Android下NFC的简单使用
Android下NFC的简单使用
现在很多手机已经配备了NFC(Near Field Communication 近场通信)的功能,我就为此专门研究过,可以到本文末尾下载源代码。Android官方资料:
https://www.360docs.net/doc/096474784.html,/guide/topics/connectivity/nfc/i ndex.html相关资料参考:
https://www.360docs.net/doc/096474784.html,/nicebooks/article/details/6223956相关Android应用:
https://https://www.360docs.net/doc/096474784.html,/store/apps/details?id=com.nxp.nfc .tagwriter关于NFC的知识就不讲了,下面直接看代码,主要是读取、写入的功能。先自己新建一个Android工程,下面是用到的变量:private NfcAdapter mNfcAdapter;//NFC适配器,就是那个NFC读卡器PendingIntent mNfcPendingIntent;//用于截获系统Intent,因为系统检测到NFC卡片时会选择程序去响应
IntentFilter[] mWriteTagFilters;//IntentFilter表示满足本程序响应的条件private boolean mWriteMode = false;//控制读写模式切换还是建议看看官方资料,这样才能明白某些函数的意思。接下来,在onCreate函数里检测NFC://获取默认NFC设备mNfcAdapter = NfcAdapter.getDefaultAdapter(this); if
(mNfcAdapter == null) { Toast.makeText(this, "该设备不支持NFC!", Toast.LENGTH_LONG).show(); finish(); return; } //查看NFC是否开启if
(!mNfcAdapter.isEnabled()){ Toast.makeText( this, "请在系统设置中先启用NFC功能",
Toast.LENGTH_LONG).show(); finish(); return; } mNfcPendingIntent = PendingIntent.getActivity(this, 0, new Intent(this,
getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_T OP), 0); IntentFilter ndefDetected = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED); try
{ ndefDetected.addDataType("text/plain");
} catch (MalformedMimeTypeException e)
{ e.printStackTrace(); } mWriteTagFilters = new IntentFilter[] { ndefDetected };这里先检测手机是否支持NFC,finish()表示退出程序。最后,给上面变量赋值,添加截获的NFC数据类型为"text/plain",表示纯文本。所以,如果NFC卡片存的是URL地址,我们的程序将无法截获,系统会用浏览器打开。当我们按下Home
键,这时就无需截获系统Intent了,添加如下代码:
@Override protected void onResume()
{ super.onResume();
mNfcAdapter.enableForegroundDispatch(this, mNfcPendingIntent, mWriteTagFilters, null); }
@Override protected void onPause()
{ super.onPause();
mNfcAdapter.disableForegroundNdefPush(this); }手机发现了NFC Tag,如果我们已经添加了PendingIntent,并且满足我们的IntentFilter条件,就会触发一个如下事件://必须的函数,截获系统itent,然后触发读取和写入操作@Override protected void onNewIntent(Intent intent) { if (!mWriteMode &&
NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent. getAction())) { NdefMessage[] msgs = getNdefMessages(intent); String body = new String(msgs[0].getRecords()[0].getPayload()); System.out.println("***读取数据***" + body);
tagInfo.setText(body); } if (mWriteMode &&
NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent. getAction())) { Tag detectedTag =
intent.getParcelableExtra(NfcAdapter.EXTRA_TAG); boolean writesuccess = writeTag(getNoteAsNdef(), detectedTag); System.out.println("***写入数
据***"); if
(writesuccess){ Toast.makeText(this, "写入成功", Toast.LENGTH_SHORT).show(); } else{ Toast.makeText(this, "写入失败!", Toast.LENGTH_SHORT).show(); } } }系统检测到Tag时,会将其所有信息封装到Intent中,我们截获了它就可以读取了。如果要写入,需要构造NdefMessage信息才行。上面代码中的getNoteAsNdef用来根据输入构造NdefMessage://从输入框获取信息,然后构造NdefMessage用于写入private NdefMessage getNoteAsNdef() { byte[] textBytes = (inputText.getText().toString()).getBytes();
NdefRecord textRecord = new
NdefRecord(NdefRecord.TNF_MIME_MEDIA,
"text/plain".getBytes(), new byte[] {}, textBytes);
return new NdefMessage(new NdefRecord[]
{ textRecord }); }实际读取数据部分如下://实际读取数据部分private NdefMessage[] getNdefMessages(Intent intent)
{ NdefMessage[] msgs = null; String action = intent.getAction(); if
(NfcAdapter.ACTION_TAG_DISCOVERED.equals(action) ||
NfcAdapter.ACTION_NDEF_DISCOVERED.equals(action)) { Parcelable[] rawMsgs =
intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF _MESSAGES); 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[] {}; NdefRecord record = new NdefRecord(NdefRecord.TNF_UNKNOWN, empty, empty, empty); NdefMessage msg = new NdefMessage(new NdefRecord[] { record }); msgs = new NdefMessage[]
{ msg }; } } else
{ // Log.d(TAG, "Unknown intent.");
finish(); } return msgs; }实际写入部分
如下://实际写入数据部分boolean
writeTag(NdefMessage message, Tag tag)
{ int size = message.toByteArray().length;
try { Ndef ndef = Ndef.get(tag);
if (ndef != null)
{ ndef.connect(); if (!ndef.isWritable())
{ System.out.println("Tag is
read-only."); return
false; } if
(ndef.getMaxSize() < size)
{ System.out.println("Tag capacity is " + ndef.getMaxSize() + " bytes, message is " + size + " bytes."); return
false; }
ndef.writeNdefMessage(message);
System.out.println("****写入数据成功***");
return true; } else
{ NdefFormatable format = NdefFormatable.get(tag); if (format != null) { try
{ format.connect();
format.format(message);
System.out.println("**Formatted tag and wrote
message**"); return
true; } catch (IOException e)
{ System.out.println("==Failed to format tag.=="); return false; } } else
{ System.out.println("Tag doesn't support NDEF."); return
false; } } } catch (Exception e) { System.out.println("!!写入数据失败!!"); } return false; }上面的写入、读取部分都不是很简洁,因为要兼容到android 2.3(API 10)的版本,Android 4.0以上提供了跟简单的读写方式,可以参考下面的文章:
https://www.360docs.net/doc/096474784.html,/2012/12/writing-custom-data-to-nfc-t ags-with-android-example/如果你需要这样的功能,比如检测到文本时便启动你的程序,你可以在配置文件里设置,查看官方文档即可,我这里没有这样的需求。最后,打开AndroidManifest.xml文件,添加如下代码用于开启NFC权限。注意,我的源代码。<uses-sdk
android:minSdkVersion="10"
android:targetSdkVersion="14" />
<uses-permission
android:name="android.permission.NFC" />