JavaFX Panel inside Panel auto resizing

Question

I have a JavaFX application which has only one FXML file. In this file I have one AnchorPane which has a StackPane inside it. Here is the screenshot:

Answer 1

I was designing a GUI in SceneBuilder, trying to make the main container adapt to whatever the window size is. It should always be 100% wide.

This is where you can set these values in SceneBuilder:

Toggling the dotted/red lines will actually just add/remove the attributes that Korki posted in his solution (AnchorPane.topAnchor etc.).