android: call javascript from java problem

I want to know if there is way to call javascript from java on android? In my program, I interact java and javascript together. I am using java to receive response(json data) from TCP server and save them into a file. In webview I am using javascript jQuery getJSON() function to retrieve that file and using jQuery plot chart library to draw chart. Now, there is no relationship between java and javasc开发者_开发问答ript. Every time when I update data and file, I still need to click a button in webview to trigger the draw function. I want the programmes to be smart and handy. Is that a way to call or execute javascript from java. I know one way:

Button update = (Button)findViewById(R.id.update);
        update.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                wv.loadUrl("javascript:document.write('hello')");
            }
        });

But the problem is I already do a index page by loadurl().

final WebView wv = (WebView) findViewById(R.id.webkankan);
        wv.getSettings().setJavaScriptEnabled(true);
        wv.loadUrl("file:///android_asset/index.html");

When I trigger this click event, all contents were gone only a string "hello" there. Another thing is why I need to change webview's type to final to avoid eclipse error. Does this is the problem to trigger my main problem? If so, how can I fix it? Thanks for you patience. Cheers!

For instance you have a javascript method in the index.html called loadData() which reads the file you saved in the java, then what you can do is wv.loadUrl("javascript:loadData()");. This actually call the javascript method and you can then read the file in that method. Hope this solves your problem.

or in simple terms. jus do this webView.loadUrl("javascript:jsmethodname()"); to execute javascript from java.

You can try to communicate java with javascript registering a java object to the webview that is executing the javascript.

The method addJavascriptInterface from Webview will allow you to make available a Java object to the Javascript scope, something like this:

WebView mWebView = new WebView(mContext);
//... webview initialization, js enabling etc.
MyProxyObject obj = new MyProxyObject(); //This object can interchange just basic types, but Strings are basic types
mWebView.addJavascriptInterface(obj,"myproxyobj");

With that code what you will have in the Javascript context you will have an object 'myproxyobj' that is actually a Java object.

Remember, you can interchange just basic types.

For more info check the following url:

http://developer.android.com/guide/webapps/webview.html

Specially check the section: Binding JavaScript code to Android code

Cheers, Francisco