NFC读取无效

编程问答 2022-04-26

问题描述

| 我是开发Android应用程序的新手。目前，我正在尝试开发自己的标签读取器，它可以读取mifare Ultralight标签。 但是我无法读取标签，因为NfcAdapter.ACTION_TECH_disCOVERED.equals（action）始终返回false。有人可以帮我吗？ NfcReader.java 
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mText = (TextView) findViewById(R.id.text);
    mText.setText(\"Scan a tag\");

    mAdapter = NfcAdapter.getDefaultAdapter();

    // Create a generic PendingIntent that will be deliver to this activity. The NFC stack
    // will fill in the intent with the details of the discovered tag before delivering to
    // this activity.
    mPendingIntent = PendingIntent.getActivity(this,new Intent(this,getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),0);

    // Setup an intent filter for all MIME based dispatches
    IntentFilter ndef = new IntentFilter(NfcAdapter.ACTION_TECH_disCOVERED);
    try {
        ndef.addDataType(\"*/*\");
    } catch (MalformedMimeTypeException e) {
        throw new RuntimeException(\"fail\",e);
    }
    mFilters = new IntentFilter[] {
            ndef,};

    // Setup a tech list for all NfcF tags
    mTechLists = new String[][] { new String[] { NfcF.class.getName() } };

    Intent intent = getIntent();

    getNdefMessages(intent);
}

public void getNdefMessages(Intent intent) {
    // Parse the intent
    NdefMessage[] msgs = null;
    String action = intent.getAction();
    if (NfcAdapter.ACTION_TECH_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);
            NdefMessage msg = new NdefMessage(new NdefRecord[] {record});
            msgs = new NdefMessage[] {msg};
        }
    }        
    else {
        //Log.e(TAG,\"UnkNown intent \" + intent);
        finish();
    }
}

@Override
public void onResume() {
    super.onResume();
    mAdapter.enableForegrounddispatch(this,mPendingIntent,mFilters,mTechLists);
}

@Override
public void onNewIntent(Intent intent) {
    Log.i(\"Foreground dispatch\",\"discovered tag with intent: \" + intent);
    getNdefMessages(intent);            
}

@Override
public void onPause() {
    super.onPause();
    //mAdapter.disableForegrounddispatch(this);
    throw new RuntimeException(\"onPause not implemented to fix build\");
}
Manifest.xml 
<manifest xmlns:android=\"http://schemas.android.com/apk/res/android\"
      package=\"com.nfc.reader\"
      android:versionCode=\"1\"
      android:versionName=\"1.0\">

    <uses-permission android:name=\"android.permission.NFC\" />
    <uses-sdk android:minSdkVersion=\"10\"/>
    <uses-feature android:name=\"android.hardware.nfc\" android:required=\"true\" />

    <application android:icon=\"@drawable/icon\" android:label=\"@string/app_name\">
        <activity android:name=\"NfcReader\"
            android:theme=\"@android:style/Theme.NoTitleBar\">
            <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\"/>
                <data android:mimeType=\"text/plain\" />
                <category android:name=\"android.intent.category.DEFAULT\"/>
            </intent-filter>

            <Meta-data android:name=\"android.nfc.action.TECH_disCOVERED\"
                android:resource=\"@xml/nfctech\" />
        </activity>

    </application>

</manifest>
    

解决方法

        当检测到带有NDEF消息的标签时，Android会查找具有“活动”和“意图”过滤器的所有应用程序，以执行操作“ android.nfc.action.NDEF_DISCOVERED”。如果两个或更多应用程序可以处理此操作，则具有最精确过滤器的应用程序将收到此意图。当找到具有相同过滤器的应用程序时，是选择一个的用户。因此，在AndroidManifest.xml中，您必须使用此操作来检测NDEF格式的标签。 如果您想阅读NDEF消息，则不必担心您正在阅读哪种标签（Ultralight，Felica，Topaz等）。 Android使用android.nfc.tech.Ndef来分发NDEF格式的标签。因此，要在活动处于前台时获取所有NdefMessages，可以使用以下代码段： 
//Called in onCreate()
private void nfcConfig() {
    mAdapter = NfcAdapter.getDefaultAdapter(this);
    pendingIntent = PendingIntent.getActivity(
            this,new Intent(this,getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),0);
    techListsArray = new String[][]{new String[]{
                Ndef.class.getName()
            }};     
}

@Override
public void onResume() {
    super.onResume();
    mAdapter.enableForegroundDispatch(this,pendingIntent,null,techListsArray);
}

@Override
public void onPause() {
    super.onPause();
    mAdapter.disableForegroundDispatch(this);
}

@Override
public void onNewIntent(Intent intent) {
    getNdefMessages(intent);            
}
如果要读取Ultralight标签（或其他技术），那应该是因为您需要标签中的原始数据。一定不能从主应用程序线程执行它。例如： 
private void nfcConfig(){
...
//Mifare Ultralight filter
techListsArray = new String[][]{new String[]{
            NfcA.class.getName(),MifareUltralight.class.getName()
        }};
...
}

@Override
public void onNewIntent(Intent intent) {
    getRawData(intent);            
}

private void getRawData(Intent intent){
    final Tag tag = (Tag) intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
    MifareUltralight ulTag = MifareUltralight.getTag();
    new ReadMFULTask(ulTag).execute();
}

private static class ReadMFULTask extends AsyncTask<Void,Void,Void> {

    private Tag mTag;

    public ReadMFULTask(Tag tag){
        mTag = tag;
    }

    @Override
    protected Void doInBackground(Void... arg0) {

    MifareUltralight ulTag = MifareUltralight.get(mTag);
    try {
        ulTag.connect();
            //Read all pages from an Ul tag
            for(int i=0; i < 16; i=i+4){
            byte[] data = ulTag.readPages(i);
                String dataString = HexUtilities.getHexString(data);
                Log.d(\"RAW DATA\",dataString);
            }
            ulTag.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}
    ,        在您的代码中，您将基于ACTION_TECH_DISCOVERED设置意图过滤器，但随后尝试ndef.addDataType（/），这是您为ACTION_NDEF_DISCOVERED设置意图过滤器的方式。相反，您可以简单地执行以下操作： 
IntentFilter ntech = new IntentFilter(NfcAdapter.ACTION_TECH_DISCOVERED);
mFilters = new IntentFilter[]{ ntech };
确保正确设置了nfc_tech_list.xml： 
<resources xmlns:xliff=\"urn:oasis:names:tc:xliff:document:1.2\">
    <tech-list>
        <tech>android.nfc.tech.NfcA</tech>
        <tech>android.nfc.tech.MifareUltralight</tech>
    </tech-list>
</resources>
    
无效无效读取读取读取