How do I call the getInputHtml() method of a custom fieldtype plugin from another plugin?
The problem as I see it is that the call is happening on the front-end. Because of this, the template renderer is not looking for the template at plugin1/templates/_field/input as it normally would, but at plugin1/_field/input, which explains the error message.

If Plugin 1 is your own plugin then you should be able to include the templates part of the path in the render call, for example:

return craft()-&gt;templates-&gt;render('templates/_field/input');


I haven't tested this but I think it should work. 

Alternatively, and I would recommend this, since this is a front-end call, you could create your own function getFrontEndInputHtml() to return the html appropriately.