Syntax to call javascript function from objective-c

Question

I am making an app in IOS with phonegap/cordova 2.1.0 framework. I want to invoke a javascript function residing inside index.html from objective-c. So, first i am loading the index.html and then trying to call the javascript function. My code is as under:

 NSString *path = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent:@"www"];
    NSURL *baseURL = [NSURL fileURLWithPath:path];
    NSString *myFile = [path stringByAppendingPathComponent:@"index.html"];

//NSLog(@"base url= %@",myFile);

NSData *myFileData = [[NSData alloc] initWithContentsOfFile:myFile];
NSString* myFileHtml = [[NSString alloc] initWithData:myFileData encoding:NSASCIIStringEncoding];

[theWebView loadHTMLString:myFileHtml baseURL:baseURL];

// to call javascript function 
[theWebView stringByEvaluatingJavaScriptFromString:@"onDeviceReady()"];

The second last line loads the index.html and the last line calls the function inside it. But, somehow the above code is not working. Am i going wrong somewhere syntax wise.

Alos, since the index.html is already being loaded before, so how can i specify the file name(ie. index.html) where the function exists without loading it once again? Thanks.

Javascript function is as follows:

function onDeviceReady(callback) {

                var item = window.localStorage.getItem("key");
                var message = "deviceready localStorage.getItem('key')="+item+" localStorage.length="+window.localStorage.length;

                if( item == null){
                    item = "";
                }
                item = item + "value";

                window.localStorage.setItem("key", item);

                var value = window.localStorage.getItem("key");

                if ( deviceType == 'android' && gAppControl.loadScript == false ){
                    loadScript('iscroll.js');
                    gAppControl.loadScript = true;
                    document.addEventListener("backButton", backPressed, false);
                }

                var db = window.openDatabase(dbName, "1.0", gAppConfig.dbMessage, 200000);

                db.transaction(queryDB, errorCB , callback);

                // return
                return;
            }

Answer 1

onDeviceReady()

this is the phonegap API, if the device is not ready, you will fail to call any Phonegap plugin, so What's the detail in the onDeviceReady() function? any phonegap-plugin involved?

The code seems no problem, and here is my code , with a bridge to comunicate with Objective-C and HTML-Javascript,