如何在JavaFX中将值传递到当前/上一个阶段？

Question

我正在用javafx构建一个计算器，并且试图实现一个实用程序，用户可以在其中输入要计算的公式，而不是一一键入数字和运算。该应用程序应打开一个新窗口，用户可以键入公式，然后单击计算。然后，公式窗口应关闭，结果将显示在主计算器的显示屏中。

我在主控制器中创建了一个可以设置公式值的方法

public void returnFormula(String _formula)

，然后在第二阶段调用控制器。从那里，我计划实现正则表达式以计算公式并返回结果。目前，我只想返回公式作为概念证明。但是，当我尝试显示结果时，它是空白的；调试显示公式的值为null。如何正确地将此值传递回主控制器？

IDE：Netbeans 9.0

Java版本：1.8.0_211

主控制器：

public class FXMLDocumentController implements Initializable {

//FXML Items
@FXML
private Button clearBttn;
@FXML
private Button signBttn;
@FXML
private Button percentBttn;
@FXML
private Button divBttn;
@FXML
private Button seven;
@FXML
private Button eight;
@FXML
private Button nine;
@FXML
private Button multBttn;
@FXML
private Button four;
@FXML
private Button five;
@FXML
private Button six;
@FXML
private Button subBttn;
@FXML
private Button one;
@FXML
private Button two;
@FXML
private Button three;
@FXML
private Button addBttn;
@FXML
private Button zero;
@FXML
private Button decimalPnt;
@FXML
private Button equalBttn;
@FXML
private MenuItem aboutPress;
@FXML
private TextField display;
@FXML
private AnchorPane anchor; 

//class variables
double temp, result; 
String currentNum = "",
        formula;
Operation currentOp;
boolean opPressed; 
@FXML
private MenuItem binaryMI;
@FXML
private MenuItem hexMI;
@FXML
private MenuItem formulaMI;


@Override
public void initialize(URL url, ResourceBundle rb) {


    anchor.setOnKeyPressed((KeyEvent ev) -> {   //listerner for all relevant keys
        switch(ev.getCode()){
            case DIGIT0:
                zero.fire();
                break; 
            case DIGIT1:
                one.fire();
                break;
            case DIGIT2:
                two.fire();
                break;
            case DIGIT3:
                three.fire();
                break;
            case DIGIT4:
                four.fire();
                break;
            case DIGIT5:
                five.fire();
                break;
            case DIGIT6:
                six.fire();
                break;
            case DIGIT7:
                seven.fire(); 
                break;
            case DIGIT8:
                eight.fire();
                break;
            case DIGIT9:
                nine.fire();
                break;
            case EQUALS:
            case ENTER:
                equalBttn.fire();
                break;
            case MINUS:
                subBttn.fire();
                break;
            case PLUS:
                addBttn.fire();
                break;
            case SLASH:
                divBttn.fire();
                break;
            case ASTERISK:
                multBttn.fire();
                break;
            case PERIOD:
                decimalPnt.fire();
                break;
        }
    });
}

//NUMBER BUTTONS
@FXML
private void press7(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '7';
    updateDisplay(currentNum);
}

@FXML
private void press8(ActionEvent event){
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '8';
    updateDisplay(currentNum);
}

@FXML
private void press9(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '9';
    updateDisplay(currentNum);
}


@FXML
private void press4(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '4';
    updateDisplay(currentNum);
}

@FXML
private void press5(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '5';
    updateDisplay(currentNum);
}

@FXML
private void press6(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '6';
    updateDisplay(currentNum);
}


@FXML
private void press1(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '1';
    updateDisplay(currentNum);
}

@FXML
private void press2(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '2';
    updateDisplay(currentNum);
}

@FXML
private void press3(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '3';
    updateDisplay(currentNum);
}



@FXML
private void press0(ActionEvent event) {
    if(opPressed){
        currentNum = "";
        opPressed = false;
    }
    currentNum += '0';
    updateDisplay(currentNum);
}


//OPERATIONAL BUTTONS

//Clear calculator
@FXML
private void clearPress(ActionEvent event) {
    currentNum = "";
    updateDisplay(currentNum);
    temp = 0; 
    result = 0; 
}



//alternate sign button
@FXML
private void signPress(ActionEvent event) {
    if(getNum() == 0)
        return; 
    try{
    currentNum = Double.toString(getNum() * -1);
    updateDisplay(currentNum);
    }catch(NumberFormatException e){
        numberError();
    }
}

//create percent out of number
@FXML
private void percentPress(ActionEvent event) {
    try{
        currentNum = Double.toString(getNum() * .01);
        updateDisplay(currentNum);
    }catch(NumberFormatException e){
        numberError();
    }
}


//period button
@FXML
private void decPress(ActionEvent event) {
    if(display.getText().trim().isEmpty()){
        currentNum = "0.";
        updateDisplay(currentNum);
    }
    else{
        currentNum += ".";
        updateDisplay(currentNum);
    }
}


//MATH BUTTONS


//MULTIPLY
@FXML
private void multPress(ActionEvent event) {
    currentOp = Operation.MUL;
    opCheck();
}

//DIVIDE
@FXML
private void divPress(ActionEvent event) {
    currentOp = Operation.DIV;
    opCheck();
}

//SUBTRACT
@FXML
private void subPress(ActionEvent event) {
    currentOp = Operation.SUB;
    opCheck(); 
}

//ADD
@FXML
private void addPress(ActionEvent event) {
    currentOp = Operation.ADD;
    opCheck();
}

//EQUALS
@FXML
private void equalPress(ActionEvent event) {
    try{
        result = currentOp.math(temp, getNum());
        currentNum = "";
        temp = 0;
        updateDisplay(result);
    }
    catch(NumberFormatException e){
        numberError();
    }
}


//INTERNAL FUNCTIONS

//checks if it's currently in an operation state
private void opCheck(){
    if(!opPressed){
        opPressed = true;
        temp = getNum();
    }
    else{
        opPressed = false; 
        equalBttn.fire();
    }
}

//complete a math operations
private void completeOp(Operation _op){
    try{
        result = currentOp.math(result, getNum());
        currentNum = "";
        temp = 0;
        updateDisplay(result);
    }catch(NumberFormatException e){
        numberError();
    }
}

//get the current number from the display
private double getNum(){
    return Double.parseDouble(display.getText());
}

//OVERLOADED update display using string
public void updateDisplay(String _num){
    display.setText(_num);
}

//OVERLOADED UPDATE DISPLAY USING DOUBLE
private void updateDisplay(Double _num){
    updateDisplay(Double.toString(_num));
}

//function to call if a number occurs, resets the calculator and present an error
private void numberError(){
    Alert alert = new Alert(Alert.AlertType.ERROR, "Error parsing number input, calculator has been reset.");
    alert.showAndWait();
    currentNum = "";
    updateDisplay(currentNum);
    temp = 0; 
    result = 0;
}

@FXML
private void binPressed(ActionEvent event) {
    if(display.getText().trim().isEmpty()){
        Alert alert = new Alert(Alert.AlertType.ERROR, "Nothing to convert.");
        alert.showAndWait();
        return; 
    }
    currentNum = "";
    temp = 0; 
    result = 0; 
    opPressed = true;
    int bin = (int)getNum();
    TextField text = new TextField(Integer.toBinaryString(bin));
    Stage stage = new Stage();
    stage.setTitle("Binary Value");
    stage.setScene(new Scene(text, 250, 25));
    text.setEditable(false);
    stage.setResizable(false);
    stage.show();
}

@FXML
private void hexPressed(ActionEvent event) {
    if(display.getText().trim().isEmpty()){
        Alert alert = new Alert(Alert.AlertType.ERROR, "Nothing to convert.");
        alert.showAndWait();
        return; 
    }
    currentNum = "";
    temp = 0; 
    result = 0; 
    opPressed = true;
    TextField text = new TextField(Double.toHexString(getNum()));
    Stage stage = new Stage();
    stage.setTitle("Hexedecimal Value");
    stage.setScene(new Scene(text, 250, 25));
    text.setEditable(false);
    stage.setResizable(false);
    stage.show();
}

@FXML
private void formulaPressed(ActionEvent event) {

    try{
        FXMLLoader fxmlLoader = new FXMLLoader(this.getClass().getResource("/simplecalculator/FormulaInputFXML.fxml"));
        Stage formStage = new Stage(); 
        Parent root1 = (Parent) fxmlLoader.load();
        formStage.setTitle("Formula Input");
        formStage.setScene(new Scene(root1));
        formStage.show();
    }catch(IOException e){
        e.printStackTrace();
    }
}

public void returnFormula(String _formula) {
   this.formula = _formula;
    updateDisplay(this.formula);
}
}

主要FXML

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Menu?>
<?import javafx.scene.control.MenuBar?>
<?import javafx.scene.control.MenuItem?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>
<?import javafx.scene.text.Font?>

<AnchorPane id="AnchorPane" fx:id="anchor" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="295.0" prefWidth="225.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="simplecalculator.FXMLDocumentController">
   <children>
      <GridPane alignment="CENTER" layoutY="175.0" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="225.0" prefWidth="225.0" AnchorPane.topAnchor="70.0">
        <columnConstraints>
          <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
          <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
            <ColumnConstraints halignment="CENTER" hgrow="SOMETIMES" minWidth="10.0" prefWidth="100.0" />
        </columnConstraints>
        <rowConstraints>
            <RowConstraints minHeight="10.0" prefHeight="30.0" valignment="CENTER" vgrow="SOMETIMES" />
            <RowConstraints minHeight="10.0" prefHeight="30.0" valignment="CENTER" vgrow="SOMETIMES" />
          <RowConstraints minHeight="10.0" prefHeight="30.0" valignment="CENTER" vgrow="SOMETIMES" />
          <RowConstraints minHeight="10.0" prefHeight="30.0" valignment="CENTER" vgrow="SOMETIMES" />
          <RowConstraints minHeight="10.0" prefHeight="30.0" valignment="CENTER" vgrow="SOMETIMES" />
        </rowConstraints>
         <children>
            <Button fx:id="clearBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#clearPress" prefHeight="45.0" prefWidth="55.0" text="C" textAlignment="CENTER">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="signBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#signPress" prefHeight="45.0" prefWidth="55.0" text="+/−" textAlignment="CENTER" textOverrun="CLIP" GridPane.columnIndex="1">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="percentBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#percentPress" prefHeight="45.0" prefWidth="55.0" text="\%" textAlignment="CENTER" GridPane.columnIndex="2">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="divBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#divPress" prefHeight="45.0" prefWidth="55.0" text="÷" textAlignment="CENTER" GridPane.columnIndex="3">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="seven" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press7" prefHeight="45.0" prefWidth="55.0" text="7" textAlignment="CENTER" GridPane.rowIndex="1">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="eight" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press8" prefHeight="45.0" prefWidth="55.0" text="8" textAlignment="CENTER" GridPane.columnIndex="1" GridPane.rowIndex="1">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="nine" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press9" prefHeight="45.0" prefWidth="55.0" text="9" textAlignment="CENTER" GridPane.columnIndex="2" GridPane.rowIndex="1">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="multBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#multPress" prefHeight="45.0" prefWidth="55.0" text="X" textAlignment="CENTER" GridPane.columnIndex="3" GridPane.rowIndex="1">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="four" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press4" prefHeight="45.0" prefWidth="55.0" text="4" textAlignment="CENTER" GridPane.rowIndex="2">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="five" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press5" prefHeight="45.0" prefWidth="55.0" text="5" textAlignment="CENTER" GridPane.columnIndex="1" GridPane.rowIndex="2">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="six" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press6" prefHeight="45.0" prefWidth="55.0" text="6" textAlignment="CENTER" GridPane.columnIndex="2" GridPane.rowIndex="2">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="subBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#subPress" prefHeight="45.0" prefWidth="55.0" text="−" textAlignment="CENTER" GridPane.columnIndex="3" GridPane.rowIndex="2">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="one" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press1" prefHeight="45.0" prefWidth="55.0" text="1" textAlignment="CENTER" GridPane.rowIndex="3">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="two" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press2" prefHeight="45.0" prefWidth="55.0" text="2" textAlignment="CENTER" GridPane.columnIndex="1" GridPane.rowIndex="3">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="three" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press3" prefHeight="45.0" prefWidth="55.0" text="3" textAlignment="CENTER" GridPane.columnIndex="2" GridPane.rowIndex="3">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="addBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#addPress" prefHeight="45.0" prefWidth="55.0" text="+" textAlignment="CENTER" GridPane.columnIndex="3" GridPane.rowIndex="3">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="zero" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#press0" prefHeight="45.0" prefWidth="112.0" text="0" textAlignment="CENTER" GridPane.halignment="LEFT" GridPane.rowIndex="4">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="decimalPnt" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#decPress" prefHeight="45.0" prefWidth="55.0" text="." textAlignment="CENTER" GridPane.columnIndex="2" GridPane.rowIndex="4">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
            <Button fx:id="equalBttn" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" mnemonicParsing="false" onAction="#equalPress" prefHeight="45.0" prefWidth="55.0" text="=" textAlignment="CENTER" GridPane.columnIndex="3" GridPane.rowIndex="4">
               <font>
                  <Font name="Verdana" size="16.0" />
               </font>
            </Button>
         </children>
      </GridPane>
      <MenuBar layoutY="2.0" prefHeight="25.0" prefWidth="225.0">
        <menus>
          <Menu mnemonicParsing="false" text="File">
            <items>
              <MenuItem mnemonicParsing="false" text="Save equation to file" />
            </items>
          </Menu>
          <Menu mnemonicParsing="false" text="Tools">
            <items>
                  <MenuItem fx:id="binaryMI" mnemonicParsing="false" onAction="#binPressed" text="Convert to Binary" />
                  <MenuItem fx:id="hexMI" mnemonicParsing="false" onAction="#hexPressed" text="Convert to Hex" />
                  <MenuItem fx:id="formulaMI" mnemonicParsing="false" onAction="#formulaPressed" text="Enter Formula" />
            </items>
          </Menu>
          <Menu mnemonicParsing="false" text="Help">
            <items>
              <MenuItem fx:id="aboutPress" mnemonicParsing="false" text="About" />
            </items>
          </Menu>
        </menus>
      </MenuBar>
      <TextField fx:id="display" layoutY="80.0" maxWidth="-Infinity" minWidth="-Infinity" prefHeight="45.0" prefWidth="225.0" AnchorPane.topAnchor="25.0" />
   </children>
</AnchorPane>

公式输入的控制器：

    public class FormulaInputFXMLController implements Initializable 
    {

    @FXML
    private TextField formulaField;
    @FXML
    private Button calcBttn;

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    

    @FXML
    private void calcuatePressed(ActionEvent event) {
        try{
        FXMLLoader fxmlLoader = new FXMLLoader(this.getClass().getResource("/simplecalculator/FXMLDocument.fxml"));
        fxmlLoader.load();
        FXMLDocumentController controller = fxmlLoader.getController();
        controller.returnFormula(formulaField.getText());
        Stage stage = (Stage)calcBttn.getScene().getWindow();
        stage.close();
        }catch(IOException e){
            e.printStackTrace();
        }
    }
}

公式输入FXML：

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

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.control.TitledPane?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.HBox?>

<AnchorPane id="AnchorPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="75.0" prefWidth="350.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="simplecalculator.FormulaInputFXMLController">
   <children>
      <TitledPane animated="false" collapsible="false" focusTraversable="false" layoutX="74.0" layoutY="-65.0" prefHeight="75.0" prefWidth="350.0" text="Enter Formula Below:" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
        <content>
          <AnchorPane minHeight="0.0" minWidth="0.0" prefHeight="180.0" prefWidth="200.0">
               <children>
                  <HBox alignment="CENTER" layoutX="74.0" layoutY="-25.0" prefHeight="49.0" prefWidth="348.0" spacing="10.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
                     <children>
                        <TextField fx:id="formulaField" prefHeight="25.0" prefWidth="250.0" promptText="ex. 18+32 * (9 / 12)..." />
                        <Button fx:id="calcBttn" mnemonicParsing="false" onAction="#calcuatePressed" text="Calculate" />
                     </children>
                  </HBox>
               </children>
            </AnchorPane>
        </content>
      </TitledPane>
   </children>
</AnchorPane>

很抱歉，如果我发布了太多的代码，由于我的许多功能重叠，所以不能完全确定哪些信息可能与该问题无关。