在app开发过程中需要获取通知栏开关的状态
1.针对8.0之前设备，通过AppOpsManager的checkOpNoThrow方法获取。

 public static boolean isEnableV19(Context context, String pkg, int uid) {
        try {
            String CHECK_OP_NO_THROW = "checkOpNoThrow";
            String OP_POST_NOTIFICATION = "OP_POST_NOTIFICATION";
            Class appOpsClass = null;
            AppOpsManager mAppOps = null;
            mAppOps = (AppOpsManager) context.getSystemService(Context.APP_OPS_SERVICE);
            appOpsClass = Class.forName(AppOpsManager.class.getName());
            Method checkOpNoThrowMethod = appOpsClass.getMethod(CHECK_OP_NO_THROW, Integer.TYPE,
                    Integer.TYPE, String.class);
            Field opPostNotificationValue = appOpsClass.getDeclaredField(OP_POST_NOTIFICATION);

            int value = (Integer) opPostNotificationValue.get(Integer.class);
            return ((Integer) checkOpNoThrowMethod.invoke(mAppOps, value, uid, pkg) ==
                    AppOpsManager.MODE_ALLOWED);
        } catch (Exception e) {
            return true;
        }
    }

2.针对8.0及以上设备，发现上述方式不生效。查询系统设置源码，在NotificationBackend类中发现获取通知栏状态改到INotificationManager中了

    public boolean getNotificationsBanned(String pkg, int uid) {
       try {
            final boolean enabled = sINM.areNotificationsEnabledForPackage(pkg, uid);
            return !enabled;
       } catch (Exception e) {
            Log.w(TAG, "Error calling NoMan", e);
            return false;
        }
    }

提供给APP适用的的NotificationManager 类中有INotificationManager 对象，最终我们通过反射获取通知栏开关

    public static boolean isEnableV26(Context context, String pkg, int uid) {
        try {
            NotificationManager notificationManager = (NotificationManager)
                    context.getSystemService(Context.NOTIFICATION_SERVICE);
            Method sServiceField = notificationManager.getClass().getDeclaredMethod("getService");
            sServiceField.setAccessible(true);
            Object sService = sServiceField.invoke(notificationManager);

            Method method = sService.getClass().getDeclaredMethod("areNotificationsEnabledForPackage"
                    , String.class, Integer.TYPE);
            method.setAccessible(true);
            return (boolean) method.invoke(sService, pkg, uid);
        } catch (Exception e) {
            return true;
        }
    }