Resúmenes

Nella cartella src/main/java andremo ad elencare i package di seguito, mentre nella cartella src/main/resources si trova il file css style.css. Tutto il programma gira sul view MainWindow.fxml presente in src/main/java/application/view. Il file style.css è il seguente:

// questa modifica di stile vale per tutti gli oggetti Button
.button {
    -fx-background-color: red;
}

// questa modifica di stile vale per tutti gli oggetti che richiamano lo stile "mystyle"
.mystyle {
    -fx-background-color: green;
}

PACKAGE application

Per quanto riguarda il file Main.java:

package application;

public class Main {
    public static void main(String[] args) {
        MainApplication.main(args);
    }
}

Per quanto riguarda il file MainApplication.java (una sorta di main):

package application;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Scene;
import javafx.scene.layout.AnchorPane;
import javafx.stage.Stage;

public class MainApplication extends Application {
    @Override
    public void start(Stage primaryStage) throws Exception {
        FXMLLoader loader1 = new FXMLLoader(getClass().getResource("/application/view/MainWindow.fxml"));
        AnchorPane root1 = (AnchorPane) loader1.load();
        Scene scene = new Scene(root1,600,600);
        scene.getStylesheets().add(getClass().
            getResource("/application/css/style.css").toExternalForm());
        primaryStage.setTitle("Load");
        primaryStage.setScene(scene);
        primaryStage.setMinHeight(600);
        primaryStage.setMaxHeight(600);
        primaryStage.show();
    }

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

Per quanto riguarda il file DownloadFromUrl.java (sia download pagina che download immagine):

package application;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import javafx.concurrent.Service;
import javafx.concurrent.Task;
import javafx.scene.image.Image;

public class DownloadFromUrl extends Service<Object> {
    private String urlText;
    private boolean downloadImage;

    @Override
    protected Task<Object> createTask() {
        return new Task<Object>() {
            @Override
            protected Object call() throws Exception {
                if (downloadImage) {
                    Image image = new Image(urlText, 100, 100, true, true);
                    return image;
                } else {
                    URL url = new URL(urlText);
                    BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
                    StringBuilder builder = new StringBuilder();
                    while (reader.ready()) {
                        String line = reader.readLine();
                        builder.append(line);
                    }
                    reader.close();
                    return builder.toString();
                }
            }
        };
    }

    public void setUrlAndType(String text, boolean downloadImage) {
        urlText = text;
        this.downloadImage = downloadImage;
    }
}

PACKAGE application.controller

Per quanto riguarda il file MainWindowController.java:

package application.controller;

import application.DownloadFromUrl;
import javafx.concurrent.WorkerStateEvent;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextArea;
import javafx.scene.control.TextField;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.BorderPane;

public class MainWindowController {
    @FXML
    private BorderPane borderPane;

    @FXML
    private Button loadImageButton;

    @FXML
    private Button loadButton;

    @FXML
    private TextField urlField;

    private DownloadFromUrl downloadFromUrl = new DownloadFromUrl();

    @FXML
    void load(ActionEvent event) {
        String text = urlField.getText();
        downloadFromUrl.setUrlAndType(text, false);
        downloadFromUrl.restart();
    }

    @FXML
    void loadImage(ActionEvent event) {
        String text = urlField.getText();
        downloadFromUrl.setUrlAndType(text, true);
        downloadFromUrl.restart();
    }

    @FXML
    void initialize() {
        loadButton.getStyleClass().add("mystyle");
        downloadFromUrl.setOnSucceeded(new EventHandler<WorkerStateEvent>() {
            @Override
            public void handle(WorkerStateEvent event) {
                if (event.getSource().getValue() instanceof String) {
                    String result = (String) event.getSource().getValue();
                    TextArea t = new TextArea();
                    t.setText(result);
                    t.setEditable(false);
                    borderPane.setCenter(t);
                } else if(event.getSource().getValue() instanceof Image) {
                    Image img = (Image) event.getSource().getValue();
                    Label l = new Label("", new ImageView(img));
                    borderPane.setCenter(l);
                }
            }
        });
        downloadFromUrl.setOnFailed(new EventHandler<WorkerStateEvent>() {
            @Override
            public void handle(WorkerStateEvent event) {
                Alert alert = new Alert(AlertType.ERROR);
                alert.setTitle("Connection error");
                alert.setContentText("Cannot load URL: check your connection and the inserted URL");
                alert.showAndWait();
            }
        });
    }
}