Categories: Code Examples | Java | NFC | WIMA2008

This page was last modified 16:34, 1 May 2008.

From Forum Nokia Wiki

The code shows a basic MIDlet that writes an NDEF (EXTERNAL_RTD) to a tag, in order to start an application. The application to be started requires the following line in the JAD-File:

MIDlet-Push-1: ndef:external_rtd?name=urn:nfc:ext:nfc-research.at:pushreg,at.nfcresearch.wima.examples.PushReg,*

This example does NOT work in the Emulator of the Nokia 6131, but only on the phone! You can download ZIP with two NetBeans Project to try out the functionally.

package at.nfcresearch.wima.examples;
 
import javax.microedition.contactless.ContactlessException;
import javax.microedition.contactless.DiscoveryManager;
import javax.microedition.contactless.TargetListener;
import javax.microedition.contactless.TargetProperties;
import javax.microedition.contactless.TargetType;
import javax.microedition.contactless.ndef.NDEFMessage;
import javax.microedition.contactless.ndef.NDEFRecord;
import javax.microedition.contactless.ndef.NDEFRecordType;
import javax.microedition.contactless.ndef.NDEFTagConnection;
import javax.microedition.io.Connector;
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
 
public class PushRegTagWriter extends MIDlet implements TargetListener, CommandListener {
 
    // Display Items
    private Command exitCommand;
    private StringItem text;
    private Form form; 
 
    public PushRegTagWriter() {
 
        // Display Items
        exitCommand = new Command("Exit", Command.EXIT, 1);
        form = new Form("NFC-Research.at: PushRegistry Tag Writer");
 
        form.addCommand(exitCommand);
        form.append("Touch Tag to write Ext-NDEF for PushRegistry start.");
        form.setCommandListener(this);
 
 
        // Registration of the Targetlistener
        // Look for ANY Type of RFID Tag that can be
        // read by the phone. 
        try {
            DiscoveryManager dm = DiscoveryManager.getInstance();
            dm.addTargetListener(this, TargetType.RFID_TAG);
        } catch (ContactlessException ce) {
            displayAlert("Unable to Register Targetlistener:" + ce.toString(), AlertType.ERROR);
            Display.getDisplay(this).setCurrent(form);
        }
    }
 
    protected void startApp() {
        Display.getDisplay(this).setCurrent(form);
    }
 
    protected void pauseApp() {
    }
 
    protected void destroyApp(boolean bool) {
 
    }
 
    public void commandAction(Command cmd, Displayable disp) {
        if (cmd == exitCommand) {
            DiscoveryManager dm = DiscoveryManager.getInstance();
            dm.removeTargetListener(this, TargetType.RFID_TAG);
            destroyApp(false);
            notifyDestroyed();
        }
 
 
    }
 
    /**
     * Method called by the TargetListener in case a tag
     * was detected. 
     * @param prop contains the array of tags found. 
     */
    public void targetDetected(TargetProperties[] prop) {
 
        // if there is no information available on the tags
        // found, exit Method.
        if (prop.length == 0) {
            return;
        }
 
        // Create a new NDEF Connection in order
        // to write an NDEF EXT to the tag. 
        NDEFTagConnection ndconn = null;
        try {
            // create an ndef tag connection. 
            String ur = prop[0].getUrl(Class.forName("javax.microedition.contactless.ndef.NDEFTagConnection"));
 
            // open the NDEF Connection
            ndconn = (NDEFTagConnection) Connector.open(ur);
 
            // now create the NDEFRecord
            NDEFRecordType myType = new NDEFRecordType(NDEFRecordType.EXTERNAL_RTD, "urn:nfc:ext:nfc-research.at:pushreg");
            NDEFRecord myRec;
 
            // create Data-Container for Tag
            myRec = new NDEFRecord(myType, null, null);
 
            NDEFRecord[] myRecArray = new NDEFRecord[]{myRec};
            NDEFMessage myMessage = new NDEFMessage(myRecArray);
 
            // write Information to Tag
            ndconn.writeNDEF(myMessage);
 
            displayAlert("Writing succeeded!", AlertType.INFO);
        } catch (Exception e) {
            displayAlert("Error Writing to Tag! " + e.toString(), AlertType.ERROR);
        }
        try {
            ndconn.close();
        } catch (Exception e) {
        }
    }
 
    private void displayAlert(String error, AlertType type) {
        Alert err = new Alert(form.getTitle(), error, null, type);
        Display.getDisplay(this).setCurrent(err, form);
    }
}