Android Question How to call B4A sub from html loaded into WebView

[cenyu]

Hi, I have to call B4A sub from html loaded into WebView. I am using this libs:

• WevViewExtras2 version 2.20
• WevViewSettings version 1.30

I am using B4A version 10.

I am using WevViewExtras2 becouse i have to load https web page from specific url...
But into my app i first must check internet connection and show error page when there is no connection...
Into this web page i have one button "ExitApp"
My error.html is into file:///android_asset folder


This is my html code:

  <div class="fixed-footer">
                <div class="row">
                    <div class="col-6">
                        <a href="javascript:B4A.CallSubPlus('AppClose_Request', true,'1');" class="btn btn-secondary btn-lg btn-block">ExitApp</a>
                    </div>
                    <div class="col-6">
                        <a href="javascript:B4A.CallSubPlus('AppReload_Request', true,'1');" class="btn btn-primary btn-lg btn-block">Reload</a>
                    </div>
                </div>
            </div>
        </div>

And this i my B4A code:

Sub Activity_Create(FirstTime As Boolean) 
  
    WebView1.Initialize("WebView1")
     WebViewExtras1.Initialize(WebView1)
    Dim client As DefaultWebViewClient
    client.Initialize("client")
    WebViewExtras1.SetWebViewClient(client)
    
    Activity.AddView(WebView1, 0, 0, 100%x, Activity.Height)
  
    WebSettings.setDefaultTextEncodingName(WebView1,"utf-8")
    WebViewExtras1.addJavascriptInterface(WebView1, "B4A")
    WebView1.JavaScriptEnabled = True
    WebView1.ZoomEnabled=False
  
End Sub 
  
Sub AppClose_Request()
   ToastMessageShow("Exiting...",True)
   ExitApplication
 
End Sub

But when i press button i can't run Sub AppClose_Request() into B4A app!

May be this is limitation of WebViewExtras2

 

[Alex_197]

It looks like you are going to create a trojan

 

[cenyu]

It's look like you can't help me... And not this is not trojan...
I trying to start B4A sub code from html page...
What trojan...?????

 

[rraswisak]

Try this code snippet:

WebViewExtra: Call B4A Sub from WebView

Hi All, Here with Attached simple project to demonstrate how to call B4A Sub in WebView using WebViewExtra (v1.42). I'm not play often with this lib, but found some interest on how B4A can interact with WebView via Javascript. The project will: - Load html from asset - Call Javascript...

www.b4x.com

 

[JohnC]

Try this change:

<a href="javascript:void(0);" onclick="B4A.CallSubPlus('AppClose_Request', true,'1');" class="btn btn-secondary btn-lg btn-block">ExitApp</a>

 

[cenyu]

Still not working...
When i use WebViewExtra (v1.42) all works perfect but with WevViewExtras2 version 2.20 not work Thats why i thinking - there is WevViewExtras2 version 2.20 limitation.
As i say WevViewExtras2 version 2.20 i MUST use because into other part of my app i read https content wtch can not read with ... WebViewExtra (v1.42)

 

[cenyu]

rraswisak do you try to read https content with WebViewExtra (v1.42) ?

 

[mc73]

As a workaround, why don't you use overrideURL?

 

[cenyu]

When i put this code

Sub WebView1_OverrideUrl (Url As String) As Boolean
  
    ToastMessageShow("Fired",True)
    Return True 'Don't try to navigate to this URL
  
  
  
End Sub

Nothing changes.... I found that i can't call javascript function wtiten into html like this

<a href="javascript:doCallBack();"   class="btn btn-secondary btn-lg btn-block">Exit</a>

<script>
 function doCallBack(){
    alert(1)
     
    }
   </script>

May be i have error when enabling javascript on WebView and WebViewExtras?

WebView1.Initialize("WebView1")
    WebView1.JavaScriptEnabled = True
    WebView1.ZoomEnabled=False
  
  
    Dim client As DefaultWebViewClient
    client.Initialize("client")
  
    WebViewExtras1.Initialize(WebView1)
    WebViewExtras1.JavaScriptEnabled=True
    WebViewExtras1.SetWebViewClient(client)
    WebViewExtras1.addJavascriptInterface(WebView1, "B4A")
    WebSettings.setDefaultTextEncodingName(WebView1,"utf-8")
    Activity.AddView(WebView1, 0, 0, 100%x, Activity.Height)