how canBecomeFirstResponder bring custom inputAccessoryView - ios

Question

I'm trying to make custom inputAccessoryView contain UITextField and docking it bottom like chat application
but if i didn't use canBecomeFirstResponder = true inputAccessoryView are hidden(?)
this is my code
class MainVC: UITableViewController {
lazy var inputTextFieldContainer: UIView = {
// custom inputAccessoryView
}()
override func viewDidLoad(){
super.viewDidLoad()
}
override var inputAccessoryView: UIView? {
get{
return containerView
}
}
override var canBecomeFirstResponder: Bool {
get {
return true
}
}
}
how canBecomeFirstResponder bring custom inputAccessoryView
i read about UIResponder and responder chain on Apple docs
but i couldn't match that concept to this issue.
They said UIResponder will handle the events and i make my MainVC become first responder by canBecomeFirstResponder = true
and inputAccessoryView are shown
but what is the exact event in this case and situation

Answer 1

Since your code inherits from UITableViewController here a complete example with it:
Start with defining a accessory view. Since you mentioned as an example a chat app it could be a textfield and a send button:
class SendMessageView: UIView {
private let textField = UITextField()
private let sendButton = UIButton()
init() {
super.init(frame: CGRect.zero)
self.setup()
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) not implemented")
}
private func setup() {
sendButton.setTitle("Send", for: UIControlState.normal)
sendButton.setTitleColor(UIColor.blue, for: UIControlState.normal)
self.addSubview(textField)
self.addSubview(sendButton)
self.backgroundColor = UIColor.groupTableViewBackground
textField.backgroundColor = UIColor.white
self.autoresizingMask = .flexibleHeight
textField.translatesAutoresizingMaskIntoConstraints = false
sendButton.translatesAutoresizingMaskIntoConstraints = false
textField.topAnchor.constraint(equalTo: self.topAnchor, constant: 8).isActive = true
textField.leadingAnchor.constraint(equalTo: self.leadingAnchor, constant: 16).isActive = true
sendButton.leadingAnchor.constraint(equalTo: textField.trailingAnchor, constant: 8).isActive = true
sendButton.trailingAnchor.constraint(equalTo: self.trailingAnchor, constant: -16).isActive = true
sendButton.centerYAnchor.constraint(equalTo: textField.centerYAnchor).isActive = true
}
override var intrinsicContentSize: CGSize {
let contentHeight = self.textField.intrinsicContentSize.height + 16
return CGSize(width: UIScreen.main.bounds.width, height: contentHeight)
}
}
Next you need a custom UITableView which uses our accessory view:
class CustomTableView: UITableView {
private let sendMessageView = SendMessageView()
override var canBecomeFirstResponder: Bool {
return true
}
override var inputAccessoryView: UIView? {
return self.sendMessageView
}
}
Finally one could define a TableViewController using this custom table view:
class TableViewController: UITableViewController {
override func loadView() {
self.tableView = CustomTableView()
self.view = self.tableView
}
override func viewDidLoad() {
super.viewDidLoad()
self.tableView.becomeFirstResponder()
}
...
The result would look like this:
[