HistoryActivity.kt

package com.example.todoapp

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.view.Menu
import android.view.MenuItem
import androidx.appcompat.widget.SearchView
import androidx.lifecycle.Observer
import androidx.recyclerview.widget.LinearLayoutManager
import kotlinx.android.synthetic.main.activity_history.*
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.launch

class HistoryActivity : AppCompatActivity() {

    val db by lazy {
        AppDatabase.getDatabase(this)
    }


    val list = arrayListOf<TodoModel>()
    var com_adapter = TodoAdapter(list)

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_history)
        setSupportActionBar(toolbar)
        completedRv.apply {
            layoutManager = LinearLayoutManager(this@HistoryActivity)
            adapter = this@HistoryActivity.com_adapter
        }


        db.todoDao().getFinishedTask().observe(this, Observer {
            if (!it.isNullOrEmpty()) {
                list.clear()
                list.addAll(it)
                com_adapter.notifyDataSetChanged()
            }else{
                list.clear()
                com_adapter.notifyDataSetChanged()
            }
        })
    }

    override fun onCreateOptionsMenu(menu: Menu): Boolean {
        menuInflater.inflate(R.menu.history, menu)
        val item = menu.findItem(R.id.search)
        val searchView = item.actionView as SearchView
        item.setOnActionExpandListener(object :MenuItem.OnActionExpandListener{
            override fun onMenuItemActionExpand(item: MenuItem?): Boolean {
                displayTodo()
                return true
            }

            override fun onMenuItemActionCollapse(item: MenuItem?): Boolean {
                displayTodo()
                return true
            }

        })
        searchView.setOnQueryTextListener(object : SearchView.OnQueryTextListener{
            override fun onQueryTextSubmit(query: String?): Boolean {
                return false
            }

            override fun onQueryTextChange(newText: String?): Boolean {
                if(!newText.isNullOrEmpty()){
                    displayTodo(newText)
                }
                return true
            }

        })

        return super.onCreateOptionsMenu(menu)
    }

    fun displayTodo(newText: String = "") {
        db.todoDao().getFinishedTask().observe(this, Observer {
            if(it.isNotEmpty()){
                list.clear()
                list.addAll(
                    it.filter { todo ->
                        todo.title.contains(newText,true)
                    }
                )
                com_adapter.notifyDataSetChanged()
            }
        })
    }

    override fun onOptionsItemSelected(item: MenuItem): Boolean {
        when (item.itemId) {
            R.id.delete -> {

                GlobalScope.launch(Dispatchers.IO) {
                    db.todoDao().delete_finished_task()
                }

            }
        }
        return super.onOptionsItemSelected(item)
    }
}