i want to set brightness of my android activity,but it cannot take effect ,below is the code

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http://stackoverflow.com – public class MenuSettingFragment extends Fragment implements OnKeyListener,OnFocusChangeListener { private String TAG = "MenuSettingFragment"; private TextView languageText,brightText; private String[] brightArray; private int brightIndex; private Drawable bitmapBg,bitmapSelectBg; private RelativeLayout languageLayout,brightLayout; private View view; private ContentResolver contentResolver; private WindowManager.LayoutParams lp; private Context mContext; private ActivityManager am; public View onCreateView(LayoutInflater inflater, ViewGroup co (HowTos)