Ok! I did like Mark told me (Thanks a lot!!)
The thing is ...
i want to click on an app on a groups homepage. the link is something like "... /index.php/de/groups/1-my-group/214-planner"
i want to open this in an canvas but it opens me as if it is "embed".
i have a view.html.php under ".../apps/group/planner/groups". this view is called. Shouldn't there be something with an directory with canvas?
in the file"..../apps/group/planner/planner.xml" i defined my app as following ...

<?xml version="1.0" encoding="utf-8"?>

<social type="apps" group="group">

	<name>Planner</name>

	<element>planner</element>

	<version>1.0.0</version>

	<license>http://www.gnu.org/licenses/gpl-2.0.html GNU/GPL</license>

	<installable>true</installable>

	<core>false</core>

	<views>

		<view type="canvas">groups</view>

	</views>

....
What do i have to do, make an app under a group page appear as canvas??

Thanks Greg