JavaFX的WebView中通过JavaScript回调Java的程序

解决webview首次加载的html页面无法使用js调用java程序问题。

根据官网给出的例子，自己写了个总是调用不成功。以下是官网例子代码：

http://docs.oracle.com/javase/8/javafx/embedded-browser-tutorial/js-javafx.htm

import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Worker.State;
import javafx.event.ActionEvent;
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.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.WebEngine;
import javafx.scene.web.WebView;
import javafx.stage.Stage;
import netscape.javascript.JSObject;

public class WebViewSample extends Application {

private Scene scene;

@Override
public void start(Stage stage) {
// create scene
stage.setTitle("Web View Sample");
scene = new Scene(new Browser(stage), 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 final 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 toggleHelpTopics = new Button("Toggle Help Topics");
private boolean needDocumentationButton = false;

public Browser(final Stage stage) {
//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("Help"));

// process event
hpl.setOnAction((ActionEvent e) -> {
needDocumentationButton = addButton;
webEngine.load(url);
});

}

// create the toolbar
toolBar = new HBox();
toolBar.setAlignment(Pos.CENTER);
toolBar.getStyleClass().add("browser-toolbar");
toolBar.getChildren().addAll(hpls);
toolBar.getChildren().add(createSpacer());

//set action for the button
toggleHelpTopics.setOnAction((ActionEvent t) -> {
webEngine.executeScript("toggle_visibility('help_topics')");
});

// process page loading
webEngine.getLoadWorker().stateProperty().addListener(
(ObservableValue<? extends State> ov, State oldState,
State newState) -> {
toolBar.getChildren().remove(toggleHelpTopics);
if (newState == State.SUCCEEDED) {
JSObject win
= (JSObject) webEngine.executeScript("window");
win.setMember("app", new JavaApp());
if (needDocumentationButton) {
toolBar.getChildren().add(toggleHelpTopics);
}
}
});

// 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;
}
}

Example 5-1 help.html file
<html lang="en">
<head>
<!-- Visibility toggle script -->
<script type="text/javascript">
<!--
function toggle_visibility(id) {
var e = document.getElementById(id);
if (e.style.display == 'block')
e.style.display = 'none';
else
e.style.display = 'block';
}
//-->
</script>
</head>
<body>
<h1>Online Help</h1>
<p class="boxtitle"><a href="#" onclick="toggle_visibility('help_topics');"
class="boxtitle">[+] Show/Hide Help Topics</a></p>
<ul id="help_topics" style='display:none;'>
<li>Products - Extensive overview of Oracle hardware and software products,
and summary Oracle consulting, support, and educational services. </li>
<li>Blogs - Oracle blogging community (use the Hide All and Show All buttons
to collapse and expand the list of topics).</li>
<li>Documentation - Landing page to start learning Java. The page contains
links to the Java tutorials, developer guides, and API documentation.</li>
<li>Partners - Oracle partner solutions and programs. Popular resources and
membership opportunities.</li>
</ul>
<p><a href="about:blank" onclick="openAppUtil.exit()">Exit the Application</a></p>
</body>
</html>

弄了几个小时，最后怀疑是不是javafx版本问题，我的版本和官网给的例子不一致导致的。

于是我就把官网的例子代码拷贝下来，直接使用它的例子，居然成功了。看来是程序哪里出问题了。

接下来就是不停的对照代码，希望能发现问题所在。又是2个多小时过去了，终于找到问题所在了，原来要右键点击重新加载一次页面，js才能调用java程序。

好奇怪的现象！！！官网例子不用重新加载是因为进入help.html页面是通过点击工具栏上的help按钮，浏览器才加载进去的，浏览器首次加载的是Oracle首页。

如果把官网例子

webEngine.load("http://www.oracle.com/products/index.html");

改为

webEngine.load(WebViewSample.class.getResource("help.html").toExternalForm());

那么一样也会出现点击超链接后不会退出程序，而是会进入一个空白页面，然后需要鼠标右击选择退回，再次点击超链接才能退出程序。

也就是说help.html页面要第二次加载js中才能调用java程序。

下面是我写的例子的解决方案。

package application.view;

import application.Main;
import application.util.ConfigUtil;
import application.util.OpenAppUtil;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.concurrent.Worker;
import javafx.concurrent.Worker.State;
import javafx.fxml.FXML;
import javafx.scene.web.WebEngine;
import javafx.scene.web.WebView;
import netscape.javascript.JSObject;

/**
* 根面板控制器
* @author pelin
*/
public class RootLayoutController {
@FXML
WebView browser;

WebEngine webEngine;
/**
* 初始化，类似与构造函数. fxml加载完成后自动调用该方法
*/
@FXML
private void initialize() {
webEngine = browser.getEngine();
OpenAppUtil openAppUtil = new OpenAppUtil();
webEngine.getLoadWorker().stateProperty().addListener(
new ChangeListener<State>() {
@Override public void changed(ObservableValue ov, State oldState, State newState) {
if (newState == Worker.State.SUCCEEDED) {
//                        stage.setTitle(webEngine.getLocation());
//                    	  System.out.println(newState);
JSObject win = (JSObject) webEngine.executeScript("window");
win.setMember("openAppUtil", openAppUtil);
}
else if (newState == Worker.State.FAILED){
//                    	  System.out.println(newState);
//                    	  webEngine.load(HtmlPath.class.getResource("home.html").toExternalForm());
}
else{
//                    	  System.out.println(newState);
}
}
});
//    	webEngine.load(ConfigUtil.getValue("homePage"));
webEngine.load(Main.class.getResource("view/test.html").toExternalForm());
//    	webEngine.load("http://10.100.1.240:8089/test.html");

}

}

主要修改的地方是：

win.setMember("openAppUtil", new OpenAppUtil());

改为

win.setMember("openAppUtil", openAppUtil);

并且在webEngine.getLoadWorker().stateProperty().addListener之前创建openAppUtil对象。即：OpenAppUtil openAppUtil = new OpenAppUtil();

这样webview在首次加载html后就可以调用java程序了。