Android Reading and Writing NFC Tags

October 21, 2016Raj AmalAndroid Development4

NFC (Near Field Communication) is a communication protocol which allows two devices to communicate and transfer data within a short distance. Some of the midrange to high-end Android devices has NFC support which allows you to utilize the feature.

NFC Tags are small chips which you can get in the form of stickers, cards, rings or even keychain. They can store a small amount of data in the range of hundreds of bytes. These are passive things which can work without a power supply or rely on other devices for power such as an NFC Tag depends on your Phone or the NFC readers to work.

Here I have bought a set of 5 tags for 4$ (₹250) from Amazon. The NFC tags I have can store data up to 144 bytes. There are different types of NFC tags which can store a larger amount of data.

Uses of NFC Tags

-> Read and Write a small amount of data such as URL, Contact information, etc.

-> Can be used to launch apps.

-> Can be used to unlock your device.

-> Security keys for App.

These are some of the applications. NFC Tags can have endless possibilities.

In this tutorial, we are going to make an app which can read and write text to an NFC tag.

Prerequisites

Make sure your device supports NFC. You can confirm this by Settings -> More -> NFC

Buy NFC Tags to test with our App. You can get NFC Tags from online retailers such as Amazon.

Creating Project

Here I have created an Android Studio project with package com.learn2crack.nfc also Activity as MainActivity and layout as activity_main.

Adding Permissions to Manifest

We need to add the NFC permission to Manifest to use the NFC capability.

<uses-permission android:name="android.permission.NFC" />

Adding Java 8 Support

Since we are using Java 8 Lambda functions, we need to enable Jack compiler and set compileOptions to Java version 8. Insert the snippet similar to the one defined below.

build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 25
    buildToolsVersion "25.0.0"
    defaultConfig {
        applicationId "com.learn2crack.nfc"
        minSdkVersion 19
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

        jackOptions {
            enabled true
        }
    }

    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.0.0'
    testCompile 'junit:junit:4.12'
}

Defining String constants

Instead of hard coding we define strings in res-> values-> strings.xml and refer it from this file whenever needed.

strings.xml

<resources>
    <string name="app_name">NFC</string>
    <string name="message_write_error">Error Writing Message !</string>
    <string name="message_write_success">Successfully written to Tag !</string>
    <string name="message_write_progress">Writing to Tag..</string>
    <string name="message_tag_detected">NFC Tag Detected !</string>
    <string name="message_read_tag">Read from NFC Tag</string>
    <string name="message_write_tag">Write to NFC Tag</string>
    <string name="message_tap_tag">Tap the NFC Tag to your device !</string>
    <string name="hint_message">Message</string>
</resources>

Creating Layout

Our main activity layout has an input EditText widget and two Buttons.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:gravity="center"
    tools:context="com.learn2crack.nfc.MainActivity">

    <EditText
        android:id="@+id/et_message"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="@string/hint_message"/>

    <Button
        android:id="@+id/btn_write"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/et_message"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:text="@string/message_write_tag"
        style="@style/Widget.AppCompat.Button.Colored"/>

    <Button
        android:id="@+id/btn_read"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btn_write"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:text="@string/message_read_tag"
        style="@style/Widget.AppCompat.Button.Colored"/>
</RelativeLayout>

The next layout is for write dialog which is a DialogFragment. It has two TextViews and an ImageView widget.

fragment_write.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/activity_horizontal_margin">

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:text="@string/message_write_tag"
        android:textAppearance="?android:attr/textAppearanceLarge"/>

    <ImageView
        android:id="@+id/logo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:src="@drawable/ic_nfc"
        android:tint="@color/colorAccent"/>

    <ProgressBar
        android:id="@+id/progress"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:visibility="gone"/>

    <TextView
        android:id="@+id/tv_message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:text="@string/message_tap_tag"/>

</LinearLayout>

The next layout is for read dialog which displays the contents of the NFC tag.

fragment_read.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="@dimen/activity_horizontal_margin">

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/message_read_tag"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:layout_gravity="center"/>

    <ImageView
        android:id="@+id/logo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:src="@drawable/ic_nfc"
        android:tint="@color/colorAccent"
        android:layout_gravity="center"/>

    <TextView
        android:id="@+id/tv_message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="@dimen/activity_horizontal_margin"
        android:layout_gravity="center"
        android:textAppearance="?android:attr/textAppearanceMedium"/>

</LinearLayout>

Creating Listener interface

We create a listener interface which implements two methods onDialogDisplayed() and onDialogDismissed().

Listener.java

package com.learn2crack.nfc;

public interface Listener {

    void onDialogDisplayed();

    void onDialogDismissed();
}

Creating DialogFragments

Here we override two Fragment lifecycle methods onAttach() and onDetach(). Our MainActivity implements the interface we created before. We call the listener’s onDialogDisplayed() method in onAttach() so that the MainActivity can be notified when the dialog is displayed. Similarly, onDialogDismissed() is called in onDetach() so that the MainActivity knows when the dialog is dismissed.

We define the writeToNfc() method to write data to the NFC tag. In NFCs data is written in a standardized format called NDEF (NFC Data Exchange Format). Android has inbuilt support to create and write NDEF messages. Here we are going to write a plain text message to NFC tag. So we use the MIME type text/plain. Then we create a new NdefRecord object with MIME type and text we want to write in the tag. Then we write the data using the writeNdefMessage() method.

NFCWriteFragment.java

package com.learn2crack.nfc;

import android.app.DialogFragment;
import android.content.Context;
import android.nfc.FormatException;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.tech.Ndef;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ProgressBar;
import android.widget.TextView;

import java.io.IOException;
import java.nio.charset.Charset;

public class NFCWriteFragment extends DialogFragment {

    public static final String TAG = NFCWriteFragment.class.getSimpleName();

    public static NFCWriteFragment newInstance() {

        return new NFCWriteFragment();
    }

    private TextView mTvMessage;
    private ProgressBar mProgress;
    private Listener mListener;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_write,container,false);
        initViews(view);
        return view;
    }

    private void initViews(View view) {

        mTvMessage = (TextView) view.findViewById(R.id.tv_message);
        mProgress = (ProgressBar) view.findViewById(R.id.progress);
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        mListener = (MainActivity)context;
        mListener.onDialogDisplayed();
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener.onDialogDismissed();
    }

    public void onNfcDetected(Ndef ndef, String messageToWrite){

        mProgress.setVisibility(View.VISIBLE);
        writeToNfc(ndef,messageToWrite);
    }

    private void writeToNfc(Ndef ndef, String message){

        mTvMessage.setText(getString(R.string.message_write_progress));
        if (ndef != null) {

            try {
                ndef.connect();
                NdefRecord mimeRecord = NdefRecord.createMime("text/plain", message.getBytes(Charset.forName("US-ASCII")));
                ndef.writeNdefMessage(new NdefMessage(mimeRecord));
                ndef.close();
                //Write Successful
                mTvMessage.setText(getString(R.string.message_write_success));

            } catch (IOException | FormatException e) {
                e.printStackTrace();
                mTvMessage.setText(getString(R.string.message_write_error));

            } finally {
                mProgress.setVisibility(View.GONE);
            }

        }
    }
}

Similarly for reading the message we define readFromNFC() method. We read data using getNdefMessage() method which returns NdefMessage object.

NFCReadFragment.java

package com.learn2crack.nfc;

import android.app.DialogFragment;
import android.content.Context;
import android.nfc.FormatException;
import android.nfc.NdefMessage;
import android.nfc.tech.Ndef;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.io.IOException;

public class NFCReadFragment extends DialogFragment {

    public static final String TAG = NFCReadFragment.class.getSimpleName();

    public static NFCReadFragment newInstance() {

        return new NFCReadFragment();
    }

    private TextView mTvMessage;
    private Listener mListener;

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_read,container,false);
        initViews(view);
        return view;
    }

    private void initViews(View view) {

        mTvMessage = (TextView) view.findViewById(R.id.tv_message);
    }

    @Override
    public void onAttach(Context context) {
        super.onAttach(context);
        mListener = (MainActivity)context;
        mListener.onDialogDisplayed();
    }

    @Override
    public void onDetach() {
        super.onDetach();
        mListener.onDialogDismissed();
    }

    public void onNfcDetected(Ndef ndef){

        readFromNFC(ndef);
    }

    private void readFromNFC(Ndef ndef) {

        try {
            ndef.connect();
            NdefMessage ndefMessage = ndef.getNdefMessage();
            String message = new String(ndefMessage.getRecords()[0].getPayload());
            Log.d(TAG, "readFromNFC: "+message);
            mTvMessage.setText(message);
            ndef.close();

        } catch (IOException | FormatException e) {
            e.printStackTrace();

        }
    }
}

Creating Activity

Our MainActivity is the entry point for our application. Instead of defining Intent filters for the NFC tag in Manifest we define within out Activity and use it with enableForegroundDispatch() method. We also need to pass a PendingIntent to this enableForegroundDispatch() method. We use the Intent flag as FLAG_ACTIVITY_SINGLE_TOP which makes sure if the Activity is already running it pass the data to our running Activity instead of launching a new one. This enableForegroundDispatch() method intercepts all the NFC events and makes sure our Activity is the first one to receive it. We use this in our Activity lifecycle onResume() method. Similarly, we disable using disableForegroundDispatch() method on Activity’s onPause() method.

The Activity’s newIntent() method is called on an NFC event. We obtain the Tag object from the Intent parcelable extra. We then get a Ndef object from the Tag object and pass it to the respective read or write fragment for read or write operation.

MainActivity.java

package com.learn2crack.nfc;

import android.app.PendingIntent;
import android.content.Intent;
import android.content.IntentFilter;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.nfc.tech.Ndef;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements Listener{

    public static final String TAG = MainActivity.class.getSimpleName();

    private EditText mEtMessage;
    private Button mBtWrite;
    private Button mBtRead;

    private NFCWriteFragment mNfcWriteFragment;
    private NFCReadFragment mNfcReadFragment;

    private boolean isDialogDisplayed = false;
    private boolean isWrite = false;

    private NfcAdapter mNfcAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        initViews();
        initNFC();
    }

    private void initViews() {

        mEtMessage = (EditText) findViewById(R.id.et_message);
        mBtWrite = (Button) findViewById(R.id.btn_write);
        mBtRead = (Button) findViewById(R.id.btn_read);

        mBtWrite.setOnClickListener(view -> showWriteFragment());
        mBtRead.setOnClickListener(view -> showReadFragment());
    }

    private void initNFC(){

        mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
    }

    private void showWriteFragment() {

        isWrite = true;

        mNfcWriteFragment = (NFCWriteFragment) getFragmentManager().findFragmentByTag(NFCWriteFragment.TAG);

        if (mNfcWriteFragment == null) {

            mNfcWriteFragment = NFCWriteFragment.newInstance();
        }
        mNfcWriteFragment.show(getFragmentManager(),NFCWriteFragment.TAG);

    }

    private void showReadFragment() {

        mNfcReadFragment = (NFCReadFragment) getFragmentManager().findFragmentByTag(NFCReadFragment.TAG);

        if (mNfcReadFragment == null) {

            mNfcReadFragment = NFCReadFragment.newInstance();
        }
        mNfcReadFragment.show(getFragmentManager(),NFCReadFragment.TAG);

    }

    @Override
    public void onDialogDisplayed() {

        isDialogDisplayed = true;
    }

    @Override
    public void onDialogDismissed() {

        isDialogDisplayed = false;
        isWrite = false;
    }

    @Override
    protected void onResume() {
        super.onResume();
        IntentFilter tagDetected = new IntentFilter(NfcAdapter.ACTION_TAG_DISCOVERED);
        IntentFilter ndefDetected = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
        IntentFilter techDetected = new IntentFilter(NfcAdapter.ACTION_TECH_DISCOVERED);
        IntentFilter[] nfcIntentFilter = new IntentFilter[]{techDetected,tagDetected,ndefDetected};

        PendingIntent pendingIntent = PendingIntent.getActivity(
                this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
        if(mNfcAdapter!= null)
            mNfcAdapter.enableForegroundDispatch(this, pendingIntent, nfcIntentFilter, null);

    }

    @Override
    protected void onPause() {
        super.onPause();
        if(mNfcAdapter!= null)
            mNfcAdapter.disableForegroundDispatch(this);
    }

    @Override
    protected void onNewIntent(Intent intent) {
        Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);

        Log.d(TAG, "onNewIntent: "+intent.getAction());

        if(tag != null) {
            Toast.makeText(this, getString(R.string.message_tag_detected), Toast.LENGTH_SHORT).show();
            Ndef ndef = Ndef.get(tag);

            if (isDialogDisplayed) {

                if (isWrite) {

                    String messageToWrite = mEtMessage.getText().toString();
                    mNfcWriteFragment = (NFCWriteFragment) getFragmentManager().findFragmentByTag(NFCWriteFragment.TAG);
                    mNfcWriteFragment.onNfcDetected(ndef,messageToWrite);

                } else {

                    mNfcReadFragment = (NFCReadFragment)getFragmentManager().findFragmentByTag(NFCReadFragment.TAG);
                    mNfcReadFragment.onNfcDetected(ndef);
                }
            }
        }
    }
}

This program will not work on a virtual device. Make sure you test it on a physical device with NFC.

Demo Video

Screenshots

Complete Project Files

You can download the complete project as zip or fork from our Github repository.

Download (Github)

Download

Fork

This is just the intro tutorial. NFC has enormous potential and a ton of applications. You can expect more tutorials on NFC from us.

Stay tuned!

Enjoy coding 🙂

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Viswanath Tippi
Excellent Info & very useful information for new learner on NFC !!! Thanks a lot. 1000 likes for my side
- Raj Amal
  Welcome
Ash Hickey
very good information indeed… I’m noobies btw.. haha.. just want to ask you one question.. How can I pass/intent the value/data/object i got from NFC tag to another screen/activity or in MainActivity if referring from your code.. Thanks in advance for guidance
ZELKAMEL1
Does this work with these tags : https://www.amazon.co.uk/protection-NTAG216-Semiconductors-Verification-NFC-enabled/dp/B01DMZPUOK/ref=sr_1_5?rps=1&ie=UTF8&qid=1491348975&sr=8-5&keywords=nfc+tag

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