The problem about the Stage's minWidth or minHeight property.

Question

From the JavaFX 2.2 api, I see the minWidth or minHeight property, and then I attempt to use them to limit the contraction of stage when dragging. But it takes no effect. Are there some implications for using these properties?
I have finally to write some codes in the dragging listener of the stage to set manually width or height of the stage to achieve the minWidth or minHeight effect.

Answer 1

Hi, here is the test case: when we resize the stage UNDECORATED by dragging, we can minimize the stage size to zero even I set the minWidth and minHeight properties at first.
import javafx.animation.KeyFrame;
import javafx.animation.KeyValue;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.beans.binding.DoubleBinding;
import javafx.beans.property.ObjectProperty;
import javafx.beans.property.SimpleDoubleProperty;
import javafx.beans.property.SimpleObjectProperty;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.Bounds;
import javafx.geometry.Point2D;
import javafx.scene.Cursor;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ScrollPane;
import javafx.scene.effect.DropShadow;
import javafx.scene.effect.Reflection;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.AnchorPane;
import javafx.scene.layout.FlowPane;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.stage.StageStyle;
import javafx.stage.Window;
import javafx.util.Duration;
public class TestMinSizeStage extends Application {
  private ScrollPane scrollPane;
  private ObjectProperty<Point2D> anchor = new SimpleObjectProperty<Point2D>(null);
  private SimpleDoubleProperty widthStage = new SimpleDoubleProperty();
  private SimpleDoubleProperty heightStage = new SimpleDoubleProperty();
  public static void main(String[] args) {
  launch(args);
  @Override
  public void start(final Stage primaryStage) {
  Pane mainContainer = initstage(primaryStage);
  mainContainer.getChildren().addAll(
  createButton());
  primaryStage.show();// Show the primaryStage
  private Pane initstage(Stage primaryStage) {
  primaryStage.setTitle("Hello Java");
  primaryStage.initStyle(StageStyle.TRANSPARENT);
  /* The minWidth or minHeight is for the stage "DECORATED", it has on effect to the stage non "DECORATED". */
  primaryStage.setMinWidth(600);
  primaryStage.setMinHeight(400);
  final FlowPane mainContainer = new FlowPane();
  mainContainer.setStyle(
  "-fx-background-color: white; " +
  "-fx-background-radius: 10px; " +
  "-fx-padding: 10px;" +
  "-fx-hgap: 30px; " +
  "-fx-vgap: 50px;");
  scrollPane = new ScrollPane();
  scrollPane.setStyle("-fx-background-radius: 10px;");
  scrollPane.setContent(mainContainer);
  scrollPane.setPannable(true);
  mainContainer.prefWidthProperty().bind(new DoubleBinding() {
  super.bind(scrollPane.viewportBoundsProperty());
  @Override
  protected double computeValue() {
  Bounds bounds = scrollPane.getViewportBounds();
  if (bounds == null) {
  return 0;
  } else {
  return bounds.getWidth();
  AnchorPane root = new AnchorPane();
  root.setStyle(
  "-fx-border-color: black; " +
  "-fx-border-width: 1px; " +
  "-fx-border-radius: 10px; " +
  "-fx-background-color: rgba(0, 0, 0, 0); " +
  "-fx-background-radius: 10px;");
  DropShadow dropShadow = new DropShadow();
  dropShadow.setRadius(20.0);
  // dropShadow.setSpread(0.2);
  root.setEffect(dropShadow);
  enableDragging(root);
  root.getChildren().add(scrollPane);
  AnchorPane.setTopAnchor(scrollPane, 0.0);
  AnchorPane.setRightAnchor(scrollPane, 10.0);
  AnchorPane.setBottomAnchor(scrollPane, 10.0);
  AnchorPane.setLeftAnchor(scrollPane, 10.0);
  AnchorPane superRoot = new AnchorPane();
  superRoot.getChildren().add(root);
  AnchorPane.setTopAnchor(root, 10.0);
  AnchorPane.setRightAnchor(root, 10.0);
  AnchorPane.setBottomAnchor(root, 10.0);
  AnchorPane.setLeftAnchor(root, 10.0);
  Scene scene = new Scene(superRoot, 950, 650, Color.TRANSPARENT);
  scene.getStylesheets().add(getClass().getResource("controls.css").toExternalForm());
  primaryStage.setScene(scene);
  return mainContainer;
  * Enable the root node to be dragged. Realize some drag functions.
  * @param root - the root node
  private void enableDragging(final AnchorPane root) {
  /* This mouse event is for resizing window. Define some specific cursor patterns. */
  root.setOnMouseMoved(new EventHandler<MouseEvent>() {
  public void handle(MouseEvent me) {
  if ((me.getX() > root.getWidth() - 10 && me.getX() < root.getWidth() + 10)
  && (me.getY() > root.getHeight() - 10 && me.getY() < root.getHeight() + 10)) {
  root.setCursor(Cursor.SE_RESIZE);
  } else if (me.getX() > root.getWidth() - 5 && me.getX() < root.getWidth() + 5) {
  root.setCursor(Cursor.H_RESIZE);
  } else if (me.getY() > root.getHeight() - 5 && me.getY() < root.getHeight() + 5) {
  root.setCursor(Cursor.V_RESIZE);
  } else {
  root.setCursor(Cursor.DEFAULT);
  /* when mouse button is pressed, save the initial position of screen. */
  root.setOnMousePressed(new EventHandler<MouseEvent>() {
  public void handle(MouseEvent me) {
  Window primaryStage = root.getScene().getWindow();
  anchor.set(new Point2D(me.getScreenX() - primaryStage.getX(), me.getScreenY() - primaryStage.getY()));
  widthStage.set(primaryStage.getWidth());
  heightStage.set(primaryStage.getHeight());
  /* when mouse button is released, clear the initial position of screen. */
  root.setOnMouseReleased(new EventHandler<MouseEvent>() {
  public void handle(MouseEvent me) {
  anchor.set(null);
  /* when screen is dragged, translate it accordingly. */
  root.setOnMouseDragged(new EventHandler<MouseEvent>() {
  public void handle(MouseEvent me) {
  if (anchor.get() != null) {// The drag event on the root really takes place.
  Window primaryStage = root.getScene().getWindow();
  if (root.getCursor() == Cursor.H_RESIZE) {
  primaryStage.setWidth(widthStage.get() + (me.getScreenX() - (anchor.get().getX() + primaryStage.getX())));
  } else if (root.getCursor() == Cursor.V_RESIZE) {
  primaryStage.setHeight(heightStage.get() + (me.getScreenY() - (anchor.get().getY() + primaryStage.getY())));
  } else if (root.getCursor() == Cursor.SE_RESIZE) {
  primaryStage.setWidth(widthStage.get() + (me.getScreenX() - (anchor.get().getX() + primaryStage.getX())));
  primaryStage.setHeight(heightStage.get() + (me.getScreenY() - (anchor.get().getY() + primaryStage.getY())));
  } else {// moving the stage
  primaryStage.setX(me.getScreenX() - anchor.get().getX());
  primaryStage.setY(me.getScreenY() - anchor.get().getY());
  * Define a button
  * @return a button
  private Node createButton() {
  Button button = new Button();
  button.setEffect(new Reflection());
  button.setText("Say 'Hello Java'");
  button.setOnAction(new EventHandler<ActionEvent>() {
  @Override
  public void handle(ActionEvent event) {
  System.out.println("Hello Java!");
  /* add an animation effect */
  Timeline timeline = new Timeline();
  timeline.setCycleCount(Timeline.INDEFINITE);
  timeline.setAutoReverse(true);
  timeline.getKeyFrames().addAll(
  new KeyFrame(Duration.ZERO, new KeyValue(button.opacityProperty(), 1.0)),
  new KeyFrame(new Duration(5000), new KeyValue(button.opacityProperty(), 0.0)));
  timeline.play();
  /* set CSS style */
  button.setStyle(
  "-fx-font: 14px 'Cambria'; " +
  "-fx-text-fill: #006464; " +
  "-fx-background-color: #e79423; " +
  "-fx-background-radius: 20.0; " +
  "-fx-padding: 5.0;");
  return button;