Not able to debug app on android device - Android Studio 2.0

There are two possibilities:

1.USB Debugging off :

• Start Developer Option of your devices
• Switch On USB Debugging

2.In Android-Studio : File -> Invalidate Caches / Restart

anyone can be useful for you.Try it

Restarting Android Studios (2.1.1) resolved this for me.

The problem is that after installing and starting to launch the app, that debugger client that AndroidStudio starts is unable to connect to the debugger server on the device. This can have many causes, see this answer and the other answer shown on this page and see if one solves the problem for you

To help figure out the problem, look at the 'Console' tab of the 'Debugger' window in AS. One of the first few lines should look like this:

$ adb shell am start -n "com.acme.audtest/com.acme.AudTest" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER -D

Cut and paste that line into a command prompt, REMOVE THE '-D', and execute it. It your app ('AudTest') comes up without error, the problem is in AS, is communication to the device, or the configuration of the device. If the app doesn't start, it is in the .apk. (Not the complete solution, but starts to point you in the right direction -- for which of the solutions below applies to your situation.)

First I select the second option, and it worked fine. But then don't know why I change to select first option. So, the debugger shows the message Waiting for application to come online forever. And I did not notice that, just thought another app prevent me debug or that was an issue with Android Studio 2.0.

So, just check to second option will solve my issue. Thank all.