How to make a VBox with animated "close up"? - animation

Question

I have built a form which has a VBox inside of a VBox. I want to make the internal VBox "close up" from the bottom to the top transitionally.
Afterwards, the next elements from the outer VBox should move up to fill the empty space, like when you remove items from a VBox.
How can I achieve this?

Answer 1

You can try next approach: use clipping to hide "disappearing" content and control height of the inner VBox during animation:
public class ShrinkingVBox extends Application {
private static class SmartVBox extends Region {
private Rectangle clipRect = new Rectangle();
private VBox content = new VBox();
public SmartVBox() {
setClip(clipRect);
getChildren().add(content);
}
// we need next methods to adjust our clipping to inner vbox content
#Override
protected void setWidth(double value) {
super.setWidth(value);
clipRect.setWidth(value);
}
#Override
protected void setHeight(double value) {
super.setHeight(value);
clipRect.setHeight(value);
}
// here we will do all animation
public void closeup() {
setMaxHeight(getHeight());
// animation hides content by moving it out of clipped area
// and reduces control height simultaneously
Timeline animation = TimelineBuilder.create().cycleCount(1).keyFrames(
new KeyFrame(Duration.seconds(1),
new KeyValue(content.translateYProperty(), -getHeight()),
new KeyValue(maxHeightProperty(), 0))).build();
animation.play();
}
protected ObservableList<Node> getContent() {
return content.getChildren();
}
}
#Override
public void start(Stage primaryStage) {
VBox outer = new VBox();
final SmartVBox inner = new SmartVBox();
//some random content for inner vbox
inner.getContent().addAll(
CircleBuilder.create().radius(25).fill(Color.YELLOW).build(),
CircleBuilder.create().radius(25).fill(Color.PINK).build());
// content for outer vbox, including inner vbox and button to run animation
outer.getChildren().addAll(
RectangleBuilder.create().width(50).height(50).fill(Color.GRAY).build(),
inner,
RectangleBuilder.create().width(50).height(50).fill(Color.RED).build(),
RectangleBuilder.create().width(50).height(50).fill(Color.BLUE).build(),
ButtonBuilder.create().text("go").onAction(new EventHandler<ActionEvent>() {
#Override
public void handle(ActionEvent t) {
inner.closeup();
}
}).build());
primaryStage.setScene(new Scene(new Group(outer)));
primaryStage.show();
}
public static void main(String[] args) {
launch();
}
}