Use Media upload in custom widget on wordpress 3.5

I’m creating a small widget for wordpress 3.5 that allows you to upload images.

The widget is loaded correctly by wordpress. When I add the widget to a sidebar upload button does not work. If I update the page of keeping my widget in the sidebar, button works and I can load and save the image correctly.

To build the widget I was inspired by these links:

https://stackoverflow.com/questions/13863087/wordpress-custom-widget-image-upload

https://stackoverflow.com/questions/13847714/wordpress-3-5-custom-media-upload-for-your-theme-options/13901303#13901303

My widget Code:

<?php

add_action('widgets_init', 'ctUp_ads_widget');
function ctUp_ads_widget() {
    register_widget( 'ctUp_ads' );
}

function ctUp_wdScript(){
  wp_enqueue_media();
  wp_enqueue_script('adsScript', get_template_directory_uri() . '/js/ads.js');
}
add_action('admin_enqueue_scripts', 'ctUp_wdScript');

class ctUp_ads extends WP_Widget{

    function ctUp_ads() {
        $widget_ops = array( 'classname' => 'ctUp-ads' );
        $control_ops = array( 'width' => 250, 'height' => 350, 'id_base' => 'ctUp-ads-widget' );
        $this->WP_Widget( 'ctUp-ads-widget',THEMENAME .' - Ads', $widget_ops, $control_ops );
    }

    public function widget($args, $instance){ 
        extract( $args );   
    ?>
    <a href="#"><img src="<?php echo esc_url($instance['image_uri']); ?>" /></a>
    <?php }

    function update($new_instance, $old_instance) {
        $instance = $old_instance;
        $instance['text'] = strip_tags( $new_instance['text'] );
        $instance['image_uri'] = strip_tags( $new_instance['image_uri'] );
        return $instance;
    }

  public function form($instance){ ?>
    <p>
      <label for="<?php echo $this->get_field_id('text'); ?>"><?php _e('Text', THEMENAME); ?></label><br />
      <input type="text" name="<?php echo $this->get_field_name('text'); ?>" id="<?php echo $this->get_field_id('text'); ?>" value="<?php echo $instance['text']; ?>" class="widefat" />
    </p>
    <p>
      <label for="<?php echo $this->get_field_id('image_uri'); ?>">Image</label><br />
        <img class="custom_media_image" src="<?php if(!empty($instance['image_uri'])){echo $instance['image_uri'];} ?>" style="margin:0;padding:0;max-width:100px;float:left;display:inline-block" />
        <input type="text" class="widefat custom_media_url" name="<?php echo $this->get_field_name('image_uri'); ?>" id="<?php echo $this->get_field_id('image_uri'); ?>" value="<?php echo $instance['image_uri']; ?>">
        <a href="#" class="button custom_media_upload"><?php _e('Upload', THEMENAME); ?></a>
    </p>
    <?php
  }


}

Js code:

jQuery(function($){
    $('.custom_media_upload').click(function(e) {
        e.preventDefault();
        var custom_uploader = wp.media({
            title: 'Custom Title',
            button: {
                text: 'Custom Button Text',
            },
            multiple: false  // Set this to true to allow multiple files to be selected
        })
        .on('select', function() {
            var attachment = custom_uploader.state().get('selection').first().toJSON();
            $('.custom_media_image').attr('src', attachment.url);
            $('.custom_media_url').val(attachment.url);
            $('.custom_media_id').val(attachment.id);
        })
        .open();
    });
});

Thanks in advance for help!