Updating UI from another Thread extended Class

Question

What I want to do:

[Web Scraping with Jsoup]

Adding elements to a TableView from an another Thread extended Class.

Button click -> start Thread -> Thread add elements to TableView.

Files

|javafxapplication5
|-->FXMLDocuments.fxml
|-->FXMLDocumentController.java
|-->JavaFXApplication5.java
|-->Scraper.java

FXMLDocumentController.java

package javafxapplication5;

import java.net.URL;
import java.util.ResourceBundle;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.input.MouseEvent;


public class FXMLDocumentController implements Initializable {
    Scraper scraper = new Scraper();
    
    @FXML
    private Label label;
    
    @FXML
    private Button shareButton;
    
    @FXML
    private TextField searchInput;

    @FXML
    private Button searchTorrents;

    @FXML
    private void handleButtonAction(ActionEvent event) {
        System.out.println("You clicked me!");
    }
    
    @FXML
    private void setMouseEntered(MouseEvent event)
    {
        searchTorrents.setStyle("-fx-border-color:blue");
    }
    @FXML
    private void setMouseLeaved(MouseEvent event)
    {
        searchTorrents.setStyle("-fx-border-color:black");
    }
    
    @FXML
    private void shareButton(ActionEvent event)
    {
        Alert alert = new Alert(Alert.AlertType.INFORMATION);
        alert.setHeaderText("Hai cliccato il bottone share");
        alert.showAndWait();
    }
    
    @FXML
    private void scrapButton(ActionEvent event)
    {
        scraper.start();
    }
     
    @Override
    public void initialize(URL url, ResourceBundle rb) {
        // TODO
    }    
    
}

Scraper.java

package javafxapplication5;

import java.io.IOException;
import java.util.logging.Level;
import java.util.logging.Logger;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;


public class Scraper extends Thread{
    public void run()
    {
        Document doc;
        try {
            doc = Jsoup.connect("https://www.allkeyshop.com/blog/daily-deals/").get();
            Elements gamesNames = doc.select(".search-results-row-game-title");
            for (Element element:gamesNames)
            {
                //Update TableView
            }
        } catch (IOException ex) {
            Logger.getLogger(TorrentScraper.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

I hope is everything clear, if not please answer me with a constructive suggestion.

There are ways to signal that an update to your gui is happening. Swing used InvokeLater to have a thread do this. I'm not sure what JavaFX uses for this. — NomadMaker, Oct 21 '20 at 19:22
I would suggest using a `Task`. In the `Task's` `onsucceded` return a `List`. In the `ObservableArrayList` for the `TableView` use `setAll`. — SedJ601, Oct 22 '20 at 04:08
You can listen to updates made by the tread. See and example [here](https://stackoverflow.com/a/54604889/3992939) — c0der, Oct 22 '20 at 04:13

score 1 · Accepted Answer · answered Oct 22 '20 at 05:53

Here is an example you can use as a guide. The URL you use does not have a result list. I would suggest you use something like https://www.allkeyshop.com/blog/catalogue/search-game/. It appears, what comes after the hyphen is what is being searched. You may need to do a few complicated searches to see how the URL changes.

This example uses Task. In the Task setOnSuccedded updates the TableView.

Main

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.concurrent.Task;
import javafx.concurrent.WorkerStateEvent;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.jsoup.select.Elements;

/**
 * JavaFX App
 */
public class App extends Application
{

    @Override
    public void start(Stage primaryStage)
    {
        TableView<JSoupData> tvMain = new TableView();
        ObservableList<JSoupData> tableItems = FXCollections.observableArrayList();
        tvMain.setItems(tableItems);

        TableColumn<JSoupData, String> tcTagName = new TableColumn<>("Tag Name");
        tcTagName.setCellValueFactory(new PropertyValueFactory<>("tagName"));
        TableColumn<JSoupData, String> tcText = new TableColumn<>("Text");
        tcText.setCellValueFactory(new PropertyValueFactory<>("text"));
        tvMain.getColumns().add(tcTagName);
        tvMain.getColumns().add(tcText);

        TextField tfUrl = new TextField("https://www.allkeyshop.com/blog/catalogue/search-game/");
        tfUrl.setPromptText("Enter URL Here!");

        Button btnProcess = new Button("Process URL");
        btnProcess.setOnAction((t) -> {
            btnProcess.setDisable(true);

            Task<List<JSoupData>> task = scrapper(tfUrl.getText());
            task.setOnSucceeded((WorkerStateEvent t1) -> {
                List<JSoupData> tempList = task.getValue();
                tableItems.setAll(tempList);
                btnProcess.setDisable(false);
            });
            Thread thread = new Thread(task);
            thread.setDaemon(true);
            thread.start();
        });
        VBox root = new VBox(tvMain, tfUrl, btnProcess);

        Scene scene = new Scene(root);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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

    public Task<List<JSoupData>> scrapper(String url)
    {
        Task<List<JSoupData>> scrapperTask = new Task<List<JSoupData>>()
        {
            @Override
            protected List<JSoupData> call()
            {
                List<JSoupData> jSoupDatas = new ArrayList();
                try {
                    System.out.println("url: " + url);
                    Document document = Jsoup.connect(url).get();
                    System.out.println("Title: " + document.title());
                    Elements gamesNames = document.select(".search-results-row");
                    System.out.println("search-results-row");
                    for (Element element : gamesNames) {
                        jSoupDatas.add(new JSoupData(element.tagName(), element.text()));
                        System.out.println("Tag Name: " + element.tagName() + " - Text: " + element.text());
                    }
                }
                catch (IOException e) {
                    System.out.println(e.toString());
                }

                return jSoupDatas;
            }
        };

        return scrapperTask;
    }
}

JSoupData

 *
 * @author sedrick (sedj601)
 */
public class JSoupData
{

    private String tagName;
    private String text;

    public JSoupData(String tagName, String text)
    {
        this.tagName = tagName;
        this.text = text;
    }

    public String getText()
    {
        return text;
    }

    public void setText(String text)
    {
        this.text = text;
    }

    public String getTagName()
    {
        return tagName;
    }

    public void setTagName(String tagName)
    {
        this.tagName = tagName;
    }

    @Override
    public String toString()
    {
        StringBuilder sb = new StringBuilder();
        sb.append("JSoupData{tagName=").append(tagName);
        sb.append(", text=").append(text);
        sb.append('}');
        return sb.toString();
    }
}

I have been doing `web-scraping` a long time now... (I wrote a scraper) I don't do **Android**, though... It's pretty neat when you see it loaded up in an App like a browser, though. — Y2020-09, Oct 22 '20 at 09:58

score 0 · Answer 2 · answered Oct 21 '20 at 19:43

0

Usually, Platform.runLater() can be used to execute those updates on the JavaFX application thread.

You can get more information from documentation here and an example from here

answered Oct 21 '20 at 19:43

Tcheutchoua Steve

526
5
11

Updating UI from another Thread extended Class

What I want to do:

Files

FXMLDocumentController.java

Scraper.java

2 Answers2