IOS 添加一小段代码时键盘不会显示

Question

我有以下自定义键盘代码：

   override func viewDidLoad() {
    super.viewDidLoad()

    //As soon as I add in this code the keyboard will not showup and instead
    //selecting this keyboard just reverts back to the normal keyboard
    let testOne = UIButton()
    testOne.backgroundColor = UIColor.blackColor()
    testOne.translatesAutoresizingMaskIntoConstraints = false
    testOne.widthAnchor.constraintEqualToAnchor(self.view.widthAnchor, multiplier: 0.5).active = true
    testOne.heightAnchor.constraintEqualToAnchor(self.view.heightAnchor, multiplier: 0.5).active = true
    testOne.leftAnchor.constraintEqualToAnchor(self.view.leftAnchor).active = true
    testOne.topAnchor.constraintEqualToAnchor(self.view.topAnchor).active = true
    self.view.addSubview(testOne)


    // Default system generated code that creates a "next keyboard" button.
    self.nextKeyboardButton = UIButton(type: .System)

    self.nextKeyboardButton.setTitle(NSLocalizedString("Next Keyboard", comment: "Title for 'Next Keyboard' button"), forState: .Normal)
    self.nextKeyboardButton.sizeToFit()
    self.nextKeyboardButton.translatesAutoresizingMaskIntoConstraints = false

    self.nextKeyboardButton.addTarget(self, action: "advanceToNextInputMode", forControlEvents: .TouchUpInside)

    self.view.addSubview(self.nextKeyboardButton)

    let nextKeyboardButtonLeftSideConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1.0, constant: 0.0)
    let nextKeyboardButtonBottomConstraint = NSLayoutConstraint(item: self.nextKeyboardButton, attribute: .Bottom, relatedBy: .Equal, toItem: self.view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)
    self.view.addConstraints([nextKeyboardButtonLeftSideConstraint, nextKeyboardButtonBottomConstraint])


}

出于某种原因，添加我的 testOne UIButton 会导致键盘永远不会显示（相反，当我 select 它会再次显示默认键盘）。

我的按钮是否导致我的自定义键盘崩溃？

更新一：一旦我取消注释行 testOne.widthAnchor.constraintEqualToAnchor(...).active = true 错误开始发生。

是否不允许我在 viewDidLoad() 方法中创建自定义约束？

Answer 1

放行：self.view.addSubview(testOne) 在更改任何约束之前。

IOS 添加一小段代码时键盘不会显示

IOS keyboard will not show when add in small piece of code

ios

iphone-softkeyboard