Kotlin 错误：Dagger 不支持注入私有字段

我在kotlin活动中使用ViewPager，我想在kotlin片段中使用dagger 注射.我有一个错误:dagger 不支持注入私有领域.

in my kotlin activity

mPagerAdapter = object : FragmentPagerAdapter(supportFragmentManager) {

        private val mFragments = arrayOf(KotlinFragment(), JavaFragment())
        private val mFragmentNames = arrayOf(getString(R.string.cashdocuments), getString(R.string.action_absmysql))

        override fun getItem(position: Int): Fragment {
            return mFragments[position]
        }

        override fun getCount(): Int {
            return mFragments.size
        }

        override fun getPageTitle(position: Int): CharSequence {
            return mFragmentNames[position]
        }
    }

我的Kotlin 碎片

class KotlinFragment : Fragment()  {


@Inject
internal var mSharedPreferences: SharedPreferences? = null

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)

    (activity.application as SamfantozziApp).dgaeacomponent().inject(this)

}

override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
                          savedInstanceState: Bundle?): View? {
    super.onCreateView(inflater, container, savedInstanceState)
    val rootView = inflater!!.inflate(R.layout.activity_absserver, container, false)

    return rootView
}

}

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