iOS 弹出透明窗体viewcontroller【兼容iOS8以上】

UIViewController *controller = self.view.window.rootViewController;
controller.modalPresentationStyle = UIModalPresentationCurrentContext;

if (CURRENT_DEVICE >=8.0) {
lockScreenController.modalPresentationStyle = UIModalPresentationOverCurrentContext;
} else {
controller.modalPresentationStyle = UIModalPresentationCurrentContext;
}

[controller presentViewController:lockScreenController animated:YES completion:^{
// 背景色透明
lockScreenController.view.superview.backgroundColor = [UIColor clearColor];
}];