how to check if the textfield is active controlp5

Hello. Basically I'm getting outputs from key pressed buttons and I also want to have textfields. How do I make sure that when I'm writing on a textfield I don't get the outputs from the main code. I started with the code like this and I think the problem is I don't know how the function isFocus() works. Onoff is never getting true

import controlP5.*;
boolean onoff = false;
ControlP5 cp5;

void keyPressed() {
  }
  if ((key == 'a') && (onoff == false)) {
    //Do something normally
  }
}

cp5 = new ControlP5(this);
cp5.addTextfield("input_1")
.setPosition(20, 40)
.setSize(200, 40)

Textfield tf = (Textfield) cp5.getController("input_1");
    if (tf.isFocus() == true) {
      onoff=true;
    }
    else {
      onoff=false;
    }