[ 
https://issues.apache.org/jira/browse/CB-10774?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

Shazron Abdullah updated CB-10774:
----------------------------------
    Description: 
>From https://issues.apache.org/jira/browse/CB-10530 regarding app freezing at 
>launch.

...
However I was not sure about why the timer resolves due to long script 
execution times though. It seems like the intention is that whenever 
gap://ready is loaded in the iframe, the immediate response from the native 
side should be to call nativeFetchMessages() which should clear the timeout.

Therefore I dug a little deeper in the native side, and found that the 
evaluateJavaScript:completionHandler: in CDVCommandQueue expects implementation 
to to be async (a comment in the code says so), but the CDVUIWebViewEngine 
method actually is implemented synchronous.
I wrapped the entire method in a dispatch_async call (maybe a very naive 
solution, it might mess with references?):

{code}
dispatch_async(dispatch_get_main_queue(), ^{
  NSString* ret = [(UIWebView*)_engineWebView 
stringByEvaluatingJavaScriptFromString:javaScriptString];
if (completionHandler)
{ completionHandler(ret, nil); }
});
{code}

This also solves the original issue on cordova-ios 4.0.1 as the timeout never 
resolves, so maybe asyncing this method should also be a part of the proper fix?

  was:
>From https://issues.apache.org/jira/browse/CB-10530 regarding app freezing at 
>launch.

...
However I was not sure about why the timer resolves due to long script 
execution times though. It seems like the intention is that whenever 
gap://ready is loaded in the iframe, the immediate response from the native 
side should be to call nativeFetchMessages() which should clear the timeout.

Therefore I dug a little deeper in the native side, and found that the 
evaluateJavaScript:completionHandler: in CDVCommandQueue expects implementation 
to to be async (a comment in the code says so), but the CDVUIWebViewEngine 
method actually is implemented synchronous.
I wrapped the entire method in a dispatch_async call (maybe a very naive 
solution, it might mess with references?):

dispatch_async(dispatch_get_main_queue(), ^{
  NSString* ret = [(UIWebView*)_engineWebView 
stringByEvaluatingJavaScriptFromString:javaScriptString];
if (completionHandler)
{ completionHandler(ret, nil); }
});

This also solves the original issue on cordova-ios 4.0.1 as the timeout never 
resolves, so maybe asyncing this method should also be a part of the proper fix?


> CDVUIWebView performs javascript synchronous, but command queue expects it to 
> be async
> --------------------------------------------------------------------------------------
>
>                 Key: CB-10774
>                 URL: https://issues.apache.org/jira/browse/CB-10774
>             Project: Apache Cordova
>          Issue Type: Bug
>          Components: iOS
>    Affects Versions: 4.1.0
>            Reporter: Torsten Freyhall
>            Assignee: Shazron Abdullah
>              Labels: cordova-ios-4.1.1
>
> From https://issues.apache.org/jira/browse/CB-10530 regarding app freezing at 
> launch.
> ...
> However I was not sure about why the timer resolves due to long script 
> execution times though. It seems like the intention is that whenever 
> gap://ready is loaded in the iframe, the immediate response from the native 
> side should be to call nativeFetchMessages() which should clear the timeout.
> Therefore I dug a little deeper in the native side, and found that the 
> evaluateJavaScript:completionHandler: in CDVCommandQueue expects 
> implementation to to be async (a comment in the code says so), but the 
> CDVUIWebViewEngine method actually is implemented synchronous.
> I wrapped the entire method in a dispatch_async call (maybe a very naive 
> solution, it might mess with references?):
> {code}
> dispatch_async(dispatch_get_main_queue(), ^{
>   NSString* ret = [(UIWebView*)_engineWebView 
> stringByEvaluatingJavaScriptFromString:javaScriptString];
> if (completionHandler)
> { completionHandler(ret, nil); }
> });
> {code}
> This also solves the original issue on cordova-ios 4.0.1 as the timeout never 
> resolves, so maybe asyncing this method should also be a part of the proper 
> fix?



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