Question

我是android的新手，只是kotlin的初学者。我有带有标签布局和viewpager的android应用。我有两个选项卡的两个片段。我需要一些从main.kt到fragment.kt的值，我不知道如何将这些值从main.kt传递给fragment.kt。

在我的fragment.kt文件中，我有一个要调用这样的另一个类

recyclerView.adapter = TransactionRecyclerAdapter(transactionList,appDatabase,direction,networkDefinitionProvider)

此类必须有一个参数，因此我需要main.kt中的值。

我无法传递捆绑包中的值，因为值返回的类型是这样的

private val mfragmentAB = appDatabase
        private val mfragmentIT: List<TransactionEntity>? = it
        private val mfragmentINC : TransactionAdapterDirection? = incoming
        private val mfragmentnetwork : NetworkDefinitionProvider? = networkDefinitionProvider
        private val mfragmentviewpager : ViewPager? = viewPager

，所以序列化和可缩放不起作用。请指导我。

main.kt

private fun setupViewPager(viewPager: ViewPager, it: List<TransactionEntity>?, incoming: TransactionAdapterDirection) {
        val incomingData = ArrayList<TransactionEntity>()
        val outgoingData = ArrayList<TransactionEntity>()

        val adapter = ViewPagerAdapter(supportFragmentManager, viewPager, it, incoming, appDatabase, networkDefinitionProvider)
        if(incoming == INCOMING) {
            if (it != null) {
                incomingData.addAll(it)
            }
        }else {
            if (it != null) {
                outgoingData.addAll(it)
            }
        }
        adapter.addFragment(ReceiveFragment(), "SEND")
        adapter.addFragment(SendingFragment(), "RECEIVE")
        viewPager.adapter = adapter
        adapter.notifyDataSetChanged();
    }

    class ViewPagerAdapter(manager: FragmentManager, viewPager: ViewPager?, it: List<TransactionEntity>?, incoming: TransactionAdapterDirection?, appDatabase: AppDatabase?, networkDefinitionProvider: NetworkDefinitionProvider?) : FragmentPagerAdapter(manager)
    {


        private val mFragmentList: ArrayList<Fragment> = ArrayList<Fragment>()
        private val mFragmentTitleList: ArrayList<String>  = ArrayList<String>()

        private val mfragmentAB = appDatabase
        private val mfragmentIT: List<TransactionEntity>? = it
        private val mfragmentINC : TransactionAdapterDirection? = incoming
        private val mfragmentnetwork : NetworkDefinitionProvider? = networkDefinitionProvider
        private val mfragmentviewpager : ViewPager? = viewPager

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

         override fun getItem(position: Int): Fragment? {
             var fragment: Fragment? = null
             if (position == 0) {
                 fragment = SendingFragment()
             } else if (position == 1) {
                 fragment = ReceiveFragment()
             }
             return fragment
         }


        fun addFragment(fragment: Fragment, title: String) {
            mFragmentList.add(fragment)
            mFragmentTitleList.add(title)
        }

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

        override fun getItemPosition(fragItem: Any): Int {
            var position = 0
            if (fragItem is ReceiveFragment) {
                position = 0
            } else if (fragItem is SendingFragment) {
                position = 1
            }
            return if (position >= 0) position else PagerAdapter.POSITION_NONE
        }

    }

frgment.kt

class ReceiveFragment : Fragment(){


    private var linearLayoutManager: LinearLayoutManager? = null

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

    }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {

        val rootView = inflater.inflate(R.layout.receive_fragment, container, false)
        val recyclerView = rootView.findViewById<RecyclerView>(R.id.transaction_recycler_in) as RecyclerView
        linearLayoutManager = LinearLayoutManager(getActivity(), LinearLayout.VERTICAL, false)
        recyclerView.layoutManager = linearLayoutManager
        recyclerView.adapter = TransactionRecyclerAdapter(transactionList,appDatabase,direction,networkDefinitionProvider)
        recyclerView.setHasFixedSize(true);
        return rootView
    }
}

更新

companion object {
        /**
         * new instance pattern for fragment
         */
        @JvmStatic
        fun newInstance(myObject: List<TransactionEntity>?): ReceiveFragment {
            val newsFragment = ReceiveFragment()
            val args = Bundle()
            args.putParcelable(ARG_PARAM, myObject) ------**-Here i can not pass my values to onCreateView**
            return newsFragment
        }
    }

UPADTE -1

    companion object {
            /**
             * new instance pattern for fragment
             */
            @JvmStatic
            fun newInstance(myObject: List<TransactionEntity>?): ReceiveFragment {
                val gson = Gson()
                val model = myObject as List<TransactionEntity>
                val json = gson.toJson(model)
                System.out.println("json representation :" + json)
                val bundle = Bundle()
                bundle.putString("bundleValue", json)
                val receiveFragment: ReceiveFragment = ReceiveFragment()
                receiveFragment.setArguments(bundle)
                return receiveFragment
            }
        }

    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {

            val gson = Gson()
            val parsedValue = arguments!!.getString("bundleValue")
 val turnsType = TypeToken<List<TransactionEntity>>() {}.type
        //val animals = gson.fromJson(parsedValue,turnsType )
            val animals = gson.fromJson(parsedValue, ) -------- how to get value here

并且TypeToken是错误，显示没有构造函数

Answer 1

您可以像这样使用Gson（）解析对象：

val parsedValue = Gson().toJson(value, object: TypeToken<StrangeType>(){}.type)
val bundle = Bundle()
bundle.putString("bundleValue", parsedValue)
val receiveFragment: ReceiveFragment = ReceiveFragment()
receiveFragment.setArguments(bundle)

，然后在您片段的onCreateView()

中

val parsedValue = arguments.getString("bundleValue")
val value: StrangeType = Gson().fromJson(parsedValue!!, object: TypeToken<StrangeType>(){}.type)

StrangeType是要发送到Fragment的对象的类型。

Answer 2

尝试一下：TransactionEntity必须实现Serializable

fun newInstance(myObject: ArrayList<TransactionEntity>?): ReceiveFragment {
        val newsFragment = ReceiveFragment()
        val args = Bundle()
        args.putSerializable(ARG_PARAM, myObject) 
        return newsFragment
    }

及之后：

arguments.getSerializable(ARG_PARAM) as ArrayList<TransactionEntity>

如何在Kotlin中的片段中传递我的自定义类型值？

2 个答案: