import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

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

    public Parent createContent() {
        final WebBrowser browser = new WebBrowser();
        return browser;
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        primaryStage.setResizable(true);
        Scene scene = new Scene(createContent());
        primaryStage.setTitle("Eric's Web Demo");
        scene.getStylesheets().add("style/template.css");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}

import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

import javafx.beans.value.ObservableValue;
import javafx.collections.FXCollections;
import javafx.collections.ListChangeListener.Change;
import javafx.event.ActionEvent;
import javafx.geometry.Dimension2D;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.VPos;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Label;
import javafx.scene.control.ProgressBar;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebHistory;
import javafx.scene.web.WebHistory.Entry;
import javafx.scene.web.WebView;

public class WebBrowser extends BorderPane {

    private static final Dimension2D DIM = new Dimension2D(1220, 680);
    private final WebView webView;
    private final WebEngine webEngine;
    private final ComboBox<String> addressBox;
    private final TextField searchField;
    private final Button backButton;
    private final Button forwardButton;
    private final Button proceedButton;
    private final Button searchButton;
    private final ProgressBar progressBar;
    private final Label statusLabel;

    public WebBrowser() {

        this.setMinSize(DIM.getWidth(), DIM.getHeight());
        this.setPrefSize(DIM.getWidth(), DIM.getHeight());

        backButton = new Button("uD83EuDC78");
        backButton.setOnAction(this::backButtonListener);

        forwardButton = new Button("u2794");
        forwardButton.setDefaultButton(true);
        forwardButton.setOnAction(this::forwardButtonListener);

        proceedButton = new Button("Go");
        proceedButton.setOnAction(this::proceedButtonListener);

        final HBox buttonGroup = new HBox();
        buttonGroup.setSpacing(5);
        buttonGroup.setPadding(new Insets(10, 5, 10, 5));
        buttonGroup.getChildren().addAll(backButton, forwardButton, proceedButton);

        addressBox = new ComboBox<String>();
        addressBox.setItems(FXCollections.observableArrayList());
        addressBox.setValue("http://stackoverflow.com/questions/32783532/applying-css-file-to-javafx-webview");
        addressBox.setOnAction(this::proceedButtonListener);
        addressBox.setEditable(true);
        addressBox.setMaxWidth(Double.MAX_VALUE);

        searchField = new TextField();
        searchField.setPromptText("uD83DuDD0D Search");

        searchButton = new Button("uD83DuDD0D");
        searchButton.setDefaultButton(true);
        searchButton.setOnAction(this::searchButtonListener);

        statusLabel = new Label("Status: ");
        progressBar = new ProgressBar(0);

        webView = new WebView();
        webEngine = webView.getEngine();
        webEngine.load(addressBox.getValue());
        webEngine.getLoadWorker().stateProperty().addListener(this::stateChangeListener);
        webEngine.locationProperty().addListener(this::urlChangeListener);
        progressBar.progressProperty().bind(webEngine.getLoadWorker().progressProperty());

        final WebHistory history = webEngine.getHistory();
        history.getEntries().addListener(this::historyListener);

        final GridPane root = new GridPane();
        GridPane.setConstraints(buttonGroup,  0, 0, 1, 1, HPos.LEFT,   VPos.CENTER, Priority.NEVER,  Priority.NEVER);
        GridPane.setConstraints(addressBox,   1, 0, 1, 1, HPos.CENTER, VPos.CENTER, Priority.ALWAYS, Priority.NEVER);
        GridPane.setConstraints(searchField,  2, 0, 1, 1, HPos.RIGHT,  VPos.CENTER, Priority.NEVER,  Priority.NEVER);
        GridPane.setConstraints(searchButton, 3, 0, 1, 1, HPos.RIGHT,  VPos.CENTER, Priority.NEVER,  Priority.NEVER);
        GridPane.setConstraints(webView,      0, 1, 4, 1, HPos.LEFT,   VPos.CENTER, Priority.ALWAYS, Priority.ALWAYS);
        GridPane.setConstraints(statusLabel,  0, 2, 1, 1, HPos.LEFT,   VPos.CENTER, Priority.NEVER,  Priority.NEVER);
        GridPane.setConstraints(progressBar,  3, 2, 3, 1, HPos.RIGHT,  VPos.CENTER, Priority.NEVER,  Priority.NEVER);
        GridPane.setFillWidth(webView, true);
        GridPane.setMargin(addressBox,   new Insets(5, 0, 5, 0));
        GridPane.setMargin(searchField,  new Insets(5, 5, 5, 5));
        GridPane.setMargin(searchButton, new Insets(5, 8, 5, 0));
        GridPane.setMargin(statusLabel,  new Insets(5, 0, 5, 5));
        GridPane.setMargin(progressBar,  new Insets(5, 5, 5, 5));
        root.addRow(0, buttonGroup, addressBox, searchField, searchButton);
        root.addRow(1, webView);
        root.addRow(2,statusLabel, progressBar);

        this.setCenter(root);
    }

    public void historyListener(Change<? extends Entry> changeValue) {
        changeValue.next();
        for (Entry entry : changeValue.getRemoved()) {
            addressBox.getItems().remove(entry.getUrl());
            System.out.print("Removed url: ");
            System.out.println(entry.getUrl());
        }
        for (Entry entry : changeValue.getAddedSubList()) {
            System.out.print("Added url: ");
            addressBox.getItems().add(entry.getUrl());
            System.out.println(entry.getUrl());
        }
    }

    public void progressBarListener(ObservableValue<? extends Number> ov, Number old_val, Number new_val) {
        progressBar.setProgress(new_val.doubleValue());
    }

    private void stateChangeListener(ObservableValue<? extends Object> observable, Object oldValue, Object newValue) {
        setWebpageTheme(true);
        String output = newValue.toString().toLowerCase();
        statusLabel.setText("Status: " + output);
    }

    private void urlChangeListener(ObservableValue<? extends String> observable, String oldValue, String newValue) {
        addressBox.setValue(newValue);
    }

    public void forwardButtonListener(ActionEvent event) {
        webEngine.executeScript("history.forward()");
    }

    private void backButtonListener(ActionEvent event) {
        webEngine.executeScript("history.back()");
    }

    private void searchButtonListener(ActionEvent event) {
        String google = "http://www.google.com/search?q=" + searchField.getText();
        webEngine.load(google.startsWith("http://") || google.startsWith("https://")
                ? google : "http://" + google);
    }

    private void proceedButtonListener(ActionEvent event) {
        String url = addressBox.valueProperty().getValue();
        webEngine.load(url.startsWith("http://") || url.startsWith("https://")
                ? url : "http://" + url);
    }

    private void setWebpageTheme(Boolean succeeded) {
        // Can safely access DOM and set styles.
        if (succeeded == true) {
            // This gives the DOM Document for the web page.
            Document doc = webEngine.getDocument();
            Attr newAttr = null;
            NodeList htmlTags = doc.getElementsByTagName("*");
            for (int i = 0; i < htmlTags.getLength(); i++) {
                if (htmlTags != null) {
                    Node htmlNode = htmlTags.item(i);
                    newAttr = doc.createAttribute("style");
                    newAttr.setValue("background-color: #222; border-color: #333; background: #222; color: #bbb; ");
                    htmlNode.getAttributes().setNamedItem(newAttr);
                }
            }
        }
    }
}

.root{
   -fx-background: rgb(44,44,44);
}

.button {
   -fx-border-radius: 5;
   -fx-background-radius: 5;
    -fx-min-height: 32;
     -fx-min-width: 40;
   -fx-background-color: radial-gradient(radius 100%, rgb(22, 33, 188), rgb(3,22,122));
   -fx-text-fill: rgb(196,188,222);
}

TextField {
   -fx-border-radius: 5;
   -fx-background-radius: 5;
   -fx-max-height: 32;
    -fx-min-width: 280;
   -fx-border-color: #555;
   -fx-border-width: 1 1 1 1;
   -fx-background-color: #333;
   -fx-text-fill: rgb(196,188,222);
}

.combo-box-base {
    -fx-border-radius: 5;
   -fx-background-radius: 5;
    -fx-min-height: 35;
    -fx-background-color: #333;
    -fx-border-color: transparent;
    -fx-border-width: 2 2 2 2;
}

.combo-box-base .arrow-button {
    -fx-background-color: radial-gradient(radius 100%, rgb(22, 33, 188), rgb(3,22,122));
}

.combo-box .combo-box-popup, .list-view, .list-cell {
    -fx-background-color:  #333;
    -fx-text-fill: rgb(155,188,166);
}

.combo-box .text-input {
    -fx-border-radius: 5;
    -fx-background-radius: 5;
    -fx-background-color: #333;
    -fx-border-color: #555;
    -fx-border-width: 1 1 1 1;
    -fx-text-fill: rgb(155,188,166);
}

.scroll-bar {
    -fx-background-color: #222;
}

.scroll-bar .thumb {
    -fx-background-color: radial-gradient(radius 100%, rgb(22, 33, 188), rgb(3,22,122));
}

.label {
    -fx-font: 14px "Arial";
    -fx-border-color: rgb(57, 58, 59);
    -fx-border-width: 2 2 2 2;
    -fx-text-fill: rgb(155,188,166);
}

.progress-bar > .track {
  -fx-text-box-border: rgb(44, 44, 44);
  -fx-control-inner-background: rgb(22, 22, 44);
}