UIImagePickerController *imagePicker = [[UIImagePickerController alloc] init];
    imagePicker.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    imagePicker.delegate = self;
    imagePicker.navigationBar.translucent = NO;
    [_controller presentViewController:imagePicker animated:YES completion:nil];

iOS13系统下 设置了translucent = NO方法还是没效果，最后在自定义navigationController里加了这个好了

    [[UINavigationBar appearance] setTranslucent:NO];