Ios 无法创建带有自定义约束的标签浏览器

我用于在iMessage extension中创建标签浏览器的代码是：

func createStickerBrowser() {

    let controller = MSStickerBrowserViewController(stickerSize: .small)

    view.translatesAutoresizingMaskIntoConstraints = false

    addChildViewController(controller)
    view.addSubview(controller.view)

    controller.stickerBrowserView.dataSource = self
    controller.view.backgroundColor = UIColor.green

    let leading = NSLayoutConstraint(item: controller.view, attribute: .leading, relatedBy: .equal, toItem: view, attribute: .leading, multiplier: 1, constant: 0)
    let trailing = NSLayoutConstraint(item: controller.view, attribute: .trailing, relatedBy: .equal, toItem: view, attribute: .trailing, multiplier: 1, constant: 0)
    let bottom = NSLayoutConstraint(item: controller.view, attribute: .bottom, relatedBy: .equal, toItem: view, attribute: .bottom, multiplier: 1, constant: 0)
    let top = NSLayoutConstraint(item: controller.view, attribute: .top, relatedBy: .equal, toItem: view, attribute: .top, multiplier: 1, constant: 0)

    view.addConstraints([leading, trailing, top, bottom])
}

但我的故事板是这样的：

---

为什么不将其添加到视图层次结构中？我需要把它放在按钮旁边。按钮是固定的，但标签浏览有自己的滚动条。如何执行此操作？

放置或替换MSMessageAppViewController类的ViewWillDisplay方法：

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

   requestPresentationStyle(.expanded)           
}