Android NFC传输联系人VCF

import android.app.Activity;
import android.content.ContentResolver;
import android.content.Context;
import android.net.Uri;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.NfcEvent;
import android.provider.ContactsContract.Contacts;
import android.provider.ContactsContract.Profile;
import android.util.Log;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

/**
* This class implements sharing the currently displayed
* contact to another device using NFC. NFC sharing is only
* enabled when the activity is in the foreground and resumed.
* When an NFC link is established, {@link #createMessage}
* will be called to create the data to be sent over the link,
* which is a vCard in this case.
*/
public class NfcHandler implements NfcAdapter.CreateNdefMessageCallback {

private static final String TAG = "ContactNfcHandler";
private static final String PROFILE_LOOKUP_KEY = "profile";
private final Context mContext;
private final Uri mContactUri;

/* Register NFC handler. This should be called in activities' onCreate(), or similar methods */
public static void register(Activity activity, Uri contactUri) {
NfcAdapter adapter = NfcAdapter.getDefaultAdapter(activity.getApplicationContext());
if (adapter == null) {
return;  // NFC not available on this device
}
adapter.setNdefPushMessageCallback(new NfcHandler(activity, contactUri), activity);
}

public NfcHandler(Context context, Uri contactUri) {
mContext = context;
mContactUri = contactUri;
}

@Override
public NdefMessage createNdefMessage(NfcEvent event) {
ContentResolver resolver = mContext.getContentResolver();
if (mContactUri != null) {
final String lookupKey = Uri.encode(mContactUri.getPathSegments().get(2));
final Uri shareUri;
// TODO find out where to get this constant from, or find another way
// of determining this.
if (lookupKey.equals(PROFILE_LOOKUP_KEY)) {
shareUri = Profile.CONTENT_VCARD_URI.buildUpon().
appendQueryParameter(Contacts.QUERY_PARAMETER_VCARD_NO_PHOTO, "true").
build();
} else {
shareUri = Contacts.CONTENT_VCARD_URI.buildUpon().
appendPath(lookupKey).
appendQueryParameter(Contacts.QUERY_PARAMETER_VCARD_NO_PHOTO, "true").
build();
}
ByteArrayOutputStream ndefBytes = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int r;
try {
InputStream vcardInputStream = resolver.openInputStream(shareUri);
while ((r = vcardInputStream.read(buffer)) > 0) {
ndefBytes.write(buffer, 0, r);
}

NdefRecord record = NdefRecord.createMime("text/x-vcard", ndefBytes.toByteArray());
return new NdefMessage(record);
} catch (IOException e) {
Log.e(TAG, "IOException creating vcard.");
return null;
}
} else {
Log.w(TAG, "No contact URI to share.");
return null;
}
}
}

NfcHandler.register(this, mLookupUri);