Cannot call a kotlin class (kanban) within my java class(myFragment) at position= 1. Below is the code. It appears to be not recognized by the IDE. Ive added the kanban.kt as well as the myFragment class. Subsequently cannot call the class Kanban.kt in the latter's class.

public class MyFragment extends FragmentStateAdapter {

    public MyFragment(@NonNull FragmentManager fm,Lifecycle lifecycle) {
        super(fm,lifecycle);
    }

    @NonNull
    @Override
    public Fragment createFragment(int position) {
        if(position==1)
        {
            return new com.example.myhouse.kanban();  //add kotlin class
        }
        if(position==2) {
            return new signOut();
        }
            return new Navigation_Bar();
    }
    @Override
    public int getItemCount() {
        return 3;
    }
}

package com.example.myhouse;
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import androidx.appcompat.app.AppCompatActivity
import androidx.fragment.app.Fragment
import androidx.fragment.app.FragmentActivity
import androidx.lifecycle.ViewModelProvider
import androidx.viewpager2.adapter.FragmentStateAdapter
import androidx.viewpager2.widget.ViewPager2
import com.brsthegck.kanbanboard.TaskViewModel
import com.example.myhouse.R
import com.example.myhouse.Task
import com.google.android.material.tabs.TabLayout
import com.google.android.material.tabs.TabLayoutMediator
import com.google.gson.Gson
import com.google.gson.reflect.TypeToken
import java.util.*

private const val ARG_TASKLIST_TYPE = "tasklist_type"
private const val TASKLIST_TYPE_TODO = 0
private const val TASKLIST_TYPE_DOING = 1
private const val TASKLIST_TYPE_DONE = 2
private const val NUM_TASKLIST_PAGES = 3

private const val KEY_TODO_JSON = "todo_json"
private const val KEY_DOING_JSON = "doing_json"
private const val KEY_DONE_JSON = "done_json"

class Kanban : AppCompatActivity(), TasklistFragment.Callbacks {
    private lateinit var viewPager: ViewPager2
    private lateinit var tabLayout: TabLayout

    private lateinit var taskViewModel: TaskViewModel

    //When add action bar button is pressed
    override fun onOptionsItemSelected(item: MenuItem) = when(item.itemId){
        R.id.action_new_task -> {
            val currentTasklistType = viewPager.currentItem

            val currentTasklist = when(currentTasklistType){
                TASKLIST_TYPE_TODO -> taskViewModel.todoTaskList
                TASKLIST_TYPE_DOING -> taskViewModel.doingTaskList
                TASKLIST_TYPE_DONE -> taskViewModel.doneTaskList
                else -> throw Exception("Unrecognized tasklist type")
            }

            val currentFragment = (supportFragmentManager.fragments[currentTasklistType] as TasklistFragment)

            addTaskToViewModel(Task(), currentTasklistType)

            currentFragment.taskRecyclerView.scrollToPosition(currentTasklist.size - 1)
            true
        }
        else -> super.onOptionsItemSelected(item)
    }

    //Inflate the action bar menu resource on options menu creation
    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
        menuInflater.inflate(R.menu.menu_action_bar, menu)
        return true
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //Get viewmodel
        taskViewModel = ViewModelProvider(this).get(TaskViewModel::class.java)

        //Read tasklist data from shared prefs and populate viewmodel lists with it
        readSharedPrefsToViewModel()

        //Get ref to viewpager and set up its adapter & attributes
        viewPager = findViewById(R.id.view_pager)
        val viewPagerAdapter = TasklistFragmentStateAdapter(this)
        viewPager.apply{
            adapter = viewPagerAdapter
            offscreenPageLimit = 2
        }

        //Get ref to tablayout, set up & attach its mediator
        tabLayout = findViewById(R.id.tab_layout)
        TabLayoutMediator(tabLayout, viewPager) {tab, position ->
            tab.text = when(position){
                0 -> getString(R.string.tab_label_todo)
                1 -> getString(R.string.tab_label_doing)
                else -> getString(R.string.tab_label_done)
            }
        }.attach()
    }

    //When activity is stopped, write all viewmodel list data to shared prefs
    override fun onStop() {
        super.onStop()
        writeViewModelToSharedPrefs()
    }

    //Adapter class for view pager
    private inner class TasklistFragmentStateAdapter(fa: FragmentActivity) : FragmentStateAdapter(fa){
        override fun createFragment(position: Int): Fragment {
            //Create argument bundle with task list type
            val tasklistFragmentArguments = Bundle().apply{
                putInt(ARG_TASKLIST_TYPE, position)
            }

            //Attach the argument bundle to new fragment instance and return the fragment
            return TasklistFragment().apply{
                arguments = tasklistFragmentArguments
            }
        }

        override fun getItemCount(): Int = NUM_TASKLIST_PAGES
    }

    //TasklistFragment.Callbacks interface method implementations

    //Adds given task to end of given tasklist and notifies corresponding recyclerview to update state
    override fun addTaskToViewModel(task: Task, destinationTasklistType: Int) {
        val destinationFragment = (supportFragmentManager.fragments[destinationTasklistType] as TasklistFragment)
        val taskList = getTaskListFromViewModel(destinationTasklistType)
        taskList.add(task)

        destinationFragment.taskRecyclerView.adapter?.notifyItemInserted(taskList.size)
    }

    //Get tasklist of given tasklist type from corresponding viewmodel
    override fun getTaskListFromViewModel(tasklistType: Int): LinkedList<Task> =
        when(tasklistType){
            TASKLIST_TYPE_TODO -> taskViewModel.todoTaskList
            TASKLIST_TYPE_DOING -> taskViewModel.doingTaskList
            TASKLIST_TYPE_DONE -> taskViewModel.doneTaskList
            else -> throw Exception("Unrecognized tasklist type") }

    //Deletes item at given position from task list and notifies corresponding recyclerview to update state
    override fun deleteTaskFromViewModel(tasklistType: Int, adapterPosition: Int) {
        val tasklistFragment = (supportFragmentManager.fragments[tasklistType] as TasklistFragment)
        getTaskListFromViewModel(tasklistType).removeAt(adapterPosition)
        tasklistFragment.taskRecyclerView.adapter?.notifyItemRemoved(adapterPosition)
    }

    private fun writeViewModelToSharedPrefs(){
        val gson = Gson()
        //Convert list to json string
        val todoJSON = gson.toJson(taskViewModel.todoTaskList)
        val doingJSON = gson.toJson(taskViewModel.doingTaskList)
        val doneJSON = gson.toJson(taskViewModel.doneTaskList)

        //Save json strings into shared preferences
        getPreferences(MODE_PRIVATE).edit().apply {
            putString(KEY_TODO_JSON, todoJSON)
            putString(KEY_DOING_JSON, doingJSON)
            putString(KEY_DONE_JSON, doneJSON)
        }.apply()
    }

    private fun readSharedPrefsToViewModel(){
        val gson = Gson()
        val sharedPrefs = getPreferences(MODE_PRIVATE)

        val todoJSON = sharedPrefs.getString(KEY_TODO_JSON, "[]")
        val doingJSON = sharedPrefs.getString(KEY_DOING_JSON, "[]")
        val doneJSON = sharedPrefs.getString(KEY_DONE_JSON, "[]")

        val type = object: TypeToken<LinkedList<Task>>() {}.type //Gson requires type ref for generic types
        taskViewModel.todoTaskList = gson.fromJson(todoJSON, type)
        taskViewModel.doingTaskList = gson.fromJson(doingJSON, type)
        taskViewModel.doneTaskList = gson.fromJson(doneJSON, type)
    }
}

CodePudding user response：

First of all, the class's name is Kanban with capital k, not kanban, but that still won't work because Kanban is an Activity, not a Fragment

CodePudding user response：

Please share you kanban.kt file, it looks like the file has some issue. You can try kanbanKt.whayYouNeed.