Swift - 解决键盘弹出遮挡textField问题

1.先注册对键盘的监听：

    NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillShow:", name: UIKeyboardWillShowNotification, object: nil)
    NSNotificationCenter.defaultCenter().addObserver(self, selector: "keyboardWillHide", name: UIKeyboardWillHideNotification, object: nil)

2.实现两个Selector：

@objc private func keyboardWillShow(notification: NSNotification) {
    let info = notification.userInfo!
    let keyboardFrame = info[UIKeyboardFrameEndUserInfoKey]!.CGRectValue
    let responderTextField = textFields.filter({ $0.isFirstResponder() }).first!
    
    let distanceToKeyboard = keyboardFrame.origin.y - CGRectGetMaxY(responderTextField.convertRect(responderTextField.frame, toView: view))
    
    if distanceToKeyboard < 0 {
        view.frame.origin.y -= -distanceToKeyboard
    }
}
@objc private func keyboardWillHide() {
    view.frame.origin.y = 0
}

但不知道为什么不需要加UIView.animateWithDuration就有了动画呢？

3.记得要移除监听哦：

deinit {
    NSNotificationCenter.defaultCenter().removeObserver(self)
    NSLog("LoginViewController deinits")
}