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Java Build a JavaFX Application Design a Better App Separating the Layout

Razvan Cirstea
Razvan Cirstea
2,493 Points
Posted by Razvan Cirstea
Razvan Cirstea
2,493 Points

Upcasting to (GridPane) questions

I don't understand the whole "GridPane example= (GridPane) root;" bit . I have so many questions about this :)

  1. Why do we need to go through all this "trouble" ? What is the purpose ?
  2. Why do we then decide we do not need to do so, and we erase that code ?
  3. Why do we upcast to (GridPane) , when we saw in the documentation it is the lowest library of all ?

I am sure I am missing something here ! Hope I'm not missing something ridiculously obvious :)

1 Answer

Doli Harahap
Doli Harahap
6,246 Points
Doli Harahap
Doli Harahap
6,246 Points

Hi,

  1. Why do we need to go through all this "trouble" ? What is the purpose ?
  2. Why do we then decide we do not need to do so, and we erase that code ? Look at this FXMLLoader.load() https://docs.oracle.com/javase/8/javafx/api/javafx/fxml/FXMLLoader.html#load--

It returns a generic type which is designed so programmer can return any type that defined in the FXML document. You don't have to do that, you can directly catch the Class:

GridPane root = FXMLLoader.load(getClass().getResource("sample.fxml"));

  1. Why do we upcast to (GridPane) , when we saw in the documentation it is the lowest library of all ? It's not like have to be GridPane, it follows your root tag in your FXML.

Hope it helps.