Android Tutorial Reading NDEF data from NFC tags

Erel · Feb 12, 2012

Using the NFC library you can read NFC tags formatted in NDEF form (NFC Data Exchange Format).
You can read more information about the internal process here: NFC Basics | Android Developers

This library requires Android version 2.3.3 or above (API level 10 or above).

Whenever an NDEF tag is read, Android sends an intent with the extracted data. You should declare that your activity wants to handle such intents.
This is done by adding "intent filters" with the manifest editor.

There are two types of data that you can handle: text data and Uri data.

When your activity receives an Intent, the activity is first created. If the activity is currently running then it will be paused and created again.

You can use code similar to the following code to test whether the starting intent is actually an Ndef intent and then extract the records (usually a single record) from the intent:

B4X:

Sub Process_Globals
   Dim NFC As NFC
End Sub

Sub Activity_Resume
   If NFC.IsNdefIntent(Activity.GetStartingIntent) Then
      Dim records As List
      records = NFC.GetNdefRecords(Activity.GetStartingIntent)
      For i = 0 To records.Size - 1
         Dim r As NdefRecord
         r = records.Get(i)
         Log(r.GetAsTextType)
      Next
   End If
End Sub

Text data
Tags with text data include a MIME field that helps the OS decide which application should handle the intent.
For example if you want to handle messages with the "text/plain" mime (with the main activity) then you should add the following code in the manifest editor:

B4X:

AddActivityText(main, <intent-filter>
    <action android:name="android.nfc.action.NDEF_DISCOVERED"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:mimeType="text/plain" />
</intent-filter>)

Note that you can add any number of intent filters.

Call NdefRecord.GetAsTextType to convert the payload to a string.

Uri data
The intent filter of Uri tags should look like:

B4X:

AddActivityText(main, <intent-filter>
    <action android:name="android.nfc.action.NDEF_DISCOVERED" />
    <category android:name="android.intent.category.DEFAULT" />
    <data android:scheme="http"
        android:host="www.b4x.com" />
</intent-filter>)

The above example will handle any Uri that points to a page starting with ht*p://www.b4x.com.

Call NdefRecord.GetAsUriType to convert the payload to the Uri.

Testing NFC tags
I recommend you to use an application such as NFC TagWriter by NXP.
It allows you to store data formatted as Ndef on many types of tags.

NFC TagInfo is also useful to find the stored data and the mime type.

The library is available here: http://www.b4x.com/forum/additional-libraries-official-updates/14933-nfc-library.html

Erel · Sep 2, 2013

You can use an app such as this one to write the data: https://play.google.com/store/apps/details?id=com.nxp.nfc.tagwriter&hl=en

According to your code in the manifest editor it should have a URL with the host: www.b4x.com

NeoTechni · Sep 2, 2013

Im not trying to make an app to write data, the app i got the data from in the link already does that. Im trying to make an app to use the data.
The url is a placeholder, just to keep the code

When i scan a tag, my app does not show up in the list of apps that can receive the data

Erel · Sep 3, 2013

Your app will only show if the data in the tag is in NDEF format and it holds a URL with www.b4x.com as the host. This is configured in the manifest file.

Try to use the app I posted above to create such a tag and test it.

NeoTechni · Sep 3, 2013

I can't create a tag, I'm trying to read the data on an existing one (it came out for a game recently)

Erel · Sep 3, 2013

You should set the correct intent filters based on the tag data. It will only work if the tag is formatted as NDEF tag.

NeoTechni · Sep 3, 2013

It is an ndef tag

ferdztech · Oct 5, 2013

How to write/store data in NFC card. which version of NFC library support write method. I need to store data .

ixdev · Jun 16, 2014

How to read UID of unformated tags like the app from nxp app?

Erel · Jun 16, 2014

The NFC only supports NDEF formatted tags.

ixdev · Jun 16, 2014

is there no way to make it read just the UID like the NFC Taginfo?

aeropic · Oct 25, 2014

I'm playing around with NFC librairy and some tags.
It's amazing how simple it is to get it working. Many thanks for this librairy !

I'm trying to use it from a locked device. I hoped that the nfc tag could be read just when switching the screen on and that the NFC intent could wake up an activity to which I would give the "setshowwhenlocked" rights with the reflection

B4X:

Sub SetShowWhenLocked
   Dim r As Reflector
   r.Target = r.GetActivity
   r.Target = r.RunMethod("getWindow")
'  r.RunMethod2("addFlags", 6815872, "java.lang.int") 'combination of: FLAG_TURN_SCREEN_ON, FLAG_DISMISS_KEYGUARD, FLAG_SHOW_WHEN_LOCKED and FLAG_KEEP_SCREEN_ON.
   r.RunMethod2("addFlags", 2621440, "java.lang.int") 'combination of: FLAG_TURN_SCREEN_ON,  FLAG_SHOW_WHEN_LOCKED (API 5)
End Sub

But this does not work

Does anybody know a way to do it ?

Thanks
Alain

Erel · Oct 26, 2014

Try the first combination instead of the second (the commented one).

Also add this line to the manifest editor:

B4X:

SetActivityAttribute(main, android:showOnLockScreen, "true")

aeropic · Oct 26, 2014

Thanks Erel for your answer.
Trying the first combination does not solve the problem
and when adding the line in the manifest I get a compile error :

B4X:

AndroidManifest.xml:22: error: No resource identifier found for attribute 'showOnLockScreen' in package 'android'

I do not know this attribute, how does it work ?

Nevertheless, I've the feeling NFC is blocked in the android system both during sleep and when screen is locked.
see http://www.androidauthority.com/galaxy-s3-i9300-nfc-lockscreen-screen-off-mod-125744/

XDA developpers have issued a mod working only on rooted phones...

The good news is that Lollipop is supposed to give more freedom to trusted devices (bluetooth but also NFC):
http://www.androidheadlines.com/201...th-nfc-nearby-automatic-device-unlocking.html

freedom2000 · Nov 22, 2014

aeropic said:
The good news is that Lollipop is supposed to give more freedom to trusted devices (bluetooth but also NFC):
http://www.androidheadlines.com/201...th-nfc-nearby-automatic-device-unlocking.html

Yes it's there now and it works very very well :

NFC trusted device
Bluetooth trusted device
trusted location
trusted face

Impressive improvment of the lock screen.

vincentehsu · Jan 7, 2015

Dear All:
I've try this code via my Samsung Galaxy Note3

B4X:

If NFC.IsNdefIntent(Activity.GetStartingIntent) Then
      Dim records As List
      records = NFC.GetNdefRecords(Activity.GetStartingIntent)
      For i = 0 To records.Size - 1
         Dim r As NdefRecord
         r = records.Get(i)
         Log(r.GetAsTextType)
      Next
   End If

Why NFC.IsNdefIntent(Activity.GetStartingIntent) always false?
I use the quick pass credit card as my nfc tag,is this an NDEF tags?

Erel · Jan 8, 2015

Probably no. You can use one of the tag writers apps from Google Play to find more details about the tag.

wildfandango · Dec 18, 2015

Erel said:
Using the NFC library you can read NFC tags formatted in NDEF form (NFC Data Exchange Format).
You can read more information about the internal process here: NFC Basics | Android Developers

This library requires Android version 2.3.3 or above (API level 10 or above).

Whenever an NDEF tag is read, Android sends an intent with the extracted data. You should declare that your activity wants to handle such intents.
This is done by adding "intent filters" with the manifest editor.

There are two types of data that you can handle: text data and Uri data.

When your activity receives an Intent, the activity is first created. If the activity is currently running then it will be paused and created again.

You can use code similar to the following code to test whether the starting intent is actually an Ndef intent and then extract the records (usually a single record) from the intent:

B4X:

Sub Process_Globals Dim NFC As NFC End Sub Sub Activity_Resume If NFC.IsNdefIntent(Activity.GetStartingIntent) Then Dim records As List records = NFC.GetNdefRecords(Activity.GetStartingIntent) For i = 0 To records.Size - 1 Dim r As NdefRecord r = records.Get(i) Log(r.GetAsTextType) Next End If End Sub

Text data
Tags with text data include a MIME field that helps the OS decide which application should handle the intent.
For example if you want to handle messages with the "text/plain" mime (with the main activity) then you should add the following code in the manifest editor:

B4X:

AddActivityText(main, <intent-filter> <action android:name="android.nfc.action.NDEF_DISCOVERED"/> <category android:name="android.intent.category.DEFAULT"/> <data android:mimeType="text/plain" /> </intent-filter>)

Note that you can add any number of intent filters.

Call NdefRecord.GetAsTextType to convert the payload to a string.

Uri data
The intent filter of Uri tags should look like:

B4X:

AddActivityText(main, <intent-filter> <action android:name="android.nfc.action.NDEF_DISCOVERED" /> <category android:name="android.intent.category.DEFAULT" /> <data android:scheme="http" android:host="www.b4x.com" /> </intent-filter>)

The above example will handle any Uri that points to a page starting with ht*p://www.b4x.com.

Call NdefRecord.GetAsUriType to convert the payload to the Uri.

Testing NFC tags
I recommend you to use an application such as NFC TagWriter by NXP.
It allows you to store data formatted as Ndef on many types of tags.

NFC TagInfo is also useful to find the stored data and the mime type.

The library is available here: http://www.b4x.com/forum/additional-libraries-official-updates/14933-nfc-library.html

Hi Erel, one more time thx in advanc for this library...

How i can define a intent to capture the intent for reading EMPTY NFC "devices"?

i have tried

B4X:

AddActivityText(main, <intent-filter>
    <action android:name="android.nfc.action.NDEF_DISCOVERED"/>
    <action android:name="android.nfc.action.TAG_DISCOVERED"/>
    <action android:name="android.nfc.action.TECH_DISCOVERED"/>
    <category android:name="android.intent.category.DEFAULT"/>
    <data android:mimeType="text/plain"/>
</intent-filter>)

but not works...

Erel · Dec 18, 2015

wildfandango said:
Hi Erel,

1. Please don't limit your questions to a specific member.
2. You should have started a new thread for this question.

The NDEF intent will not be sent for an empty tag.

kaudie · Jun 17, 2016

how can I read out the sector 0?

DonManfred · Jun 17, 2016

See post #1

Android Tutorial Reading NDEF data from NFC tags

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