Can you call a javascript function from native code (not in a callback) using PhoneGap and iOS?

Question

I'm hoping to be able to use PhoneGap for my app. I will have to build a custom protocol/plugin so that I can call Native methods from the Javascript. I know you can call a success function in the Javascript when the native code returns.

What I need to be able to do is call a javascript function from the native code. Basically the app will connect to an OSX companion app over local network and when the OSX app send data to the iOS app it is processed in an Objective C method, I need to be able to send the result into the PhoneGap/javascript and do something with it in the WebView.

Is this possible? I have only been able to find information about calling native from javascript not the other way around.

Thanks, Thomas

Using the code from Answer below here:

MyPhoneGapPlugin.m

- (void)onSocket:(AsyncSocket *)sock didConnectToHost:(NSString *)host port:(UInt16)port {
    NSLog(@"Connected To %@:%i.", host, port);

    NSString* jsString = [NSString stringWithFormat:@"alert(connected to: %@);", host];
    [theWebView stringByEvaluatingJavaScriptFromString:jsString];

    [self readWithTag:2];
}

Giving me the error 'Unknown receiver 'theWebView' did you mean 'UIWebView'?

UPDATE: Found the answer: using the phonegap helper I can write something like this...

    [super writeJavascript:@"alert('connected');"];

score 10 · Accepted Answer · 2012-10-06 01:28:56Z

10

You can easily call JavaScript from native code with a UIWebView:

[webView stringByEvaluatingJavaScriptFromString:@"myJSFunction()"];

To use the result of a function somewhere as an arg to a JS function:

NSString *stringData = getStringData(); // however you get it
[webView stringByEvaluatingJavaScriptFromString:
 [NSString stringWithFormat:@"myJSFunction(%@)", stringData]];

edited Oct 6, 2012 at 1:28

answered Oct 10, 2011 at 23:44

user244343

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9 Comments

tsdexter Over a year ago

Awesome this should work for me. I didn't even think to use the UIWebView class, I was too focused on the PhoneGap API I guess. Thanks so much!

tsdexter Over a year ago

Thanks for the update. That probably would have been my next question.

tsdexter Over a year ago

Can this only be used in certain places? I'm trying to use it in a PhoneGap plugin file 'MyPhoneGapPlugin.m' inside an AsyncSockets didConnectToHost so I can alert to the webview that it connected successfully and display the IP but it it throwing an error, please see question for updated code and error.

user244343 Over a year ago

Hmm. Well, that would mean that theWebView isn't visible from inside that function. You need to be able to see an @property UIWebView *theWebView or UIWebView *theWebView from MyPhoneGapPlugin.m. You've probably already tried to ensure that, but.. apart from that I don't really know off the top of my head why it wouldn't be working.

dijipiji Over a year ago

Cut n pasters , Watch the case sensitivity: stringByEvaluatingJavaScriptFromString NOT stringByEvaluatingJavascriptFromString

|

tsdexter · Accepted Answer · 2011-10-24 23:09:28Z

4

Found the PhoneGap helper to accomplish this... Write javascript to the webView using:

    [super writeJavascript:@"alert('it works');"];

answered Oct 24, 2011 at 23:09

tsdexter

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2 Comments

bhuwansahni Over a year ago

Can you please elaborate your answer. I am having the same issue and am new to Cordova. I called it from the MainViewController and also from my Phonegap plugin, it did not responded in the webview. Is their something I am missing?

tsdexter Over a year ago

@bhuwansahni I'm afraid cordova may have changed a lot since I did this so I'm not quite sure what would be required now. I was able to call it just like that from any methods in my app - maybe check out this article on the docs for more info: docs.phonegap.com/en/2.0.0/…

Hemang · Accepted Answer · 2012-10-06 13:22:32Z

2

You should try this,

[webView stringByEvaluatingJavaScriptFromString:@"sendSelectedDate()"];

edited Oct 6, 2012 at 13:22

Hemang

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answered Sep 13, 2012 at 19:11

master

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Comments

Jason Sperske · Accepted Answer · 2011-10-10 23:43:39Z

0

Will this work for you?

http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/DisplayWebContent/Tasks/JavaScriptFromObjC.html

Taken from this page:

You can also call JavaScript functions with arguments. Assume that you have written a JavaScript function which looks like this:

function addImage(image, width, height) { ... }

Its purpose is to add an image to a web page. It is called with three arguments: image, the URL of the image; width, the screen width of the image; and height, the screen height of the image. You can call this method one of two ways from Objective-C. The first creates the array of arguments prior to using the WebScriptObject bridge:

id win = [webView windowScriptObject];



NSArray *args = [NSArray arrayWithObjects:
                 @"sample_graphic.jpg",
                 [NSNumber numberWithInt:320],
                 [NSNumber numberWithInt:240],
                  nil];

[win callWebScriptMethod:@"addImage"
            withArguments:args];

answered Oct 10, 2011 at 23:43

Jason Sperske

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2 Comments

user244343 Over a year ago

Unfortunately, this is OSX-specific, and the OP is using PhoneGap and iOS.

tsdexter Over a year ago

Yes, I need this capability on the iOS App not the Mac OSX Companion App. Thank you though.

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