after adding the state variable to show the alert dialog

MainActivity.kt

package com.death.demo

import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.compose.Composable
import androidx.compose.State
import androidx.compose.state
import androidx.compose.unaryPlus
import androidx.ui.core.Text
import androidx.ui.core.setContent
import androidx.ui.layout.Column
import androidx.ui.layout.Container
import androidx.ui.material.AlertDialog
import androidx.ui.material.Button
import androidx.ui.material.MaterialTheme


// Here i created the variable of type State<Boolean> which will be used to
// show/hide the alert dialog
private val showDialog  = +state{
    false
}


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            MaterialTheme {
                Column {
                    showAlertButton()
                    presentDialog()
                }
            }
        }
    }

    @Composable
    fun showAlertButton(){
        Button("Show Alert",
                onClick = {
                    // Here changing the value to true so that the alert dialog can be shown
                    showDialog.value = true
                }
        )
    }


    @Composable
    fun presentDialog() {
        if(showDialog.value)
            AlertDialog(
                    onCloseRequest = {
                    },
                    title = {
                        Text(text = "Alert Dialog")
                    },
                    text = {
                        Text("JetPack Compose Alert Dialog!")
                    },
                    confirmButton = {
                        Button("Confirm", onClick = {

                        })
                    }
            )
    }
}