android - Kotlin Android Jetpack 在后台 fragment 之间导航

Question

我有一个小应用程序。 1 个 Activity (MainActivity.kt) 和两个 fragment (MainFragment & CreateNewJobFragment)。

Mainfragment 有一个 Recyclerview。 CreateNewJobFragment 包含一个 6 个微调器和一个编辑文本。当用户做出选择并单击“创建作业”按钮时，我试图从微调器和编辑文本中进行选择以填充 RecyclerView。

问题是，当单击此按钮时，应用程序将返回返回堆栈到 MainFragment，但它不会用新项目填充 recyclerview，而是再次运行 onCreate 并且没有任何反应。

MainFragment.kt

class MainFragment : Fragment() ,ItemClickedCustomListener{
override fun onCustomSpinnerItemSelected(selectedItems: JobData) {

    Log.v("MainFragment","onCustomSpinnerItemSelected")
    Log.v("MainFragment","selectedItems --> "
            + selectedItems.companyName + " "
            + selectedItems.location + " "
            + selectedItems.pumpTruck + " "
            + selectedItems.smartPiggers)
    jobs.add(selectedItems)
    adapter = recyclerView.adapter as JobAdapter
    adapter.data(jobs)
}

var jobs = ArrayList<JobData>()
lateinit var  adapter : JobAdapter

private lateinit var binding: FragmentMainBinding
lateinit var recyclerView : RecyclerView

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

        if (savedInstanceState == null) {
            binding = FragmentMainBinding.inflate(inflater)
            //getting recyclerview from xml and binding it
            recyclerView = binding.jobRecyclerView

            //adding a layoutmanager
            recyclerView.layoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, false)

            //Arraylist to store jobs using the data class JobData.
            // TODO: Change this to a user created list from CreateNewJobFragment.kt
            jobs = ArrayList()

            Log.v("MainFragment", "onCreateView --> ")

            //creating adapter
            adapter = JobAdapter(jobs)

            //add adapter to recyclerView
            recyclerView.adapter = adapter

            //Setting onClickListener for FAB(floating action button) using Navigation
            binding.createNewJobFAB.setOnClickListener { v: View ->
                v.findNavController().navigate(R.id.action_mainFragment_to_createNewJobFragment)
            }
        }
    return binding.root
}

CreateNewJobFragment.kt

class CreateNewJobFragment : Fragment() {

private lateinit var binding: FragmentCreateNewJobBinding

override fun onCreateView(
    inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    binding = FragmentCreateNewJobBinding.inflate(inflater)
    return binding.root
}

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)

    var addJobToRecyclerview = JobData("","","","")


    //String array.
    //TODO: Move this to res/strings
    val companyNames = arrayOf("Company A", "Company B", "Company C", "Company D", "Company E")

    var nameSpinner = binding.spinnerCustomerName

    //Adapter for spinner
    nameSpinner.adapter = ArrayAdapter(activity, android.R.layout.simple_spinner_dropdown_item, companyNames)

    //item selected listener for spinner
    nameSpinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
        override fun onNothingSelected(p0: AdapterView<*>?) {
            TODO("not implemented yet")
        }

        override fun onItemSelected(p0: AdapterView<*>?, p1: View?, p2: Int, p3: Long) {
            //user selected spinner choice added
            addJobToRecyclerview.companyName = companyNames[p2]
        }
    }

    //String array.
    //TODO: Move this to res/strings
    val refineryTown = arrayOf("Long Beach", "Houston", "Cherry Point", "Wood River", "Bismark")

    var townSpinner = binding.spinnerLocation

    //Adapter for spinner
    townSpinner.adapter = ArrayAdapter(activity, android.R.layout.simple_spinner_dropdown_item, refineryTown)

    //item selected listener for spinner
    townSpinner.onItemSelectedListener = object : AdapterView.OnItemSelectedListener {
        override fun onNothingSelected(p0: AdapterView<*>?) {
            TODO("not implemented yet")
        }

        override fun onItemSelected(p0: AdapterView<*>?, p1: View?, p2: Int, p3: Long) {
            addJobToRecyclerview.location = refineryTown[p2]
        }
    }

    <SNIP>Cutting out 5 repeated spinners and editText to save some space</SNIP>


    //Setting onClickListener for 'Create Job' button using Navigation
    binding.buttonCreateJob.setOnClickListener { v: View ->
        (activity as MainActivity).itemClickedCustomListener.onCustomSpinnerItemSelected(addJobToRecyclerview)
        Log.v("CreateNewJobFragment", "Job data added -->$addJobToRecyclerview")
        Log.v("CreateNewJobFragment", "Create job button --> clicked")

        v.findNavController().navigate(R.id.action_createNewJobFragment_to_mainFragment)

    }

}

我使用以下 Android 文档作为指南:Implementing Navigation

这部分特别用于返回 MainFragment 的导航:Tie destinations to UI widgets

点击“创建作业”按钮后。 App 确实返回到 MainFragment。但如前所述，Recyclerview 中没有显示任何内容。

我有一些日志记录。这是来自日志:

日志样本

2018-12-07 22:03:17.959 5806-5806/com.palarran.pigtimer V/MainActivity: onCustomSpinnerItemSelected

2018-12-07 22:03:17.959 5806-5806/com.palarran.pigtimer V/MainActivity: selectedItems --> Company A Long Beach Company 1 Company 4

2018-12-07 22:03:17.960 5806-5806/com.palarran.pigtimer V/CreateNewJobFragment: Job data added -->JobData(companyName=Company A, location=Long Beach, pumpTruck=Company 1, smartPiggers=Company 4)

2018-12-07 22:03:17.960 5806-5806/com.palarran.pigtimer V/CreateNewJobFragment: Create job button --> clicked

2018-12-07 22:03:18.026 5806-5806/com.palarran.pigtimer V/MainFragment: onCreateView -->

2018-12-07 22:03:18.146 5806-5806/com.palarran.pigtimer V/JobAdapter: getItemCount 0

2018-12-07 22:03:18.146 5806-5806/com.palarran.pigtimer V/JobAdapter: getItemCount 0

如您所见，在“创建作业按钮 --> 单击”的日志条目之后，它跳转到 MainFragment 中的“onCreateView”，并且我的自定义适配器 (JobAdapter.kt) 中的项目计数没有增加。

JobAdapter.kt

class JobAdapter(private var jobList: ArrayList<JobData>) : RecyclerView.Adapter<JobAdapter.ViewHolder>() {

//Returning view for each item in the list
override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): JobAdapter.ViewHolder {
    val v = LayoutInflater.from(parent.context).inflate(R.layout.job_list_item, parent, false)
    Log.v("JobAdapter","onCreateViewHolder")
    return ViewHolder(v)
}

//Binding the data on the list
override fun onBindViewHolder(holder: JobAdapter.ViewHolder, position: Int) {
    Log.v("JobAdapter","onBindViewHolder")
    holder.bindItems(jobList[position])
}

override fun getItemCount(): Int {
    Log.v("JobAdapter","getItemCount " + jobList.size)
    return jobList.size
}

fun data(jobs: ArrayList<JobData>) {
    Log.v("JobAdapter","DataSetChanged")
    jobList = jobs
    notifyDataSetChanged()
}

//Class holds the job list view
class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {

    fun bindItems(job: JobData) {
        val textViewCompanyName = itemView.findViewById(R.id.tv_companyName) as TextView
        val textViewLocation  = itemView.findViewById(R.id.tv_job_location) as TextView

        textViewCompanyName.text = job.companyName
        Log.v("JobAdapter", "bindItems" + textViewCompanyName.text)
        textViewLocation.text = job.location
        Log.v("JobAdapter", "bindItems" + textViewLocation.text)
    }
}

我是否遗漏了文档中的某些内容或阅读错误？我肯定误会了什么。

Answer 1

对此回复晚了。

我能够弄清楚这一点。通过使用 Sugar ORM 数据库。在我的 MainFragment 中的 onResume() 中调用它。

这是一个愚蠢的问题，我应该在发布之前进行更多研究。