问如何在中心xcode中设置框架

EN

 UIImagePickerController * picker = [[UIImagePickerController alloc] init];
// picker.delegate = self;
[picker setSourceType:UIImagePickerControllerSourceTypeCamera];
// creating overlayView
UIView* overlayView = [[UIView alloc] initWithFrame:picker.view.frame];
// letting png transparency be
overlayView.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"f2.png"]];
[overlayView.layer setOpaque:NO];
overlayView.opaque = NO;

picker.showsCameraControls = NO;
picker.cameraOverlayView = overlayView;

//[self presentModalViewController:picker animated:YES];
[self presentViewController:picker animated:YES completion:nil];