Mediaplayers get not muted / unmuted properly

I set up a Checkbox, If it is unchecked the mediaplayers should Immediately be unmuted, when checked immediately muted, now I have the problem that when I check / uncheck the checkbox the sound will not be muted / unmuted immediately but as recently I restart the activity... How can I set up that it willimmediately be muted?

Code of the muted section:

      checkBoxmp.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {


        @Override
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {

            editor.putBoolean("playSounds", !isChecked);
            editor.apply();
            if (null != mp && null != mp2) {
                if (!isChecked) {
                    mp.setVolume(1, 1);
                    mp2.setVolume(1, 1);
                } else {
                    mp.setVolume(0, 0);
                    mp2.setVolume(0, 0);
                }
            }
        }
    });