How to use Google log in to log into apps without being phished?

[THX1141]

When I sign in to Google as a way to log into an app how do I know whether my Google login details are going to Google or a malicious app developer? Surely this interface wouldn't be hard to spoof?

I screenshotted an app asking for my details and I don't see any way to figure out whether it's legitimate.

 

[B. Diddy]

You may want to edit that image, or replace it, since your email address is visible.