JavaFX 节点未初始化

Question

我试图更改应用程序中的场景，并且加载场景后需要直接更新其中一个节点，但问题是该节点尚未初始化，所以我总是得到 NPE。如何强制初始化节点或等到所有节点都已初始化后再调用该 ndoe 的方法

我从未成功尝试调用节点，但是如果我在事件中调用节点(例如按下按钮)，它似乎确实有效。

package za.holmes.PAT;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.layout.AnchorPane;

public class EventHandler implements Initializable {

    @FXML
    private AnchorPane changePane;
    @FXML
    private TextField IDField;
    @FXML
    private PasswordField passField;
    @FXML
    private Label errorField;
    @FXML
    private Label nameText;

    private User currentUser;

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

//    @FXML
//    private void initialize() {
//    }

    @FXML
    private void start(ActionEvent event) {
        ((Button) event.getSource()).setDisable(true);;
        System.out.println("Program started");
        try {
            System.out.println("Connecting to database");
            Class.forName("za.holmes.PAT.DataHandler");
        } catch (Exception e) {
            e.printStackTrace();
        }
        updateScreen("Login.fxml");
    }

    private void updateScreen(String fileName) {
        try {
            FXMLLoader loader = new FXMLLoader();
            AnchorPane pane = (AnchorPane)loader.load(Oldage.class.getResourceAsStream("/scenes/" + fileName));
            changePane.getChildren().setAll(pane);

        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    //Init complete
    @FXML
    private void login(ActionEvent event) {
        String userIDText = "", passText = "";
        int user = 0;
        try {
            errorField.setVisible(false);
            userIDText = IDField.getText();
            passText = passField.getText();
            // This is a call to another method that gets the type of user 
            // attempting to log in(it will be 1)
            user = DataHandler.checkUser(userIDText, passText);
            switch (user) {
                case 0:
                    errorField.setVisible(true);
                    break;
                case 1:
                    updateScreen("Old.fxml");
                    currentUser = DataHandler.getInfoElder(userIDText);
                    nameText.setText("Hello");
                    break;
                case 2:
                    break;
                case 3:
                    break;
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Answer 1

是的，只是不要使用单个 Controller 。使用多个 Controller ，而不是通过改变元素的可见性来改变屏幕，而不是让每个“场景”成为一个全新的 FXML 文件