Using Cordova and Android Studio with emulator, event log keeps showing "Unable to open connection to: localhost/12

To fix the issue you can do I've finally have it running. I did as Simon said. I removed all the android files, component inside mac. Then I re-install it again. During installation, I picked custom installation as it detected I have a previous android sdk, avd files. Delete the files associated with it.
I have to install the sdk, avd again... but at least I got it running without having to call terminal each time I open android studio. Might not be the best solutions, (since I have to reinstall everything again) but it will do.

I hope this helps . Try deleting Android Studio default setting.
Go to users[user_name], find folder .AndroidStudio and delete it. This will reset all setting of Android Studio.

help you fix your problem All I had to do was enable Android USB Debug on my phone.
Go to Configuration > System > About the Phone (My Phone is in Portuguese, so the menu options may differ a little bit) Scroll to the bottom and tap on "Version number" around 10 times A new option called "Developer" will be available under Configuration > System. Open it Enable USB Debugging Deploy the app again

it helps some times I'm taking the first steps in android development. Started working through this guide https://developer.android.com/training/basics/firstapp/running-app and the error occurred when the program is run on the device. , I forgot. I edited /etc/hosts and commented line

I hope this helps you . I solved that problem following steps
disabling Hyper-v reinstalling HAXM