iOS Question jsinterface

mauro vicamini

Active Member
Licensed User
Hi Erel,
is there a library like jsinterface of B4A in B4I to comunicate from a webview javascript to B4I code?
I've seen that is possible to interact from B4I to javascript, but I don't have seen the opposite.

Thank a lot
 

Derek Johnson

Active Member
Licensed User
Another way that you could communicate from the Javascript to B4I would be to change some property of the document eg for simplicity the title

B4X:
document.title= 'Element ' + i +' not found ' + id
then when the Javascript has completed you can recover this as follows:

B4X:
Dim no As NativeObject = WebView1
Dim Result As String
Result=no.RunMethod("stringByEvaluatingJavaScriptFromString:", Array('document.title')).AsString
If you get a bit more clever you could probably write something that was invisible on the end of the document and recover it in a similar way. I'm sure someone in this forum could suggest how to do this.
 

Derek Johnson

Active Member
Licensed User
I've now written and tested some code that allows you to write some hidden data into a WebPage and then retrieve that data using B4I. This isn't quite synchronous, but you could poll for the data using a timer if you wished.

Here is the code:

B4X:
Sub Test
    Dim no As NativeObject = WebView1
    Dim html=$"
    //Create style that is not displayed
    var x = document.createElement("STYLE");
    var t = document.createTextNode("#obscurename {display:none; visibility:hidden;}");
    x.appendChild(t);  
    document.head.appendChild(x);  

    //Write something at the end of the document
    var newNode = document.createElement('div');
    newNode.id = 'obscurename';
    newNode.innerHTML = 'Text to be returned....';
    document.body.appendChild(newNode);        
"$
    no.RunMethod("stringByEvaluatingJavaScriptFromString:", Array(html))
   
End Sub   
   
Sub GetIT   
    'Now retrieve the data
    Dim no As NativeObject = WebView1
    Dim result As String 
    result=no.RunMethod("stringByEvaluatingJavaScriptFromString:", Array("document.getElementById('obscurename').innerHTML")).AsString
    Log($"Result was '${result}'  "$)
   
End Sub
I verified that this works on an iPad with IOS8 and on an iPhone 4 with IOS7.

The actual text is not visible and does not take up space on the current webpage.
 
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