[英]NFC Android reading NDEF tag multiple times
我有一個可以讀取NDEF標簽的應用程序,沒什么大不了:-)
我想多次讀取NDEF標簽,並且顯然要相應地更新標簽。 想象一下,我的NDEF標簽會包含時間(hh:mm:ss),當我用我的應用程序閱讀時,我想看看手機上的時間在變化。 如果我將手機一直放在標簽上的位置,則可以使用這種方法,但是我希望能夠自動檢測NDEF標簽,只要它在那里,我想每x秒讀取一次它的內容。
我發現此鏈接: 將NDEF消息多次寫入同一標簽? 但是要寫幾次,我想讀。
我找到了此鏈接: 如何查找NFC標簽現在是否仍在Android范圍內? 這是一個開始,但是我不知道如何更新標簽。
我很掙扎,甚至不知道我嘗試做的事在技術上是否可行。
有人對此有一些提示嗎? 干杯
更多信息
這是我的onCreate
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/// trying something
ScheduledExecutorService exec = Executors.newSingleThreadScheduledExecutor();
exec.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
// do stuff
Log.d(TAG, "i am printing ");
}
}, 0, 5, TimeUnit.SECONDS);
new Thread(new Runnable() {
@Override
public void run() {
// here ask for TAG
// read the TAG
// and update the clock
}
}).start(); // Start the operation
/////////////////
mTextView = (TextView) findViewById(R.id.textView_explanation);
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 currently disabled on this device.");
}
handleIntent(getIntent());
}
和我的handleIntent:
private void handleIntent(Intent intent) {
String action = intent.getAction();
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;
}
}
}
}
在ScheduledExecutorService的內部,我添加了“ Log.d(TAG,“我正在打印”);”,以試圖了解它並能正常工作並定期打印。 我沒有得到的是是否要求TAG,讀取TAG並更新新線程內的時鍾,我在ScheduledExecutorService內部應該做什么以及如何要求TAG,讀取TAG並更新當前在onCreate方法之外完成操作時在新線程內部計時? 例如,讀取結果將發布在我的onPostExecute方法內的textView中。
抱歉,我嘗試觀看一些教程和示例,但仍然聽不懂。
這是我的整個代碼。 讀取標簽需要花費更長的時間,有時則不需要。 我無法弄清楚如何以及在何處更新標簽,以防出現問題。 完全迷失了:-(
package uk.co.xxx.xxx;
import android.nfc.FormatException;
import android.support.v7.app.AppCompatActivity;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Arrays;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import android.app.Activity;
import android.app.PendingIntent;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.IntentFilter.MalformedMimeTypeException;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.nfc.tech.Ndef;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;
import android.widget.Toast;
public class MainActivity 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.activity_main);
/// trying something
ScheduledExecutorService exec = Executors.newSingleThreadScheduledExecutor();
exec.scheduleAtFixedRate(new Runnable() {
@Override
public void run() {
// do stuff
handleIntent(getIntent());
Log.d(TAG, "i am printing ");
}
}, 0, 5, TimeUnit.SECONDS);
/////////////////
mTextView = (TextView) findViewById(R.id.textView_explanation);
mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
if (mNfcAdapter == null) {
Toast.makeText(this, "This device doesn't support NFC.",
Toast.LENGTH_LONG).show();
finish();
return;
}
if (!mNfcAdapter.isEnabled()) {
mTextView.setText("NFC is currently disabled on this device.");
}
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();
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;
}
}
}
}
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[][]{};
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);
}
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.
*/
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 {
byte[] payload = record.getPayload();
// Get the Text Encoding
String textEncoding = new String ("");
if ((payload[0] & 128) == 0) {
textEncoding = "UTF-8";
} else {
textEncoding = "UTF-16";
}
// Get the Language Code
int languageCodeLength = payload[0] & 63;
// 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("The time is: \n" + result);
}
}
}
}
使用TAG = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
您可以獲得TAG。 現在,您可以每隔x秒檢查一次TAG,如果它不為null(或上次檢測到的類型),則讀取該標簽並更新時鍾(我想它是文本視圖)。 您可以像這樣在Thread中執行此操作:
new Thread(new Runnable() {
@Override
public void run() {
// here ask for TAG
// read the TAG
// and update the clock
}
}).start(); // Start the operation
希望我能正確理解您的問題。
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