<=Api 23 时 相信大家都是通过installPackage这个类反射来静默安装apk的。但是呢api24及其之后就没有这个方法了，你再PackageManagerService或IPackageManager都是没有这个方法了。所以我们只能通过installPacakageAsUser来实现静默安装了。代码如下：

   /**
     * void installPackageAsUser(in String originPath,
     * in IPackageInstallObserver2 observer,
     * int flags,
     * in String installerPackageName,
     * int userId);
     * @param installPath
     */
    private void installApkInSilence(String installPath,String packageName) {
        Class<?> pmService;
        Class<?> activityTherad;
        Method method;
        try {
            activityTherad = Class.forName("android.app.ActivityThread");
            Class<?> paramTypes[] = getParamTypes(activityTherad, "getPackageManager");
            method = activityTherad.getMethod("getPackageManager", paramTypes);
            Object PackageManagerService = method.invoke(activityTherad);
            pmService = PackageManagerService.getClass();
            Class<?> paramTypes1[] = getParamTypes(pmService, "installPackageAsUser");
            method = pmService.getMethod("installPackageAsUser", paramTypes1);
            method.invoke(PackageManagerService, installPath, null, 0x00000040, packageName, getUserId(Binder.getCallingUid()));//getUserId
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
    }

    private Class<?>[] getParamTypes(Class<?> cls, String mName) {
        Class<?> cs[] = null;
        Method[] mtd = cls.getMethods();
        for (int i = 0; i < mtd.length; i++) {
            if (!mtd[i].getName().equals(mName)) {
                continue;
            }

            cs = mtd[i].getParameterTypes();
        }
        return cs;
    }
    public static final int PER_USER_RANGE = 100000;
    public static int getUserId(int uid) {
        return uid / PER_USER_RANGE;
    }