This is from android pos sdk manual in the signature apk file step.
I need to
1.include android:shareUserId="android.uid.system" in Androidmanifest
2.use signature tools to sign apk file
java -jar signapk.jar platform.x509.pem platform.pk8 unsigned.apk signed.apk
(*unsigned.apk = my unsigned app)
I create b4a library from android pos sdk and use in my b4a app.
My android pos device is android 5.1.1