在对话框上执行字段检查时不显示JavaFX警报

我是JavaFX的初学者，正在一个小应用程序上练习。问题是，我试图在对话框字段为空时执行检查，如果为空，则填充警告类型的警报，但未成功。 如果未填写所有字段，则该对话框确实没有输入数据，但警报从未显示

这是主控制器代码：

  @FXML
    public void showAddReportDialog () {
        Dialog<ButtonType> dialog = new Dialog<ButtonType>();
        dialog.initOwner(mainPanel.getScene().getWindow());
        dialog.setTitle("Add new report");
        FXMLLoader fxmlLoader = new FXMLLoader();
        fxmlLoader.setLocation(getClass().getResource("addReportDialog.fxml"));
        try {
            dialog.getDialogPane().setContent(fxmlLoader.load());
        } catch (IOException e) {
            System.out.println("Could not load the dialog");
            e.printStackTrace();
            return;
        }
        dialog.getDialogPane().getButtonTypes().add(ButtonType.OK);
        dialog.getDialogPane().getButtonTypes().add(ButtonType.CANCEL);
        final Button btOK = (Button) dialog.getDialogPane().lookupButton(ButtonType.OK);
        btOK.addEventFilter(ActionEvent.ACTION, event -> {
            AddDialogController addDialogController = fxmlLoader.getController();
            Report newReport = addDialogController.getNewReport();
            if (newReport != null) {
                data.addReport(newReport);
                data.saveReports();
            } else {
                event.consume();
            }
        });
        Optional<ButtonType> result = dialog.showAndWait();
    }

---

非常感谢你的帮助

您可以使用执行此操作，但是

对话框将在
警报关闭后始终关闭。我建议将登录
按钮
绑定到
文本字段

回答您的问题：

import java.util.Optional;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.geometry.Insets;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBar.ButtonData;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.Pair;


/**
 * JavaFX App
 */
public class App extends Application {

    @Override
    public void start(Stage stage) {        
        Button button = new Button("Show Add Report Dialog");
        button.setOnAction((e) -> {
            showAddReportDialog();
        });

        StackPane layout = new StackPane();
        layout.getChildren().add(button);

        Scene scene = new Scene(layout, 300, 250);
        stage.setScene(scene);
        stage.show();
    }

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

    public void showAddReportDialog () {
        //Code from https://code.makery.ch/blog/javafx-dialogs-official/.
        Dialog<Pair<String, String>> dialog = new Dialog<>();
        dialog.setTitle("Login Dialog");
        dialog.setHeaderText("Look, a Custom Login Dialog");

        // Set the icon (must be included in the project).
        //dialog.setGraphic(new ImageView(this.getClass().getResource("login.png").toString()));

        // Set the button types.
        ButtonType loginButtonType = new ButtonType("Login", ButtonData.OK_DONE);
        dialog.getDialogPane().getButtonTypes().addAll(loginButtonType, ButtonType.CANCEL);

        // Create the username and password labels and fields.
        GridPane grid = new GridPane();
        grid.setHgap(10);
        grid.setVgap(10);
        grid.setPadding(new Insets(20, 150, 10, 10));

        TextField username = new TextField();
        username.setPromptText("Username");
        PasswordField password = new PasswordField();
        password.setPromptText("Password");

        grid.add(new Label("Username:"), 0, 0);
        grid.add(username, 1, 0);
        grid.add(new Label("Password:"), 0, 1);
        grid.add(password, 1, 1);

        // Enable/Disable login button depending on whether a username was entered.
        Node loginButton = dialog.getDialogPane().lookupButton(loginButtonType);
        //loginButton.setDisable(true);

        // Do some validation (using the Java 8 lambda syntax).
//        loginButton.disableProperty().bind(Bindings.createBooleanBinding(
//            () -> username.getText().isEmpty() || password.getText().isEmpty(),
//            username.textProperty(), password.textProperty()));

        dialog.getDialogPane().setContent(grid);

        // Request focus on the username field by default.
        Platform.runLater(() -> username.requestFocus());

        // Convert the result to a username-password-pair when the login button is clicked.
        dialog.setResultConverter(dialogButton -> {
            if (dialogButton == loginButtonType) {
                if(username.getText().isBlank() || password.getText().isBlank())
                {
                    Alert alert = new Alert(Alert.AlertType.WARNING);
                    alert.setTitle("Fields incomplete");
                    alert.setHeaderText(null);
                    alert.setContentText("Please complete all the form fields");
                    alert.showAndWait();
                }
                else
                {
                    return new Pair<String, String>(username.getText(), password.getText());
                }
                
            }
            
            return null;
        });

        Optional<Pair<String, String>> result = dialog.showAndWait();

        result.ifPresent(usernamePassword -> {
            System.out.println("Username=" + usernamePassword.getKey() + ", Password=" + usernamePassword.getValue());
        });
    }
}

谢谢绑定有帮助，我发现由于对话框字段的验证，我的警报没有显示。当我使用：if（（iDField.getText（）==null | | iDField.getText（）.trim（）.isEmpty（））而不是：if（iDField.getText（）.equals（“”））时，警报工作了！
import java.util.Optional;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.geometry.Insets;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBar.ButtonData;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.Pair;


/**
 * JavaFX App
 */
public class App extends Application {

    @Override
    public void start(Stage stage) {        
        Button button = new Button("Show Add Report Dialog");
        button.setOnAction((e) -> {
            showAddReportDialog();
        });

        StackPane layout = new StackPane();
        layout.getChildren().add(button);

        Scene scene = new Scene(layout, 300, 250);
        stage.setScene(scene);
        stage.show();
    }

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

    public void showAddReportDialog () {
        //Code from https://code.makery.ch/blog/javafx-dialogs-official/.
        Dialog<Pair<String, String>> dialog = new Dialog<>();
        dialog.setTitle("Login Dialog");
        dialog.setHeaderText("Look, a Custom Login Dialog");

        // Set the icon (must be included in the project).
        //dialog.setGraphic(new ImageView(this.getClass().getResource("login.png").toString()));

        // Set the button types.
        ButtonType loginButtonType = new ButtonType("Login", ButtonData.OK_DONE);
        dialog.getDialogPane().getButtonTypes().addAll(loginButtonType, ButtonType.CANCEL);

        // Create the username and password labels and fields.
        GridPane grid = new GridPane();
        grid.setHgap(10);
        grid.setVgap(10);
        grid.setPadding(new Insets(20, 150, 10, 10));

        TextField username = new TextField();
        username.setPromptText("Username");
        PasswordField password = new PasswordField();
        password.setPromptText("Password");

        grid.add(new Label("Username:"), 0, 0);
        grid.add(username, 1, 0);
        grid.add(new Label("Password:"), 0, 1);
        grid.add(password, 1, 1);

        // Enable/Disable login button depending on whether a username was entered.
        Node loginButton = dialog.getDialogPane().lookupButton(loginButtonType);
        //loginButton.setDisable(true);

        // Do some validation (using the Java 8 lambda syntax).
//        loginButton.disableProperty().bind(Bindings.createBooleanBinding(
//            () -> username.getText().isEmpty() || password.getText().isEmpty(),
//            username.textProperty(), password.textProperty()));

        dialog.getDialogPane().setContent(grid);

        // Request focus on the username field by default.
        Platform.runLater(() -> username.requestFocus());

        // Convert the result to a username-password-pair when the login button is clicked.
        dialog.setResultConverter(dialogButton -> {
            if (dialogButton == loginButtonType) {
                if(username.getText().isBlank() || password.getText().isBlank())
                {
                    Alert alert = new Alert(Alert.AlertType.WARNING);
                    alert.setTitle("Fields incomplete");
                    alert.setHeaderText(null);
                    alert.setContentText("Please complete all the form fields");
                    alert.showAndWait();
                }
                else
                {
                    return new Pair<String, String>(username.getText(), password.getText());
                }
                
            }
            
            return null;
        });

        Optional<Pair<String, String>> result = dialog.showAndWait();

        result.ifPresent(usernamePassword -> {
            System.out.println("Username=" + usernamePassword.getKey() + ", Password=" + usernamePassword.getValue());
        });
    }
}

import java.util.Optional;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.binding.Bindings;
import javafx.geometry.Insets;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBar.ButtonData;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.util.Pair;


/**
 * JavaFX App
 */
public class App extends Application {

    @Override
    public void start(Stage stage) {        
        Button button = new Button("Show Add Report Dialog");
        button.setOnAction((e) -> {
            showAddReportDialog();
        });

        StackPane layout = new StackPane();
        layout.getChildren().add(button);

        Scene scene = new Scene(layout, 300, 250);
        stage.setScene(scene);
        stage.show();
    }

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

    public void showAddReportDialog () {
        //Code from https://code.makery.ch/blog/javafx-dialogs-official/.
        Dialog<Pair<String, String>> dialog = new Dialog<>();
        dialog.setTitle("Login Dialog");
        dialog.setHeaderText("Look, a Custom Login Dialog");

        // Set the icon (must be included in the project).
        //dialog.setGraphic(new ImageView(this.getClass().getResource("login.png").toString()));

        // Set the button types.
        ButtonType loginButtonType = new ButtonType("Login", ButtonData.OK_DONE);
        dialog.getDialogPane().getButtonTypes().addAll(loginButtonType, ButtonType.CANCEL);

        // Create the username and password labels and fields.
        GridPane grid = new GridPane();
        grid.setHgap(10);
        grid.setVgap(10);
        grid.setPadding(new Insets(20, 150, 10, 10));

        TextField username = new TextField();
        username.setPromptText("Username");
        PasswordField password = new PasswordField();
        password.setPromptText("Password");

        grid.add(new Label("Username:"), 0, 0);
        grid.add(username, 1, 0);
        grid.add(new Label("Password:"), 0, 1);
        grid.add(password, 1, 1);

        // Enable/Disable login button depending on whether a username was entered.
        Node loginButton = dialog.getDialogPane().lookupButton(loginButtonType);
        loginButton.setDisable(true);

        // Do some validation (using the Java 8 lambda syntax).
        loginButton.disableProperty().bind(Bindings.createBooleanBinding(
            () -> username.getText().isEmpty() || password.getText().isEmpty(),
            username.textProperty(), password.textProperty()));

        dialog.getDialogPane().setContent(grid);

        // Request focus on the username field by default.
        Platform.runLater(() -> username.requestFocus());

        // Convert the result to a username-password-pair when the login button is clicked.
        dialog.setResultConverter(dialogButton -> {
            if (dialogButton == loginButtonType) {               
                return new Pair<>(username.getText(), password.getText());
            }
            
            return null;
        });

        Optional<Pair<String, String>> result = dialog.showAndWait();

        result.ifPresent(usernamePassword -> {
            System.out.println("Username=" + usernamePassword.getKey() + ", Password=" + usernamePassword.getValue());
        });
    }
}