How to restrict textfields in TornadoFX to numbers only

Question

The problem here is that I wanna make sure that the user doesn't enter any strings or text especially that I need to enter his choice into a database later so I don't things to get messed up in the database's part, here is part of code which is the view I wish to use the textview with restricted Integers (specifically the amount am field). PS: I'm still new to both JavaFX and TornadoFX so hope this doesn't sound like a rather silly question.

My Code:

package com.company.view

import javafx.beans.property.SimpleIntegerProperty
import javafx.scene.control.CheckBox
import tornadofx.*
import javafx.scene.control.TextField
import javafx.util.converter.NumberStringConverter
import java.sql.Connection

class Add: View() {
    override val root = Form()
    private val mainMenu: MainMenu by inject()
    private var cname: TextField by singleAssign()
    private var address: TextField by singleAssign()
    private var sname: TextField by singleAssign()
    private var ch: CheckBox by singleAssign()
    private var am: TextField by singleAssign()
    var conn: Connection?= mainMenu.conn

    init {
        with(root) {
            vbox(30.0) {
                fieldset("Enter Your Info below") {
                    field("Enter The Customer's Name") {
                            cname = textfield()
                    }
                    field("Enter the Customer's address") {
                        address = textfield()
                    }
                    field("Enter Bought Stock's Name") {
                        sname = textfield()
                    }
                    field("Do you wish to pay now?") {
                        ch = checkbox()
                    }
                    field("Enter the amount you wish to buy"){
                        am = textfield()
                    }
                    button("Submit")
                    {
                        setOnAction {
                            addPayment(cname.text, address.text, sname.text, ch.isSelected, am.text)
                        }
                    }
                }
            }
        }
    }

   private fun addPayment(cusName: String, caddress: String, stname: String, che: Boolean,am: String){
//required code for inserting into the database here.


    }
}

Answer 1

You can use the filterInput extension function we've added to TextField and check that the text after the addition is in int. If it's not, deny the last input change:

textfield {
    filterInput { it.controlNewText.isInt() } 
}

On another note, you really need to look into ItemViewModel. It's an anti-pattern to assign each input element to a variable and extract the values from the input values on submit. Your code will be a lot cleaner and easier to reason about and refactor later if you use view models.

PS: The filterInput function is available in the soon to be released TornadoFX 1.7.15, in the mean time you can add this extension function to your project:

fun TextInputControl.filterInput(discriminator: (TextFormatter.Change) -> Boolean) {
    textFormatter = TextFormatter<Any>(CustomTextFilter(discriminator))
}