public class MainActivity extends AppCompatActivity  implements Listener,
NFCReadFragment.OnDataPass {

private Button mBtRead;
private NFCReadFragment mNfcReadFragment;
public static final String TAG = MainActivity.class.getSimpleName();
private boolean isDialogDisplayed = false;
private boolean isWrite = false;
private NfcAdapter mNfcAdapter;

PendingIntent pendingIntent;
IntentFilter writeTagFilters[];

Context context;
LinearLayout llMain;

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

    initViews();
    initNFC();
    initViews();
}

private void initViews() {
    mBtRead = (Button) findViewById(R.id.button);
    mBtRead.setOnClickListener(view -> showReadFragment());
}

private void initNFC(){
    mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
}

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

public void transfToData(byte[][] buf){
    Intent intent = new Intent(MainActivity.this, Tabs.class);
    intent.putExtra("record_ndef", buf);

    startActivity(intent);
}

private byte[][] readFromNFC(Ndef ndef) {

    try {
        ndef.connect();
        NdefMessage ndefMessage = ndef.getNdefMessage();
        byte buf[][] = new byte[ndefMessage.getRecords().length][];

        //ID[i] = GetId();
        //i++;
        String f;
        for (int i = 0; i < ndefMessage.getRecords().length; i++) {
            buf[i] = ndefMessage.getRecords()[i].getPayload();
            f = new String(buf[i]);
        }

        ndef.close();

        return buf;

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

}

private String GetId(){
    Tag myTag = (Tag) getIntent().getParcelableExtra(NfcAdapter.EXTRA_TAG);
    String ID = bytesToHexString(myTag.getId());
    return ID;
}

private String bytesToHexString(byte[] src){
    StringBuilder stringBuilder = new StringBuilder("0x");
    if(src == null || src.length <= 0){
        return null;
    }

    char[] buffer = new char[2];
    for(int i = 0; i < src.length; i++){
        buffer[0] = Character.forDigit((src[i] >>> 4) & 0x0F, 16);
        buffer[1] = Character.forDigit(src[i] & 0x0F, 16);
        System.out.println(buffer);
        stringBuilder.append(buffer);
    }

    return stringBuilder.toString();
}

@Override
public void onDataPass(byte[][] data) {
    Intent intent = new Intent(this, Tabs.class);
    intent.putExtra("record_ndef", data);
    startActivity(intent);
}

public class NFCWriteFragment extends DialogFragment {

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

public static NFCWriteFragment newInstance() {

    return new NFCWriteFragment();
}

public interface OnWriteDataPass {
    void onWriteDataPass(byte[] data);
}

OnWriteDataPass writeDataPass;

public void passWriteData(byte[] data){
    writeDataPass.onWriteDataPass(data);
}

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 = (Tabs)context;
    mListener.onDialogDisplayed();
}

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

public void onNfcDetected(Ndef ndef, byte[] messageToWrite){

    mProgress.setVisibility(View.VISIBLE);
    byte[] buf = writeToNfc(ndef,messageToWrite);
    if(buf != null){
        passWriteData(buf);
    }
    //getActivity().getFragmentManager().beginTransaction().remove(this).commit();
}

private byte[] writeToNfc(Ndef ndef, byte[] message){

    mTvMessage.setText(getString(R.string.message_write_progress));
    if (ndef != null) {
        String as = new String(message);
        NdefRecord mimeRecord = NdefRecord.createMime("text/plain", message);
        NdefRecord applicationRecord = NdefRecord.createApplicationRecord("com.learn2crack.nfc");

        try {

            ndef.connect();
            ndef.writeNdefMessage(new NdefMessage(applicationRecord , mimeRecord));
            ndef.close();
            //Write Successful
            mTvMessage.setText(getString(R.string.message_write_success));
            return message;

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

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

    }
    return null;
}
}