我这是工作的时间以及90％的相机预览窗口。 然而，有时回到我的应用程序时，如果它一直在后台，预览将不显示。 这就是我所说的观点加载时的代码：
- (void) startCamera {
session = [[AVCaptureSession alloc] init];
session.sessionPreset = AVCaptureSessionPresetPhoto;
AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
captureVideoPreviewLayer.frame = _cameraView.bounds;
[_cameraView.layer addSublayer:captureVideoPreviewLayer];
captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
captureVideoPreviewLayer.position=CGPointMake(CGRectGetMidX(_cameraView.bounds), 160);
AVCaptureDevice *device = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
NSError *error = nil;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if (!input) {
NSLog(@"ERROR: %@", error);
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Important!"
message:@"Unable to find a camera."
delegate:nil
cancelButtonTitle:@"Ok"
otherButtonTitles:nil];
[alert show];
[alert autorelease];
}
[session addInput:input];
stillImage = [[AVCaptureStillImageOutput alloc] init];
NSDictionary *outputSettings = [[NSDictionary alloc] initWithObjectsAndKeys:AVVideoCodecJPEG , AVVideoCodecKey, nil];
[stillImage setOutputSettings:outputSettings];
[session addOutput:stillImage];
[session startRunning];
}
如果发生这种情况，我可以切换到我的喜好视图，然后再返回和人是很好的，但它是一个恼人的错误，我想杀人。 预览窗口在我的故事板一个UIView。
