Total NOOB: Call URL from button on Toolbar

I need to call a URL when user clicks a button on the tooldbar The URL will print the selected grid row and redirect to a pdf

/wTxnMgr?task=Print&txnlogid=<datastore.txnlogid>

Ext.define('TxnLog.view.vtxnlog', {

extend: 'Ext.grid.Panel',

....

this.dockedItems = [{

xtype: 'toolbar',

dock: 'top',

items: [{

iconCls: 'icon-print',

text: 'Print',

disabled: false,

itemId: 'btnPrint',

scope: this,

handler: this.onPrintClick

Total NOOB: Call URL from button on Toolbar