我正在尝试实施一款nfc-p2p comunication Android应用。
我想同时在两台设备之间交换字符串。
从这篇文章开始 #25963691我发现简单的方法是使用方法android.nfc.NfcAdapter.invokeBeam()在第一次广播后再次调用Android Beam，让接收用户只需点击显示并启动第二个广播（没有移动和放置在设备附近）。
我已尝试将其应用于在线教程中的示例应用。
我的应用程序暂时不起作用：在第一次字符串传输后，Android Beam不会再次启动，即使在调试模式下我可以检查调用方法invokeBeam。
有人可以帮助我吗？
这是我的明确权限：
<uses-permission android:name="android.permission.NFC" />
<uses-feature android:name="android.hardware.nfc" android:required="true"/>
这是我的活动：
public class MainActivity extends Activity implements NfcAdapter.OnNdefPushCompleteCallback, NfcAdapter.CreateNdefMessageCallback {
//The array lists to hold our messages
private ArrayList<String> messagesToSendArray = new ArrayList<>();
private ArrayList<String> messagesReceivedArray = new ArrayList<>();
//Text boxes to add and display our messages
private EditText txtBoxAddMessage;
private TextView txtReceivedMessages;
private TextView txtMessagesToSend;
private NfcAdapter mNfcAdapter;
private Boolean checkSent;
private Boolean checkReceived;
public void addMessage(View view) {
String newMessage = txtBoxAddMessage.getText().toString();
messagesToSendArray.add(newMessage);
txtBoxAddMessage.setText(null);
updateTextViews();
Toast.makeText(this, "Added Message", Toast.LENGTH_LONG).show();
}
@Override
public void onNdefPushComplete(NfcEvent event) {
messagesToSendArray.clear();
//This is called when the system detects that our NdefMessage was
//Successfully sent
checkSent = true;
}
public NdefRecord[] createRecords() {
NdefRecord[] records = new NdefRecord[messagesToSendArray.size() + 1];
//To Create Messages Manually if API is less than
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN) {
for (int i = 0; i < messagesToSendArray.size(); i++){
byte[] payload = messagesToSendArray.get(i).
getBytes(Charset.forName("UTF-8"));
NdefRecord record = new NdefRecord(
NdefRecord.TNF_WELL_KNOWN, //Our 3-bit Type name format
NdefRecord.RTD_TEXT, //Description of our payload
new byte[0], //The optional id for our Record
payload); //Our payload for the Record
records[i] = record;
}
}
//Api is high enough that we can use createMime, which is preferred.
else {
for (int i = 0; i < messagesToSendArray.size(); i++){
byte[] payload = messagesToSendArray.get(i).
getBytes(Charset.forName("UTF-8"));
NdefRecord record = NdefRecord.createMime("text/plain",payload);
records[i] = record;
}
}
records[messagesToSendArray.size()] = NdefRecord.createApplicationRecord(getPackageName());
return records;
}
@Override
public NdefMessage createNdefMessage(NfcEvent event) {
//This will be called when another NFC capable device is detected.
if (messagesToSendArray.size() == 0) {
return null;
}
//We'll write the createRecords() method in just a moment
NdefRecord[] recordsToAttach = createRecords();
//When creating an NdefMessage we need to provide an NdefRecord[]
return new NdefMessage(recordsToAttach);
}
private void handleNfcIntent(Intent NfcIntent) {
if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(NfcIntent.getAction())) {
Parcelable[] receivedArray =
NfcIntent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
if(receivedArray != null) {
messagesReceivedArray.clear();
NdefMessage receivedMessage = (NdefMessage) receivedArray[0];
NdefRecord[] attachedRecords = receivedMessage.getRecords();
for (NdefRecord record:attachedRecords) {
String string = new String(record.getPayload());
//Make sure we don't pass along our AAR (Android Applicatoin Record)
if (string.equals(getPackageName())) { continue; }
messagesReceivedArray.add(string);
}
Toast.makeText(this, "Received " + messagesReceivedArray.size() +
" Messages", Toast.LENGTH_LONG).show();
updateTextViews();
}
else {
Toast.makeText(this, "Received Blank Parcel", Toast.LENGTH_LONG).show();
}
}
}
@Override
public void onNewIntent(Intent intent) {
handleNfcIntent(intent);
}
@Override
public void onResume() {
super.onResume();
updateTextViews();
if(checkReceived){
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
mNfcAdapter.invokeBeam(MainActivity.this);
//Toast.makeText(this, "invocato", Toast.LENGTH_SHORT).show();
Log.e("DEBUG ---", "invocato");
}
}
handleNfcIntent(getIntent());
}
private void updateTextViews() {
txtMessagesToSend.setText("Messages To Send:\n");
//Populate Our list of messages we want to send
if(messagesToSendArray.size() > 0) {
for (int i = 0; i < messagesToSendArray.size(); i++) {
txtMessagesToSend.append(messagesToSendArray.get(i));
txtMessagesToSend.append("\n");
}
}
txtReceivedMessages.setText("Messages Received:\n");
//Populate our list of messages we have received
if (messagesReceivedArray.size() > 0) {
for (int i = 0; i < messagesReceivedArray.size(); i++) {
txtReceivedMessages.append(messagesReceivedArray.get(i));
txtReceivedMessages.append("\n");
}
checkReceived = true;
}
}
//Save our Array Lists of Messages for if the user navigates away
@Override
public void onSaveInstanceState(@NonNull Bundle savedInstanceState) {
super.onSaveInstanceState(savedInstanceState);
savedInstanceState.putStringArrayList("messagesToSend", messagesToSendArray);
savedInstanceState.putStringArrayList("lastMessagesReceived",messagesReceivedArray);
}
//Load our Array Lists of Messages for when the user navigates back
@Override
public void onRestoreInstanceState(@NonNull Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
messagesToSendArray = savedInstanceState.getStringArrayList("messagesToSend");
messagesReceivedArray = savedInstanceState.getStringArrayList("lastMessagesReceived");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
checkSent = false;
checkReceived = false;
//Check if NFC is available on device
mNfcAdapter = NfcAdapter.getDefaultAdapter(this);
if(mNfcAdapter != null) {
//This will refer back to createNdefMessage for what it will send
mNfcAdapter.setNdefPushMessageCallback(this, this);
//This will be called if the message is sent successfully
mNfcAdapter.setOnNdefPushCompleteCallback(this, this);
}
else {
Toast.makeText(this, "NFC not available on this device",
Toast.LENGTH_SHORT).show();
}
txtBoxAddMessage = (EditText) findViewById(R.id.txtBoxAddMessage);
txtMessagesToSend = (TextView) findViewById(R.id.txtMessageToSend);
txtReceivedMessages = (TextView) findViewById(R.id.txtMessagesReceived);
Button btnAddMessage = (Button) findViewById(R.id.buttonAddMessage);
btnAddMessage.setText("Add Message");
updateTextViews();
if (getIntent().getAction().equals(NfcAdapter.ACTION_NDEF_DISCOVERED)) {
handleNfcIntent(getIntent());
}
}
}