将Fragment与制表符一起使用。指定的子级已具有父级

Question

我正在使用3个标签构建一个像WhatsApp一样的应用程序，每个标签都有一个< code >片段。在我的第一个< code >片段中，我有一个< code > recycle view 。

赢取一套SectionsPager适配器，开始宽度Recy，如下图所示：

inner class SectionsPagerAdapter(fm: FragmentManager) : FragmentPagerAdapter(fm) {

        override fun getItem(position: Int): Fragment {
            // getItem is called to instantiate the fragment for the given page.
            // Return a PlaceholderFragment (defined as a static inner class below).
            //return PlaceholderFragment.newInstance(position + 1)
            when(position){
                0 ->  return Fragmenttask.newInstance()
                1 ->  return FragmentChat.newInstance()
                2 ->  return FragmentMaps.newInstance()
                else  -> {
                    return null!!
                }
            }
        }

        override fun getCount(): Int {
            // Show 3 total pages.
            return 3
        }
    }

它给了我这个错误：

E/AndroidRuntime:致命异常：主进程：com.deraah.mohamed。deraahpro，PID:21993 java.lang.IllegalStateException：指定的子级已经有父级。必须首先对孩子的父级调用removeView（）。位于android.support.v4.view.ViewPager.addView（ViewPager.java:1477）的android.view.ViewGroup.addView（视图组java:4937），位于androids.support.v4.app.FragmentManagerImpl.moveToState（FragmentManager java:1425）android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState（FragmentManager.java:1740），位于android.support.v 4.app.BackStackRecord.executeOps（BackStack Record.java:794），位于Android.support.v4.app.碎片管理器Impl.execute Ops（碎片管理器.java:2580）android.support.v4.app.FragmentManagerImpl.removeRedundantOperationsAndExecute（FragmentManager.java:2322），位于android/support.v 4.app.FragmentManager Impl.execSingleAction（Fragment Manager.java：2199），位于android.support.v4.app.BackStackRecord.commitNowAllowingStateLoss（BackStack Record.java:651），位于android.support.v4.view.ViewPager.setCurrentItemInternal（ViewPager.java:662）位于android.support.v4.view.ViewPagerandroid.support.design.widget.TabLayout.dispatchTabSelected（TabLayer.java:1165）位于android/support.ddesign.wikit.TabLayout.selectTab（TabLayout.java:1158），位于androidsupport.destig.widget.Tab Layout.selectionTab（TabLayout_java:1128），位于android.support.design.widget.Tab2Layout$TabSelect（TabLayout.java:1537）位于android.view.view$PerformClick.run（view.java:24770），位于androids.os.Handler.handlerCallback（Handler.java:790），位于Android.os.Handler.dispatchMessage（Hanler.java:99），位于android.app.ActivityThread.main（ActivityThread.java:6494），位于java.lang.reflect.Method。在com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run（RuntimeInite.java:438）在com.aandroid.iinternal.os.ZygoteInit.main（Zygote Init.java:807）调用（本机方法）

更新

我的碎片：

聊天：

/**
 * A simple [Fragment] subclass.
 * Activities that contain this fragment must implement the
 * [FragmentChat.OnFragmentInteractionListener] interface
 * to handle interaction events.
 * Use the [FragmentChat.newInstance] factory method to
 * create an instance of this fragment.
 */
class FragmentChat : Fragment() {

    private var mListener: OnFragmentInteractionListener? = null

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

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        return inflater!!.inflate(R.layout.fragment_fragment_chat, container, false)
    }

    // TODO: Rename method, update argument and hook method into UI event
    fun onButtonPressed(uri: Uri) {
        if (mListener != null) {
            mListener!!.onFragmentInteraction(uri)
        }
    }

    override fun onAttach(context: Context?) {
        super.onAttach(context)
    }

    override fun onDetach() {
        super.onDetach()
        mListener = null
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     *
     *
     * See the Android Training lesson [Communicating with Other Fragments](http://developer.android.com/training/basics/fragments/communicating.html) for more information.
     */
    interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        fun onFragmentInteraction(uri: Uri)
    }

    companion object {

        // TODO: Rename and change types and number of parameters
        fun newInstance(): FragmentChat {
            val fragment = FragmentChat()
            val args = Bundle()
            fragment.arguments = args
            return fragment
        }
    }
}// Required empty public constructor

片段映射：

/**
 * A simple [Fragment] subclass.
 * Activities that contain this fragment must implement the
 * [FragmentMaps.OnFragmentInteractionListener] interface
 * to handle interaction events.
 * Use the [FragmentMaps.newInstance] factory method to
 * create an instance of this fragment.
 */
class FragmentMaps : Fragment() {

    private var mListener: OnFragmentInteractionListener? = null

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

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        // Inflate the layout for this fragment
        return inflater!!.inflate(R.layout.fragment_fragment_maps, container, false)
    }

    // TODO: Rename method, update argument and hook method into UI event
    fun onButtonPressed(uri: Uri) {
        if (mListener != null) {
            mListener!!.onFragmentInteraction(uri)
        }
    }

    override fun onDetach() {
        super.onDetach()
        mListener = null
    }


    interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        fun onFragmentInteraction(uri: Uri)
    }

    companion object {
        // TODO: Rename and change types and number of parameters
        fun newInstance(): FragmentMaps {
            val fragment = FragmentMaps()
            val args = Bundle()
            fragment.arguments = args
            return fragment
        }
    }
}// Required empty public constructor

片段任务：

class Fragmenttask : Fragment() {

    private var mListener: OnFragmentInteractionListener? = null

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

    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        val CustumViewtask = inflater!!.inflate(R.layout.fragment_fragmenttask, container, false)
        val taskMainRV = CustumViewtask.findViewById(R.id.recyclerView_main) as RecyclerView
        //taskMainRV.setBackgroundColor(Color.BLUE)

        taskMainRV.layoutManager = LinearLayoutManager(context)
        //recyclerView_main.adapter = MainAdapter()

        fetchJson(taskMainRV)

        return taskMainRV
    }

    fun fetchJson(RSV: RecyclerView) {

        //SharedPreferences
        val MY_APP_INFO: String = "UserInfo"
        val prefs = activity.getSharedPreferences(MY_APP_INFO, AppCompatActivity.MODE_PRIVATE)
        val LoggedUserId = prefs.getString("UserId", null)
        println("your code is : $LoggedUserId")

        println("Attempting to Fetch JSON")

        val url = "http://Restful.com/get_tasks.php"

        val client = OkHttpClient()

        val formBody = FormBody.Builder().add("UserId", LoggedUserId).build()

        val request = Request.Builder().url(url)
                .post(formBody)
                .build()

        client.newCall(request).enqueue(object: Callback {
            override fun onResponse(call: Call?, response: Response?) {
                val body = response?.body()?.string()
                println("mohamed : $body")

                val gson = GsonBuilder().create()

                val tasksfeed = gson.fromJson(body, M_tasksFeed::class.java)

                activity.runOnUiThread {
                    RSV.adapter = MainAdaptertasks(tasksfeed)
                }

            }

            override fun onFailure(call: Call?, e: IOException?) {
                println("Failed to execute request")
            }
        })
    }

    // TODO: Rename method, update argument and hook method into UI event
    fun onButtonPressed(uri: Uri) {
        if (mListener != null) {
            mListener!!.onFragmentInteraction(uri)
        }
    }

    override fun onDetach() {
        super.onDetach()
        mListener = null
    }

    /**
     * This interface must be implemented by activities that contain this
     * fragment to allow an interaction in this fragment to be communicated
     * to the activity and potentially other fragments contained in that
     * activity.
     *
     *
     * See the Android Training lesson [Communicating with Other Fragments](http://developer.android.com/training/basics/fragments/communicating.html) for more information.
     */
    interface OnFragmentInteractionListener {
        // TODO: Update argument type and name
        fun onFragmentInteraction(uri: Uri)
    }

    companion object {
        fun newInstance(): Fragmenttask {
            val fragment = Fragmenttask()
            val args = Bundle()
            fragment.arguments = args
            return fragment
        }
    }
}// Required empty public constructor

Answer 1

问题来自

       else  -> {
                return null!!
            }

试试这种方式

override fun getItem(position: Int): android.support.v4.app.Fragment {

        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        //return PlaceholderFragment.newInstance(position + 1)
       var fragment: android.support.v4.app.Fragment? = null
       when (position) {
           0 -> fragment = Fragmenttask.newInstance()
           1 -> fragment = FragmentChat.newInstance()
           2 -> fragment = FragmentMaps.newInstance()
       }

       return fragment!!
   }

   override fun getCount(): Int {
       return 3           //no of cases/fragments
   }

}

< code >仅供参考

您必须调用 removeView（） 。

每个片段部分

 View viewOBJ = inflater.inflate(R.layout.layout_child, parent_layout, false);

  return viewOBJ ;

Answer 2

您确定在膨胀片段视图时将attachRootView设置为false了吗？

inflater.inflate(R.layout.fragment, container, false)

Answer 3

您返回了错误的视图签入Fragmenttask

使用这个

 return CustumViewtask

取而代之的是这个

return taskMainRV

像这样更改代码

override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?,
                              savedInstanceState: Bundle?): View? {
        val CustumViewtask = inflater!!.inflate(R.layout.fragment_fragmenttask, container, false)
        val taskMainRV = CustumViewtask.findViewById(R.id.recyclerView_main) as RecyclerView
        //taskMainRV.setBackgroundColor(Color.BLUE)

        taskMainRV.layoutManager = LinearLayoutManager(context)
        //recyclerView_main.adapter = MainAdapter()

        fetchJson(taskMainRV)

        return CustumViewtask
    }