The content of appdesigner TextArea can not be changed

I have created an appdesigner application to comunicate with serial device. However, I find the content of Textarea can not be changed. The following code in the red rectangele is the code, I am conviced that the code have been reached, but it can not work.

Answer 1

[he he]

This is the application. I think i have find the problem. When I input "clear" and the enter key, I have to click the applicaiton, then it works. So there is another question: How to make the input of "clear" and enter work immidiately.