我有一个可以读取NDEF标签的应用程序，没什么大不了的： - ）
我想多次读取NDEF标记，显然要相应地更新标签。想象一下，我的NDEF标签会包含时间（hh：mm：ss），当我用我的应用程序读取它时，我想看到手机上的时间变化。 如果我继续将手机放在标签上打开和关闭，但我希望能够自动检测NDEF标签，只要它在那里，我想每隔x秒读取一次内容
我找到了这个链接： Write NDEF message multiple times to same tag? 但它是关于写几次，我想读。
我找到了这个链接： How to find out whether an NFC tag is still in range of an Android now? 什么是开始，但我无法弄清楚如何更新标签。
我很挣扎，我甚至不知道我尝试做的事情在技术上是否可行。
有人有关于如何做的一些提示吗？ 干杯
更多信息
这是我的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中，我添加了＆＃34; Log.d（TAG，＆＃34;我正在打印＆＃34;）;＆＃34;，只是为了尝试理解它确实有效并且定期打印。我没有得到的是，如果我要求TAG，阅读TAG并更新新线程内的时钟，我应该在ScheduledExecutorService内做什么，以及我如何要求TAG，阅读TAG和更新新线程内的时钟，当它在onCreate方法之外完成时？例如，读取的结果发布在我的onPostExecute方法中的textView中。
抱歉，我曾尝试过一些教程和示例，但我仍然没有得到它。
这是我的全部代码。阅读标签需要更长的时间，有时它不会。如果出现问题，我无法弄清楚如何以及在何处更新标签。完全丢失： - （
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);
}
}
}
}
答案 0 :(得分：0)
使用TAG = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);，您可以获得TAG。现在，您可以每x秒检查一次TAG，如果它不为空（或者它有最后检测到的类型），您可以读取标签并更新时钟（我想这是一个文本视图）。
您可以将此操作转换为类似以下的线程：
new Thread(new Runnable() {
@Override
public void run() {
// here ask for TAG
// read the TAG
// and update the clock
}
}).start(); // Start the operation
我希望我能正确理解你的问题。