sample.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.geometry.Insets?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.ProgressBar?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>

<GridPane fx:id="gridPane" alignment="center" hgap="10" prefHeight="287.0" prefWidth="627.0" vgap="10" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <columnConstraints>
      <ColumnConstraints />
   </columnConstraints>
   <rowConstraints>
      <RowConstraints />
   </rowConstraints>
   <children>
      <GridPane prefHeight="234.0" prefWidth="631.0">
        <columnConstraints>
          <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
          <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
        </columnConstraints>
        <rowConstraints>
          <RowConstraints maxHeight="60.0" minHeight="10.0" prefHeight="60.0" vgrow="SOMETIMES" />
          <RowConstraints maxHeight="168.0" minHeight="10.0" prefHeight="76.0" vgrow="SOMETIMES" />
            <RowConstraints maxHeight="219.0" minHeight="10.0" prefHeight="41.0" vgrow="SOMETIMES" />
        </rowConstraints>
         <children>
            <Button fx:id="buttonChooseFile" mnemonicParsing="false" onAction="#clickButton" prefHeight="32.0" prefWidth="105.0" text="Choose File" GridPane.columnIndex="2">
               <GridPane.margin>
                  <Insets left="10.0" top="10.0" />
               </GridPane.margin>
            </Button>
            <Label fx:id="chosenFile" GridPane.columnIndex="1" />
            <TextField fx:id="textFieldInput" GridPane.rowIndex="1">
               <GridPane.margin>
                  <Insets left="10.0" right="10.0" />
               </GridPane.margin>
            </TextField>
            <TextField fx:id="textFieldOutput" GridPane.columnIndex="1" GridPane.rowIndex="1">
               <GridPane.margin>
                  <Insets left="10.0" right="10.0" />
               </GridPane.margin>
            </TextField>
             <ProgressBar fx:id="progressBar" visible="false" GridPane.columnIndex="1" GridPane.rowIndex="2" />
            <Button fx:id="saveButton" mnemonicParsing="false" onAction="#saveList" prefHeight="36.0" prefWidth="106.0" text="Save Changes" GridPane.columnIndex="2" GridPane.rowIndex="2">
               <GridPane.margin>
                  <Insets left="5.0" />
               </GridPane.margin>
            </Button>
            <Label fx:id="doneLabel" prefHeight="18.0" prefWidth="209.0" GridPane.columnIndex="1" GridPane.rowIndex="2" />
         </children>
      </GridPane>
   </children>
</GridPane>