Adding a minus sign to the UITextField's .NumberPad keyboard

问题

Fairly new to iOS development so forgive me for asking something that might be quite obvious. As you all know the UITextField's keyboard with keyboardType set to .NumberPad looks like the following...

.NumberPad keyboard

What I would like to do is replace the empty space in the lower left corner with a minus sign. Is this possible or does one need to write an entire custom keyboard to achieve this?

Would really appreciate the help.

回答1:

Add a toolbar to your textfield inputAccessoryView and when the textfield will become the responder then the keyboard will show the toolbar (Swift 3.0):

func addToolBar(){
   let toolbar = UIToolbar(frame: CGRect(x: 0, y: 0, width: self.view.bounds.size.width, height: 44))
   let minusButton = UIBarButtonItem(title: "-", style: .plain, target: self, action: #selector(toggleMinus))
   toolbar.items = [minusButton]
   theTextField.inputAccessoryView = toolbar
}

func toggleMinus(){

    // Get text from text field
    if var text = theTextField.text , text.isEmpty == false{

        // Toggle
        if text.hasPrefix("-") {
            text = text.replacingOccurrences(of: "-", with: "")
        }
        else
        {
            text = "-\(text)"
        }

        // Set text in text field
        theTextField.text = text

    }
}

hope it helps.

来源：https://stackoverflow.com/questions/36455158/adding-a-minus-sign-to-the-uitextfields-numberpad-keyboard