self.view.window.rootViewController.modalPresentationStyle = UIModalPresentationCurrentContext;//半透明
 CocoaPickerViewController *transparentView = [[CocoaPickerViewController alloc] init];
 transparentView.delegate = self;
 transparentView.modalPresentationStyle = UIModalPresentationOverFullScreen;
 transparentView.view.frame=self.view.frame;
 transparentView.view.superview.backgroundColor = [UIColor clearColor];
 [self presentViewController:transparentView animated:YES completion:nil];