Vbox和Hbox在什么情况下为其子元素分配坐标？-在哪些场景下Vbox和Hbox会为其子组件分配坐标值？

After you add the rectangles to the VBox, if you call inmediately to getBoundsInParent() you get no results.

将矩形添加到VBox后,如果您立即调用getBoundsInParent(),则不会得到任何结果。

The reason for this can be found here:

原因可以在这里找到:

Layout and CSS are also tied to pulse events. Numerous changes in the scene graph could lead to multiple layout or CSS updates, which could seriously degrade performance. The system automatically performs a CSS and layout pass once per pulse to avoid performance degradation. Application developers can also manually trigger layout passes as needed to take measurements prior to a pulse.

布局和CSS也与脉冲事件有关。场景图中的大量更改可能导致多个布局或CSS更新,这可能会严重降低性能。系统每个脉冲自动执行一次CSS和布局传递,以避免性能下降。应用程序开发人员还可以根据需要手动触发布局过程,以便在脉冲之前进行测量。

So if you really need the bounds of those rectangles in the same pass, you can call:

因此,如果你真的需要在同一个传递中的那些矩形的边界,你可以调用:

vbox.layout();

right after adding each rectangle to the box to get its final position.

在将每个矩形添加到框中以获得其最终位置之后。

According to Javadoc, layout():

根据Javadoc,layout():

Executes a top-down layout pass on the scene graph under this parent. Calling this method while the Parent is doing layout is a no-op

在此父级下的场景图上执行自上而下的布局传递。在Parent进行布局时调用此方法是一种无操作

And now this will work as you would expected:

现在,这将按照您的预期运作:

for(int i = 0; i <3 ; i++){
    Rectangle r = new Rectangle(100.0, 10.0, Color.BLACK);
    rectangles.add(r);
    vbox.getChildren().add(r);
    vbox.layout();

    System.out.println(" r Yposition :" + r.getLayoutY() + " or " + r.getBoundsInParent().getMinY() + " or " + r.getBoundsInLocal().getMinY());
    System.out.println("Vbox height : " + vbox.getBoundsInLocal().getHeight());
}

Alternatively, you could override the layoutChildren() method of vbox, as it is invoked during the layout pass to layout the children in this parent:

或者,您可以覆盖vbox的layoutChildren()方法,因为在布局传递期间调用它来布局此父级中的子级:

private VBox vbox=new VBox(){

    @Override
    protected void layoutChildren() {
        super.layoutChildren(); 
        for (Rectangle r : rectangles){         
            System.out.println(" r Yposition :" + r.getLayoutY() + " or " + r.getBoundsInParent().getMinY() + " or " + r.getBoundsInLocal().getMinY());
        }
    }

};

It will give you the same result. Note that this won't work with vbox added to the FXML file, since you need to create a new instance of it.

它会给你相同的结果。请注意,这不适用于添加到FXML文件的vbox,因为您需要创建它的新实例。