Question

我正在尝试用JavaFX创建一个简单的Contacts Application。当我想创建新的联系人时，它有一个带有TableView的主窗口和一个DialogPane打开。在DialogPane中，我想从中收集几个TextField以便创建联系人列表。我的问题是，当我想从DialogPane（从TextFields）读取输入时，该输入是带有单独控制器（与主控制器分开）的单独fxml文件，应用程序运行错误（java.lang.NullPointerException）。当我在主窗口FXML文件中放置TextField时，就可以从textField中访问此文本了。当我想从DialogPane读取数据时为什么会出现错误（错误->文件：Controller.java，我注释了发生错误的部分）？我被困住了。谁能暗示我在做什么错？这是我的代码：

Main.java

public class Main extends Application {

@Override
public void start(Stage primaryStage) throws Exception{
    Parent root = FXMLLoader.load(getClass().getResource("mainwindow.fxml"));
    primaryStage.setTitle("Your Contacts");
    primaryStage.setScene(new Scene(root, 900, 600));
    primaryStage.show();
}


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

Controller.java

public class Controller {


@FXML
private BorderPane mainPanel;


public ObservableList<Contact> contactsList = FXCollections.observableArrayList();


@FXML
public void showAddContactDialog() {
    Dialog<ButtonType> dialog = new Dialog<>();
    dialog.initOwner(mainPanel.getScene().getWindow());
    dialog.setTitle("Add new contact");
    FXMLLoader fxmlLoader = new FXMLLoader();
    fxmlLoader.setLocation(getClass().getResource("addContactDialog.fxml"));
    try {
       dialog.getDialogPane().setContent(fxmlLoader.load());
    } catch (IOException e) {
        Alert alert = new Alert(Alert.AlertType.ERROR);
        alert.setTitle("Error");
        alert.setHeaderText(null);
        alert.setContentText("Couldn't load the dialog");
        alert.showAndWait();
        e.printStackTrace();
        return;
    }

    dialog.getDialogPane().getButtonTypes().add(ButtonType.OK);
    dialog.getDialogPane().getButtonTypes().add(ButtonType.CANCEL);

    Optional<ButtonType> result = dialog.showAndWait();
    if(result.isPresent() && result.get() == ButtonType.OK) {

    //========================================================================================

        //here is the error, I cannot read values from addContactDialog controller

        ContactController contactController = new ContactController();

        String firstName = contactController.getNewContact().getFirstName();
        String lastName = contactController.getNewContact().getLastName();
        String phoneNumber = contactController.getNewContact().getPhoneNumber();
        String emailAddress = contactController.getNewContact().getEmailAddress();

        Contact newContact = new Contact(firstName, lastName, phoneNumber, emailAddress);
        contactsList.add(newContact);

        //or alternatively
        //            Contact newContact = contactController.getNewContact();
        //            contactsList.add(newContact);


    //========================================================================================
    }

}
}

ContactController.java

public class ContactController {


@FXML
private TextField firstNameField;

@FXML
private TextField lastNameField;

@FXML
private TextField phoneNumberFiled;

@FXML
private TextField emailField;


public Contact getNewContact() {

    String firstName = firstNameField.getText();
    String lastName = lastNameField.getText();
    String phoneNumber = phoneNumberFiled.getText();
    String emailAddress = emailField.getText();

    Contact newContact = new Contact(firstName, lastName, phoneNumber, emailAddress);
    return newContact;
}

Contact.java

public class Contact {

private SimpleStringProperty firstName = new SimpleStringProperty("");
private SimpleStringProperty lastName = new SimpleStringProperty("");
private SimpleStringProperty phoneNumber = new SimpleStringProperty("");
private SimpleStringProperty emailAddress = new SimpleStringProperty("");

public Contact() {
}

public Contact(String firstName, String lastName, String phoneNumber, String emailAddress) {
    this.firstName.set(firstName);
    this.lastName.set(lastName);
    this.phoneNumber.set(phoneNumber);
    this.emailAddress.set(emailAddress);
}



public String getFirstName() {
    return firstName.get();
}

public SimpleStringProperty firstNameProperty() {
    return firstName;
}

public void setFirstName(String firstName) {
    this.firstName.set(firstName);
}

public String getLastName() {
    return lastName.get();
}

public SimpleStringProperty lastNameProperty() {
    return lastName;
}

public void setLastName(String lastName) {
    this.lastName.set(lastName);
}

public String getPhoneNumber() {
    return phoneNumber.get();
}

public SimpleStringProperty phoneNumberProperty() {
    return phoneNumber;
}

public void setPhoneNumber(String phoneNumber) {
    this.phoneNumber.set(phoneNumber);
}

public String getEmailAddress() {
    return emailAddress.get();
}

public SimpleStringProperty emailAddressProperty() {
    return emailAddress;
}

public void setEmailAddress(String emailAddress) {
    this.emailAddress.set(emailAddress);
}


@Override
public String toString() {
    return "Contact{" +
            "firstName=" + firstName +
            ", lastName=" + lastName +
            ", phoneNumber=" + phoneNumber +
            ", emailAddress=" + emailAddress +
            '}';
}
}

mainwindow.fxml

<BorderPane fx:id="mainPanel" fx:controller="sample.Controller"
        xmlns:fx="http://javafx.com/fxml">


<top>
    <MenuBar>
        <menus>
            <Menu text="Contacts">
                <items>
                    <MenuItem text="Add new" onAction="#showAddContactDialog"/>
                </items>
                <items>
                    <MenuItem text="Edit" />
                </items>
                <items>
                    <MenuItem text="Delete"/>
                </items>
                <items>
                    <MenuItem text="Exit"/>
                </items>
            </Menu>
        </menus>
        <menus>
            <Menu text="Info">
                <items>
                    <MenuItem text="About"/>
                </items>

            </Menu>
        </menus>
    </MenuBar>
</top>

<center>
    <TableView fx:id="contactsTable">
        <columnResizePolicy>
            <TableView fx:constant="CONSTRAINED_RESIZE_POLICY"/>
        </columnResizePolicy>
        <columns>
            <TableColumn text="First Name">
                <cellValueFactory>
                    <PropertyValueFactory property="firstName"/>
                </cellValueFactory>
            </TableColumn>

            <TableColumn text="Last Name">
                <cellValueFactory>
                    <PropertyValueFactory property="lastName"/>
                </cellValueFactory>
            </TableColumn>

            <TableColumn text="Phone Number">
                <cellValueFactory>
                    <PropertyValueFactory property="phoneNumber"/>
                </cellValueFactory>
            </TableColumn>

            <TableColumn text="Email">
                <cellValueFactory>
                    <PropertyValueFactory property="emailAddress"/>
                </cellValueFactory>
            </TableColumn>
        </columns>
    </TableView>
</center>
</BorderPane>

addContactDialog.fxml

<DialogPane fx:controller="sample.ContactController" xmlns:fx="http://javafx.com/fxml">
    <headerText>
    Fill in the information for the new Contact
</headerText>
<content>
    <GridPane vgap="10" hgap="10">
        <Label text="First Name: " GridPane.rowIndex="0" GridPane.columnIndex="0"/>
        <TextField fx:id="firstNameField" GridPane.rowIndex="0" GridPane.columnIndex="1"/>

        <Label text="Last Name: " GridPane.rowIndex="1" GridPane.columnIndex="0"/>
        <TextField fx:id="lastNameField" GridPane.rowIndex="1" GridPane.columnIndex="1"/>

        <Label text="Phone Number: " GridPane.rowIndex="2" GridPane.columnIndex="0"/>
        <TextField fx:id="phoneNumberField" GridPane.rowIndex="2" GridPane.columnIndex="1"/>

        <Label text="Notes: " GridPane.rowIndex="3" GridPane.columnIndex="0"/>
        <TextField fx:id="notesField" GridPane.rowIndex="3" GridPane.columnIndex="1"/>

    </GridPane>
</content>
</DialogPane>

Answer 1

好的，我发现了错误-我在ContactController.java文件中打了一个错字。它应该具有phoneNumberField而不是phoneNumberFiled字符串...

Answer 2

您是否尝试过放.toString 像这样 String firstName = contactController.getNewContact().getFirstName().toString();

无法从DialogPane，JavaFX的TextField输入中读取文本

2 个答案: