每次我在 JavaFX 中更改场景时都会重置变量值

Question

我一直在尝试实现的是一个 JavaFX 应用程序，它计算通过各种类别选择的项目的成本，在这种情况下只有两个：比萨饼和汉堡。

当我单击带有文本“pizzas”的按钮时，pizzas.fxml 文件被加载，我选择一个项目，因此变量 Pizzatotal 增加，然后我回到主页。直到这一步，变量 Pizzatotal 的值保持与它更改为的增量值相同。但是一旦我从主页点击按钮“汉堡”，变量 Pizzatotal 的值就会重置为 0。

我希望变量 Pizzatotal 的值在应用程序中的场景之间的整个导航过程中保持不变。

我一共构建了 3 个 fxml 文件。 一个用于主页，其中包含两个按钮，分别用于导航到第二页和第三页。

这是主页的 fxml 代码：

"'

<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.layout.AnchorPane?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="- 
Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" 
xmlns="http://javafx.com/javafx/17" xmlns:fx="http://javafx.com/fxml/1" 
fx:controller="com.example.demo.HelloController">
<children>
  <Button layoutX="32.0" layoutY="34.0" mnemonicParsing="false" onAction="#switchtoOrderpage" prefHeight="71.0" prefWidth="114.0" text="Pizzas" />
  <Button layoutX="166.0" layoutY="34.0" mnemonicParsing="false" onAction="#switchtoburger" prefHeight="71.0" prefWidth="114.0" text="Burgers" />
</children>
</AnchorPane>

第二个 FXML 文件包含一个网格窗格，其中包含用于执行不同方法的按钮。坦率地说，这个屏幕上的每个按钮都会将所选披萨的成本添加到变量中：total。

第二个FXML文件的代码如下：

"'

<?import javafx.scene.control.Button?>
<?import javafx.scene.layout.ColumnConstraints?>
<?import javafx.scene.layout.GridPane?>
<?import javafx.scene.layout.RowConstraints?>

<GridPane hgap="50.0" maxHeight="-Infinity" maxWidth="-Infinity" 
 minHeight="-Infinity" minWidth="-Infinity" prefHeight="1080.0" 
 prefWidth="1922.0" vgap="20.0" xmlns="http://javafx.com/javafx/17" 
 xmlns:fx="http://javafx.com/fxml/1" 
 fx:controller="com.example.demo.PizzaController">
 <columnConstraints>
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="348.1999786376953" 
 minWidth="10.0" prefWidth="297.0000274658203" />
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="433.80001220703133" 
 minWidth="0.0" prefWidth="298.7999633789062" />
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="456.0" minWidth="0.0" 
 prefWidth="314.99990234375" />
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="698.4000122070313" 
 minWidth="10.0" prefWidth="296.39997558593745" />
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="939.8000610351562" 
 minWidth="10.0" prefWidth="282.20002441406245" />
 <ColumnConstraints hgrow="SOMETIMES" maxWidth="939.8000610351562" 
 minWidth="10.0" prefWidth="281.800048828125" />
 </columnConstraints>
 <rowConstraints>
 <RowConstraints maxHeight="238.39998779296874" minHeight="10.0" 
  prefHeight="238.39998779296874" vgrow="SOMETIMES" />
 <RowConstraints maxHeight="188.80000000000004" minHeight="0.0" 
  prefHeight="47.800012207031244" vgrow="SOMETIMES" />
 <RowConstraints maxHeight="312.80000000000007" minHeight="10.0" 
  prefHeight="228.60000000000002" vgrow="SOMETIMES" />
 <RowConstraints maxHeight="312.80000000000007" minHeight="0.0" 
  prefHeight="52.999987792968795" vgrow="SOMETIMES" />
 <RowConstraints maxHeight="494.6000122070312" 
  minHeight="3.5999755859375" prefHeight="262.79998779296875" 
  vgrow="SOMETIMES" />
 <RowConstraints maxHeight="480.8000122070313" minHeight="10.0" 
  prefHeight="158.00001220703132" vgrow="SOMETIMES" />
  </rowConstraints>
  <children>
  <Button fx:id="pizza" mnemonicParsing="false" onAction="#addpizza" 
  prefHeight="54.0" prefWidth="301.0" text="Paneer Pizza" 
  GridPane.rowIndex="1" />
  <Button fx:id="addMargherita" mnemonicParsing="false" 
  prefHeight="56.0" prefWidth="298.0" text="Margherita Pizza" 
  GridPane.columnIndex="1" GridPane.rowIndex="1" />
  <Button fx:id="pizza1" mnemonicParsing="false" prefHeight="54.0" 
  prefWidth="301.0" text="Chicken Pizza" GridPane.rowIndex="3" />
  <Button fx:id="pizza2" mnemonicParsing="false" prefHeight="54.0" 
  prefWidth="301.0" text="Cheese Burst" GridPane.columnIndex="1" GridPane.rowIndex="3" />
  <Button mnemonicParsing="false" prefHeight="49.0" prefWidth="358.0" text="Chilli Pizza" GridPane.columnIndex="2" GridPane.rowIndex="1" />
  <Button fx:id="gotomain" mnemonicParsing="false" onAction="#switchtomainpagefromPizza" prefHeight="157.0" prefWidth="266.0" text="Main page" GridPane.columnIndex="5" GridPane.rowIndex="5" />
  <Button layoutX="645.0" layoutY="584.0" mnemonicParsing="false" prefHeight="49.0" prefWidth="358.0" text="Pan Pizza" GridPane.columnIndex="3" GridPane.rowIndex="3" />
  <Button mnemonicParsing="false" prefHeight="62.0" prefWidth="395.0" text="Sicilian Pizza" GridPane.columnIndex="3" GridPane.rowIndex="1" />
  <Button mnemonicParsing="false" prefHeight="47.0" prefWidth="286.0" text="Chicago-Style Pizza" GridPane.columnIndex="4" GridPane.rowIndex="1" />
  <Button mnemonicParsing="false" prefHeight="66.0" prefWidth="266.0" text="New York - Style Pizza" GridPane.columnIndex="5" GridPane.rowIndex="1" />
  <Button fx:id="pizza21" mnemonicParsing="false" prefHeight="54.0" prefWidth="301.0" text="Hawaiian Pizza" GridPane.columnIndex="2" GridPane.rowIndex="3" />
  <Button layoutX="1022.0" layoutY="584.0" mnemonicParsing="false" prefHeight="49.0" prefWidth="358.0" text="Greek Pizza" GridPane.columnIndex="4" GridPane.rowIndex="3" />
  <Button mnemonicParsing="false" prefHeight="49.0" prefWidth="358.0" text="Crust Pizza" GridPane.columnIndex="2" GridPane.rowIndex="5" />
  <Button mnemonicParsing="false" prefHeight="49.0" prefWidth="358.0" text="Momo Pizza" GridPane.columnIndex="1" GridPane.rowIndex="5" />
  <Button mnemonicParsing="false" prefHeight="49.0" prefWidth="358.0" text="Corn Pizza" GridPane.columnIndex="5" GridPane.rowIndex="3" />
  <Button mnemonicParsing="false" prefHeight="49.0" prefWidth="358.0" text="Prime Pizza" GridPane.rowIndex="5" />
  <Button fx:id="pizza3" mnemonicParsing="false" prefHeight="54.0" prefWidth="301.0" text="Sauce Pizza" GridPane.columnIndex="3" GridPane.rowIndex="5" />
  <Button fx:id="pizza4" mnemonicParsing="false" prefHeight="54.0" prefWidth="301.0" text="Oregano Pizza" GridPane.columnIndex="4" GridPane.rowIndex="5" />
  </children>
  </GridPane>

'"

第三个 FXML 文件也与此完全相同，因此我没有将代码包含在其中以缩短它。

我已经构建了 3 个差异控制器类来控制主页面、比萨饼页面和汉堡页面。

主页面的控制器类如下：

"'
公共类 HelloController 扩展 PizzaController{

public void switchtopizzapage(ActionEvent event) throws IOException {
    Parent root = FXMLLoader.load(getClass().getResource("pizzas.fxml"));
    Stage stage = (Stage) (((Node) event.getSource()).getScene().getWindow());
    Scene scene = new Scene(root);
    stage.setScene(scene);
    stage.setFullScreen(false);
    stage.setHeight(400);stage.setWidth(600);
    stage.show();
}


public  void switchtoburger(ActionEvent event) throws IOException {
    Parent root = FXMLLoader.load(HelloController.class.getResource("Burgers.fxml"));
    Stage stage = (Stage) (((Node) event.getSource()).getScene().getWindow());
    Scene scene = new Scene(root);
    stage.setScene(scene);
    stage.setFullScreen(false);
    System.out.println(total);
    stage.show();
}

}'"

方法'switchtopizzapage'打开披萨页面，这是第二个FXML场景，'switchtoburger'打开第三个FXML场景。

主页面如下所示：

This is the main-page.

pizzas.fxml 文件的控制器类如下：

public class PizzaController {

public  int total;



public void addpizza(){
    int pizzaCost = 100;
    total = total + pizzaCost;
    System.out.println(total);
}


public void switchtomainpagefromPizza(ActionEvent event) throws IOException {
    Parent root = FXMLLoader.load(getClass().getResource("Main-Page.fxml"));
    Stage stage = (Stage) (((Node) event.getSource()).getScene().getWindow());
    Scene scene = new Scene(root);
    stage.setScene(scene);
    stage.setFullScreen(false);
    System.out.println(total);
    stage.show();
}

}

Burgers.fxml 的控制器类如下：

public class BurgerController extends PizzaController{



public  void addChickenBurger(){
    int ChickenBurgerCost = 100;
   total = total+ ChickenBurgerCost;
   System.out.println(total);


}
public  void switchtomainpagefromBurger(ActionEvent event) throws IOException {
    Parent root = FXMLLoader.load(getClass().getResource("Main-Page.fxml"));
    Stage stage = (Stage) (((Node) event.getSource()).getScene().getWindow());
    Scene scene = new Scene(root);
    stage.setScene(scene);
    stage.setFullScreen(false);
    stage.show();
}

}

Answer 1

将变量更改为静态可以解决问题。