I had the same problem just now and found the solution so I'm sharing it here. I hope it's not too late.
First to be able to use WP Add Media button you would have to enqueue the needed script. This is easy, just call the wp_enqueue_media() function like so:
add_action('admin_enqueue_scripts', 'enqueue_scripts_styles_admin');
function enqueue_scripts_styles_admin(){
wp_enqueue_media();
}
This call ensures you have the needed libraries to use the WP Media button.
Of course you should also have the HTML elements to hold the uploaded/selected media file URL, something like this:
<input type="text" class="selected_image" />
<input type="button" class="upload_image_button" value="Upload Image">
The first text field will hold the URL of the media file while the second is a button to open the media popup window itself.
Then in your jscript, you'd have something like this:
var custom_uploader;
$('.upload_image_button').click(function(e) {
e.preventDefault();
var $upload_button = $(this);
//Extend the wp.media object
custom_uploader = wp.media.frames.file_frame = wp.media({
title: 'Choose Image',
button: {
text: 'Choose Image'
},
multiple: false
});
//When a file is selected, grab the URL and set it as the text field's value
custom_uploader.on('select', function() {
var attachment = custom_uploader.state().get('selection').first().toJSON();
$upload_button.siblings('input[type="text"]').val(attachment.url);
});
//Open the uploader dialog
custom_uploader.open();
});
Now I'm not going to explain every line because it's not that hard to understand. The most important part is the one that uses the wp object to make all these to work.
The tricky part is making all these work on a TinyMCE popup(which is the problem I faced). I've searched hi and lo for the solution and here's what worked for me. But before that, I'll talk about what problem I encountered first. When I first tried to implement this, I encountered the "WP is undefined" problem on the popup itself. To solve this, you just have to pass the WP object to the script like so:
(function() {
tinymce.create('tinymce.plugins.someplugin', {
init : function(ed, url) {
// Register commands
ed.addCommand('mcebutton', function() {
ed.windowManager.open(
{
file : url + '/editor_button.php', // file that contains HTML for our modal window
width : 800 + parseInt(ed.getLang('button.delta_width', 0)), // size of our window
height : 600 + parseInt(ed.getLang('button.delta_height', 0)), // size of our window
inline : 1
},
{
plugin_url : url,
wp: wp
}
);
});
// Register buttons
ed.addButton('someplugin_button', {title : 'Insert Seomthing', cmd : 'mcebutton', image: url + '/images/some_button.gif' });
}
});
// Register plugin
// first parameter is the button ID and must match ID elsewhere
// second parameter must match the first parameter of the tinymce.create() function above
tinymce.PluginManager.add('someplugin_button', tinymce.plugins.someplugin);
})();
What we're interested in is this line => "wp: wp" . This line ensures that we are passing the wp object to the popup window (an iframe really...) that is to be opened when we click the tinymce button. You can actually pass anything to the popup window via this object (the 2nd parameter of the ed.windowManager.open method)!
Last but not the least you'd have to reference that passed wp object on your javascript like so:
var args = top.tinymce.activeEditor.windowManager.getParams();
var wp = args.wp;
Make sure you do that before calling/using the WP object.
That's all you have to do to make this work. It worked for me, I hope it works for you :)