Android NFC开发实战 Android开发技术

  对于Android 4.0 SDK中提供的Beam例子，对于NFC开发来说的确是一个不错的模板。对于了解NFC的NDEF消息处理过程不妨看下面的代码。

public class Beam extends Activity implements CreateNdefMessageCallback,
        OnNdefPushCompleteCallback {
    NfcAdapter mNfcAdapter;
    TextView mInfoText;
    private static final int MESSAGE_SENT = 1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mInfoText = (TextView) findViewById(R.id.textView);

        mNfcAdapter = NfcAdapter.getDefaultAdapter(this);  //实例化NFC设备
        if (mNfcAdapter == null) {
            mInfoText = (TextView) findViewById(R.id.textView);
            mInfoText.setText("NFC is not available on this device.");
        }

        mNfcAdapter.setNdefPushMessageCallback(this, this); //注册NDEF回调消息
        mNfcAdapter.setOnNdefPushCompleteCallback(this, this);
    }

    @Override
    public NdefMessage createNdefMessage(NfcEvent event) {
        Time time = new Time();
        time.setToNow();
        String text = ("Beam me up!\n\n" +
                "Beam Time: " + time.format("%H:%M:%S"));
        NdefMessage msg = new NdefMessage(
                new NdefRecord[] { createMimeRecord(
                        "application/com.example.android.beam", text.getBytes())
        });
        return msg;
    }

    @Override
    public void onNdefPushComplete(NfcEvent arg0) {
        // A handler is needed to send messages to the activity when this
        // callback occurs, because it happens from a binder thread
        mHandler.obtainMessage(MESSAGE_SENT).sendToTarget();
    }

    private final Handler mHandler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
            case MESSAGE_SENT:
                Toast.makeText(getApplicationContext(), "Message sent!", Toast.LENGTH_LONG).show();
                break;
            }
        }
    };

    @Override
    public void onResume() {
        super.onResume();
        if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(getIntent().getAction())) {
            processIntent(getIntent());
        }
    }

    @Override
    public void onNewIntent(Intent intent) {
        // onResume gets called after this to handle the intent
        setIntent(intent);
    }

    /**
     * Parses the NDEF Message from the intent and prints to the TextView
     */
    void processIntent(Intent intent) {
        Parcelable[] rawMsgs = intent.getParcelableArrayExtra(
                NfcAdapter.EXTRA_NDEF_MESSAGES);
        // only one message sent during the beam
        NdefMessage msg = (NdefMessage) rawMsgs[0];
        // record 0 contains the MIME type, record 1 is the AAR, if present
        mInfoText.setText(new String(msg.getRecords()[0].getPayload()));
    }

    /**
     * Creates a custom MIME type encapsulated in an NDEF record
     *
     * @param mimeType
     */
    public NdefRecord createMimeRecord(String mimeType, byte[] payload) {
        byte[] mimeBytes = mimeType.getBytes(Charset.forName("US-ASCII"));
        NdefRecord mimeRecord = new NdefRecord(
                NdefRecord.TNF_MIME_MEDIA, mimeBytes, new byte[0], payload);
        return mimeRecord;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // If NFC is not available, we won’t be needing this menu
        if (mNfcAdapter == null) {
            return super.onCreateOptionsMenu(menu);
        }
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.options, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.menu_settings:
                Intent intent = new Intent(Settings.ACTION_NFCSHARING_SETTINGS);
                startActivity(intent);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}