为什么TextField继承自JavaFX中的javafx.scene.Parent？

Question

I am reading javafx TextField API:

 java.lang.Object
    javafx.scene.Node
        javafx.scene.Parent
            javafx.scene.layout.Region
                javafx.scene.control.Control
                    javafx.scene.control.TextInputControl
                        javafx.scene.control.TextField 

As you see, TextField inherits from javafx.scene.Parent class. From Parent class javadoc The base class for all nodes that have children in the scene graph. But I can't understand what child nodes TextField can have. Can anyone explain?

Answer 1

This is because a TextField is not made up of a single Node . For instance, it uses (different) Text nodes for the prompt and normal text. It also uses a Path for the caret. For Control s, this is implemented using a Skin (eg TextInputControlSkin and TextFieldSkin ).

Notice, however, that TextField doesn't expose its children publicly for modification; random code can't just go adding nodes to it. But you can view the children in an unmodifiable fashion.

Answer 2

It can have any child node you want it to - there's no inherent reason why you couldn't add something like a label, a graphic, or a weird shape as its child. Try it out - it works!

In practice you probably wouldn't do this, you'd add both the textfield and the weird shape (or whatever else) to a StackPane or similar instead, as that gives you greater control over layout and extensibility.