My Android Application keeps crashing. Kotlin and Android Studio - android-studio

Question

I am new to Kotlin and Android Studio. I tried implementing Fragments and Navigation in my application. Following is my code. When the Application is run, it keeps on crashing. I don't understand where I ve made mistake. The application does not show any compilation error.
MainActivity.kt :
package com.example.firstandroid
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.example.firstandroid.databinding.ActivityMainBinding
import androidx.navigation.fragment.NavHostFragment
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
}
// Get the navigation host fragment from this Activity
val navHostFragment = supportFragmentManager
.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
// Instantiate the navController using the NavHostFragment
val navController = navHostFragment.navController
// Make sure actions in the ActionBar get propagated to the NavController
}
StartOrder.kt :
package com.example.firstandroid
import android.os.Bundle
import androidx.fragment.app.Fragment
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.navigation.fragment.findNavController
import com.example.firstandroid.databinding.FragmentStartOrderBinding
class StartOrder : Fragment() {
private var binding: FragmentStartOrderBinding?=null
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding=FragmentStartOrderBinding.inflate(inflater, container, false)
return binding?.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding?.StartOrderButton?.setOnClickListener{orderDish()}
}
override fun onDestroyView() {
super.onDestroyView()
binding = null
}
fun orderDish(){
findNavController().navigate(R.id.action_startOrder_to_chooseDish)
}
}
chooseDish.kt :
package com.example.firstandroid
import android.os.Bundle
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import androidx.fragment.app.Fragment
import androidx.navigation.fragment.findNavController
import com.example.firstandroid.databinding.FragmentChooseDishBinding
class ChooseDish : Fragment() {
private var binding: FragmentChooseDishBinding?=null
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
binding= FragmentChooseDishBinding.inflate(inflater, container, false)
return binding?.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding?.chooseDishNext?.setOnClickListener{orderSidedish()}
}
override fun onDestroyView() {
super.onDestroyView()
binding = null
}
fun orderSidedish(){
findNavController().navigate(R.id.action_chooseDish_to_sidedish)
}
}

Answer 1

Try this Solution:
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.example.firstandroid.databinding.ActivityMainBinding
import androidx.navigation.fragment.NavHostFragment
class MainActivity : AppCompatActivity() {
private lateinit var binding: ActivityMainBinding
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
binding = ActivityMainBinding.inflate(layoutInflater)
setContentView(binding.root)
val navHostFragment = supportFragmentManager
.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
val navController = navHostFragment.navController
}
}