anonymous function in event handler

[salvatore fusto]

Hi' all,

i'm trying to use an anonymous function in a button event handler:

btn.SetOnTouch(function({myCallback(arg1,arg2...)})) to pass arguments to the callback, but on running i always obtain an invalid token error on the very first line of the code, even if this is an instruction, a comment or a blank line.

can anyone help me to solve?

thanks and regards

salvatore

[Dave Smart]

Hi Salvatore,

Sorry, AndroidScript does not support anonymous functions as callback parameters.  This is due to a limitation within the Android WebView->Java bridge.

But this might be a good thing in the long run as too many Anonymous functions can make code very messy and hard to read (especially for beginners)

Regards

David

[salvatore fusto]

thanks Dave, but how can i call a callback with arguments?

regards

Salvatore

[Dave Smart]

Hi Salvatore,

You can't pass your own parameters to AndroidScript callbacks as AndroidScript will often pass it's own set of parameters for various callbacks.  Although the SetOnTouch callback of the button control does not actually send any parameters (but the Image control does). 

You can however use the app.GetLastButton() method to get the last button pressed.  Also, since AndroidScript objects are all JavaScript objects you can add custom properties and methods, so you might like to save your parameter values within the button object and retrieve them in a shared OnTouch handler like this:-

function OnStart()

{

   lay = app.CreateLayout( "linear", "VCenter,FillXY" );

   btn1 = app.CreateButton( "Press Me", 0.3, 0.1 );

   btn1.SetOnTouch( btn_OnTouch );

   lay.AddChild( btn1 );

   btn1.myVal = "hi from button 1";

    

  btn2 = app.CreateButton( "Press Me", 0.3, 0.1 );

  btn2.SetOnTouch( btn_OnTouch );

  lay.AddChild( btn2 );

  btn2.myVal = "hi from button 2";

  app.AddLayout( lay );

}

function btn_OnTouch()

{

  app.ShowPopup( app.GetLastButton().myVal );

}

Does this help?

[salvatore fusto]

Dave this may be a solution but imho it is not a best practic as anomimous funcs are much more abstract.
Thanks and regardds
Salvatore

[Mark van der Velden]

Hi, I tried something similar:

 

xxxx.Button = function(parent) {

    this.parent = parent;

    this.handle = app.CreateButton(...);

 

    this.OnTouch = function() {

        "dosomething";

    }

 

    this.handle.SetOnTouch(this.OnTouch);

    this.parent.AddChild(this.handle);

}

 

This gives the same error as an anonymous function. Is this the same problem?

 

I have not found a way to have the callback live in the namespace xxx. With the info above I can work around it ;-).

 

Mark

[Steve Garman]

It is the same problem but the problem has often been described narrowly as being about anonymous functions.

In fact, DroidScript controls cannot take anything but a global function as a callback.