Question

我正在尝试将一个字符串从一个类传递到另一个类，因此我可以根据用户名初始化标签。

这是我的代码：

    while (rs.next()) {
                    uID = rs.getString("ID");
                    uLoginName = rs.getString("user_login");
                    uNiceName = rs.getString("user_nicename");
                    password = rs.getString("user_pass");

                    if (uLoginName.equals(username) && password.equals(enteredPass)) {

                        ***//Values That I am Trying to pass***

                        TutorControlPanelController  panel  = new TutorControlPanelController();
                        panel.setUserLoginName(uLoginName);
                        try {

                            Parent root = FXMLLoader.load(getClass().getResource("SomePath"));
                            Scene scene = new Scene(root);
                            String css = this.getClass().getResource("Style.css").toExternalForm();
                            scene.getStylesheets().add(css);
                            Stage stage = new Stage();
                            stage.setTitle("Tutor Control Panel");
                            stage.setScene(scene);

                            stage.show();

                        } catch (IOException ex) {
                            Logger.getLogger(LoginController.class.getName()).log(Level.SEVERE, null, ex);
                        }
                    } else {
                        System.out.println("user not found");

                    }

                }

            } catch (SQLException ex) {
                Logger.getLogger(LoginController.class.getName()).log(Level.SEVERE, null, ex);
            }

在其他课程中，我正在进行更新

      public class SomeClass implements Initializable {

    @FXML
    private GridPane gridView;
    @FXML
    private Button recordButton;
    @FXML
    private Button stopButton;
    @FXML
    private MenuButton settingsButton;
    @FXML
    private MenuItem qualitySettings;
    @FXML
    private MenuItem videoSettings;
    @FXML
    private Button lessoncategory;
    @FXML
    private MenuButton serverUpload;
    @FXML
    private MenuItem startUpload;
    @FXML
    private MenuItem stopUpload;
    @FXML
    private Button timer;
    @FXML
    private Label timerHours;
    @FXML
    private Label timerMinutes;
    @FXML
    private Label timerSeconds;
    @FXML
    private Button logOut;
    @FXML
    private Label uNameLabel;

    private String uID;
    private String username;
    private String userLoginName;
    private String userNiceName;

    public TutorControlPanelController(String uID, String username, String userNiceName) {
        this.uID = uID;
        this.username = username;
        this.userNiceName = userNiceName;

    }

    /**
     * Initializes the controller class.
     */
    public TutorControlPanelController() {

    }

    public String getuID() {
        return uID;
    }

    public void setuID(String uID) {
        this.uID = uID;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getUserNiceName() {
        return userNiceName;
    }

    public void setUserNiceName(String userNiceName) {
        this.userNiceName = userNiceName;
    }

    public String getUserLoginName() {
        return userLoginName;
    }

    public void setUserLoginName(String userLoginName) {
        this.userLoginName = userLoginName;
    }

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

        assert uNameLabel != null : "fx:id=\"someID\" was not injected: check your FXML file 'somePath'.";

        setlabels();


    }

    public void setlabels() {
       uNameLabel.setText(getUserLoginName());

       // and just to check also printing the value

        System.out.println(getUserLoginName());
    }

我得到的只是空我发现很难弄清究到底发生了什么。

Answer 1

我不知道你在第二堂课的第一堂课叫哪里。你必须调用第一个作为seconde的属性作为例子，然后你才能获得userLoginName。

这是你在第二堂课中可以做的事情：

Instr()

Answer 2

目前，类TutorControlPanelController有一个默认构造函数和一个参数化构造函数。调用默认构造函数时，String实例变量全部初始化为null。他们可以通过调用各种方法来设置，但不能保证它们会成为。

更好的方法是删除默认构造函数（删除此代码）：

public TutorControlPanelController() {

}

在带有rs.next（）的代码片段中，更改调用以使用参数化构造函数：

if (uLoginName.equals(username) && password.equals(enteredPass)) {
  TutorControlPanelController  panel  = new TutorControlPanelController(uId, uLoginName, uNiceName);

  try {
   ...

这种方法可以确保大多数实例变量都已初始化。

然而，因为这里代码不足，我不知道默认构造函数是否有框架要求。如果是，则初始化String实例变量以使其具有空String

private String uID = "";
private String username = "";
private String userLoginName = "";
private String userNiceName = "";

在这种情况下，您将避免使用NPE。

Java - 将值从一个类传递到另一个类

2 个答案: