Apply changes button in android studio is disabled(gray color)

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I have set up my project's minSdkVersion as 19 and enabled Instant Run . I have deployed the app in my device running on API 21 But the "Apply Changes" button is grayed out.When I hover over the button it says "No Active 'App' launch" although I am running the app in my device at that time .

android studio version : 2.3

gradle version gradle : 3.3

How to Enable Apply changes in android studio?

1. You must enable instant run to use it. On Windows and Linux, click File → Settings In the Settings/Preferences dialog, go to Build, Execution, Deployment → Instant Run. If you want take advantage of instant run, first run it by green play button (shift + F10).

Steps to enable Apply changes option

Step 1: Enable Instant run from Android Studio -> Preferences -> Build,Execution and Deployment ->Enable Instant Run -> Apply -> Ok.

Step 2: Check your minSdkversion should be 21 greater than that and gradle version.

Step 3: Launch your application and it will enable apply changes icon/ option. :)