This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
In line 12 you are creating a new local variable called message that isn't used. You probably wanted to set the member variable declared in line 6 to some message. If that's the case, change line 12 to:
Without the type String in front of it, because that means you're declaring a new variable instead of setting the existing member variable.
In line 21 you're drawing the empty string "". You probably meant to draw the message there instead: