前言

       最近沒怎麼寫東西了，主要是在瞭解Beam這個東東。找到一些高手寫的文章，奈何水平有限看的雲裡霧裡的。沒辦法，只好去複習官方文件。

正文： 

先摘取一部分官方文件：

Beaming NDEF Messages to Other Devices

Android Beam allows simple peer-to-peer data exchange between two Android-powered devices. The application that wants to beam data to another device must be in the foreground and the device receiving the data must not be locked. When the beaming device comes in close enough contact with a receiving device, the beaming device displays the "Touch to Beam" UI. The user can then choose whether or not to beam the message to the receiving device.

Note: Foreground NDEF pushing was available at API level 10, which provides similar functionality to Android Beam. These APIs have since been deprecated, but are available to support older devices. See for more information.

You can enable Android Beam for your application by calling one of the two methods:

• : Accepts an  to set as the message to beam. Automatically beams the message when two devices are in close enough proximity.
• : Accepts a callback that contains a  which is called when a device is in range to beam data to. The callback lets you create the NDEF message only when necessary.

An activity can only push one NDEF message at a time, so  takes precedence over  if both are set. To use Android Beam, the following general guidelines must be met:

• The activity that is beaming the data must be in the foreground. Both devices must have their screens unlocked.
• You must encapsulate the data that you are beaming in an  object.
• The NFC device that is receiving the beamed data must support the com.android.npp NDEF push protocol or NFC Forum's SNEP (Simple NDEF Exchange Protocol). The com.android.npp protocol is required for devices on API level 9 (Android 2.3) to API level 13 (Android 3.2). com.android.npp and SNEP are both required on API level 14 (Android 4.0) and later.

Note: If your activity enables Android Beam and is in the foreground, the standard intent dispatch system is disabled. However, if your activity also enables foreground dispatching, then it can still scan tags that match the intent filters set in the foreground dispatching.

To enable Android Beam:

1. Create an  that contains the s that you want to push onto the other device.
2. Call  with a  or call  passing in a object in the onCreate() method of your activity. These methods require at least one activity that you want to enable with Android Beam, along with an optional list of other activities to activate.

   In general, you normally use  if your Activity only needs to push the same NDEF message at all times, when two devices are in range to communicate. You use when your application cares about the current context of the application and wants to push an NDEF message depending on what the user is doing in your application.

主要是理解上面這部分東西，多看即便會有不一樣的感覺。

下面是我按照官方的例子調試出來的一篇Beam程式碼，功能和官方的一樣。我還在完善，先貼出來，以後更新。

package com.example.beamtest;
/**
 * Time: 2012.8.11
 * Author: kehr
 * Aim: Test Android beam
 */
import java.nio.charset.Charset;

import android.app.Activity;
import android.content.Intent;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.NfcAdapter.CreateNdefMessageCallback;
import android.nfc.NfcEvent;
import android.os.Bundle;
import android.os.Parcelable;
import android.view.Window;
import android.view.WindowManager;
import android.widget.EditText;
import android.widget.Toast;

public class Beam extends Activity implements CreateNdefMessageCallback {

	NfcAdapter mNfcAdapter;
	// TextView mEditText;
	EditText mEditText;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		// TODO Auto-generated method stub
		super.onCreate(savedInstanceState);
		// fullscreen
		getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
				WindowManager.LayoutParams.FLAG_FULLSCREEN);
		// no title
		requestWindowFeature(Window.FEATURE_NO_TITLE);

		setContentView(R.layout.beam_layout);
		mEditText = (EditText) findViewById(R.id.beam_input_EditText);
		// 檢測裝置是否支援NFC
		mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
		if (mNfcAdapter == null) {
			Toast.makeText(this, "你的裝置不支援", Toast.LENGTH_LONG).show();

			// 檢測NFC是否開啟
		} else if (mNfcAdapter.isEnabled()) {

			Toast.makeText(this, "NFC開啟！", Toast.LENGTH_LONG).show();
		} else {

			Toast.makeText(this, "NFC未開啟！請手動設定～", Toast.LENGTH_LONG).show();
		}

		// 註冊回撥函式
		mNfcAdapter.setNdefPushMessageCallback(this, this);
	}

	// 傳送訊息-------------------------------------------------------------------------
	// 這是CreateNdefMessageCallback中需要實現的方法
	@Override
	public NdefMessage createNdefMessage(NfcEvent event) {
		// TODO Auto-generated method stub
		// 獲取文字框中的內容
		String text = mEditText.getText().toString();
		NdefMessage msg = new NdefMessage(new NdefRecord[] { createMimeRecord(
				"application/com.example.android.beam", text.getBytes()) });
		return msg;
	}

	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;
	}

	// 訊息傳送完成的處理------------------------------------------------
         //------------不是主要功能，官方例子裡面有，我給去掉了----------------待實現……
	// 處理接收的訊息----------------------------------------------------------------------
	// 第一步，接收Intent
	@Override
	protected void onNewIntent(Intent intent) {
		// super.onNewIntent(intent);

		setIntent(intent);
	}

	// 第二步，判斷Intent
	@Override
	protected void onResume() {
		// TODO Auto-generated method stub
		super.onResume();
		if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(getIntent().getAction())) {
			processIntent(getIntent());
		}
	}

	// 第三步。處理Intent
	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
		mEditText.setText(new String(msg.getRecords()[0].getPayload()));
	}

}

上面這是Beam實現的主程式碼，執行起來還需要一些其它的配置。

如果需要完整的工程檔案，請留言聯絡我。