what is activity https://www.runoob.com/android/android-acitivities.html
Chinese tutoral https://www.jianshu.com/p/a27f3ca027e3
https://www.youtube.com/watch?v=Fz_GT7VGGaQ
BluetoothDevice https://developer.android.com/reference/android/bluetooth/BluetoothDevice
scanResult https://developer.android.com/reference/android/bluetooth/le/ScanResult#getDevice()
Bluetooth Chat example https://github.com/android/connectivity-samples/tree/master/BluetoothChat/#readme\
some odd examples https://github.com/search?q=Android-BLE-Connect-Example
https://github.com/joelwass/Android-BLE-Scan-Example
https://github.com/adafruit/Bluefruit_LE_Connect_Android_v2