How to talk to a Javascript function from SWT

My HTML file has a javascript function xxx_return(), which will return a string value. Is there any way i can take this value from Java layer?.

I am using SWT shell to display this html. Does SWT carry any feature to get the return values of a script function?

edit:

My code is something like below: package test.html.simulation;

import org.eclipse.swt.SWT;
import org.eclipse.swt.SWTException;
import org.eclipse.swt.browser.Browser;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;

public class BrowserExample{
public static void main(String[] args) 
{
  Display display = new Display();
  final Shell shell = new Shell(display);
  String html="";
  Object ob=null;
    shell.setText("Browser Example");
    shell.setSize(500, 350);

        final Browser browser = new Browser(shell, SWT.NONE);
        browser.setBounds(5, 75, 600, 400);

        browser.setUrl("http://localhost/test/tryxml.html");

        shell.open();
        //System.out.println(browser.getUrl());
        //try
        {
        html=(String)browser.evaluate("returnHTML();");
        }/*catch(SWTException e)
        {
            System.out.println(e.getMessage());

        }*/
        System.out.println(html);

        while (!shell.isDisposed()) {
            if (!display.readAndDispatch())
                display.sleep();
            }

        display.dispose();


}

This code gives me an SWT Exception like Object expected:

Exception in thread "main" org.eclipse.swt.SWTException: Object expected
at org.eclipse.swt.browser.WebBrowser$EvaluateFunction.function(Unknown Source)
at org.eclipse.swt.browser.WebSite.Invoke(Unknown Source)
at org.eclipse.swt.browser.WebSite$7.method6(Unknown Source)
at org.eclipse.swt.internal.ole.win32.COMObject.callback6(Unknown Source)
at org.eclipse.swt.internal.ole.win32.COM.VtblCall(Native Method)
at org.eclipse.swt.internal.ole.win32.IDispatch.Invoke(Unknown Source)
at org.eclipse.swt.ole.win32.OleAutomation.invoke(Unknown Source)
at org.eclipse.swt.ole.win32.OleAutomation.invoke(Unknown Source)
at org.eclipse.swt.browser.IE.execute(Unknown Source)
at org.eclipse.swt.browser.WebBrowser.evaluate(Unknown Source)
at org.eclipse.swt.browser.Browser.evaluate(Unknown Source)
at test.html.simulation.BrowserExample.main(BrowserExample.java:29)

In the java script i have written a function in the script tag like:

<script>
function returnHTML()
  {
   var str=document.body.innerHTML;
   //alert(str);
   return str;
  }
</script>

Can anyone find the error in this?. I don't understand where it hits the error.

Thanks.

Use an SWT Browser object. Then you can simply use String result = (String)Browser.evaluate("xxx_return();").

I found it, the exception occurred since the Browser.evaluate() was getting called before the page was loaded in the shell. I added a ProgressListener to know the completion, and tried calling it worked.

browser.addProgressListener(new ProgressListener() {
              public void changed(ProgressEvent event)
              {

              }
              public void completed(ProgressEvent event)
              {String htm;
                htm=(String)browser.evaluate("return returnHTML()"); 
                System.out.println(htm);
              }
            });

Thanks All

In addition the above solutions, add "return" in front of the expression. Also depending on what you are evaluating, completed event can be ignored. Following expression just works.

browser.evaluate("return 4 + 5;")

Of course if you're evaluating javascript from the page loaded in the browser, evaluate must be called after completed event, otherwise the javascript may not have been loaded.

来源：https://stackoverflow.com/questions/7792385/how-to-talk-to-a-javascript-function-from-swt

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