Phone state listener called multiple times

[bhagavathram]

Hi all ,
When i try to detect incoming calls with phonestatelistener, it excites multiple times. This is my code. onCallStateChanged method is called multiple times.

1. onCallStateChanged o Service
2 .public int onStartCommand(Intent intent, int flags, int startId)
{
callHelper = new CallHelper(this);
callHelperl.start

}

-------------
callHelper.java

public void start()
{

TelephonyManager tm = (TelephonyManager) ctx.getSystemService(Context.TELEPHONY_SERVICE);
tm.listen(callStateListener, PhoneStateListener.LISTEN_CALL_STATE);

}

private class CallStateListener extends PhoneStateListener
{

Context context;
public void PhoneStateListener(Context context)
{
this.context = context;
}
@Override
public void onCallStateChanged(int state, final String incomingNumber)
{
System.out.println("onCallStateChanged Method" +state );

String ip = null;

switch (state)
{

case TelephonyManager.CALL_STATE_RINGING:
sysout("call ring ")
break;
}
}
}


Thanks in advance.
bhagavath