Question

以下代码演示了对话框的居中和屏幕中央的舞台。应首先显示该对话框，供用户输入登录凭据。成功登录后，将显示主窗口（阶段）。我找到了从这个网站集中对话和舞台的解决方案，但它似乎并不理想。对于对话框和舞台，在我们计算坐标然后将它们放在中心之前，必须先显示它们。这意味着我们可以看到对话框和主窗口在显示后移动到中心。有没有更好的办法？理想情况下，它们应该在显示之前定位在中心。

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.geometry.Rectangle2D;
import javafx.scene.Cursor;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.stage.Screen;
import javafx.stage.Stage;
import javafx.stage.Window;

public class Demo extends Application {

    private Stage primaryStage;
    private Dialog<String> dialog;
    private Button createUserButton = new Button("Create User");

    @Override
    public void start(Stage primaryStage) throws Exception {
        this.primaryStage = primaryStage;
        Text usersLabel = new Text("Current Users:");
        TableColumn<User, String> indexColumn = new TableColumn<User, String>("No.");
        indexColumn.setMaxWidth(1f * Integer.MAX_VALUE * 10);
        indexColumn.setCellValueFactory(p -> p.getValue().indexProperty());
        TableColumn<User, String> userNameColumn = new TableColumn<User, String>("User Name");
        userNameColumn.setMaxWidth(1f * Integer.MAX_VALUE * 60);
        userNameColumn.setCellValueFactory(p -> p.getValue().userNameProperty());
        TableColumn<User, String> roleColumn = new TableColumn<User, String>("Role");
        roleColumn.setMaxWidth(1f * Integer.MAX_VALUE * 30);
        roleColumn.setCellValueFactory(p -> p.getValue().roleProperty());
        TableView<User> tableView = new TableView<User>();
        tableView.getColumns().add(indexColumn);
        tableView.getColumns().add(userNameColumn);
        tableView.getColumns().add(roleColumn);
        tableView.setColumnResizePolicy(TableView.CONSTRAINED_RESIZE_POLICY);
        Text dummyLabel = new Text("");
        VBox leftPane = new VBox(5);
        leftPane.getChildren().addAll(usersLabel, tableView);
        VBox rightPane = new VBox(20);
        rightPane.setFillWidth(true);
        rightPane.getChildren().addAll(dummyLabel, createUserButton);
        GridPane mainPane = new GridPane();
        mainPane.setPadding(new Insets(10, 0, 0, 10));
        mainPane.setHgap(20);
        mainPane.add(leftPane, 0, 0);
        mainPane.add(rightPane, 1, 0);
        Scene scene = new Scene(mainPane);
        primaryStage.setScene(scene);
        primaryStage.setResizable(false);
        showDialog();
    }

    private void showDialog() {
        dialog = new Dialog<>();
        dialog.setTitle("Login");
        dialog.setHeaderText("Please enter User Name and Password to login.");
        dialog.setResizable(false);
        Label userNameLabel = new Label("User Name:");
        Label passwordLabel = new Label("Password:");
        TextField userNameField = new TextField();
        PasswordField passwordField = new PasswordField();
        GridPane grid = new GridPane();
        grid.setAlignment(Pos.CENTER);
        grid.setHgap(10);
        grid.setVgap(10);
        grid.setPadding(new Insets(20, 35, 20, 35));
        grid.add(userNameLabel, 1, 1);
        grid.add(userNameField, 2, 1);
        grid.add(passwordLabel, 1, 2);
        grid.add(passwordField, 2, 2);
        dialog.getDialogPane().setContent(grid);
        dialog.getDialogPane().getButtonTypes().add(ButtonType.OK);
        Button okButton = (Button) dialog.getDialogPane().lookupButton(ButtonType.OK);
        okButton.addEventFilter(ActionEvent.ACTION, event -> {
            createUser(userNameField.getText().trim(), passwordField.getText());
            event.consume();
        });
        dialog.getDialogPane().getButtonTypes().add(ButtonType.CANCEL);
        Platform.runLater(() -> {
            Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
            Window window = dialog.getDialogPane().getScene().getWindow();
            window.setX((screenBounds.getWidth() - window.getWidth()) / 2);
            window.setY((screenBounds.getHeight() - window.getHeight()) / 2);
        });
        dialog.showAndWait();
    }

    private void createUser(String userName, String password) {
        dialog.getDialogPane().setDisable(true);
        dialog.getDialogPane().getScene().setCursor(Cursor.WAIT);
        Task<Boolean> task = new Task<Boolean>() {
            @Override
            public Boolean call() {
                try {
                    Thread.sleep(100);
                } catch (InterruptedException exception) {
                }
                return Boolean.TRUE;
            }
        };
        task.setOnSucceeded(e -> {
            Boolean success = task.getValue();
            dialog.getDialogPane().setDisable(false);
            dialog.getDialogPane().getScene().setCursor(Cursor.DEFAULT);
            if (success.booleanValue()) {
                Platform.runLater(() -> {
                    dialog.close();
                    primaryStage.show();
                    Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
                    primaryStage.setX((screenBounds.getWidth() - primaryStage.getWidth()) / 2);
                    primaryStage.setY((screenBounds.getHeight() - primaryStage.getHeight()) / 2);
                });
            } else {
                Alert alert = new Alert(AlertType.ERROR);
                alert.setTitle("Login Error");
                alert.setHeaderText("Unable to login.");
                alert.showAndWait();
            }
        });
        new Thread(task).start();
    }

    public static void main(String[] arguments) {
        Application.launch(arguments);
    }

}

class User {

    private StringProperty index;

    private StringProperty userName;

    private StringProperty role;

    public String getIndex() {
        return indexProperty().get();
    }

    public StringProperty indexProperty() {
        if (index == null) {
            index = new SimpleStringProperty(this, "index");
        }
        return index;
    }

    public void setIndex(String index) {
        indexProperty().set(index);
    }

    public String getUserName() {
        return userNameProperty().get();
    }

    public StringProperty userNameProperty() {
        if (userName == null) {
            userName = new SimpleStringProperty(this, "userName");
        }
        return userName;
    }

    public void setUserName(String userName) {
        userNameProperty().set(userName);
    }

    public String getRole() {
        return roleProperty().get();
    }

    public StringProperty roleProperty() {
        if (role == null) {
            role = new SimpleStringProperty(this, "role");
        }
        return role;
    }

    public void setRole(String role) {
        roleProperty().set(role);
    }

}

以下是将自定义尺寸设置为舞台和对话框的解决方案。它适用于舞台，但它不适用于对话框。

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.property.SimpleStringProperty;
import javafx.beans.property.StringProperty;
import javafx.concurrent.Task;
import javafx.event.ActionEvent;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.geometry.Rectangle2D;
import javafx.scene.Cursor;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonType;
import javafx.scene.control.Dialog;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.scene.text.Text;
import javafx.stage.Screen;
import javafx.stage.Stage;
import javafx.stage.Window;
import javafx.stage.WindowEvent;

public class Demo extends Application {

    private Stage primaryStage;
    private Dialog<String> dialog;
    private Button createUserButton = new Button("Create User");

    @Override
    public void start(Stage primaryStage) throws Exception {
        this.primaryStage = primaryStage;
        Text usersLabel = new Text("Current Users:");
        TableColumn<User, String> indexColumn = new TableColumn<User, String>("No.");
        indexColumn.setMaxWidth(1f * Integer.MAX_VALUE * 10);
        indexColumn.setCellValueFactory(p -> p.getValue().indexProperty());
        TableColumn<User, String> userNameColumn = new TableColumn<User, String>("User Name");
        userNameColumn.setMaxWidth(1f * Integer.MAX_VALUE * 60);
        userNameColumn.setCellValueFactory(p -> p.getValue().userNameProperty());
        TableColumn<User, String> roleColumn = new TableColumn<User, String>("Role");
        roleColumn.setMaxWidth(1f * Integer.MAX_VALUE * 30);
        roleColumn.setCellValueFactory(p -> p.getValue().roleProperty());
        TableView<User> tableView = new TableView<User>();
        tableView.getColumns().add(indexColumn);
        tableView.getColumns().add(userNameColumn);
        tableView.getColumns().add(roleColumn);
        tableView.setColumnResizePolicy(TableView.CONSTRAINED_RESIZE_POLICY);
        Text dummyLabel = new Text("");
        VBox leftPane = new VBox(5);
        leftPane.getChildren().addAll(usersLabel, tableView);
        VBox rightPane = new VBox(20);
        rightPane.setFillWidth(true);
        rightPane.getChildren().addAll(dummyLabel, createUserButton);
        GridPane mainPane = new GridPane();
        mainPane.setPadding(new Insets(10, 0, 0, 10));
        mainPane.setHgap(20);
        mainPane.add(leftPane, 0, 0);
        mainPane.add(rightPane, 1, 0);
        float width = 372f;
        float height = 470f;
        Scene scene = new Scene(mainPane, width, height);
        primaryStage.setScene(scene);
        primaryStage.setResizable(false);
        Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
        primaryStage.setX((screenBounds.getWidth() - width) / 2);
        primaryStage.setY((screenBounds.getHeight() - height) / 2);
        showDialog();
    }

    private void showDialog() {
        dialog = new Dialog<>();
        dialog.setTitle("Login");
        dialog.setHeaderText("Please enter User Name and Password to login.");
        dialog.setResizable(false);
        Label userNameLabel = new Label("User Name:");
        Label passwordLabel = new Label("Password:");
        TextField userNameField = new TextField();
        PasswordField passwordField = new PasswordField();
        GridPane grid = new GridPane();
        grid.setAlignment(Pos.CENTER);
        grid.setHgap(10);
        grid.setVgap(10);
        grid.setPadding(new Insets(20, 35, 20, 35));
        grid.add(userNameLabel, 1, 1);
        grid.add(userNameField, 2, 1);
        grid.add(passwordLabel, 1, 2);
        grid.add(passwordField, 2, 2);
        dialog.getDialogPane().setContent(grid);
        dialog.getDialogPane().getButtonTypes().add(ButtonType.OK);
        Button okButton = (Button) dialog.getDialogPane().lookupButton(ButtonType.OK);
        okButton.addEventFilter(ActionEvent.ACTION, event -> {
            login(userNameField.getText().trim(), passwordField.getText());
            event.consume();
        });
        dialog.getDialogPane().getButtonTypes().add(ButtonType.CANCEL);
        float width = 509f;
        float height = 168f;
        dialog.setWidth(width);
        dialog.setHeight(height);
        Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
        dialog.setX((screenBounds.getWidth() - width) / 2);
        dialog.setY((screenBounds.getHeight() - height) / 2);
        dialog.showAndWait();
    }

    private void login(String userName, String password) {
        dialog.getDialogPane().setDisable(true);
        dialog.getDialogPane().getScene().setCursor(Cursor.WAIT);
        Task<Boolean> task = new Task<Boolean>() {
            @Override
            public Boolean call() {
                try {
                    Thread.sleep(100);
                } catch (InterruptedException exception) {
                }
                return Boolean.TRUE;
            }
        };
        task.setOnSucceeded(e -> {
            Boolean success = task.getValue();
            dialog.getDialogPane().setDisable(false);
            dialog.getDialogPane().getScene().setCursor(Cursor.DEFAULT);
            if (success.booleanValue()) {
                Platform.runLater(() -> {
                    primaryStage.show();
                });
            } else {
                Alert alert = new Alert(AlertType.ERROR);
                alert.setTitle("Login Error");
                alert.setHeaderText("Unable to login.");
                alert.showAndWait();
            }
        });
        new Thread(task).start();
    }

    public static void main(String[] arguments) {
        Application.launch(arguments);
    }

}

class User {

    private StringProperty index;

    private StringProperty userName;

    private StringProperty role;

    public String getIndex() {
        return indexProperty().get();
    }

    public StringProperty indexProperty() {
        if (index == null) {
            index = new SimpleStringProperty(this, "index");
        }
        return index;
    }

    public void setIndex(String index) {
        indexProperty().set(index);
    }

    public String getUserName() {
        return userNameProperty().get();
    }

    public StringProperty userNameProperty() {
        if (userName == null) {
            userName = new SimpleStringProperty(this, "userName");
        }
        return userName;
    }

    public void setUserName(String userName) {
        userNameProperty().set(userName);
    }

    public String getRole() {
        return roleProperty().get();
    }

    public StringProperty roleProperty() {
        if (role == null) {
            role = new SimpleStringProperty(this, "role");
        }
        return role;
    }

    public void setRole(String role) {
        roleProperty().set(role);
    }

}

JKostikiadis的解决方案：

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.geometry.Rectangle2D;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.layout.HBox;
import javafx.stage.Screen;
import javafx.stage.Stage;

public class TestApp extends Application {

    private static final double WIDTH = 316.0;
    private static final double HEIGHT = 339.0;

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

    @Override
    public void start(Stage stage) throws Exception {

        HBox pane = new HBox();
        pane.setAlignment(Pos.CENTER);

        Button b = new Button("click me");
        b.setOnAction(e -> {
            showDialog();
        });

        pane.getChildren().add(b);

        Scene scene = new Scene(pane, 300, 300);

        stage.setScene(scene);

        centerStage(stage, WIDTH, HEIGHT);
        stage.show();


    }

    private void showDialog() {
        Alert dialog = new Alert(AlertType.ERROR);
        dialog.setTitle("Error Dialog");
        dialog.setHeaderText("Look, an Error Dialog");
        dialog.setContentText("Ooops, there was an error!\nOoops, there was an error!");

        Stage stage = (Stage) dialog.getDialogPane().getScene().getWindow();
        centerStage(stage, -10000, -10000);
        dialog.show();
        System.out.println(stage.getWidth() + " " + stage.getHeight());
        dialog.hide();
        centerStage(stage, stage.getWidth(), stage.getHeight());        
        dialog.showAndWait();

    }

    private void centerStage(Stage stage, double width, double height) {
        Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
        stage.setX((screenBounds.getWidth() - width) / 2);
        stage.setY((screenBounds.getHeight() - height) / 2);
    }
}

Answer 1

不幸的是，您必须等待计算Window（或Dialog）的宽度/高度以及Window的宽度/高度。由于Window可见，因此在更新xy位置时，您将始终注意到窗口正在移动。

触发WindowEvent.WINDOW_SHOWN事件时执行更新可能会提供更好的结果：

   final Window window = dialog.getDialogPane().getScene().getWindow();

    window.addEventHandler(WindowEvent.WINDOW_SHOWN, new EventHandler<WindowEvent>() {
        @Override
        public void handle(WindowEvent event) {
            Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
            window.setX((screenBounds.getWidth() - window.getWidth()) / 2);
            window.setY((screenBounds.getHeight() - window.getHeight()) / 2);

        }
    });

对于primaryStage

    primaryStage.addEventHandler(WindowEvent.WINDOW_SHOWN, new EventHandler<WindowEvent>() {

    @Override
    public void handle(WindowEvent event) {
        Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
        primaryStage.setX((screenBounds.getWidth() - primaryStage.getWidth()) / 2);
        primaryStage.setY((screenBounds.getHeight() - primaryStage.getHeight()) / 2);
    }
});
primaryStage.show();

但正如JKostikiadis所提到的，更好和更合适的解决方案可能是根据当前屏幕尺寸计算自己的尺寸。

这是我能看到的小改进。在我的机器上运行演示时，移动是不稳定的：

使用WindowEvent.WINDOW_SHOWN（第一个对话框不使用Platform.runLater）时，我可以看到一个小小的改进：

无论如何，我不认为使用Platform.runLater来显示第一个窗口是理想的，因为无法保证在showAndWait()之前始终执行Runnable

Answer 2

您可以在渲染它之前将舞台居中在另一个舞台上，方法是应用将为您提供宽度/高度的css。

例如。

从你创建舞台的地方开始：

WindowHelper.centerChildWindowOnStage(stage, primaryStage);  //assuming primary is the stage you want to center on
stage.show();

下面是未示出的窗口居中的代码（假设这是在一个WindowHelper类上，可以在应用程序中重用）。

public static void centerChildWindowOnStage(Stage stage, Stage primaryStage ) {

    if(primaryStage == null){
        return;
    }

    double x = stage.getX();
    double y = stage.getY();

    // Firstly we need to force CSS and layout to happen, as the dialogPane
    // may not have been shown yet (so it has no dimensions)
    stage.getScene().getRoot().applyCss();
    stage.getScene().getRoot().layout();

    final Scene ownerScene = primaryStage.getScene();
    final double titleBarHeight = ownerScene.getY();

    // because Stage does not seem to centre itself over its owner, we
    // do it here.

    // then we can get the dimensions and position the dialog appropriately.
    final double dialogWidth = stage.getScene().getRoot().prefWidth(-1);
    final double dialogHeight = stage.getScene().getRoot().prefHeight(dialogWidth);

    final double ownerWidth = primaryStage.getScene().getRoot().prefWidth(-1);
    final double ownerHeight = primaryStage.getScene().getRoot().prefHeight(ownerWidth);

    if(dialogWidth < ownerWidth){
        x = primaryStage.getX() + (ownerScene.getWidth() / 2.0) - (dialogWidth / 2.0);
    }else {
        x = primaryStage.getX();
        stage.setWidth(dialogWidth);
    }

    if(dialogHeight < ownerHeight){
        y = primaryStage.getY() + titleBarHeight / 2.0 + (ownerScene.getHeight() / 2.0) - (dialogHeight / 2.0);
    }else {
        y = primaryStage.getY();
    }

    stage.setX(x);
    stage.setY(y);
}

Answer 3

好吧，因为你在评价中问我，我将提供一个例子，通过早期初始化它们的尺寸，将舞台（主应用程序或对话框）设置到屏幕中心。

import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.geometry.Rectangle2D;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.layout.HBox;
import javafx.stage.Screen;
import javafx.stage.Stage;

public class TestApp extends Application {

    private static final double WIDTH = 316.0;
    private static final double HEIGHT = 339.0;

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

    @Override
    public void start(Stage stage) throws Exception {

        HBox pane = new HBox();
        pane.setAlignment(Pos.CENTER);

        Button b = new Button("click me");
        b.setOnAction(e -> {
            showDialog();
        });

        pane.getChildren().add(b);

        Scene scene = new Scene(pane, 300, 300);

        stage.setScene(scene);

        centerStage(stage, WIDTH, HEIGHT);
        stage.show();

        System.out.println(stage.getWidth() + " " + stage.getHeight());
    }

    private void showDialog() {
        Alert dialog = new Alert(AlertType.ERROR);
        dialog.setTitle("Error Dialog");
        dialog.setHeaderText("Look, an Error Dialog");
        dialog.setContentText("Ooops, there was an error!");

        Stage stage = (Stage) dialog.getDialogPane().getScene().getWindow();
        centerStage(stage, 366, 175);

        dialog.showAndWait();

    }

    private void centerStage(Stage stage, double width, double height) {
        Rectangle2D screenBounds = Screen.getPrimary().getVisualBounds();
        stage.setX((screenBounds.getWidth() - width) / 2);
        stage.setY((screenBounds.getHeight() - height) / 2);
    }
}

在上面的示例中，您将看到我已将应用程序维度指定为300,300，但我使用的是width = 316.0和height = 339.0，您可能想知道为什么。这是因为舞台大小总是比场景（边框+标题栏等）大一些，所以为了找到舞台的真实宽度和高度，你必须在你之后打印舞台的尺寸展示下。对话框也出现了同样的逻辑。

重要提示：当然，您可以忘记以上所有内容，并且只是这样做：

stage.setWidth(300); // or a variable here 
stage.setHeight(300);

但这会影响你的内部组件，因为如果之前场景的组件大小为300,300，那么现在它们将被挤压到更少的东西，以便使舞台固定300,300的大小，以便case yes它可能会影响你的应用程序的样子。

在过去，我一直在寻找一种方法来查找标签的尺寸。我发现可以通过将其添加到场景中然后调用

来获得它的尺寸

labe.impl_processCSS(true);
System.out.println(labe.prefWidth(-1) + "/" + labe.prefHeight(-1));

现在如果我尝试对上面的应用程序中的主窗格执行相同的操作，它会显示59/25这是按钮本身的尺寸，所以这种方法在某人想知道它的情况下不会起作用。

修改：

我真的不想展示这个＆＃34; hack＆＃34;因为我发现它很愚蠢，我确信有更好的方法，但直到我在这里找到你：

private void showDialog() {
    Alert dialog = new Alert(AlertType.ERROR);
    dialog.setTitle("Error Dialog");
    dialog.setHeaderText("Look, an Error Dialog");
    dialog.setContentText("Ooops, there was an error!\nOoops, there was an error!");

    Stage stage = (Stage) dialog.getDialogPane().getScene().getWindow();
    centerStage(stage, -10000, -10000);
    dialog.show();
    centerStage(stage, stage.getWidth(), stage.getHeight());   
}

JavaFX位置对话框和屏幕中心的舞台

3 个答案: