android NFC开发

先说说NFC开发总结，看了几天NFC开发资料，搜集了不少关于这方面的资料、demo、以及他人的总结。以下有部分是摘录总结的。因为要是现在总结也是那些，最后附送代码。关于demo我也有，有需要在评论去发邮箱给我。

一、NFC的配置总结

第一：屏幕没有锁住 。     第二：NFC功能已经在设置中打开
当系统检测到一个NFC标签的时候，他会自动去寻找最合适的activity去处理这个intent.
NFC发出的这个Intent将会有三种action:
ACTION_NDEF_DISCOVERED:当系统检测到tag中含有NDEF格式的数据时，且系统中有activity声明可以接受包含NDEF数据的Intent的时候，系统会优先发出这个action的intent。

ACTION_TECH_DISCOVERED：当没有任何一个activity声明自己可以响应ACTION_NDEF_DISCOVERED时，系统会尝试发出TECH的intent.即便你的tag中所包含的数据是NDEF的，但是如果这个数据的MIMEtype或URI不能和任何一个activity所声明的想吻合，系统也一样会尝试发出tech格式的intent，而不是NDEF.

ACTION_TAG_DISCOVERED:当系统发现前两个intent在系统中无人会接受的时候，就只好发这个默认的TAG类型的

二、NFC相关androidManifest文件设置

首先是权限：
<uses-permissionandroid:name="android.permission.NFC"/>

然后是sdk级别限制：我个人建议API11开始比较合适：
<uses-sdkandroid:minSdkVersion="11"/>

如果是API8，在代码中，nfc功能设置的代码会出错，要抛出
例如：
  NfcAdapter mAdapter = NfcAdapter.getDefaultAdapter(this);
  mAdapter.isEnabled()

接着是特殊功能限制：
<uses-featureandroid:name="android.hardware.nfc"android:required="true"/>这个生命可以让你的应用在googleplay上被声明使用者必须拥有nfc功能。

三、NFC标签过滤，也在androidManifest文件设置

在activity的intent过滤xml声明中，你可以同时声明过滤这三种action.但是由之前所说，你应该知道系统在发送intent的时候是有优先级的，所以你最好清楚自己最想处理哪个。

1：过滤ACTION_TAG_DISCOVERED:

    <intent-filter>
        <action android:name="android.nfc.action.TAG_DISCOVERED"/>
        <category android:name="android.intent.category.DEFAULT"/>
    </intent-filter>

这个最简单，也是最后一个被尝试接受intent的选项。

2：过滤ACTION_NDEF_DISCOVERED:

<intent-filter> 
<action android:name="android.nfc.action.NDEF_DISCOVERED"/> 
<category android:name="android.intent.category.DEFAULT"/> 
<data android:mimeType="text/plain" />
 </intent-filter>

其中最重要的应该算是data的mimeType类型了，这个定义的越准确，intent指向你这个activity的成功率就越高，否则系统可能不会发出你想要的NDEF intent了。下面在讲如何使用NDEF写入NFC标签的时候会多举几个类型的例子。

3:过滤ACTION_TECH_DISCOVERED:

你首先需要在你的<project-path>/res/xml下面创建一个过滤规则文件。名字任取，比如可以叫做nfc_tech_filter.xml。这个里面定义的是nfc实现的各种标准，每一个nfc卡都会符合多个不同的标准，个人理解为这些标准有些相互之间也是兼容的。你可以在检测到nfc标签后使用getTechList()方法来查看你所检测的tag到底支持哪些nfc标准。
一个nfc_tech_filter.xml中可以定义多个<tech-list>结构组。

<span style="font-size:18px;"><resources xmlns:xliff="urn:oasis:names:tc:xliff:documen</span>t:1.2">
<tech-list> 
<tech>
android.nfc.tech.IsoDep</tech>
 <tech>android.nfc.tech.NfcA</tech> 
  <tech>android.nfc.tech.NfcB</tech> 
<tech>android.nfc.tech.NfcF</tech> 
</tech-list>
<tech-list>
<tech>android.nfc.tech.NfcV</tech> 
<tech>android.nfc.tech.Ndef</tech> 
<tech>android.nfc.tech.NdefFormatable</tech>
 <tech>android.nfc.tech.MifareClassic</tech> 
<tech>android.nfc.tech.MifareUltralight</tech>
 </tech-list> 
</resources>

在androidManifest文件中声明xml过滤的举例如下：

<activity> 
 <intent-filter> 
<action android:name="android.nfc.action.TECH_DISCOVERED"/> 
</intent-filter> 
<meta-data android:name="android.nfc.action.TECH_DISCOVERED"      
android:resource="@xml/nfc_tech_filter" />
 </activity>

四、看具体代码：

1、主要代码实现如下：

package org.reno.Beam;

import java.io.ByteArrayOutputStream;
import java.nio.charset.Charset;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.Locale;
import org.nfc.read.ParsedNdefRecord;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.PendingIntent;
import android.content.DialogInterface;
import android.content.Intent;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.nfc.tech.MifareClassic;
import android.nfc.tech.MifareUltralight;
import android.os.Bundle;
import android.os.Parcelable;
import android.provider.Settings;
import android.widget.TextView;

public class MainActivity extends Activity {
	private static final DateFormat TIME_FORMAT = SimpleDateFormat
			.getDateTimeInstance();
	private NfcAdapter mAdapter;
	private PendingIntent mPendingIntent;
	private NdefMessage mNdefPushMessage;
	private TextView promt;
	private AlertDialog mDialog;

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		promt = (TextView) findViewById(R.id.promt);

		resolveIntent(getIntent());

		mDialog = new AlertDialog.Builder(this).setNeutralButton("Ok", null)
				.create();
		// 获取默认的NFC控制器
		mAdapter = NfcAdapter.getDefaultAdapter(this);

		//拦截系统级的NFC扫描，例如扫描蓝牙
		mPendingIntent = PendingIntent.getActivity(this, 0, new Intent(this,
				getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
		mNdefPushMessage = new NdefMessage(new NdefRecord[] { newTextRecord("",
				Locale.ENGLISH, true) });
	}

	@Override
	protected void onResume() {
		super.onResume();
		if (mAdapter == null) {
			if (!mAdapter.isEnabled()) {
				showWirelessSettingsDialog();
			}

			showMessage(R.string.error, R.string.no_nfc);
			promt.setText("设备不支持NFC！");
			return;
		}
		if (!mAdapter.isEnabled()) {
			promt.setText("请在系统设置中先启用NFC功能！");
			return;
		}

		if (mAdapter != null) {
			//隐式启动
			mAdapter.enableForegroundDispatch(this, mPendingIntent, null, null);
			mAdapter.enableForegroundNdefPush(this, mNdefPushMessage);
		}
	}

	@Override
	protected void onPause() {
		super.onPause();
		if (mAdapter != null) {
			//隐式启动
			mAdapter.disableForegroundDispatch(this);
			mAdapter.disableForegroundNdefPush(this);
		}
	}

	//16进制字符串转换为String
	private String hexString = "0123456789ABCDEF";
	public String decode(String bytes) {
		if (bytes.length() != 30) {
			return null;
		}
		ByteArrayOutputStream baos = new ByteArrayOutputStream(
				bytes.length() / 2);
		// 将每2位16进制整数组装成一个字节
		for (int i = 0; i < bytes.length(); i += 2)
			baos.write((hexString.indexOf(bytes.charAt(i)) << 4 | hexString
					.indexOf(bytes.charAt(i + 1))));
		return new String(baos.toByteArray());
	}

	// 字符序列转换为16进制字符串
	private static String bytesToHexString(byte[] src, boolean isPrefix) {
		StringBuilder stringBuilder = new StringBuilder();
		if (isPrefix == true) {
			stringBuilder.append("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.toUpperCase(Character.forDigit(
					(src[i] >>> 4) & 0x0F, 16));
			buffer[1] = Character.toUpperCase(Character.forDigit(src[i] & 0x0F,
					16));
			System.out.println(buffer);
			stringBuilder.append(buffer);
		}
		return stringBuilder.toString();
	}

	private void showMessage(int title, int message) {
		mDialog.setTitle(title);
		mDialog.setMessage(getText(message));
		mDialog.show();
	}

	private NdefRecord newTextRecord(String text, Locale locale,
			boolean encodeInUtf8) {
		byte[] langBytes = locale.getLanguage().getBytes(
				Charset.forName("US-ASCII"));

		Charset utfEncoding = encodeInUtf8 ? Charset.forName("UTF-8") : Charset
				.forName("UTF-16");
		byte[] textBytes = text.getBytes(utfEncoding);

		int utfBit = encodeInUtf8 ? 0 : (1 << 7);
		char status = (char) (utfBit + langBytes.length);

		byte[] data = new byte[1 + langBytes.length + textBytes.length];
		data[0] = (byte) status;
		System.arraycopy(langBytes, 0, data, 1, langBytes.length);
		System.arraycopy(textBytes, 0, data, 1 + langBytes.length,
				textBytes.length);

		return new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_TEXT,
				new byte[0], data);
	}

	private void showWirelessSettingsDialog() {
		AlertDialog.Builder builder = new AlertDialog.Builder(this);
		builder.setMessage(R.string.nfc_disabled);
		builder.setPositiveButton(android.R.string.ok,
				new DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialogInterface, int i) {
						Intent intent = new Intent(
								Settings.ACTION_WIRELESS_SETTINGS);
						startActivity(intent);
					}
				});
		builder.setNegativeButton(android.R.string.cancel,
				new DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialogInterface, int i) {
						finish();
					}
				});
		builder.create().show();
		return;
	}

	//初步判断是什么类型NFC卡
	private void resolveIntent(Intent intent) {
		String action = intent.getAction();
		if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(action)
				|| NfcAdapter.ACTION_TECH_DISCOVERED.equals(action)
				|| NfcAdapter.ACTION_NDEF_DISCOVERED.equals(action)) {
			Parcelable[] rawMsgs = intent
					.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
			NdefMessage[] msgs;
			if (rawMsgs != null) {
				msgs = new NdefMessage[rawMsgs.length];
				for (int i = 0; i < rawMsgs.length; i++) {
					msgs[i] = (NdefMessage) rawMsgs[i];
				}
			} else {
				// Unknown tag type
				byte[] empty = new byte[0];
				byte[] id = intent.getByteArrayExtra(NfcAdapter.EXTRA_ID);
				Parcelable tag = intent
						.getParcelableExtra(NfcAdapter.EXTRA_TAG);
				byte[] payload = dumpTagData(tag).getBytes();
				NdefRecord record = new NdefRecord(NdefRecord.TNF_UNKNOWN,
						empty, id, payload);
				NdefMessage msg = new NdefMessage(new NdefRecord[] { record });
				msgs = new NdefMessage[] { msg };
			}
			// Setup the views
			buildTagViews(msgs);
		}
	}

	//一般公家卡，扫描的信息
	private String dumpTagData(Parcelable p) {
		StringBuilder sb = new StringBuilder();
		Tag tag = (Tag) p;
		byte[] id = tag.getId();
		sb.append("Tag ID (hex): ").append(getHex(id)).append("\n");
		sb.append("Tag ID (dec): ").append(getDec(id)).append("\n");
		sb.append("ID (reversed): ").append(getReversed(id)).append("\n");

		String prefix = "android.nfc.tech.";
		sb.append("Technologies: ");
		for (String tech : tag.getTechList()) {
			sb.append(tech.substring(prefix.length()));
			sb.append(", ");
		}
		sb.delete(sb.length() - 2, sb.length());
		for (String tech : tag.getTechList()) {
			if (tech.equals(MifareClassic.class.getName())) {
				sb.append('\n');
				MifareClassic mifareTag = MifareClassic.get(tag);
				String type = "Unknown";
				switch (mifareTag.getType()) {
				case MifareClassic.TYPE_CLASSIC:
					type = "Classic";
					break;
				case MifareClassic.TYPE_PLUS:
					type = "Plus";
					break;
				case MifareClassic.TYPE_PRO:
					type = "Pro";
					break;
				}
				sb.append("Mifare Classic type: ");
				sb.append(type);
				sb.append('\n');

				sb.append("Mifare size: ");
				sb.append(mifareTag.getSize() + " bytes");
				sb.append('\n');

				sb.append("Mifare sectors: ");
				sb.append(mifareTag.getSectorCount());
				sb.append('\n');

				sb.append("Mifare blocks: ");
				sb.append(mifareTag.getBlockCount());
			}

			if (tech.equals(MifareUltralight.class.getName())) {
				sb.append('\n');
				MifareUltralight mifareUlTag = MifareUltralight.get(tag);
				String type = "Unknown";
				switch (mifareUlTag.getType()) {
				case MifareUltralight.TYPE_ULTRALIGHT:
					type = "Ultralight";
					break;
				case MifareUltralight.TYPE_ULTRALIGHT_C:
					type = "Ultralight C";
					break;
				}
				sb.append("Mifare Ultralight type: ");
				sb.append(type);
			}
		}

		return sb.toString();
	}

	private String getHex(byte[] bytes) {
		StringBuilder sb = new StringBuilder();
		for (int i = bytes.length - 1; i >= 0; --i) {
			int b = bytes[i] & 0xff;
			if (b < 0x10)
				sb.append('0');
			sb.append(Integer.toHexString(b));
			if (i > 0) {
				sb.append(" ");
			}
		}
		return sb.toString();
	}

	private long getDec(byte[] bytes) {
		long result = 0;
		long factor = 1;
		for (int i = 0; i < bytes.length; ++i) {
			long value = bytes[i] & 0xffl;
			result += value * factor;
			factor *= 256l;
		}
		return result;
	}

	private long getReversed(byte[] bytes) {
		long result = 0;
		long factor = 1;
		for (int i = bytes.length - 1; i >= 0; --i) {
			long value = bytes[i] & 0xffl;
			result += value * factor;
			factor *= 256l;
		}
		return result;
	}

	//显示NFC扫描的数据
	private void buildTagViews(NdefMessage[] msgs) {
		if (msgs == null || msgs.length == 0) {
			return;
		}
		// Parse the first message in the list
		// Build views for all of the sub records
		Date now = new Date();
		List<ParsedNdefRecord> records = NdefMessageParser.parse(msgs[0]);
		final int size = records.size();
		for (int i = 0; i < size; i++) {
			TextView timeView = new TextView(this);
			timeView.setText(TIME_FORMAT.format(now));
			ParsedNdefRecord record = records.get(i);
			promt.append(record.getViewText());
		}
	}

	//获取系统隐式启动的
	@Override
	public void onNewIntent(Intent intent) {
		setIntent(intent);
		resolveIntent(intent);
	}
}

2、androidManifest配置

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="org.reno.Beam"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="11"
        android:targetSdkVersion="16" />

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

    <!-- 是否支持谷歌什么硬件一般可以忽略 -->
    <uses-feature android:name="android.hardware.nfc" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="org.reno.Beam.MainActivity"
            android:alwaysRetainTaskState="true"
            android:label="@string/app_name"
            android:launchMode="singleInstance"
            android:screenOrientation="nosensor" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.nfc.action.TECH_DISCOVERED" />
                <!-- 添加这一条默认设置，能拦截当前页面所有扫描NFC的配置 -->
                <category android:name="android.intent.category.DEFAULT" />
            </intent-filter>

            <!--
                  这个过滤条件我就没有使用了
                <meta-data
                android:name="android.nfc.action.TECH_DISCOVERED"
                android:resource="@xml/nfc_tech_filter" />
            -->
        </activity>
    </application>

</manifest>