Add “upload media” button in meta box field

See this media uploader skeleton. You can also use it in your custom markup, like Meta Box.

A hint, check, that you only use the scripts on the page, where you active your Meta Box. Otherwise is it often a problem on the default pages and the uploader.

Now a attempt to clear the important parts to include the uploader to your custom part.

First include an button in the meta box:

<input id="upload_image" type="text" size="36" name="upload_image" value="" />
<input id="upload_image_button" type="button" value="Upload Image" />

Now enqueue the scripts:

function my_admin_scripts() {    
    wp_enqueue_script('media-upload');
    wp_enqueue_script('thickbox');
    wp_register_script('my-upload', WP_PLUGIN_URL.'/my-script.js', array('jquery','media-upload','thickbox'));
    wp_enqueue_script('my-upload');
}

function my_admin_styles() {

    wp_enqueue_style('thickbox');
}

// better use get_current_screen(); or the global $current_screen
if (isset($_GET['page']) && $_GET['page'] == 'my_plugin_page') {

    add_action('admin_print_scripts', 'my_admin_scripts');
    add_action('admin_print_styles', 'my_admin_styles');
}

The last part is your custom script to use the thickbox and the uploader inside this.

jQuery(document).ready( function( $ ) {

    $('#upload_image_button').click(function() {

        formfield = $('#upload_image').attr('name');
        tb_show( '', 'media-upload.php?type=image&TB_iframe=true' );
        window.send_to_editor = function(html) {
           imgurl = $(html).attr('src');
           $('#upload_image').val(imgurl);
           tb_remove();
        }

        return false;
    });

});