JavaFX我的文件保存不起作用

Question

I have this shopping basket see here https://i.stack.imgur.com/9ty3E.png

And everything works but my File save, what's meant to happen is when you file save and an existing project is open and it overwrites the old xml files but it's completely skipping over it and going to the else statement.

@FXML
private void handleSave() {
    File itemFile = mainApp.getItemFilePath();
    if (itemFile != null) {
        mainApp.saveItemDataToFile(itemFile);
    } else {
        handleSaveAs();
    }
}

And heres my Save as code for reference

@FXML
private void handleSaveAs() {
    FileChooser fileChooser = new FileChooser();

    // Set extension filter
    FileChooser.ExtensionFilter extFilter = new FileChooser.ExtensionFilter(
            "XML files (*.xml)", "*.xml");
    fileChooser.getExtensionFilters().add(extFilter);

    // Show save file dialog
    File file = fileChooser.showSaveDialog(mainApp.getPrimaryStage());

    if (file != null) {
        // Make sure it has the correct extension
        if (!file.getPath().endsWith(".xml")) {
            file = new File(file.getPath() + ".xml");
        }
        mainApp.saveItemDataToFile(file);
    }
}

public File getItemFilePath() {
        Preferences prefs = Preferences.userNodeForPackage(MainApp.class);
        String filePath = prefs.get("Filepath", null);
        if (filePath != null) {
            return new File(filePath);
        } else {
            return null;
        }
    }
public void setItemFilePath(File file) {
    Preferences prefs = Preferences.userNodeForPackage(MainApp.class);
    if (file != null) {
        prefs.put("filePath", file.getPath());

        primaryStage.setTitle("Shopping Basket - " + file.getName());
    } else {
        prefs.remove("filePath");
        primaryStage.setTitle("Shopping Basket");
    }
}


public void loadItemDataFromFile(File file) {
        try {
            JAXBContext context = JAXBContext
                    .newInstance(BasketListWrapper.class);
            Unmarshaller um = context.createUnmarshaller();

            BasketListWrapper wrapper = (BasketListWrapper) um.unmarshal(file);

            itemData.clear();
            itemData.addAll(wrapper.getItems());


            setItemFilePath(file);

        } catch (Exception e) {
            Alert alert = new Alert(AlertType.ERROR);
            alert.setTitle("Error");
            alert.setHeaderText("Could not load data");
            alert.setContentText("Could not load data from file:\n"
                    + file.getPath());

            alert.showAndWait();

        }
    }

    public void saveItemDataToFile(File file) {
        try {
            JAXBContext context = JAXBContext
                    .newInstance(BasketListWrapper.class);
            Marshaller m = context.createMarshaller();
            m.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

            BasketListWrapper wrapper = new BasketListWrapper();
            wrapper.setItems(itemData);

            m.marshal(wrapper, file);

            setItemFilePath(file);
        } catch (Exception e) {
            Alert alert = new Alert(AlertType.ERROR);
            alert.setTitle("Error");
            alert.setHeaderText("Could not load data");
            alert.setContentText("Could not load data from file:\n"
                    + file.getPath());

            alert.showAndWait();
        }
    }

Answer 1

In getItemFilePath method you're trying to get the " F ilepath" preference:

String filePath = prefs.get("Filepath", null);

But in the setItemFilePath method you're setting the "file P ath" preference:

prefs.put("filePath", file.getPath());

Since preferences keys are case sensitive, just like any other String , you're always getting the default value, which is null.