如何将值从第二控制器传递到已打开的Stage（First Contrller）？

Question

我有两个控制器

1. [FXMLDocumentController具有TableView CustomerTable。
2. NewCustomerController第二个控制器添加新行。

这是我的代码

FXMLDocument.fxml

<AnchorPane id="AnchorPane" prefHeight="283.0" prefWidth="437.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="mytableview.FXMLDocumentController">
    <children>
        <Button fx:id="button" layoutX="309.0" layoutY="25.0" onAction="#handleButtonAction" text="New Customer" />
      <TableView fx:id="customerTable" layoutX="6.0" layoutY="61.0" prefHeight="215.0" prefWidth="426.0">
        <columns>
          <TableColumn fx:id="custname" prefWidth="75.0" text="Customer Name" />
          <TableColumn fx:id="city" prefWidth="75.0" text="City" />
        </columns>
         <columnResizePolicy>
            <TableView fx:constant="CONSTRAINED_RESIZE_POLICY" />
         </columnResizePolicy>
      </TableView>
    </children>
</AnchorPane>  

NewCustomer.fxml

<AnchorPane id="AnchorPane" prefHeight="172.0" prefWidth="209.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/8.0.171" fx:controller="com.newcustomer.NewCustomerController">
   <children>
      <Button layoutX="141.0" layoutY="129.0" mnemonicParsing="false" onAction="#newCustomer" text="Add" />
      <TextField fx:id="cNameTextField" layoutX="14.0" layoutY="26.0" promptText="Customer Name" />
      <TextField fx:id="custCityTextField" layoutX="14.0" layoutY="77.0" promptText="City" />
   </children>
</AnchorPane>

FXMLDocumentController.java

public class FXMLDocumentController implements Initializable {

@FXML
public TableView<Customer> customerTable;

@FXML
public TableColumn<Customer, String> custname;

@FXML
public TableColumn<Customer, String> city;  

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

@FXML
private void handleButtonAction(ActionEvent event) throws IOException {
    Parent parent = FXMLLoader.load(getClass().getResource("/com/newcustomer/NewCustomer.fxml"));
    Stage stage = new Stage();
    Scene scene = new Scene(parent);
    stage.setScene(scene);
    stage.show();
}

public void inflateUI(Customer customer) {
    custname.setCellValueFactory(new PropertyValueFactory<>("name"));
    city.setCellValueFactory(new PropertyValueFactory<>("city"));
    customerTable.getItems().add(customer);
}

NewCustomerController.java

public class NewCustomerController implements Initializable {

@FXML
private TextField cNameTextField;

@FXML
private TextField custCityTextField;

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

public void newCustomer(ActionEvent e) throws IOException {
    String name = cNameTextField.getText();
    String stringCity = custCityTextField.getText();

    Customer customer = new Customer(10, name, stringCity);
    FXMLLoader fXMLLoader = new FXMLLoader(getClass().getResource("/mytableview/FXMLDocument.fxml"));
    FXMLDocumentController fXMLDocumentController = fXMLLoader.<FXMLDocumentController>getController();
    fXMLDocumentController.inflateUI(customer); // Getting NPE at this line.
    }

}

MyTableView.java

public class MyTableView extends Application {

    public MyTableView() {
    }

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("FXMLDocument.fxml"));

        Scene scene = new Scene(root);

        stage.setScene(scene);
        stage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }

}

我希望在TableView中添加一行，但是它不起作用。我错过了什么？

Answer 1

首先，我建议通过@kleopatra提供的链接来了解控制器之间的通信概念。

谈到您的实际问题，我注意到您的代码中存在三个问题。其中，@ kleopatra已指定一个。

关于您要使用newCustomer（）方法的NPE，您启动了FXMLLoader实例，但未加载它。因此，getController（）为null。要解决此问题，您需要先调用load（）方法，然后再调用getController（）。

public void newCustomer(ActionEvent e) throws IOException {
    String name = cNameTextField.getText();
    String stringCity = custCityTextField.getText();
    Customer customer = new Customer(10, name, stringCity);
    FXMLLoader fXMLLoader = new FXMLLoader(getClass().getResource("/mytableview/FXMLDocument.fxml"));
    fXMLLoader.load(); // YOU ARE MISSING THIS LINE
    FXMLDocumentController fXMLDocumentController = fXMLLoader.<FXMLDocumentController>getController();
    fXMLDocumentController.inflateUI(customer); // Getting NPE at this line.
}

但是，上面的修复方法是USELESS，因为您正在创建未被使用的FXMLDocumentController的新实例（由@kleopatra指定）。您实际上必须将要通信的控制器实例传递给它。您需要在NewCustomerController中创建此控制器的实例变量并将其设置为它。

@FXML
private void handleButtonAction(ActionEvent event) throws IOException {
    FXMLLoader fXMLLoader = new FXMLLoader(getClass().getResource("/com/newcustomer/NewCustomer.fxml"));
    Parent parent = fXMLLoader.load();
    NewCustomerController controller = fXMLLoader.getController();
    controller.setFXMLDocumentController(this); // Pass this controller to NewCustomerController
    Stage stage = new Stage();
    Scene scene = new Scene(parent);
    stage.setScene(scene);
    stage.show();
}

NewCustomerController.java

private FXMLDocumentController fXMLDocumentController;

public void setFXMLDocumentController(FXMLDocumentController fXMLDocumentController) {
    this.fXMLDocumentController = fXMLDocumentController;
}

public void newCustomer(ActionEvent e) throws IOException {
    String name = cNameTextField.getText();
    String stringCity = custCityTextField.getText();
    Customer customer = new Customer(10, name, stringCity);
    fXMLDocumentController.inflateUI(customer);//You are passing to the currently loaded controller
}

最后，您只需要对TableColumns设置一次CellValueFactory，而不必每次都设置客户。您可以将这两行移动到initialize（）方法。

@Override
public void initialize(URL url, ResourceBundle rb) {
    custname.setCellValueFactory(new PropertyValueFactory<>("name"));
    city.setCellValueFactory(new PropertyValueFactory<>("city"));
}