Android NFC开发教程(3)

前面例子介绍了检测，读写NFC TAG开发的一般步骤，本例针对常用的Mifare Tag 具体说明。

Mifare Tag 可以有1K ,2K, 4K，其内存分区大同小异，下图给出了1K字节容量的Tag的内存分布:

 

数据分为16个区(Sector) ,每个区有4个块(Block) ，每个块可以存放16字节的数据，其大小为16 X 4 X 16 =1024 bytes

每个区最后一个块称为Trailer ，主要用来存放读写该区Block数据的Key ，可以有A，B两个Key，每个Key 长度为6个字节，缺省的Key值一般为全FF或是0. 由 MifareClassic.KEY_DEFAULT 定义。

因此读写Mifare Tag 首先需要有正确的Key值（起到保护的作用），如果鉴权成功

auth = mfc.authenticateSectorWithKeyA(j,
MifareClassic.KEY_DEFAULT);

然后才可以读写该区数据。

本例定义几个Mifare相关的类 MifareClassCard ，MifareSector, MifareBlock 和MifareKey 以方便读写Mifare Tag.

Android 系统来检测到NFC Tag， 将其封装成Tag类，存放到Intent的NfcAdapter.EXTRA_TAG Extra 数据包中，可以使用MifareClassic.get(Tag) 获取对象的 MifareClassic类。

[java]
Tag tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG); 
// 4) Get an instance of the Mifare classic card from this TAG  
// intent  
MifareClassic mfc = MifareClassic.get(tagFromIntent); 
Tag tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
// 4) Get an instance of the Mifare classic card from this TAG
// intent
MifareClassic mfc = MifareClassic.get(tagFromIntent);
下面为读取Mifare card 的主要代码：

[java]
// 1) Parse the intent and get the action that triggered this intent  
String action = intent.getAction(); 
// 2) Check if it was triggered by a tag discovered interruption.  
if (NfcAdapter.ACTION_TECH_DISCOVERED.equals(action)) { 
 // 3) Get an instance of the TAG from the NfcAdapter  
 Tag tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG); 
 // 4) Get an instance of the Mifare classic card from this TAG  
 // intent  
 MifareClassic mfc = MifareClassic.get(tagFromIntent); 
 MifareClassCard mifareClassCard=null; 
  
 try { // 5.1) Connect to card  
 mfc.connect(); 
 boolean auth = false; 
 // 5.2) and get the number of sectors this card has..and loop  
 // thru these sectors  
 int secCount = mfc.getSectorCount(); 
 mifareClassCard= new MifareClassCard(secCount); 
 int bCount = 0; 
 int bIndex = 0; 
 for (int j = 0; j < secCount; j++) { 
 MifareSector mifareSector = new MifareSector(); 
 mifareSector.sectorIndex = j; 
 // 6.1) authenticate the sector  
 auth = mfc.authenticateSectorWithKeyA(j, 
 MifareClassic.KEY_DEFAULT); 
 mifareSector.authorized = auth; 
 if (auth) { 
 // 6.2) In each sector - get the block count  
 bCount = mfc.getBlockCountInSector(j); 
 bCount =Math.min(bCount, MifareSector.BLOCKCOUNT); 
 bIndex = mfc.sectorToBlock(j); 
 for (int i = 0; i < bCount; i++) { 
  
 // 6.3) Read the block  
 byte []data = mfc.readBlock(bIndex); 
 MifareBlock mifareBlock = new MifareBlock(data); 
 mifareBlock.blockIndex = bIndex; 
 // 7) Convert the data into a string from Hex  
 // format.  
  
 bIndex++; 
 mifareSector.blocks[i] = mifareBlock; 
  
 } 
 mifareClassCard.setSector(mifareSector.sectorIndex, 
 mifareSector); 
 } else { // Authentication failed - Handle it  
  
 } 
 } 
 ArrayList blockData=new ArrayList(); 
 int blockIndex=0; 
 for(int i=0;i   
 MifareSector mifareSector=mifareClassCard.getSector(i); 
 for(int j=0;j  MifareBlock mifareBlock=mifareSector.blocks[j]; 
 byte []data=mifareBlock.getData(); 
 blockData.add("Block "+ blockIndex++ +" : "+ 
 Converter.getHexString(data, data.length)); 
 } 
 } 
 String []contents=new String[blockData.size()]; 
 blockData.toArray(contents); 
 setListAdapter(new ArrayAdapter(this, 
 android.R.layout.simple_list_item_1, contents)); 
 getListView().setTextFilterEnabled(true); 
  
 } catch (IOException e) { 
 Log.e(TAG, e.getLocalizedMessage()); 
 showAlert(3); 
 }finally{ 
  
 if(mifareClassCard!=null){ 
 mifareClassCard.debugPrint(); 
 } 
 } 
}// End of method 
// 1) Parse the intent and get the action that triggered this intent
String action = intent.getAction();
// 2) Check if it was triggered by a tag discovered interruption.
if (NfcAdapter.ACTION_TECH_DISCOVERED.equals(action)) {
 // 3) Get an instance of the TAG from the NfcAdapter
 Tag tagFromIntent = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
 // 4) Get an instance of the Mifare classic card from this TAG
 // intent
 MifareClassic mfc = MifareClassic.get(tagFromIntent);
 MifareClassCard mifareClassCard=null;
 
 try { // 5.1) Connect to card
 mfc.connect();
 boolean auth = false;
 // 5.2) and get the number of sectors this card has..and loop
 // thru these sectors
 int secCount = mfc.getSectorCount();
 mifareClassCard= new MifareClassCard(secCount);
 int bCount = 0;
 int bIndex = 0;
 for (int j = 0; j < secCount; j++) {
 MifareSector mifareSector = new MifareSector();
 mifareSector.sectorIndex = j;
 // 6.1) authenticate the sector
 auth = mfc.authenticateSectorWithKeyA(j,
 MifareClassic.KEY_DEFAULT);
 mifareSector.authorized = auth;
 if (auth) {
 // 6.2) In each sector - get the block count
 bCount = mfc.getBlockCountInSector(j);
 bCount =Math.min(bCount, MifareSector.BLOCKCOUNT);
 bIndex = mfc.sectorToBlock(j);
 for (int i = 0; i < bCount; i++) {
 
 // 6.3) Read the block
 byte []data = mfc.readBlock(bIndex);
 MifareBlock mifareBlock = new MifareBlock(data);
 mifareBlock.blockIndex = bIndex;
 // 7) Convert the data into a string from Hex
 // format.
 
 bIndex++;
 mifareSector.blocks[i] = mifareBlock;
 
 }
 mifareClassCard.setSector(mifareSector.sectorIndex,
 mifareSector);
 } else { // Authentication failed - Handle it
 
 }
 }
 ArrayList blockData=new ArrayList();
 int blockIndex=0;
 for(int i=0;i  
 MifareSector mifareSector=mifareClassCard.getSector(i);
 for(int j=0;j  MifareBlock mifareBlock=mifareSector.blocks[j];
 byte []data=mifareBlock.getData();
 blockData.add("Block "+ blockIndex++ +" : "+
 Converter.getHexString(data, data.length));
 }
 }
 String []contents=new String[blockData.size()];
 blockData.toArray(contents);
 setListAdapter(new ArrayAdapter(this,
 android.R.layout.simple_list_item_1, contents));
 getListView().setTextFilterEnabled(true);
 
 } catch (IOException e) {
 Log.e(TAG, e.getLocalizedMessage());
 showAlert(3);
 }finally{
 
 if(mifareClassCard!=null){
 mifareClassCard.debugPrint();
 }
 }
}// End of method

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