sencha touch prompt issue

I try to create a prompt dialog in the following manner:

Ext.Msg.prompt('Add item',
   'Add an i开发者_运维知识库tem to this list:',
    function(btn, text){
      if(btn == 'ok'){
        //do stuff...
      }
    },
    null, false, 'foo', null); 

Unfortunately this gives me an empty prompt box (no possibility of entering text, and the default value 'foo' does not appear in the text field).

What am I doing wrong? (tested on chromium and an android 2.1 phone).

Cheers

Probably Sencha bug

Instead of promptConfig set to null, try to set maxlength property in it

Example:

Ext.Msg.prompt('Add item', 
'Add an item to this list:',
    function(btn, text){
         if(btn == 'ok'){
             //do stuff...
         }
    },
this, false, 'foo', {maxlength: 100});

Works in Chrome 15