Wireless Messaging API - Beginning J2ME: From Novice to Professional - page 176

Creating an Independent Receive Thread
SMSMIDlet actually uses a separate receive thread to process incoming messages. This thread
will also set the ImageItem of the GUI with a different Image depending on incoming SMS messages.
The startReceive() method in Listing 11-1 contains the code that starts the receive thread.
The run() method contains the logic of the receive thread. The blocking receive() call is used
in this case. The mEndNow boolean flag stops the thread when the application is destroyed; see
the destroyApp() implementation.
The receive thread opens a server mode MessageConnection on port 1234 . When there are
no incoming messages, the receive thread is blocked in one of the receive() methods. Upon
receipt of a message, the text payload is extracted and compared to “red” or “blue”. Then
Display.callSerially() updates the image shown on the GUI. Two helper classes, SetRed and
SetBlue , are used when calling this method.
Sending SMS Messages
Listing 11-2 shows the class, called Sender , that is used to send SMS messages. SMSMIDlet main-
tains an instance of this class called mSender . The instance is used to send SMS messages when
the user selects either Send Red or Send Blue from the menu.
Listing 11-2. Sending SMS Message with Sender
import javax.microedition.io.*;
import javax.wireless.messaging.*;
import java.io.IOException;
public class Sender implements Runnable {
private static Sender inst = new Sender();
private Sender() {
}
public static Sender getInstance() {
return inst;
}
private String mReceiver = null;
private String mPort = null;
private String msgString = null;
private boolean mSending = false;
public void sendMsg(String rcvr, String port, String msgText) {
if (mSending) return;
mReceiver = rcvr;
mPort = port;
msgString = msgText;
Thread th = new Thread(this);
th.start();
}