videoDeviceWithPosition:newPosition];
AVCaptureDeviceInput *deviceInput = [[AVCaptureDeviceInput alloc] initWithDevice:device error:nil];
[_captureSession beginConfiguration];
[_captureSession removeInput:self.deviceInput];
[_captureSession setSessionPreset:AVCaptureSessionPresetHigh]; //Always reset preset before testing canAddInput because preset will cause it to return NO
if ([_captureSession canAddInput:deviceInput]) {
[_captureSession addInput:deviceInput];
self.deviceInput = deviceInput;
self.currentCameraPossition = newPosition;
} else {
[_captureSession addInput:self.deviceInput];
}
if ([device supportsAVCaptureSessionPreset:self.sessionPreset]) {
[_captureSession setSessionPreset:self.sessionPreset];
}
if ([device lockForConfiguration:nil]) {
[device setSubjectAreaChangeMonitoringEnabled:YES];
[device unlockForConfiguration];
}
[_captureSession commitConfiguration];
}

Answer 2

I have seen issues with toggle code not working if it is not run on the main thread. Can you try wrapping your code with the following block:
dispatch_async(dispatch_get_main_queue(), ^{
// Your camera toggle code goes here
});