Question

我尝试删除约束。我想对肖像和风景有不同的限制。如果我将方向更改为纵向，则调用函数 setupConstrainsInPortrait ，反之亦然。我有两个功能。

此功能设定纵向模式。

func setupConstrainsInPortrait() {

    view.addSubview(myView)

    myView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    myView.topAnchor.constraint(equalTo: view.topAnchor, constant: 50).isActive = true
    myView.heightAnchor.constraint(equalToConstant: 300).isActive = true
    myView.widthAnchor.constraint(equalToConstant: view.frame.size.width).isActive = true

    view.addSubview(switchKmM)

    switchKmM.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    switchKmM.topAnchor.constraint(equalTo: myView.bottomAnchor, constant: 10).isActive = true
    switchKmM.heightAnchor.constraint(equalToConstant: 50).isActive = true
    switchKmM.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true

    view.addSubview(speedLbl)

    speedLbl.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
    speedLbl.topAnchor.constraint(equalTo: view.bottomAnchor, constant: -50).isActive = true
    speedLbl.heightAnchor.constraint(equalToConstant: 50).isActive = true
    speedLbl.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true

}

此功能设置横向模式。

    func setupConstrainsInLandScape() {
    view.addSubview(myView)

    myView.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 10).isActive = true
    myView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true
    myView.heightAnchor.constraint(equalToConstant: 300).isActive = true
    myView.widthAnchor.constraint(equalToConstant: 150).isActive = true

    view.addSubview(switchKmM)

    switchKmM.leftAnchor.constraint(equalTo: myView.rightAnchor, constant: 30).isActive = true
    switchKmM.topAnchor.constraint(equalTo: view.topAnchor, constant: 30).isActive = true
    switchKmM.heightAnchor.constraint(equalToConstant: 50).isActive = true
    switchKmM.widthAnchor.constraint(equalTo: view.widthAnchor).isActive = true
}

我在viewWillTransition

中使用这些函数

override func viewWillTransition(to size: CGSize, with coordinator: UIViewControllerTransitionCoordinator) {
    if UIDevice.current.orientation.isLandscape {
        print("landscape!")
        view.backgroundColor = .green
        setupConstrainsInLandScape()
        self.viewWillLayoutSubviews()


    }
    else {
        print("portrét")
        view.backgroundColor = .white
        setupConstrainsInPortrait()
        self.viewWillLayoutSubviews()

    }
    super.viewWillTransition(to: size, with: coordinator)
}

问题是，横向模式中的约束（来自肖像功能）不会被删除

我希望有人可以帮助我...谢谢

Answer 1

你做得不够好。您需要保留对所激活的所有约束的引用，以便稍后可以停用它们。例如，您说：

myView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
myView.topAnchor.constraint(equalTo: view.topAnchor, constant: 50).isActive = true
myView.heightAnchor.constraint(equalToConstant: 300).isActive = true
myView.widthAnchor.constraint(equalToConstant: view.frame.size.width).isActive = true

相反，你需要说出类似

的内容

self.myConstraints1 = [
    myView.centerXAnchor.constraint(equalTo: view.centerXAnchor),
    myView.topAnchor.constraint(equalTo: view.topAnchor, constant: 50),
    myView.heightAnchor.constraint(equalToConstant: 300),
    myView.widthAnchor.constraint(equalToConstant: view.frame.size.width),
]

现在激活所有这些约束。始终以同样的方式进行。

因此，当由于方向发生变化而停止约束时，您可以参考它们并且可以这样做。

Answer 2

您可以使用以下方法删除约束：

myView.constraints.removeAll()

在设置新的之前。

删除约束iOS

2 个答案: