Swift: Push Objects under the Label according to the number of lines - ios

Question

I'm trying to make the same behavior of the Material design textfield with a custom textfield.
I created a class that inherits from textfield and every thing is working fine. The only problem is in one scenario. when I have an object under the textfield, and i add the error label under the text field. the error label might be more than one line. so it overlays the object under the textfield. However, in the material design library, the objects under the textfield are automatically pushed down according ton the number of lines of the error label.
here is my custom textfield code:
import UIKit
import RxSwift
import RxCocoa
class FloatingTextField2: UITextField {
var placeholderLabel: UILabel!
var line: UIView!
var errorLabel: UILabel!
let bag = DisposeBag()
var activeColor = Constants.colorBlue
var inActiveColor = UIColor(red: 84/255.0, green: 110/255.0, blue: 122/255.0, alpha: 0.8)
var errorColorFull = UIColor(red: 254/255.0, green: 103/255.0, blue: 103/255.0, alpha: 1.0)
//var errorColorParcial = UIColor(red: 254/255.0, green: 103/255.0, blue: 103/255.0, alpha: 0.5)
private var lineYPosition: CGFloat!
private var lineXPosition: CGFloat!
private var lineWidth: CGFloat!
private var lineHeight: CGFloat!
private var errorLabelYPosition: CGFloat!
private var errorLabelXPosition: CGFloat!
private var errorLabelWidth: CGFloat!
private var errorLabelHeight: CGFloat!
var maxFontSize: CGFloat = 14
var minFontSize: CGFloat = 11
let errorLabelFont = UIFont(name: "Lato-Regular", size: 12)
var animationDuration = 0.35
var placeholderText: String = "" {
didSet {
if placeholderLabel != nil {
placeholderLabel.text = placeholderText
}
}
}
var isTextEntrySecured: Bool = false {
didSet {
self.isSecureTextEntry = isTextEntrySecured
}
}
override func draw(_ rect: CGRect) {
//setUpUI()
}
override func awakeFromNib() {
setUpUI()
}
func setUpUI() {
if placeholderLabel == nil {
placeholderLabel = UILabel(frame: CGRect(x: 0, y: 0, width: self.frame.width, height: 20))
self.addSubview(placeholderLabel)
self.borderStyle = .none
placeholderLabel.text = "Placeholder Preview"
placeholderLabel.textColor = inActiveColor
self.font = UIFont(name: "Lato-Regular", size: maxFontSize)
self.placeholderLabel.font = UIFont(name: "Lato-Regular", size: maxFontSize)
self.placeholder = ""
self.textColor = .black
setUpTextField()
}
if line == nil {
lineYPosition = self.frame.height
lineXPosition = -16
lineWidth = self.frame.width + 32
lineHeight = 1
line = UIView(frame: CGRect(x: lineXPosition, y: lineYPosition, width: lineWidth, height: lineHeight))
self.addSubview(line)
line.backgroundColor = inActiveColor
}
if errorLabel == nil {
errorLabelYPosition = lineYPosition + 8
errorLabelXPosition = 0
errorLabelWidth = self.frame.width
errorLabelHeight = calculateErrorLabelHeight(text: "")
errorLabel = UILabel(frame: CGRect(x: 0, y: errorLabelYPosition, width: errorLabelWidth, height: errorLabelHeight))
self.addSubview(errorLabel)
errorLabel.numberOfLines = 0
errorLabel.textColor = errorColorFull
errorLabel.text = ""
errorLabel.font = errorLabelFont
sizeToFit()
}
}
func setUpTextField(){
self.rx.controlEvent(.editingDidBegin).subscribe(onNext: { (next) in
if self.text?.isEmpty ?? false {
self.animatePlaceholderUp()
}
}).disposed(by: bag)
self.rx.controlEvent(.editingDidEnd).subscribe(onNext: { (next) in
if self.text?.isEmpty ?? false {
self.animatePlaceholderCenter()
}
}).disposed(by: bag)
}
func setErrorText(_ error: String?, errorAccessibilityValue: String?) {
if let errorText = error {
self.resignFirstResponder()
errorLabelHeight = calculateErrorLabelHeight(text: errorText)
self.errorLabel.frame = CGRect(x: 0, y: errorLabelYPosition, width: errorLabelWidth, height: errorLabelHeight)
self.errorLabel.text = errorText
self.errorLabel.isHidden = false
self.line.backgroundColor = errorColorFull
}else{
self.errorLabel.text = ""
self.errorLabel.isHidden = true
}
errorLabel.accessibilityIdentifier = errorAccessibilityValue ?? "textinput_error"
}
func animatePlaceholderUp(){
UIView.animate(withDuration: animationDuration, animations: {
self.line.frame.size.height = 2
self.line.backgroundColor = self.activeColor
self.placeholderLabel.font = self.placeholderLabel.font.withSize(self.minFontSize)
self.placeholderLabel.textColor = self.activeColor
self.placeholderLabel.frame = CGRect(x: 0, y: (self.frame.height/2 + 8) * -1, width: self.frame.width, height: self.frame.height)
self.layoutIfNeeded()
}) { (done) in
}
}
func animatePlaceholderCenter(){
UIView.animate(withDuration: animationDuration, animations: {
self.line.frame.size.height = 1
self.line.backgroundColor = self.inActiveColor
self.placeholderLabel.font = self.placeholderLabel.font.withSize(self.maxFontSize)
self.placeholderLabel.textColor = self.inActiveColor
self.placeholderLabel.frame = CGRect(x: 0, y: 0, width: self.frame.width, height: self.frame.height)
self.layoutIfNeeded()
}) { (done) in
}
}
func calculateErrorLabelHeight(text:String) -> CGFloat{
let font = errorLabelFont
let width = self.frame.width
let label:UILabel = UILabel(frame: CGRect(x: 0, y: 0, width: width, height: CGFloat.greatestFiniteMagnitude))
label.numberOfLines = 0
label.lineBreakMode = NSLineBreakMode.byWordWrapping
label.font = font
label.text = text
label.sizeToFit()
return label.frame.height
}
}
How can I solve this problem? I could not find anything on stack overflow or google related to my problem.

Answer 1

As mentioned in the comments:
You'll be much better off using constraints rather than explicit frames
Adding subviews to a UITextField will show them outside the Bounds of the field, meaning they won't affect the frame (and thus the constraints)
If the constraints are set properly, they will control the "containing view" height
The key to getting your "error" label to expand the view is to apply multiple vertical constraints, and activate / deactivate as needed.
Here is a complete example of a custom UIView which contains a text field, a placeholder label and an error label. The example view controller includes "demo" buttons to show the capabilities.
I suggest you add this code and try it out. If it suits your needs, there are plenty of comments in it that you should be able to tweak fonts, spacing, etc to your liking.
Or, it should at least give you some ideas of how to set up your own.
FloatingTextFieldView - UIView subclass
class FloatingTextFieldView: UIView, UITextFieldDelegate {
var placeHolderTopConstraint: NSLayoutConstraint!
var placeHolderCenterYConstraint: NSLayoutConstraint!
var placeHolderLeadingConstraint: NSLayoutConstraint!
var lineHeightConstraint: NSLayoutConstraint!
var errorLabelBottomConstraint: NSLayoutConstraint!
var activeColor: UIColor = UIColor.blue
var inActiveColor: UIColor = UIColor(red: 84/255.0, green: 110/255.0, blue: 122/255.0, alpha: 0.8)
var errorColorFull: UIColor = UIColor(red: 254/255.0, green: 103/255.0, blue: 103/255.0, alpha: 1.0)
var animationDuration = 0.35
var maxFontSize: CGFloat = 14
var minFontSize: CGFloat = 11
let errorLabelFont = UIFont(name: "Lato-Regular", size: 12)
let placeholderLabel: UILabel = {
let v = UILabel()
v.text = "Default Placeholder"
v.setContentHuggingPriority(.required, for: .vertical)
return v
}()
let line: UIView = {
let v = UIView()
v.backgroundColor = .lightGray
return v
}()
let errorLabel: UILabel = {
let v = UILabel()
v.numberOfLines = 0
v.text = "Default Error"
v.setContentCompressionResistancePriority(.required, for: .vertical)
return v
}()
let textField: UITextField = {
let v = UITextField()
return v
}()
override init(frame: CGRect) {
super.init(frame: frame)
commonInit()
}
required init?(coder: NSCoder) {
super.init(coder: coder)
commonInit()
}
func commonInit() -> Void {
clipsToBounds = true
backgroundColor = .white
[textField, line, placeholderLabel, errorLabel].forEach {
$0.translatesAutoresizingMaskIntoConstraints = false
addSubview($0)
}
// place holder label gets 2 vertical constraints
// top of view
// centerY to text field
placeHolderTopConstraint = placeholderLabel.topAnchor.constraint(equalTo: topAnchor, constant: 0.0)
placeHolderCenterYConstraint = placeholderLabel.centerYAnchor.constraint(equalTo: textField.centerYAnchor, constant: 0.0)
// place holder leading constraint is 16-pts (when centered on text field)
// when animated above text field, we'll change the constant to 0
placeHolderLeadingConstraint = placeholderLabel.leadingAnchor.constraint(equalTo: textField.leadingAnchor, constant: 16.0)
// error label bottom constrained to bottom of view
// will be activated when shown, deactivated when hidden
errorLabelBottomConstraint = errorLabel.bottomAnchor.constraint(equalTo: bottomAnchor, constant: 0.0)
// line height constraint constant changes between 1 and 2 (inactive / active)
lineHeightConstraint = line.heightAnchor.constraint(equalToConstant: 1.0)
NSLayoutConstraint.activate([
// text field top 16-pts from top of view
// leading and trailing = 0
textField.topAnchor.constraint(equalTo: topAnchor, constant: 16.0),
textField.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 0.0),
textField.trailingAnchor.constraint(equalTo: trailingAnchor, constant: 0.0),
// text field height = 24
textField.heightAnchor.constraint(equalToConstant: 24.0),
// text field bottom is AT LEAST 4 pts
textField.bottomAnchor.constraint(lessThanOrEqualTo: bottomAnchor, constant: -4.0),
// line view top is 2-pts below text field bottom
// leading and trailing = 0
line.topAnchor.constraint(equalTo: textField.bottomAnchor, constant: 2.0),
line.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 0.0),
line.trailingAnchor.constraint(equalTo: trailingAnchor, constant: 0.0),
// error label top is 4-pts from text field bottom
// leading and trailing = 0
errorLabel.topAnchor.constraint(equalTo: textField.bottomAnchor, constant: 4.0),
errorLabel.leadingAnchor.constraint(equalTo: leadingAnchor, constant: 0.0),
errorLabel.trailingAnchor.constraint(equalTo: trailingAnchor, constant: 0.0),
placeHolderCenterYConstraint,
placeHolderLeadingConstraint,
lineHeightConstraint,
])
// I'm not using Rx, so set the delegate
textField.delegate = self
textField.font = UIFont(name: "Lato-Regular", size: maxFontSize)
textField.textColor = .black
placeholderLabel.font = UIFont(name: "Lato-Regular", size: maxFontSize)
placeholderLabel.textColor = inActiveColor
line.backgroundColor = inActiveColor
errorLabel.textColor = errorColorFull
errorLabel.font = errorLabelFont
}
func textFieldDidBeginEditing(_ textField: UITextField) {
if textField.text?.isEmpty ?? false {
self.animatePlaceholderUp()
}
}
func textFieldDidEndEditing(_ textField: UITextField) {
if textField.text?.isEmpty ?? false {
self.animatePlaceholderCenter()
}
}
func animatePlaceholderUp() -> Void {
UIView.animate(withDuration: animationDuration, animations: {
// increase line height
self.lineHeightConstraint.constant = 2.0
// set line to activeColor
self.line.backgroundColor = self.activeColor
// set placeholder label font and color
self.placeholderLabel.font = self.placeholderLabel.font.withSize(self.minFontSize)
self.placeholderLabel.textColor = self.activeColor
// deactivate placeholder label CenterY constraint
self.placeHolderCenterYConstraint.isActive = false
// activate placeholder label Top constraint
self.placeHolderTopConstraint.isActive = true
// move placeholder label leading to 0
self.placeHolderLeadingConstraint.constant = 0
self.layoutIfNeeded()
}) { (done) in
}
}
func animatePlaceholderCenter() -> Void {
UIView.animate(withDuration: animationDuration, animations: {
// decrease line height
self.lineHeightConstraint.constant = 1.0
// set line to inactiveColor
self.line.backgroundColor = self.inActiveColor
// set placeholder label font and color
self.placeholderLabel.font = self.placeholderLabel.font.withSize(self.maxFontSize)
self.placeholderLabel.textColor = self.inActiveColor
// deactivate placeholder label Top constraint
self.placeHolderTopConstraint.isActive = false
// activate placeholder label CenterY constraint
self.placeHolderCenterYConstraint.isActive = true
// move placeholder label leading to 16
self.placeHolderLeadingConstraint.constant = 16
self.layoutIfNeeded()
}) { (done) in
}
}
func setErrorText(_ error: String?, errorAccessibilityValue: String?, endEditing: Bool) {
if let errorText = error {
UIView.animate(withDuration: 0.05, animations: {
self.errorLabel.text = errorText
self.line.backgroundColor = self.errorColorFull
self.errorLabel.isHidden = false
// activate error label Bottom constraint
self.errorLabelBottomConstraint.isActive = true
}) { (done) in
if endEditing {
self.textField.resignFirstResponder()
}
}
}else{
UIView.animate(withDuration: 0.05, animations: {
self.errorLabel.text = ""
self.line.backgroundColor = self.inActiveColor
self.errorLabel.isHidden = true
// deactivate error label Bottom constraint
self.errorLabelBottomConstraint.isActive = false
}) { (done) in
if endEditing {
self.textField.resignFirstResponder()
}
}
}
errorLabel.accessibilityIdentifier = errorAccessibilityValue ?? "textinput_error"
}
// func to set / clear element background colors
// to make it easy to see the frames
func showHideFrames(show b: Bool) -> Void {
if b {
self.backgroundColor = UIColor(red: 0.8, green: 0.8, blue: 1.0, alpha: 1.0)
placeholderLabel.backgroundColor = .cyan
errorLabel.backgroundColor = .green
textField.backgroundColor = .yellow
} else {
self.backgroundColor = .white
[placeholderLabel, errorLabel, textField].forEach {
$0.backgroundColor = .clear
}
}
}
}
DemoFLoatingTextViewController
class DemoFLoatingTextViewController: UIViewController {
// FloatingTextFieldView
let sampleFTF: FloatingTextFieldView = {
let v = FloatingTextFieldView()
return v
}()
// a label to constrain below the FloatingTextFieldView
// so we can see it gets "pushed down"
let demoLabel: UILabel = {
let v = UILabel()
v.numberOfLines = 0
v.text = "This is a label outside the Floating Text Field. As you will see, it gets \"pushed down\" when the error label is shown."
v.backgroundColor = .brown
v.textColor = .yellow
return v
}()
// buttons to Demo the functionality
let btnA: UIButton = {
let b = UIButton(type: .system)
b.setTitle("End Editing", for: .normal)
b.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
return b
}()
let btnB: UIButton = {
let b = UIButton(type: .system)
b.setTitle("Set Error", for: .normal)
b.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
return b
}()
let btnC: UIButton = {
let b = UIButton(type: .system)
b.setTitle("Clear Error", for: .normal)
b.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
return b
}()
let btnD: UIButton = {
let b = UIButton(type: .system)
b.setTitle("Set & End", for: .normal)
b.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
return b
}()
let btnE: UIButton = {
let b = UIButton(type: .system)
b.setTitle("Clear & End", for: .normal)
b.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
return b
}()
let btnF: UIButton = {
let b = UIButton(type: .system)
b.setTitle("Show Frames", for: .normal)
b.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
return b
}()
let btnG: UIButton = {
let b = UIButton(type: .system)
b.setTitle("Hide Frames", for: .normal)
b.backgroundColor = UIColor(white: 0.9, alpha: 1.0)
return b
}()
let errorMessages: [String] = [
"Simple Error",
"This will end up being a Multiline Error message. It is long enough to cause word wrapping."
]
var errorCount: Int = 0
override func viewDidLoad() {
super.viewDidLoad()
// add Demo buttons
let btnStack = UIStackView()
btnStack.axis = .vertical
btnStack.spacing = 6
btnStack.translatesAutoresizingMaskIntoConstraints = false
[[btnA], [btnB, btnC], [btnD, btnE], [btnF, btnG]].forEach { btns in
let sv = UIStackView()
sv.distribution = .fillEqually
sv.spacing = 12
sv.translatesAutoresizingMaskIntoConstraints = false
btns.forEach {
sv.addArrangedSubview($0)
}
btnStack.addArrangedSubview(sv)
}
view.addSubview(btnStack)
// add FloatingTextFieldView and demo label
view.addSubview(sampleFTF)
view.addSubview(demoLabel)
sampleFTF.translatesAutoresizingMaskIntoConstraints = false
demoLabel.translatesAutoresizingMaskIntoConstraints = false
let g = view.safeAreaLayoutGuide
NSLayoutConstraint.activate([
// buttons stack Top = 20, centerX, width = 80% of view width
btnStack.topAnchor.constraint(equalTo: g.topAnchor, constant: 20.0),
btnStack.centerXAnchor.constraint(equalTo: g.centerXAnchor),
btnStack.widthAnchor.constraint(equalTo: g.widthAnchor, multiplier: 0.8),
// FloatingTextFieldView Top = 40-pts below buttons stack
sampleFTF.topAnchor.constraint(equalTo: btnStack.bottomAnchor, constant: 40.0),
// FloatingTextFieldView Leading = 60-pts
sampleFTF.leadingAnchor.constraint(equalTo: g.leadingAnchor, constant: 60.0),
// FloatingTextFieldView width = 240
sampleFTF.widthAnchor.constraint(equalToConstant: 240.0),
// Note: we are not setting the FloatingTextFieldView Height!
// constrain demo label Top = 8-pts below FloatingTextFieldView bottom
demoLabel.topAnchor.constraint(equalTo: sampleFTF.bottomAnchor, constant: 8.0),
// Leading = FloatingTextFieldView Leading
demoLabel.leadingAnchor.constraint(equalTo: sampleFTF.leadingAnchor),
// Width = 200
demoLabel.widthAnchor.constraint(equalToConstant: 200.0),
])
// add touchUpInside targets for demo buttons
btnA.addTarget(self, action: #selector(endEditing(_:)), for: .touchUpInside)
btnB.addTarget(self, action: #selector(setError(_:)), for: .touchUpInside)
btnC.addTarget(self, action: #selector(clearError(_:)), for: .touchUpInside)
btnD.addTarget(self, action: #selector(setAndEnd(_:)), for: .touchUpInside)
btnE.addTarget(self, action: #selector(clearAndEnd(_:)), for: .touchUpInside)
btnF.addTarget(self, action: #selector(showFrames(_:)), for: .touchUpInside)
btnG.addTarget(self, action: #selector(hideFrames(_:)), for: .touchUpInside)
}
#objc func endEditing(_ sender: Any) -> Void {
sampleFTF.textField.resignFirstResponder()
}
#objc func setError(_ sender: Any) -> Void {
sampleFTF.setErrorText(errorMessages[errorCount % 2], errorAccessibilityValue: "", endEditing: false)
errorCount += 1
}
#objc func clearError(_ sender: Any) -> Void {
sampleFTF.setErrorText(nil, errorAccessibilityValue: "", endEditing: false)
}
#objc func setAndEnd(_ sender: Any) -> Void {
sampleFTF.setErrorText(errorMessages[errorCount % 2], errorAccessibilityValue: "", endEditing: true)
errorCount += 1
}
#objc func clearAndEnd(_ sender: Any) -> Void {
sampleFTF.setErrorText(nil, errorAccessibilityValue: "", endEditing: true)
}
#objc func showFrames(_ sender: Any) -> Void {
sampleFTF.showHideFrames(show: true)
}
#objc func hideFrames(_ sender: Any) -> Void {
sampleFTF.showHideFrames(show: false)
}
}
Example results: