I have a ionic2 app to test. How can I debug it ? I try to start it in android studio but how to select the apk ? Can you help me ?
When you have the Android emulator running, ionic run android should automatically launch on you emulator. Personally I prefer to use a physical device connected over USB.
More info about starting the emulator at: https://developer.android.com/studio/run/emulator.html
tks osi yes I do it, I connect directly with “cordova run android --device” and it is work fine, maybe it is the best to debug your software 
Well there is a Chrome function called remote debugging as described in https://developers.google.com/web/tools/chrome-devtools/remote-debugging/
It allows you to inspect the app via the Chrome inspector. Saved me a lot of time debugging.
Besides if you run ionic run android -c you will see all console messages in your terminal