This can be done with android studio.
To generated a signed apk:
- Go to
build
->Generate signed Bundle/APK
- You will be ask to generate a new key or import an existing one
- Click through the dialogs until you end up with a signed APK
To sign the debug apks used for development
- Go to
file
-> Project Structure -> Modules - Select the
app
- select the
Signing config
tab. - create a new signing config referencing you key file
You can also manually re-sign the downloaded .apk file using apksigner.
apksigner sign --ks my.keystore OpenMobileNetworkToolkit.apk
where my.keystore is your java keystore.