JavaFX控制元件的layoutChildren方法是繼承自Parent的方法，可監聽控制元件大小改變，在視窗展示後觸發兩次，最大化最小化時各觸發一次，height和width改變會觸發，焦點離開和回到當前視窗也會觸發。

import javafx.animation.KeyFrame;
import javafx.animation.KeyValue;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.Pane;
import javafx.stage.Stage;
import javafx.util.Duration;

public class LayoutChildrenTest extends Application {

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

    @Override
    public void start(Stage primaryStage) {
        MyButton myButton = new MyButton();
        myButton.setText("Test");
        myButton.setTranslateX(0);
        myButton.setTranslateY(0);
        Timeline timeline = new Timeline();
        timeline.getKeyFrames().addAll(new KeyFrame(new Duration(0), new KeyValue(myButton.prefWidthProperty(), 50)), new KeyFrame(new Duration(3000), new KeyValue(myButton.prefWidthProperty(), 200)));
        timeline.play();
        Pane pane = new Pane(myButton);
        primaryStage.setScene(new Scene(pane,200,200));
        primaryStage.show();
    }

    class MyButton extends Button{
        @Override
        protected void layoutChildren() {
            System.out.println("layoutChildren is using!");
            super.layoutChildren();
        }
    }
}