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class MainActivity : AppCompatActivity() {
    private lateinit var deletedTransaction: Transaction
    private lateinit var transactions : List<Transaction>
    private lateinit var oldTransactions : List<Transaction>
    private lateinit var transactionAdapter: TransactionAdapter
    private lateinit var linearLayoutManager: LinearLayoutManager
    private lateinit var db : AppDatabase

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

        transactions = arrayListOf()

        transactionAdapter = TransactionAdapter(transactions)
        linearLayoutManager = LinearLayoutManager(this)

        db = Room.databaseBuilder(this,
        AppDatabase::class.java,
        "transactions").build()

        recyclerview.apply {
            adapter = transactionAdapter
            layoutManager = linearLayoutManager
        }


        // swipe to remove
        val itemTouchHelper = object : ItemTouchHelper.SimpleCallback(0, ItemTouchHelper.RIGHT){
            override fun onMove(
                recyclerView: RecyclerView,
                viewHolder: RecyclerView.ViewHolder,
                target: RecyclerView.ViewHolder
            ): Boolean {
                return false
            }

            override fun onSwiped(viewHolder: RecyclerView.ViewHolder, direction: Int) {
                deleteTransaction(transactions[viewHolder.adapterPosition])
            }

        }

        val swipeHelper = ItemTouchHelper(itemTouchHelper)
        swipeHelper.attachToRecyclerView(recyclerview)

        addBtn.setOnClickListener {
            val intent = Intent(this, AddTransactionActivity::class.java)
            startActivity(intent)
        }
    }

    private fun fetchAll(){
        GlobalScope.launch {
            transactions = db.transactionDao().getAll()

            runOnUiThread {
                updateDashboard()
                transactionAdapter.setData(transactions)
            }
        }
    } Объясни этот код