How can i display field as hyper link in my view?In my code i added widget="url" but its not showng as link.Please help

    <?xml version="1.0" encoding="utf-8" ?>
    <openerp>
        <data>
            <record id="voip_form_view" model="ir.ui.view">
                <field name="name">Voip Details</field>
                <field name="model">filedata</field>
                <field name="arch" type="xml">
                    <form string="voip" version="7.0">
                <!--       <style> .openerp .oe_view_manager table.oe_view_manager_header { display:none } </style> -->
                       <style>.openerp .oe_application .oe_breadcrumb_title  {display:none }</style>

                        <style>.openerp .oe_view_manager table.oe_view_manager_header .oe_view_manager_buttons{display:none }</style>

        <!--                <header style="padding-left: 5px; padding-top: 60px; padding-bottom: 10px;"> -->
              <!--        <header> -->
                            <button name="get_filenames" type="object" string="List Files" />
                  <!--       </header> -->
    <!--
                        <sheet>
                        </sheet> -->
                    </form>
                </field>
            </record>

            <record id="voip_filter" model="ir.ui.view">
                <field name="name">filedata.select</field>
                <field name="model">filedata</field>
                <field name="arch" type="xml">
                    <search string="File Details">
                        <field name="file_name" string="Name"/>
                        <field name="time_created" string="Time Created"/>
                        <field name="size" string="Size"/>
                        <group expand="0" string="Group By...">
                            <filter string="Name" name="name" icon="terp-personal" domain="[]" context="{'group_by':'file_name'}"/>
                            <filter string="Time Created" icon="terp-personal" domain="[]" context="{'group_by':'time_created'}"/>
                            <filter string="Size" icon="terp-personal" domain="[]" context="{'group_by':'size'}"/>
                        </group>
                    </search>
                </field>
            </record>
     <record id="voipdata_tree_view" model="ir.ui.view">
            <field name="name">File Details</field>
            <field name="model">filedata</field>
            <field name="priority" eval="1"/>
            <field name="type">tree</field>
            <field name="arch" type="xml">
            <tree string="File Names" >
                <field name="file_name" widget='url'/>
                <field name="file_path" widget='url'/>

                <field name="time_created" string="Time Created"/>
                <field name="size" string="Size"/>
                <!--<button name="file_object" string="Download or Play" filename="file_name"/> -->
    <!--            <button name="download_file" type="object" string="Downlaod"/> -->
    <!--            <button name="play_file" type="object" string="Play or download" /> -->

            </tree>
            </field>
            </record>

            <record model="ir.actions.act_window" id="action_voipdata_form">
            <field name="name">Voip Details</field>
            <field name="res_model">filedata</field>
            <field name="view_type">tree</field>
            <field name="view_mode">tree</field>
            </record>
            <record model="ir.actions.act_window" id="action_voip_form">
                <field name="name">Voip Details</field>
                <field name="res_model">filedata</field>
                <field name="view_type">form</field>
                <field name="view_mode">form</field>
                <field name="view_id" ref="voip_form_view"/>
            </record>
      <menuitem name="Voip" parent="base.menu_reporting" id="voip_menu_mainform"/>
            <menuitem name="Voip" parent="voip_menu_mainform" id="voip_menu_subform" action="action_voip_form"/>
        </data>
    </openerp>


class filedata(osv.osv):
    _name = 'filedata'
    _log_access = False
    _columns = {
        'file_name' : fields.char('Name'),
        'file_path' : fields.char('File Path'),
        'time_created' : fields.datetime('Date Time'),
        'size' : fields.char('Size')
    }