android 6.0上只写在AndroidManifest中是不行的，还必须手动打开才行

    private void setBrightnessMode(Context context, int mode) {

        try {

            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {

                if (Settings.System.canWrite(context)) {

                    Settings.System.putInt(context.getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE, mode);

                } else {

                    Intent intent = new Intent(android.provider.Settings.ACTION_MANAGE_WRITE_SETTINGS);

                    intent.setData(Uri.parse("package:" + context.getPackageName()));

                    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);

                    context.startActivity(intent);

                }

            } else {

                Settings.System.putInt(context.getContentResolver(), Settings.System.SCREEN_BRIGHTNESS_MODE, mode);

            }

        } catch (Exception e) {

            e.printStackTrace();

        }

    }