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How we can execute a javascript function and get a return value in our android application?

rated 0 times [ 32] [ 2] / answers: 1 / hits: 18700 / 12 Years ago, fri, november 23, 2012, 12:00:00

How we can execute a javascript function and get a return value in our android appplication ?

We want to execute a javascript on a button press event, we need to pass parameters to the script and get return values, So we are using WebChromeClient to implement this,
But we got Exception is SyntaxError: Parse error at undefined:1

Following is my code

import android.app.Activity;

import android.os.Bundle;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.webkit.JsResult;

import android.webkit.WebChromeClient;

import android.webkit.WebSettings;

import android.webkit.WebView;



public class FirstTab extends Activity 

{





    private WebView webView;



    public void onCreate(Bundle savedInstanceState) {

            super.onCreate(savedInstanceState);

             setContentView(R.layout.regis);



            try{



                webView = (WebView) findViewById(R.id.webView1);

                webView.getSettings().setJavaScriptEnabled(true);

                webView.setWebChromeClient(new MyWebChromeClient());

                String customHtml = <html><head><title>iSales</title><script type=text/javascript> function fieldsOnDelete(){ var x=123; return JIJO; } </script></head><body>hi</body></html>;

                webView.loadData(customHtml, text/html,UTF-8);  



                }catch(Exception e)

                {

                     Log.v(JAC LOG,e.toString());

                }



        }

    public void onResume()

    {

        super.onResume();



            final Button button = (Button) findViewById(R.id.button1);

             button.setOnClickListener(new View.OnClickListener() {

             public void onClick(View v) {

                 try{

                    webView.loadUrl(javascript:alert(javascript:fieldsOnDelete()));

                 }

                 catch(Exception e)

                 {

                     Log.v(JAC LOG,e.toString());



                 }

              } 

             });

    }





    final class MyWebChromeClient extends WebChromeClient {

        @Override

        public boolean onJsAlert(WebView view, String url, String message, JsResult result) {



        Log.v(LogTag, message);

          result.confirm();

          return true;

        }

    }





}

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hakeemabramh

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answered 12 Years ago breonnamayah · Accepted Answer

you can use mWebView.loadUrl(javascript:checkName); to call the method...

Then you can use addJavascriptInterface() to add a Java object to the Javascript environment. Have your Java script call a method on that Java object to supply its return value.

EDIT1: Or you can use following hack:

Add this Client to your WebView:

final class MyWebChromeClient extends WebChromeClient {

        @Override

        public boolean onJsAlert(WebView view, String url, String message, JsResult result) {

            Log.d(LogTag, message);

            result.confirm();

            return true;

        }

    }

Now in your java script call do:

webView.loadUrl(javascript:alert(functionThatReturnsSomething));

Now in the onJsAlert call message will contain the returned value.

Edit2:

So it does not work if we call javascript method just after call to load the URL since the page loads take time. So I created a test program to test that...

Following is my html file (named test.html) store in the assets folder:

<html>

<head>

<script language=javascript>

    function fieldsOnDelete(message) {

        alert(i am called with  + message);

        window.myjava.returnValue(message +  JIJO);

    }

</script>

<title>iSales android</title>





</head>

<body></body>

</html>

</body>

</html>

Following is my java class that would get that i would add to java script as interface and it would receive the return value:

public class MyJS {



    public void returnValue(String string){

        Log.d(this.getClass().getSimpleName(), string);

    }



}

And following is my activity class:

public class CheckWebView extends Activity {



    private WebView webView;



    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_check_web_view);

        webView = (WebView) findViewById(R.id.webview);



        webView.setWebChromeClient(new WebChromeClient() {

            @Override

            public void onConsoleMessage(String message, int lineNumber,

                    String sourceID) {

                super.onConsoleMessage(message, lineNumber, sourceID);

                Log.d(this.getClass().getCanonicalName(), message  + message

                        +    :::line number  + lineNumber +    :::source id 

                        + sourceID);

            }



            @Override

            public boolean onConsoleMessage(ConsoleMessage consoleMessage) {

                // TODO Auto-generated method stub



                onConsoleMessage(consoleMessage.message(),

                        consoleMessage.lineNumber(), consoleMessage.sourceId());



                Log.d(this.getClass().getCanonicalName(), message::::: 

                        + consoleMessage.message());



                return super.onConsoleMessage(consoleMessage);

            }

        });



        webView.addJavascriptInterface(new MyJS(), myjava);

        webView.getSettings().setJavaScriptEnabled(true);

        webView.getSettings().setPluginsEnabled(true);

        webView.getSettings().setAllowFileAccess(true);



        webView.loadUrl(file:///android_asset/test.html);



    }



    @Override

    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.

        getMenuInflater().inflate(R.menu.activity_check_web_view, menu);

        return true;

    }



    /* (non-Javadoc)

     * @see android.app.Activity#onOptionsItemSelected(android.view.MenuItem)

     */

    @Override

    public boolean onOptionsItemSelected(MenuItem item) {

        webView.loadUrl(javascript:fieldsOnDelete('name'););

        return super.onOptionsItemSelected(item);

    }



}

The key here is that there should be some time interval between the call to load html file from assets folder and the call to javascript:method. Here I am calling it from onOptionsItemSelected and it is working fine.. if I move the webView.loadUrl(javascript:fieldsOnDelete('name');); to the end of the onCreate() method the it shows the error that it can not find fieldsOnDelete() method...

Hope it Helps...

EDIT3:

Replace following in your code

webView.loadUrl(javascript:alert(javascript:fieldsOnDelete()));

with

webView.loadUrl(javascript:alert(fieldsOnDelete()));

and try...