Question

我找到了NFC工作原理的一个例子。但是当我将NFC卡连接到Resume / OnPause电话时。为什么？函数：onNewIntent尚未调用。

活动代码：

public class AMain extends Activity {

    public static final String MIME_TEXT_PLAIN = "text/plain";
    public static final String TAG = "NfcDemo";

    private TextView mTextView;
    private NfcAdapter mNfcAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.amain);

        mTextView = (TextView) findViewById(R.id.tv);

        mNfcAdapter = NfcAdapter.getDefaultAdapter(this);

        if (mNfcAdapter == null) {
            // Stop here, we definitely need NFC
            Toast.makeText(this, "This device doesn't support NFC.", Toast.LENGTH_LONG).show();
            finish();
            return;

        }

        if (!mNfcAdapter.isEnabled()) {
            mTextView.setText("NFC is disabled.");
        } else {
            mTextView.setText("NFC is enabled.");
        }

        handleIntent(getIntent());
    }

    @Override
    protected void onResume() {
        super.onResume();

        /*
         * It's important, that the activity is in the foreground (resumed). Otherwise
         * an IllegalStateException is thrown. 
         */
        setupForegroundDispatch(this, mNfcAdapter);
    }

    @Override
    protected void onPause() {
        /*
         * Call this before onPause, otherwise an IllegalArgumentException is thrown as well.
         */
        stopForegroundDispatch(this, mNfcAdapter);

        super.onPause();
    }

    @Override
    protected void onNewIntent(Intent intent) {
        /*
         * This method gets called, when a new Intent gets associated with the current activity instance.
         * Instead of creating a new activity, onNewIntent will be called. For more information have a look
         * at the documentation.
         * 
         * In our case this method gets called, when the user attaches a Tag to the device.
         */
        handleIntent(intent);
    }

    private void handleIntent(Intent intent) {
        String action = intent.getAction();
        Log.d(TAG,action);
        if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(action)) {

            String type = intent.getType();
            if (MIME_TEXT_PLAIN.equals(type)) {

                Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
                new NdefReaderTask().execute(tag);

            } else {
                Log.d(TAG, "Wrong mime type: " + type);
            }
        } else if (NfcAdapter.ACTION_TECH_DISCOVERED.equals(action)) {

            // In case we would still use the Tech Discovered Intent
            Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
            String[] techList = tag.getTechList();
            String searchedTech = Ndef.class.getName();

            for (String tech : techList) {
                if (searchedTech.equals(tech)) {
                    new NdefReaderTask().execute(tag);
                    break;
                }
            }
        }
    }

    /**
     * @param activity The corresponding {@link Activity} requesting the foreground dispatch.
     * @param adapter The {@link NfcAdapter} used for the foreground dispatch.
     */
    public static void setupForegroundDispatch(final Activity activity, NfcAdapter adapter) {
        final Intent intent = new Intent(activity.getApplicationContext(), activity.getClass());
        intent.setFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP);

        final PendingIntent pendingIntent = PendingIntent.getActivity(activity.getApplicationContext(), 0, intent, 0);

        IntentFilter[] filters = new IntentFilter[1];
        String[][] techList = new String[][]{};

        // Notice that this is the same filter as in our manifest.
        filters[0] = new IntentFilter();
        filters[0].addAction(NfcAdapter.ACTION_NDEF_DISCOVERED);
        filters[0].addCategory(Intent.CATEGORY_DEFAULT);
        try {
            filters[0].addDataType(MIME_TEXT_PLAIN);
        } catch (MalformedMimeTypeException e) {
            throw new RuntimeException("Check your mime type.");
        }

        adapter.enableForegroundDispatch(activity, pendingIntent, filters, techList);
    }

    /**
     * @param activity The corresponding {@link BaseActivity} requesting to stop the foreground dispatch.
     * @param adapter The {@link NfcAdapter} used for the foreground dispatch.
     */
    public static void stopForegroundDispatch(final Activity activity, NfcAdapter adapter) {
        adapter.disableForegroundDispatch(activity);
    }

    /**
     * Background task for reading the data. Do not block the UI thread while reading. 
     * 
     * @author Ralf Wondratschek
     *
     */
    private class NdefReaderTask extends AsyncTask<Tag, Void, String> {

        @Override
        protected String doInBackground(Tag... params) {
            Tag tag = params[0];

            Ndef ndef = Ndef.get(tag);
            if (ndef == null) {
                // NDEF is not supported by this Tag. 
                return null;
            }

            NdefMessage ndefMessage = ndef.getCachedNdefMessage();

            NdefRecord[] records = ndefMessage.getRecords();
            for (NdefRecord ndefRecord : records) {
                if (ndefRecord.getTnf() == NdefRecord.TNF_WELL_KNOWN && Arrays.equals(ndefRecord.getType(), NdefRecord.RTD_TEXT)) {
                    try {
                        return readText(ndefRecord);
                    } catch (UnsupportedEncodingException e) {
                        Log.e(TAG, "Unsupported Encoding", e);
                    }
                }
            }

            return null;
        }

        private String readText(NdefRecord record) throws UnsupportedEncodingException {
            /*
             * See NFC forum specification for "Text Record Type Definition" at 3.2.1 
             * 
             * http://www.nfc-forum.org/specs/
             * 
             * bit_7 defines encoding
             * bit_6 reserved for future use, must be 0
             * bit_5..0 length of IANA language code
             */

            byte[] payload = record.getPayload();

            // Get the Text Encoding
            String textEncoding = ((payload[0] & 128) == 0) ? "UTF-8" : "UTF-16";

            // Get the Language Code
            int languageCodeLength = payload[0] & 0063;

            // String languageCode = new String(payload, 1, languageCodeLength, "US-ASCII");
            // e.g. "en"

            // Get the Text
            return new String(payload, languageCodeLength + 1, payload.length - languageCodeLength - 1, textEncoding);
        }

        @Override
        protected void onPostExecute(String result) {
            if (result != null) {
                mTextView.setText("Read content: " + result);
            }
        }
    }
}

清单文件：

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

    <uses-permission android:name="android.permission.NFC" />
     <uses-feature
        android:name="android.hardware.nfc"
        android:required="true" />
    <uses-sdk
        android:minSdkVersion="10"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.nfc.AMain"
            android:label="@string/app_name" >
            <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.NDEF_DISCOVERED"/>
                <category android:name="android.intent.category.DEFAULT"/>
                <data android:mimeType="text/plain" />
            </intent-filter>
            <intent-filter>
                <action android:name="android.nfc.action.TAG_DISCOVERED"/>
            </intent-filter>
            <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>

    </application>

</manifest>

Answer 1

您应该将NfcAdapter.ACTION_TAG_DISCOVERED添加到您的意图过滤器。您当前的意图过滤器（filters [0] .addAction（NfcAdapter.ACTION_NDEF_DISCOVERED）;）仅捕获包含NDEF消息的NFC标记。将您的过滤器更改为

 filters[0].addAction(NfcAdapter.ACTION_TAG_DISCOVERED);

你应该得到你想要的东西。

Answer 2

您好，您在清单中设置了<uses-permission android:name="android.permission.NFC" />吗？

Android上的NFC不起作用

2 个答案: