JavaFX在屏幕上的中心舞台

Question

我想在屏幕上居中。
这是我尝试过的：

public class Test extends Application
{
   @Override
   public void start(final Stage primaryStage)
   {
       Button btn = new Button();
       btn.setText("Say 'Hello World'");
       btn.setOnAction(new EventHandler<ActionEvent>()
       {
          @Override
          public void handle(ActionEvent event)
          {
            System.out.println("Hello World!");
          }
        });
        StackPane root = new StackPane();
        root.getChildren().add(btn);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setTitle("Hello World!");
        primaryStage.setScene(scene);
        primaryStage.centerOnScreen();
        primaryStage.show();
   }
   public static void main(String[] args)
   {
       launch(args);
   }
}

调用 centerOnScreen（） 后，舞台太高。它似乎无法正常工作。我需要自己计算 x 和 y pos 吗？或者如何正确使用此功能？

Answer 1

centerOnScreen()的默认实现如下：

Rectangle2D bounds = getWindowScreen().getVisualBounds();
double centerX = bounds.getMinX() + (bounds.getWidth() - getWidth())
                                           * CENTER_ON_SCREEN_X_FRACTION;
double centerY = bounds.getMinY() + (bounds.getHeight() - getHeight())
                                           * CENTER_ON_SCREEN_Y_FRACTION;
x.set(centerX);
y.set(centerY);

哪里

CENTER_ON_SCREEN_X_FRACTION = 1.0f / 2;
CENTER_ON_SCREEN_Y_FRACTION = 1.0f / 3;

centerY总是将舞台设置得比中心高一点。

要将舞台精确定位在正中心，您可以使用自定义 X 和 Y 值设置。

public class Main extends Application {
    @Override
    public void start(Stage primaryStage) {
        Button btn = new Button();
        btn.setText("Say 'Hello World'");
        btn.setOnAction((ActionEvent event) -> {
                System.out.println("Hello World!");
        });
        StackPane root = new StackPane();
        root.getChildren().add(btn);
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setTitle("Hello World!");
        primaryStage.setScene(scene);
        primaryStage.show();
        Rectangle2D primScreenBounds = Screen.getPrimary().getVisualBounds();
        primaryStage.setX((primScreenBounds.getWidth() - primaryStage.getWidth()) / 2);
        primaryStage.setY((primScreenBounds.getHeight() - primaryStage.getHeight()) / 2);
    }
    public static void main(String[] args) {
        launch(args);
    }
}