Adding HTML Content to JavaFX Applications

Previous
Next

Beta Draft: 2013-09-17

8 Managing Web History

This chapter introduces the WebHistory class and teaches how to obtain and show the URLs of visited pages.

You can obtain the list of visited pages by using the WebHistory class. It represents a session history associated with a WebEngine object. Use the WebEngine.getHistory() method to get the WebHistory instance for a particular web engine, as shown in the following line: WebHistory history = webEngine.getHistory();.

The history is basically a list of entries. Each entry represents a visited page and it provides access to relevant page info, such as URL, title, and the date the page was last visited. The list can be obtained by using the getEntries() method.

The history list changes as users navigate through the web. Use the ObservableList API to process the changes.

Obtaining the List of Visited Pages

You typically use a standard or custom UI control to display the history list. Example 8-1 shows how to obtain a history items and present them in the ComboBox control.

Example 8-1 Obtaining and Processing the List of Web History Items

final WebHistory history = webEngine.getHistory();
history.getEntries().addListener(new 
    ListChangeListener<WebHistory.Entry>() {
        @Override
        public void onChanged(Change<? extends Entry> c) {
            c.next();
            for (Entry e : c.getRemoved()) {
                comboBox.getItems().remove(e.getUrl());
            }
            for (Entry e : c.getAddedSubList()) {
                comboBox.getItems().add(e.getUrl());
            }
        }
    }
);
         
comboBox.setPrefWidth(60);
comboBox.setOnAction(new EventHandler<ActionEvent>() {
    @Override
    public void handle(ActionEvent ev) {
        int offset =
                comboBox.getSelectionModel().getSelectedIndex()
                - history.getCurrentIndex();
        history.go(offset);
    }
});

The ListChangeListener object tracks the changes of history entries and adds the corresponding URLs to the combo box.

When users select any item in the combo box, the web engine is navigated to the URL defined by the history entry item, which position in the list is defined by the offset value. A negative offset value specifies the position preceding the current entry, and a positive offset value specifies the position following the current entry.

Example 8-2 shows the complete code of the modified application.

Example 8-2 WebViewSample with the History Combo Box

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.collections.ListChangeListener;
import javafx.collections.ListChangeListener.Change;
import javafx.concurrent.Worker.State;
import javafx.event.ActionEvent;
import javafx.event.Event;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Pos;
import javafx.geometry.VPos;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.Hyperlink;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Priority;
import javafx.scene.layout.Region;
import javafx.scene.paint.Color;
import javafx.scene.web.PopupFeatures;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebHistory;
import javafx.scene.web.WebHistory.Entry;
import javafx.scene.web.WebView;
import javafx.stage.Stage;
import javafx.util.Callback;
import netscape.javascript.JSObject;
 
 
public class WebViewSample extends Application {
 
    private Scene scene;
 
    @Override
    public void start(Stage stage) {
        // create scene
        stage.setTitle("Web View");
        scene = new Scene(new Browser(), 900, 600, Color.web("#666970"));
        stage.setScene(scene);
        // apply CSS style
        scene.getStylesheets().add("webviewsample/BrowserToolbar.css");
        // show stage
        stage.show();
    }
 
    public static void main(String[] args) {
        launch(args);
    }
}
class Browser extends Region {
 
    private HBox toolBar;
    final private static String[] imageFiles = new String[]{
        "product.png",
        "blog.png",
        "documentation.png",
        "partners.png",
        "help.png"
    };
    final private static String[] captions = new String[]{
        "Products",
        "Blogs",
        "Documentation",
        "Partners",
        "Help"
    };
    final private static String[] urls = new String[]{
        "http://www.oracle.com/products/index.html",
        "http://blogs.oracle.com/",
        "http://docs.oracle.com/javase/index.html",
        "http://www.oracle.com/partners/index.html",
        WebViewSample.class.getResource("help.html").toExternalForm()
    };
    final ImageView selectedImage = new ImageView();
    final Hyperlink[] hpls = new Hyperlink[captions.length];
    final Image[] images = new Image[imageFiles.length];
    final WebView browser = new WebView();
    final WebEngine webEngine = browser.getEngine();
    final Button showPrevDoc = new Button("Toggle Previous Docs");
    final WebView smallView = new WebView();
    final ComboBox comboBox = new ComboBox();
    private boolean needDocumentationButton = false;
 
    public Browser() {
        //apply the styles
        getStyleClass().add("browser");
 
        for (int i = 0; i < captions.length; i++) {
            // create hyperlinks
            Hyperlink hpl = hpls[i] = new Hyperlink(captions[i]);
            Image image = images[i] =
                    new Image(getClass().getResourceAsStream(imageFiles[i]));
            hpl.setGraphic(new ImageView(image));
            final String url = urls[i];
            final boolean addButton = (hpl.getText().equals("Documentation"));
 
            // process event 
            hpl.setOnAction(new EventHandler<ActionEvent>() {
                @Override
                public void handle(ActionEvent e) {
                    needDocumentationButton = addButton;
                    webEngine.load(url);
                }
            });
        }
 
        comboBox.setPrefWidth(60);
 
        // create the toolbar
        toolBar = new HBox();
        toolBar.setAlignment(Pos.CENTER);
        toolBar.getStyleClass().add("browser-toolbar");
        toolBar.getChildren().add(comboBox);
        toolBar.getChildren().addAll(hpls);
        toolBar.getChildren().add(createSpacer());
 
        //set action for the button
        showPrevDoc.setOnAction(new EventHandler() {
            @Override
            public void handle(Event t) {
                webEngine.executeScript("toggleDisplay('PrevRel')");
            }           
        });
 
        smallView.setPrefSize(120, 80);
 
        //handle popup windows
        webEngine.setCreatePopupHandler(
            new Callback<PopupFeatures, WebEngine>() {
                @Override public WebEngine call(PopupFeatures config) {
                    smallView.setFontScale(0.8);
                    if (!toolBar.getChildren().contains(smallView)) {
                        toolBar.getChildren().add(smallView);
                    }
                    return smallView.getEngine();
                }
             }
        );
 
        //process history
        final WebHistory history = webEngine.getHistory();
        history.getEntries().addListener(new 
            ListChangeListener<WebHistory.Entry>(){
                @Override
                public void onChanged(Change<? extends Entry> c) {
                    c.next();
                    for (Entry e : c.getRemoved()) {
                        comboBox.getItems().remove(e.getUrl());
                    }
                    for (Entry e : c.getAddedSubList()) {
                        comboBox.getItems().add(e.getUrl());
                    }
                }
        });
 
        //set the behavior for the history combobox               
        comboBox.setOnAction(new EventHandler<ActionEvent>() {
            @Override
            public void handle(ActionEvent ev) {
                int offset =
                        comboBox.getSelectionModel().getSelectedIndex()
                        - history.getCurrentIndex();
                history.go(offset);
            }
        });
 
 
        // process page loading
        webEngine.getLoadWorker().stateProperty().addListener(
            new ChangeListener<State>() {
                @Override
                public void changed(ObservableValue<? extends State> ov,
                    State oldState, State newState) {
                    toolBar.getChildren().remove(showPrevDoc);    
                    if (newState == State.SUCCEEDED) {
                            JSObject win = 
                                (JSObject) webEngine.executeScript("window");
                            win.setMember("app", new JavaApp());
                            if (needDocumentationButton) {
                                toolBar.getChildren().add(showPrevDoc);
                            }
                        }
                    }
                }
        );
 
        // load the home page        
        webEngine.load("http://www.oracle.com/products/index.html");
 
        //add components
        getChildren().add(toolBar);
        getChildren().add(browser);
    }
 
    // JavaScript interface object
    public class JavaApp {
 
        public void exit() {
            Platform.exit();
        }
    }
 
    private Node createSpacer() {
        Region spacer = new Region();
        HBox.setHgrow(spacer, Priority.ALWAYS);
        return spacer;
    }
 
    @Override
    protected void layoutChildren() {
        double w = getWidth();
        double h = getHeight();
        double tbHeight = toolBar.prefHeight(w);
        layoutInArea(browser,0,0,w,h-tbHeight,0,HPos.CENTER,VPos.CENTER);
        layoutInArea(toolBar,0,h-tbHeight,w,tbHeight,0,HPos.CENTER,VPos.CENTER);
    }
 
    @Override
    protected double computePrefWidth(double height) {
        return 900;
    }
 
    @Override
    protected double computePrefHeight(double width) {
        return 600;
    }
}

When you compile and run the application, it produces the window shown in Figure 8-1.

Figure 8-1 Selecting URL from the History Combo Box

Description of Figure 8-1 follows
Description of "Figure 8-1 Selecting URL from the History Combo Box"

Previous
Next