Swift 动态更改键盘扩展的高度

我有一个键盘扩展，它以高度常数280开始。我用下面的代码给它高度限制。我称之为在视图中显示

    func normalHeight() {
    constant = 280
    UIView.animateWithDuration(1.0) {
        let heightConstraint = NSLayoutConstraint(item: self.view, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0.0, constant: self.constant)
        heightConstraint.priority = self.normalHeightPriority
        self.view.addConstraint(heightConstraint)
    }
    self.view.setNeedsUpdateConstraints()
    self.view.setNeedsDisplay()

}

我还使用下面的代码为高度约束的增加设置了动画，该代码同样有效。高度增加了

    func extendedHeight() {
    constant = 400
    UIView.animateWithDuration(1.0) { 
        let heightConstraint = NSLayoutConstraint(item: self.view, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0.0, constant: self.constant)
        heightConstraint.priority = self.extendedHeightPriority
        self.view.addConstraint(heightConstraint)
    }
    self.view.setNeedsUpdateConstraints()
    self.view.setNeedsDisplay()
}

要恢复高度，我再次从按钮调用normalHeight，但这不起作用。我认为可能是优先级问题，因为extendeHeight约束的优先级为1000，normalHeight约束的优先级为999。 因此，当调用函数时，我会翻转优先级，如下所示。还是没有骰子

    func normalHeight() {
    constant = 280
    normalPriority = 1000
    extendedPriority = 999
    UIView.animateWithDuration(1.0) {
        let heightConstraint = NSLayoutConstraint(item: self.view, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0.0, constant: self.constant)
        heightConstraint.priority = self.normalPriority
        self.view.addConstraint(heightConstraint)
    }
    print("Normal Height Called")
    self.view.setNeedsUpdateConstraints()
    self.view.setNeedsDisplay()

}

在这样的扩展优先级上

    func extendedHeight() {
    constant = 400
    extendedPriority = 1000
    normalPriority = 999
    UIView.animateWithDuration(1.0) {
        let heightConstraint = NSLayoutConstraint(item: self.view, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0.0, constant: self.constant)
        heightConstraint.priority = self.extendedPriority
        self.view.addConstraint(heightConstraint)
    }
    self.view.setNeedsUpdateConstraints()
    self.view.setNeedsDisplay()
}

我将感谢任何帮助和洞察为什么这不起作用。谢谢，我找到了解决办法。 我在视图中添加了两个高度约束，并为它们指定了高优先级和低优先级。 约束优先级应该是高优先级和低优先级，分别为750和250，而不是我之前使用的1000和999

现在，当我想要更改高度时，我会翻转两个已安装约束的优先级

    func initialHeight() {
    AConstant = 280
    BConstant = 400
    self.aheightConstraint = NSLayoutConstraint(item: self.view, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0.0, constant: self.AConstant)
    self.aheightConstraint!.priority = 750
    self.view.addConstraint(self.aheightConstraint!)

    self.bheightConstraint = NSLayoutConstraint(item: self.view, attribute: .Height, relatedBy: .Equal, toItem: nil, attribute: .NotAnAttribute, multiplier: 0.0, constant: self.BConstant)
    self.bheightConstraint.priority = 250
    self.view.addConstraint(bheightConstraint)

    self.view.setNeedsDisplay()

对于我所说的延伸高度

 func extendedHeight() {
    bheightConstraint.priority = 750
    aheightConstraint.priority = 250
    view.setNeedsLayout()

}

    func normalHeight() {
    bheightConstraint.priority = 250
    aheightConstraint.priority = 750
    view.setNeedsLayout()
}

为了恢复到正常高度，我打电话给

 func extendedHeight() {
    bheightConstraint.priority = 750
    aheightConstraint.priority = 250
    view.setNeedsLayout()

}

    func normalHeight() {
    bheightConstraint.priority = 250
    aheightConstraint.priority = 750
    view.setNeedsLayout()
}