Question

我正在尝试创建一个将简单纯文本消息写入NFC标记的应用程序。用户在EditText框中写入消息，然后在按下按钮时，应用程序将文本写入标签。我一直在关注本教程：http://www.framentos.com/it/android-tutorial/2012/07/31/write-hello-world-into-a-nfc-tag-with-a/ 但是，当我尝试将NFC标签放在它旁边时，手机会打开另一个应用程序，而不是使用已经打开的应用程序。我知道问题与意图有关，但我不想在清单中声明意图过滤器，因为我不希望应用程序在标签放在手机旁边时打开，我希望应用程序是已事先打开。这是应用程序的代码：

import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.nfc.FormatException;
import android.nfc.NdefMessage;
import android.nfc.NdefRecord;
import android.nfc.NfcAdapter;
import android.nfc.Tag;
import android.nfc.tech.Ndef;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.io.IOException;
import java.io.UnsupportedEncodingException;

public class MainActivity extends AppCompatActivity {

    NfcAdapter adapter;
    PendingIntent pendingIntent;
    IntentFilter writeTagFilters[];
    Tag mytag;
    Context ctx;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ctx=this;
        Button btnWrite = (Button) findViewById(R.id.button);
        final EditText message = (EditText)findViewById(R.id.edit_message);
        btnWrite.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View v) {
                try {
                    if(mytag==null){
                        Toast.makeText(ctx, ctx.getString(R.string.error_detected), Toast.LENGTH_LONG).show();
                    }else{
                        write(message.getText().toString(),mytag);
                        Toast.makeText(ctx, ctx.getString(R.string.ok_writing), Toast.LENGTH_LONG ).show();
                    }
                } catch (IOException e) {
                    Toast.makeText(ctx, ctx.getString(R.string.error_writing), Toast.LENGTH_LONG ).show();
                    e.printStackTrace();
                } catch (FormatException e) {
                    Toast.makeText(ctx, ctx.getString(R.string.error_writing) , Toast.LENGTH_LONG ).show();
                    e.printStackTrace();
                }
            }
        });

        adapter = NfcAdapter.getDefaultAdapter(this);
        pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0);
        IntentFilter tagDetected = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
        tagDetected.addCategory(Intent.CATEGORY_DEFAULT);
        writeTagFilters = new IntentFilter[] { tagDetected };
    }

    private NdefRecord createRecord(String text) throws UnsupportedEncodingException {

        //create the message in according with the standard
        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;

        // copy langbytes and textbytes into payload
        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;
    }

    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();
    }

    @Override
    protected void onNewIntent(Intent intent){
        if(NfcAdapter.ACTION_NDEF_DISCOVERED.equals(intent.getAction())){
            mytag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
            Toast.makeText(this, this.getString(R.string.ok_detection) + mytag.toString(), Toast.LENGTH_LONG ).show();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {


   return true;
    }

    return super.onOptionsItemSelected(item);
}

}

请帮助，我不知道我做错了什么！我只是NFC和Android编程的初学者！

Answer 1

您必须使用enable forground dispatch：http://developer.android.com/guide/topics/connectivity/nfc/advanced-nfc.html#foreground-dispatch

前台调度系统允许活动拦截意图并声称优先于处理相同的其他活动意图。

<强> UPDATE1

很难写出所有类型的标签，其中一些标签已经封闭。您可以先撰写Ndef和NdefFormatable代码。

例如：

@Override 
protected void onPause() {
    super.onPause();
    mAdapter.disableForegroundDispatch(this);
}

@Override 
protected void onResume(){
  super.onResume();
  PendingIntent pendingIntent=PendingIntent.getActivity(this,0,new Intent(this,getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP),0);
  IntentFilter ndef=new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED);
  try {
    ndef.addDataType("*/*");
  }
 catch (  MalformedMimeTypeException e) {
    Log.e(TAG,"Bad MIME type declared",e);
    return;
  }
  IntentFilter[] filters=new IntentFilter[]{ndef};
  String[][] techLists=new String[][]{new String[]{Ndef.class.getName()},new String[]{NdefFormatable.class.getName()}};
  mNfcAdapter.enableForegroundDispatch(this,pendingIntent,filters,techLists);
}

@Override 
protected void onNewIntent(Intent intent) {
    Tag tag = intent.getParcelableExtra(NfcAdapter.EXTRA_TAG);
    String[] techList = tag.getTechList();
    for (String tech : techList) {
          if (tech.equals(Ndef.class.getName())) {
              //write NDEF msg
          } else if (tech.equals(NdefFormatable.class.getName())) {
              //format and write NDEF msg
          }
    }
}

将纯文本写入NFC标签，意图存在问题

1 个答案: