Android - Activa/Desactivar btn con cb

CheckBox cb1;

    Button btn1;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        cb1 = (CheckBox) findViewById(R.id.cb1);

        btn1 = (Button) findViewById(R.id.btn1);

        if (cb1.isChecked(true)){

            btn1.isEnabled(false);

        }

}

CheckBox cb1;

Button btn1;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

cb1 = (CheckBox) findViewById(R.id.cb1);

btn1 = (Button) findViewById(R.id.btn1);

    cb1.setOnCheckedChangeListener(new OnCheckedChangeListener() {

		@Override

		public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

			if (buttonView.isChecked(true)){

                btn1.isEnabled(false);

            }

		}

	 });

}