[FIXED] How do I edit the javafx ui in another class?

Issue

AppRunner class

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.fxml.FXMLLoader;

public class AppRunner {

    public static void main(String[] args) {
        startUi.launchPanel(args);
    }

    public static void waitFiveSecToClear() {
        new Thread(
                new Runnable() {
            public void run() {
                try {
                    Thread.sleep(5000);
                } catch (InterruptedException ex) {
                    Logger.getLogger(AppRunner.class.getName()).log(Level.SEVERE, null, ex);
                }
                FXMLLoader loader = new FXMLLoader(getClass().getResource("listView.fxml"));
                try {
                    loader.load();
                } catch (IOException ex) {
                    Logger.getLogger(AppRunner.class.getName()).log(Level.SEVERE, null, ex);
                }
                System.out.println("clearing listView");
                ((ListViewController) loader.getController()).clearAll();
            }
        }).start();
    }
}

ListViewController class

package apprunner;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.application.Platform;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.ListView;

/**
 * FXML Controller class
 *
 */
public class ListViewController implements Initializable {
        
    public ListViewController() {
        
    }
    
    @FXML
    private ListView<String> listView;

    /**
     * Initializes the controller class.
     */
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
        listView.getItems().add("clear all!");
        listView.getItems().add("clear all!");
        listView.getItems().add("clear all!");
        listView.getItems().add("clear all!");
        AppRunner.waitFiveSecToClear();
    }

    public void clearAll() {
        Platform.runLater(new Runnable() {
            @Override
            public void run() {
                listView.getItems().clear();
            }
        });

    }
}

startUi class

package apprunner;

/**
 *
 */
import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class startUi extends Application {

    public static void launchPanel(String[] args) {
        launch(args);
    }

    @Override
    public void start(Stage stage) throws Exception {
        Parent root = FXMLLoader.load(getClass().getResource("listView.fxml"));
        Scene scene = new Scene(root);
        stage.setScene(scene);
        stage.show();
    }
}

listView.fxml

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.ListView?>
<?import javafx.scene.layout.AnchorPane?>


<AnchorPane id="AnchorPane" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml/1" xmlns="http://javafx.com/javafx/17" fx:controller="apprunner.ListViewController">
   <children>
      <ListView fx:id="listView" layoutX="68.0" layoutY="39.0" prefHeight="200.0" prefWidth="200.0" />
   </children>
</AnchorPane>

Currently there is no error. However my code isn't doing what I want. I want the waitFiveSecToClear() method inside the AppRunner class to clear the listView in the javafx ui. However this isn't happening. I used ((ListViewController) loader.getController()).clearAll(); to attempt to clear the listView which doesen't seem to do anything. If someone could help me figure out my problem that would be great thanks!

Context for my problem

I have a highschool capstone project. I chose to make a music internet downloader. When my program is downloading music, it would freeze the whole javafx application without the thread, so I used a thread and Thread.sleep(5000) in my waitFiveSecToClear() method to simulate that. My program has a listView which shows a queue of all the music urls currently being downloaded. I want it so that when one url is finished downloading, the listView is updated which must be done on the Javafx thread which requires Platform.runlater. So, I used Platform.runLater in the clearAll() method to simluate that. I don't want to do that in the controller because based on what I've learned that would break model, view, controller architecture. I have an AppRunner class because my teachers program example had that so I just copied it.

Solution

I solved my problem by using a Task and ObservableList as suggested by @James_D and @jewelsea. I have a Task in my model which would download music and remove the url of the music from the ObservableList once it finished downloading. I then have a Listener in my controller which would update the ListView when the ObservableList changed.

Answered By - harharprogrammer
Answer Checked By - Candace Johnson (JavaFixing Volunteer)