How to read nfc card with android phone,
The error written on the console is below, this application opens, but when I read the card to NFC, it gives an error,
Can you help me fix this code? How to read nfc card with android phone,
The error written on the console is below, this application opens, but when I read the card to NFC, it gives an error,
Can you help me fix this code?
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.myapplication, PID: 17885
java.lang.NullPointerException: Attempt to read from null array
at com.example.myapplication.MainActivity.buildTagViews(MainActivity.java:126)
at com.example.myapplication.MainActivity.readfromIntent(MainActivity.java:114)
at com.example.myapplication.MainActivity.onNewIntent(MainActivity.java:180)
at android.app.Activity.performNewIntent(Activity.java:8113)
at android.app.Instrumentation.callActivityOnNewIntent(Instrumentation.java:1410)
at android.app.Instrumentation.callActivityOnNewIntent(Instrumentation.java:1423)
at android.app.ActivityThread.deliverNewIntents(ActivityThread.java:3724)
at android.app.ActivityThread.handleNewIntent(ActivityThread.java:3736)
at android.app.servertransaction.NewIntentItem.execute(NewIntentItem.java:53)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2108)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loop(Looper.java:236)
at android.app.ActivityThread.main(ActivityThread.java:7876)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:656)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:967)
D/OOMEventManagerFK: checkEventAndDumpForJE: 0
I/Process: Sending signal. PID: 17885 SIG: 9
`public class MainActivity extends AppCompatActivity {
public static final String Error_Detected = "No NFC Tag Detected";
public static final String Write_Success = "Text Written Successfully!";
public static final String Write_Error = "Error During Writing, Try Again!";
NfcAdapter nfcAdapter;
PendingIntent pendingIntent;
IntentFilter writingTagFilters[];
boolean writeMode;
Tag myTag;
Context context;
TextView edit_message;
TextView nfc_contents;
Button ActivateButton;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
edit_message = (TextView) findViewById(R.id.edit_message);
nfc_contents = (TextView) findViewById(R.id.nfc_contents);
ActivateButton = (Button) findViewById(R.id.ActivateButton);
context = this;
ActivateButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
try {
if(myTag == null){
Toast.makeText(context,Error_Detected,Toast.LENGTH_LONG).show();
}else {
write("PlainTset|" + edit_message.getText().toString(),myTag);
Toast.makeText(context,Write_Success,Toast.LENGTH_LONG).show();
}
} catch (IOException e) {
Toast.makeText(context,Write_Error,Toast.LENGTH_LONG).show();
e.printStackTrace();
}catch (FormatException e){
Toast.makeText(context,Write_Error,Toast.LENGTH_LONG).show();
e.printStackTrace();
}
}
});
nfcAdapter = NfcAdapter.getDefaultAdapter(this);
if(nfcAdapter == null){
Toast.makeText(this,"This device does not support NFC",Toast.LENGTH_LONG).show();
finish();
}
readfromIntent(getIntent());
pendingIntent = PendingIntent.getActivity(this,0,new Intent(this,getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),0);
IntentFilter tagDetected = new IntentFilter(NfcAdapter.ACTION_TAG_DISCOVERED);
tagDetected.addCategory(Intent.CATEGORY_DEFAULT);
writingTagFilters = new IntentFilter[] { tagDetected };
}
private void readfromIntent(Intent intent){
String action = intent.getAction();
if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(action)
|| NfcAdapter.ACTION_TECH_DISCOVERED.equals(action)
|| NfcAdapter.ACTION_NDEF_DISCOVERED.equals(action)){
Parcelable[] rawMsgs = intent.getParcelableArrayExtra(NfcAdapter.EXTRA_NDEF_MESSAGES);
NdefMessage[] msgs = null;
if(rawMsgs != null){
msgs = new NdefMessage[rawMsgs.length];
for (int i = 0; i < rawMsgs.length; i++) {
msgs[i] = (NdefMessage) rawMsgs[i];
}
}
buildTagViews(msgs);
}
}
private void buildTagViews(NdefMessage[] msgs){
if (msgs == null || msgs.length == 0){
String text = "";
byte[] payload = msgs[0].getRecords()[0].getPayload();
String textEncoding = ((payload[0] & 128) == 0) ? "UTF-8" : "UTF-16";
int languageCodeLength = payload[0] & 0063;
try {
text = new String(payload,languageCodeLength+1, payload.length - languageCodeLength - 1, textEncoding);
} catch (UnsupportedEncodingException e) {
Log.e("UnsupportedEncoding", e.toString());
}
Log.d("myTag", text);
nfc_contents.setText("NFC Content" + text);
}
}
private void write (String text,Tag tag) throws IOException,FormatException{
NdefRecord[] records = { createRecord(text) };
NdefMessage message = new NdefMessage(records);
Ndef ndef = Ndef.get(tag);
ndef.connect();
ndef.writeNdefMessage(message);
ndef.close();
}
private NdefRecord createRecord(String text) throws UnsupportedEncodingException {
String lang ="en";
byte[] textBytes = text.getBytes();
byte[] langBytes = lang.getBytes("US-ASCII");
int langLength = langBytes.length;
int textLength = textBytes.length;
byte[] payload = new byte[1 + langLength + textLength];
payload[0] = (byte) langLength;
System.arraycopy(langBytes,0, payload,1, langLength);
System.arraycopy(textBytes,0,payload,1 + langLength,textLength);
NdefRecord recordNFC = new NdefRecord(NdefRecord.TNF_WELL_KNOWN, NdefRecord.RTD_TEXT, new byte[0], payload);
return recordNFC;
}
@Override
protected void onNewIntent(Intent intent){
super.onNewIntent(intent);
setIntent(intent);
readfromIntent(intent);
if (NfcAdapter.ACTION_TAG_DISCOVERED.equals(intent.getAction())){
myTag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
}
}
@Override
public void onPause(){
super.onPause();
WriteModeOff();
}
@Override
public void onResume(){
super.onResume();
WriteModeOn();
}
private void WriteModeOn(){
writeMode = true;
nfcAdapter.enableForegroundDispatch(this, pendingIntent, writingTagFilters,null);
}
private void WriteModeOff(){
writeMode = false;
nfcAdapter.disableForegroundDispatch(this);
}
}
`
