初学者提问关于NFC代码的有关问题

package my.nfc.namespace;import android.app.Activity;import android.content.Context;import android.nfc.NfcAdapter;import android.nfc.NfcManager;import android.os.Bundle;import android.widget.*;public class NFCActivity extends Activity {    /** Called when the activity is first created. */    TextView textview;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        textview = (TextView) findViewById(R.id.textview);          NfcManager manager = (NfcManager) getSystemService(Context.NFC_SERVICE);        NfcAdapter adapter = manager.getDefaultAdapter();        if(adapter.isEnabled()){            String s1 = "open";            textview.setText(s1);        }           }}