In this presentation, you will learn how to add NFC tag reading to an Android app. It registers for auto-starting when the user taps a specific NDEF NFC tag with the phone. In addition, the app reads the NDEF records from the tag. Further instructions: https://www.andreasjakl.com/nfc-tags-ndef-and-android-with-kotlin/ Open source sample app: https://github.com/andijakl/NfcDemo

1. St. Pölten University of Applied SciencesSt. Pölten University of Applied Sciences
Platzhalter für möglichen
Bildeinsatz
Android and NFC / NDEF
(with Kotlin)
Andreas Jakl
Digital Healthcare
FH St. Pölten
Platzhalter für möglichen
Bildeinsatz
Version 1.2
https://www.andreasjakl.com/nfc-tags-ndef-and-android-with-kotlin/

2. NEAR FIELD COMMUNICATION
Open NFC with NDEF
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 2

3. NFC?
3
< 1 cm
(tap)
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten

4. NFC?
4
< 424 kbit / s
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten

5. NFC?
5Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten

6. NFC Modes of Operation
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 6
Peer to PeerReader / Writer Card Emulation

7. NFC Tags
7
Tag memory size:
48 byte – few kB
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten

8. NFC & NDEF Overview
8
NDEF Message
NDEF Record
(e.g., URL)
…
NDEF = NFC Data Exchange Format
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten

9. NDEF
9
Smart Poster MIME
Hand-
over
Custom Empty
Uri
Text Image vCard
Web Sms Tel
Record types
Possible payloads
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten

10. Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten
GPS
▪ Worldwide, outdoors
▪ Uni-directional
▪ Localization
Beacons
▪ Also indoors, 0-70 m
▪ Uni-directional
▪ Proximity information
NFC
▪ Contact
▪ Bi-directional
▪ Pay, Access, Trigger
Now with iPhone support!
11

11. Open Source NDEF Library
13
Reusable
NDEF
classes
Create NDEF
messages & records
(standard compliant)
Parse information
from raw byte arrays
Fully documented
Open Source LGPL License
andijakl.github.io/ndef-nfc
library development
supported by:
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten

12. Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 14
Source: O2, https://www.youtube.com/watch?v=WVhyCWO3Y0w

13. Prepare NFC Tags
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 15
NXP TagInfo
https://play.google.com/store/apps/details?id=com.nxp.taginfolite&hl=en
NXP TagWriter
https://play.google.com/store/apps/details?id=com.nxp.nfc.tagwriter&hl=en

14. Exercise: Create URL Tag (“Link”)
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 16

15. ANDROID & NFC
Reading Tags
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 17

16. Start App
▪ Get Start App
▪ Includes scrolling message logging UI
▪ Saves TextView contents
▪ https://www.andreasjakl.com/08-android-nfcdemo-start/
▪ Finished app: https://github.com/andijakl/NfcDemo
▪ Note: no NFC support in the emulator, use phone!
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 18
logMessage("Welcome", "App started")

17. Capabilities – Manifest
▪ Get access to NFC
▪ Declare hardware / software features used by apps
▪ required = true: app doesn’t work without
▪ Google Play Store filters apps
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 19
<uses-permission android:name="android.permission.NFC" />
<uses-feature android:name="android.hardware.nfc" android:required="true" />

18. NFC Support?
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 20
var nfcAdapter = NfcAdapter.getDefaultAdapter(this)
null -> no NFC hardware
nfcAdapter?.isEnabled -> false = NFC disabled in phone.
Trigger settings UI:
startActivity(new Intent(Settings.ACTION_NFC_SETTINGS))

19. Launching Apps with NFC
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 21

20. URLs on NFC Tags to Launch Apps
▪ Register app for specific URL using deep links
▪ App not installed?
▪ User gets to web site with web version + link to app store
▪ App installed?
▪ Phone launches your app
▪ URL acts as deep link to your content
▪ https://developer.android.com/training/app-links/deep-linking.html
▪ Optional: bypass user consent with app links
▪ Place verification JSON on web server
▪ https://developer.android.com/training/app-links/verify-site-associations.html
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 22

21. Launch App Through NFC
▪ Add intent filter to Manifest for activity
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 23
<intent-filter>
<action android:name="android.nfc.action.NDEF_DISCOVERED"/>
<!-- Default category is required for the intent filter to work -->
<category android:name="android.intent.category.DEFAULT"/>
<category android:name="android.intent.category.BROWSABLE" />
<!-- Intent filters without data will never be triggered on NFC devices.
Always define the specific data you expect to be present. -->
<data android:scheme="https" android:host="www.andreasjakl.com" />
<!-- Additionally support http scheme. See:
https://developer.android.com/training/app-links/verify-site-associations.html -->
<data android:scheme="http" />
</intent-filter>
<activity android:name=".MainActivity"
android:launchMode="singleTop">
…

22. NFC / NDEF Intent
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 24
Intent
Action:
NfcAdapter.ACTION_NDEF_DISCOVERED
Parcelable Array Extra:
Raw NDEF message
NDEF Message
NDEF Record
(e.g., URL)
…

23. Receiving Intents
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 25
ActivityonCreate()
onNewIntent()
New instance of activity.
Access intent through activity’s property.
Activity is already open.
Configure activity in manifest – sends intent
to existing activity, doesn’t launch a new instance:
android:launchMode="singleTop"
Intent

24. App Started from NFC?
▪ App started from NFC Tag?
▪ Android calls onCreate()
▪ Intent available as
property from Activity
▪ App already running in the
foreground?
▪ Android calls
onNewIntent()
▪ Intent available as
parameter
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 26
override fun onCreate(savedInstanceState: Bundle?) {
// ...
if (intent != null) {
processIntent(intent)
}
}
override fun onNewIntent(intent: Intent?) {
super.onNewIntent(intent)
if (intent != null) {
processIntent(intent)
}
}

25. private fun processIntent(checkIntent: Intent) {
// Check if intent has the action of a discovered NFC tag
// with NDEF formatted contents
if (checkIntent.action == NfcAdapter.ACTION_NDEF_DISCOVERED) {
// Retrieve the raw NDEF message from the tag
val rawMessages = checkIntent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES)
// ...
}
}
Check Intent & Retrieve NDEF Message
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 27

26. private fun processIntent(checkIntent: Intent) {
// Check if intent has the action of a discovered NFC tag
// with NDEF formatted contents
if (checkIntent.action == NfcAdapter.ACTION_NDEF_DISCOVERED) {
// Retrieve the raw NDEF message from the tag
val rawMessages = checkIntent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES)
// ...
}
}
Check Intent & Retrieve NDEF Message
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 28

27. private fun processIntent(checkIntent: Intent) {
// Check if intent has the action of a discovered NFC tag
// with NDEF formatted contents
if (checkIntent.action == NfcAdapter.ACTION_NDEF_DISCOVERED) {
// Retrieve the raw NDEF message from the tag
val rawMessages = checkIntent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES)
// ...
}
}
Check Intent & Retrieve NDEF Message
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 29
Encoded https://www. into 1 byte (0x02)
https://github.com/andijakl/ndef-
nfc/blob/master/NdefLibrary/NdefLibrary/Ndef/NdefUriRecord.cs
andreasjakl.com/contact
Check ASCII table!

28. Convert NDEF Message
▪ Extract 1st NDEF message
▪ Get first record of message
▪ Extract information
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 30
var ndefMsg = rawMessages[0] as NdefMessage
var ndefRecord = ndefMsg.records[0]
if (ndefRecord.toUri() != null) {
// Use Android functionality to convert payload to URI
logMessage("URI detected", ndefRecord.toUri().toString())
} else {
// Other NFC Tags
logMessage("Payload", ndefRecord.payload.contentToString())
}
Note: always
check for null /
array size!

29. Troubleshooting: Supported Links
▪ Check app registration
▪ Android Settings
▪ Our app: registered for links?
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 31

30. Troubleshooting: Chrome as Default
▪ Defined Chrome as default handler for
all URLs?
▪ No prompt to launch our app appears
▪ Android 8
▪ Settings > Apps & notifications >
Advanced > Default apps > Opening
links > Chrome > Other defaults: clear
defaults
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 32

31. Android Application Record
▪ Associate tag with your app
▪ 2nd NDEF record: contains package name
▪ Android launches app / opens Google Play Store
▪ https://developer.android.com/guide/topics/conn
ectivity/nfc/nfc.html#aar
▪ Include with NXP Tag Writer
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 33

32. Final App
▪ Download final app
▪ https://github.com/andijakl/NfcDemo
▪ Implements additional feature:
▪ Foreground Dispatch: gets & analyzes all
NDEF messages when the app is running in
the foreground
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 34
Screenshot shows solution app:
- App launched through NFC (NDEF_DISCOVERED in onCreate()).
- NDEF message contains 2 records: URL + Android Application Record
- While running: tapped 2nd NFC tag with different (non-subscribed) URL
- Delivered through onNewIntent() thanks to active Foreground Dispatch

33. SMART CARDS & HOST CARD
EMULATION
Low Level NFC Interaction
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 35

34. Smart Cards
▪ Interface
▪ Contact
(chip)
▪ Contactless
(eg NFC compatible)
36Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten Image credits: Maestro paypass

35. Smart Card Content
▪ Can be very powerful
▪ Microprocessor
▪ Non-volatile memory and cryptography
▪ Programmable apps (e.g. Java Card)
▪ Use cases
▪ Credit card
▪ Public transport cards
▪ Key card for doors
▪ …
37Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten
Image source: created by Dacs, WhiteTimberwolf. License: CC BY-SA 3.0
https://en.wikipedia.org/wiki/File:SmartCardPinout.svg

36. Smart Card Communication: APDU
▪ Application Protocol Data Unit
▪ Communication protocol
38
Response APDU
Status code Response data
Command APDU
Header
(Instruction code)
Parameter data
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten Image source: Google Pixel 2 Press image

37. Phone
Host Card Emulation
▪ Emulate Smart Card with app
▪ NFC reader directly communicates with app
▪ Use cases: building access, loyalty, transit, …
39Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten
NFC
Controller
Secure
Element
Host CPU
Hardware component.
SIM card or embedded
Host Card Emulation
Emulate smart card with an
app, without the need for
hardware secure element
NFC Reader

38. THANK YOU!
More information:
https://www.andreasjakl.com/nfc-tags-ndef-and-android-with-kotlin/
Native Mobile App Development | 2018 | Andreas Jakl | FH St. Pölten 40