Can't enable clicked disabled button in android

I'm struggeling to enable a disabled button when it's clicked. I know it sounds weird, but let me explain: when index equals -1 the button should be disabled. If index is greater than -1 the button should be enabled. The problem is when I click on the disabled button and index is greater than -1, the button is still disabled. I tried btn.setOnclicklister(null), but it didn't work.

the code:

 btn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {


                    if (index == -1){
                        btn.setOnClickListener(null);
                        btn.setEnabled(false);
                        btn.setClickable(false);


                    }else if (index > -1){

                       btn.setOnClickListener(this);
                        btn.setEnabled(true);
                        btn.setClickable(true);

                    }


                }
            });

You should enable OnClickListener every time you set index to not -1:

View.OnClickListener listener = new View.OnClickListener() {
  @Override
  public void onClick(View v) {
     // do something helpful you want on click
     // and disable the button
      if (index == -1){
         btn.setOnClickListener(null);
         btn.setEnabled(false);
         btn.setClickable(false);
     }
  }
}

And somewhere:

...
index = 1;
btn.setOnClickListener(listener);
btn.setEnabled(true);
btn.setClickable(true);
...