Android中如何禁止音量调节至静音

public void handleKeyDown(KeyEvent event, int stream) {
        int keyCode = event.getKeyCode();
        switch (keyCode) {
            case KeyEvent.KEYCODE_VOLUME_UP:
            case KeyEvent.KEYCODE_VOLUME_DOWN:
                /*
                 * Adjust the volume in on key down since it is more
                 * responsive to the user.
                 */
                int flags = FLAG_SHOW_UI | FLAG_VIBRATE;
                /* avoid auto mute when adjust lower */
                int currentVolume = getStreamVolume(STREAM_MUSIC);
                Log.e(TAG, String.format("currentVolume=%d", currentVolume));
                if (keyCode == KeyEvent.KEYCODE_VOLUME_DOWN && currentVolume <= 1) {
                    break;
                }
                if (mUseMasterVolume) {
                    adjustMasterVolume(
                            keyCode == KeyEvent.KEYCODE_VOLUME_UP
                                    ? ADJUST_RAISE
                                    : ADJUST_LOWER,
                            flags);
                } else {