android setKeyListener event not setting the keys as desired

Myself trying to enable/disable a textfield using checkbox as,

 tv = (EditText) findViewById(R.id.tv);
 cb = (CheckBox) findViewById(R.id.cb);
 tv.setFocusable(false);
 tv.setKeyListener(null);
 tv.setEnabled(false);

  cb.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

           @Override
            public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
                    if(isChecked) {
                        tv.setFocusable(true);
                        tv.setEnabled(true);
                        tv.setKeyListener(new DigitsKeyListener(false, true));
                    } else {
                        tv.setFocusable(false);
                        tv.setEnabled(false);
                        tv.setKeyListener(null);
                    }
                }
            }
        );

The above code is in onCreate method. But even when the checkbox checked, the tv.setKeyListener(new DigitsKeyListener(false, true)); doesn't enabling the keys. Where myself missed?