I tried to just setVisible(false) them, but it says I can't.

The setVisible method works for me, try the code below. You say you want to ' delete the last line of GTextFields' - if these are in an array or ArrayList then you have to use setVisible on each textfield not the actual array.

So what is the actual error message?

Tried also with MyTextField.dispose(), and it is disposed, but not erased from the screen.

Thats good news there used to be a bug in the dispose method, and you now say it works ...

EDIT code added

1. import g4p_controls.*;
2. GTextField txf;
3. 
   
4. public void setup(){
5.   size(300,300);
6.   txf = new GTextField(this,20,20,200,20);
7.   txf.setText("Quarks");
8. }
9. 
   
10. public void draw(){
11.   background(200);
12. }
13. 
    
14. public void mouseClicked(){
15.   boolean v = txf.isVisible();
16.   txf.setVisible(!v);
17. }

Your code works, so I understood I need to clean the screen with background().....silly enough.... I didn't want to do it to save a little time (I have up to 4 GWindows opened together..), but in fact I don't know how much does background() weight on resources.

So I'm adding that and it works.

To be correct I didn't have errors with setVisible().. so just my fault.
and I was wrong again in saying that 'dispose()' worked. it was setEnabled(false) instead, which I'm using to avoid changing the first field of one line, used as the line number.

So thanks again. I have another little question, but I need to take a snapshot to explain. (and I think it's better to open another thread..)

Regards. Davide.