如何在Swift中使用NSLayoutConstraint在UITextField中添加填充？

Question

我有一个UIView的子类，其中有UITextField ，想稍微移开占位符文本。 我正在使用NSLayoutConstraint设置子视图的位置和大小。 我创建了UIView并将其添加为UITextField leftView ，但崩溃，提示“视图层次结构未为约束准备”。 下面是我的代码：

class MasterView: UIView {

let searchTextField = UITextField()
let paddingView = UIView()

override init(frame: CGRect) {
    super.init(frame: frame)

    searchTextField.placeholder = "Search videos"
    searchTextField.translatesAutoresizingMaskIntoConstraints = false
    paddingView.translatesAutoresizingMaskIntoConstraints = false
    searchTextField.leftView = paddingView
    searchTextField.leftViewMode = UITextFieldViewMode.Always

    self.addSubview(searchTextField)

}

// Gets called when using storyboard

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

override func layoutSubviews() {
    self.addConstraint(NSLayoutConstraint(item: searchTextField, attribute: NSLayoutAttribute.TopMargin, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.TopMargin, multiplier: 1.0, constant: 20))

    self.addConstraint(NSLayoutConstraint(item: searchTextField, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.Height, multiplier: 0.12, constant: 0))

    self.addConstraint(NSLayoutConstraint(item: searchTextField, attribute: NSLayoutAttribute.CenterX, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.CenterX, multiplier: 1.0, constant: 0))

    self.addConstraint(NSLayoutConstraint(item: searchTextField, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: self, attribute: NSLayoutAttribute.Width, multiplier: 1.0, constant: 0))

    self.addConstraint(NSLayoutConstraint(item: paddingView, attribute: NSLayoutAttribute.LeadingMargin, relatedBy: NSLayoutRelation.Equal, toItem: searchTextField, attribute: NSLayoutAttribute.LeadingMargin, multiplier: 1.0, constant: 0))

    self.addConstraint(NSLayoutConstraint(item: paddingView, attribute: NSLayoutAttribute.TopMargin, relatedBy: NSLayoutRelation.Equal, toItem: searchTextField, attribute: NSLayoutAttribute.TopMargin, multiplier: 1.0, constant: 0))

    self.addConstraint(NSLayoutConstraint(item: paddingView, attribute: NSLayoutAttribute.Width, relatedBy: NSLayoutRelation.Equal, toItem: searchTextField, attribute: NSLayoutAttribute.Width, multiplier: 0.12, constant: 0))

    self.addConstraint(NSLayoutConstraint(item: paddingView, attribute: NSLayoutAttribute.Height, relatedBy: NSLayoutRelation.Equal, toItem: searchTextField, attribute: NSLayoutAttribute.Height, multiplier: 1.0, constant: 0))

}

}

Answer 1

正确解决此问题的方法：

@IBDesignable
class FormTextField: UITextField {

  @IBInspectable var paddingLeft: CGFloat = 0
  @IBInspectable var paddingRight: CGFloat = 0

  override func textRect(forBounds bounds: CGRect) -> CGRect {
    return CGRect(x: bounds.origin.x + paddingLeft, y: bounds.origin.y, width: bounds.size.width - paddingLeft - paddingRight, height: bounds.size.height)
  }

  override func editingRect(forBounds bounds: CGRect) -> CGRect {
    return textRect(forBounds: bounds)
  }
}

从这里取

Answer 2

使UITextField为自定义类，并在该类中实现这两个方法，并使您的文本字段为自定义文本字段。

class customTextField: UITextField {

 override func textRectForBounds(bounds: CGRect) -> CGRect {
  return super.textRectForBounds(UIEdgeInsetsInsetRect(bounds, UIEdgeInsetsMake(0, 5, 0, 0)))
 }

 override func editingRectForBounds(bounds: CGRect) -> CGRect {
  return super.editingRectForBounds(UIEdgeInsetsInsetRect(bounds,  UIEdgeInsetsMake(0, 5, 0, 0)))
 }
}

Answer 3

let paddingForFirst = UIView(frame: CGRectMake(0, 0, 5, self.Email_Txt.frame.size.height-5))
Email_Txt.leftView = paddingForFirst
Email_Txt.leftViewMode = UITextFieldViewMode .Always

Answer 4

试试这个代码将对您有帮助

override func viewDidLoad() {
super.viewDidLoad()
let paddingView = UIView(frame: CGRectMake(0, 0, 15, self.myTextField.frame.height))
myTextField.leftView = paddingView
myTextField.leftViewMode = UITextFieldViewMode.Always
}

Answer 5

只需在下面写： -SWIFT 2.1.1

let tempView = UIView(frame:CGRectMake(6, 0, 22, 26))
tempView.backgroundColor = UIColor.clearColor()
searchTextField.leftView?.frame = CGRectMake(0, 0, tempView.frame.size.width, tempView.frame.height)

searchTextField.leftViewMode = UITextFieldViewMode.Always
searchTextField.leftView = tempView

Answer 6

yon不应设置或限制该填充视图。 删除填充视图的所有约束。 它是textfield的左视图，因此它会根据文本字段的约束自动进行调整。 并设置填充视图框架，以确保您期望填充的空间。

希望这会有所帮助:)

Answer 7

您遇到此错误“未为约束准备视图层次结构”，因为paddingView被添加为左视图/右视图，并且不需要任何约束。

注意：不需要对作为左视图/右视图添加到UITextField视图施加约束。 因此，您只需要设置paddingView框架并将其分配给leftView 。 无需对paddingView约束。