When I click a radio button its value should display in textfield

Question

Above is the sample screenshot of my form where I would like to do is:

When I click/check on radio button "One" then its value should display in textfield of "Display".

Code:

function test_radio_menu() {
  $items['test_radio'] = array(
    'title' => 'test_radio',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('test_radio_form'),
    'access arguments' => array('access content'),
    'access callback' => TRUE,
    );
  return $items;
}

/**
* Implements hook_form().
*/

function test_radio_form($form, &$form_submit){

/* the options to display in our form radio buttons */
$options = array(
  'one' => t('One'),
   'two' => t('Two'),
);

$form['count'] = array(
  '#title' => t('Count'),
  '#type' => 'radios',
  '#options' => $options,

);

$form['display'] = array(
'#title' => t('Display'),
'#type' => 'textfield',
'#value' => ,
  );

$form['submit'] = array(
'#value' => t('PROCEED'),
'#type' => 'submit',
  );

return $form;
}

Answer 1

You should use drupal ajax form try this code

function test_radio_form($form, &$form_submit){

/* the options to display in our form radio buttons */
$options = array(
  'one' => t('One'),
   'two' => t('Two'),
);

$form['count'] = array(
  '#title' => t('Count'),
  '#type' => 'radios',
  '#options' => $options,
  '#ajax' => array(
            'callback' => 'myid_print_all_submitted_id_callback',
            'wrapper' => 'myid_print_search_idnumber_wrapper',
  ),

);

$form['display'] = array(
'#title' => t('Display'),
'#type' => 'textfield',
'#value' => isset($form_state['values']['count']) ? $form_state['values']['count'] : '',
'#prefix' => '<div id="myid_print_search_idnumber_wrapper">',
'#suffix' => '</div>',
  );

$form['submit'] = array(
'#value' => t('PROCEED'),
'#type' => 'submit',
  );

return $form;
}
function myid_print_all_submitted_id_callback($form, $form_state)
{
      return $form['display'];
}

Answer 2

it should work like this

html :

  <input type="radio" name="mode" id="radio"   class="test1" value="text" onclick="BT('#message')" />

js

function BT (id) {

    $('.Bt')..attr('id', 'your-id-value');

}