Drupal 7 | Form managed file upload image preview - forms

Question

I'm can't get to work image preview on Drupal 7 Form managed file.
I have for code like this in template.php:
function testform($form, &$form_state) {
$form = array();
$form['con_image'] = array(
'#type' => 'managed_file',
'#title' => t('Image'),
'#required' => TRUE,
'#default_value' => variable_get('con_image', ''),
'#progress_indicator' => 'bar',
'#progress_message' => 'Uploading ...',
'#upload_location' => 'public://gallery/',
'#theme' => 'test',
'#upload_validators' => array(
'file_validate_is_image' => array(),
'file_validate_extensions' => array('jpg jpeg'),
'file_validate_image_resolution' => array('6000x4000','800x600'),
'file_validate_size' => array(6 * 1024 * 1024),
),
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Add to site'),
);
return $form;
}
I call testform after checking additional conditions (like userpoints) via code
$arr = drupal_get_form('testform');
print drupal_render($arr);
The form itself is working, I'm able to add image to node (programmatically) but cannot get the preview of image during upload process. I try to use #theme but it seems doesn't work at all.
My theme function looks like this:
function theme_test($variables) {
$element = $variables['element'];
$output = '';
$base = drupal_render_children($element); // renders element as usual
if($element['fid']['#value'] != 0) {
// if image is uploaded show its thumbnail to the output HTML
$output .= '<div class="multifield-thumbnail">';
$output .= theme('image_style', array('style_name' => 'thumbnail', 'path' => file_load($element['fid']['#value'])->uri, 'getsize' => FALSE));
$output .= '</div>';
}
Any ideas?

Answer 1

You need to declare your theme with a hook_theme in your module.
function yourmodule_theme() {
return array(
'test' => array(
'render element' => 'element',
)
);
}