QuickReply Offers a Quick N-Style Android Response for Older Android Versions
Android (5.0+): With Android N, you can finally respond to notifications directly from the shadow , but most users don’t have N. For Lollipop and above users, QuickReply emulates the same feature for most notifications.
QuickReply apps use Android’s notification monitoring service to detect when a message arrives and then add their own buttons labeled Reply and Direct. The former allows you to type a response to a received message directly, while Direct allows you to choose to send from a set of ready-made responses.
The Play Store description of QuickReply lists messaging apps that should be supported, but it can also work with apps not listed. Support may also differ from phone to phone, as most phones add custom Android skins.