java.lang.RuntimeException: Handler sending message to a Handler on a dead thread

Question

I'm using Google Cloud Message to send a message to my phone from a server. When I include Toast.makeText() inside of onHandleIntent, it gave me an handler error:

java.lang.RuntimeException: Handler (android.os.Handler) sending message to a Handler on a dead thread

protected void onHandleIntent(Intent intent) {
    Bundle extras = intent.getExtras();
    GoogleCloudMessaging gcm = GoogleCloudMessaging.getInstance(this);
    String messageType = gcm.getMessageType(intent);

    if (!extras.isEmpty()) { // has effect of unparcelling Bundle
        mes = extras.getString("text");
        //**********this works***********
        //showToast();
        Log.i("GCM",
                "Received : (" + messageType + ")  "
                        + extras.getString("iCal"));
        //**********doesn't work*********** 
        Toast.makeText(getApplicationContext(), mes, Toast.LENGTH_LONG).show();
    }
    // Release the wake lock provided by the WakefulBroadcastReceiver.
    GcmBroadcastReceiver.completeWakefulIntent(intent);
}

public void showToast() {
    handler.post(new Runnable() {
        public void run() {
            Toast.makeText(getApplicationContext(), mes, Toast.LENGTH_LONG)
                    .show();
        }
    });

}

But when I tried having showToast() function defined on the bottom of onHandleIntent function in onHandleIntent(), toast showed up fine. I know this is a handler problem from reading this java.lang.RuntimeException: Handler (android.os.Handler) sending message to a Handler on a dead thread

but I don't fully understand that answer. Could anyone explain more in detail so I can understand?

Thank you for your help in advance!