JavaFX iteration with .lookup

Question

I am trying to make a minigame on JavaFX but I am encountering an issue where it says "currentPlayerBox" is null; it is meant to be a variable in a for loop that goes through the player areas' components to make sure they are reset for each player (1-4); here is the code:

for (int i=1; i < 5; i++){
            Pane currentPlayerBox = (Pane) root.lookup("player" + i + "Box");
            TextArea playerTextArea = (TextArea) currentPlayerBox.lookup("player" + i + "TextArea");
            ImageView playerImgWin = (ImageView) currentPlayerBox.lookup("player" + i + "WinImg");
            ImageView playerImgLose = (ImageView) currentPlayerBox.lookup("player" + i + "LoseImg");
            playerTextArea.clear();
            playerImgWin.setOpacity(0);
            playerImgLose.setOpacity(0);
            currentPlayerBox.getChildren().forEach (button -> button.setDisable(true));
            currentPlayerBox.setVisible(false);
           }

This does work if I use the actual fx:id manually; like player1Box, player2Box; but it returns null if I use Pane currentPlayerBox = (Pane) root.lookup("player" + i + "Box"); am I using this method wrong? Can I even do this or do I have to go 1 by 1 manually? I can post the FXML code if it is needed; but I am basically just trying to lookup some Panes inside an AnchorPane with no other parent in between. And yes, the fx:id of the AnchorPane is just "root" triplechecked that.

why do you use lookup at all (vs. keeping modeling the sync between nodes and your game state, or at least keeping references)? While possible, it's a fall-back tool usually. Anyway, [mcve] please - mind the __M__!, nothing unrelated while still runnable as-is and demonstrating what _exactly_ you are doing and how it's not working as expected. — kleopatra, May 09 '23 at 09:03

Sai Dandem · Accepted Answer · 2023-05-08T22:50:37.240

If you are setting an id, then you need to lookup by prepending the # to your string. On the other hand if you are looking for a style class then you need to prepend with .

So I believe try changing the code to below and check :

for (int i=1; i < 5; i++){
            Pane currentPlayerBox = (Pane) root.lookup("#player" + i + "Box");
            TextArea playerTextArea = (TextArea) currentPlayerBox.lookup("#player" + i + "TextArea");
            ImageView playerImgWin = (ImageView) currentPlayerBox.lookup("#player" + i + "WinImg");
            ImageView playerImgLose = (ImageView) currentPlayerBox.lookup("#player" + i + "LoseImg");
            playerTextArea.clear();
            playerImgWin.setOpacity(0);
            playerImgLose.setOpacity(0);
            currentPlayerBox.getChildren().forEach (button -> button.setDisable(true));
            currentPlayerBox.setVisible(false);
           }

Out of topic, please also have a look at this to have a quick overview of id(s) and see if you are using it correctly.

JavaFX iteration with .lookup

1 Answers1