package com.example.navigationflow
import android.os.Bundle
import androidx.appcompat.app.AppCompatActivity
import androidx.navigation.fragment.NavHostFragment
import androidx.navigation.ui.setupActionBarWithNavController
import com.example.navigationflow.databinding.ActivityMainBinding
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
setupActionBarWithNavController(navController)
}
override fun onSupportNavigateUp(): Boolean {
val navHostFragment = supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as NavHostFragment
val navController = navHostFragment.navController
return navController.navigateUp() || super.onSupportNavigateUp()
}
}
// HomeFragment.kt
package com.example.navigationflow
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.navigationflow.databinding.FragmentHomeBinding
class HomeFragment : Fragment() {
private var _binding: FragmentHomeBinding? = null
private val binding get() = _binding!!
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
_binding = FragmentHomeBinding.inflate(inflater, container, false)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.buttonGoToDetails.setOnClickListener {
findNavController().navigate(R.id.action_homeFragment_to_detailsFragment)
}
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
// DetailsFragment.kt
package com.example.navigationflow
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.navigationflow.databinding.FragmentDetailsBinding
class DetailsFragment : Fragment() {
private var _binding: FragmentDetailsBinding? = null
private val binding get() = _binding!!
override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View {
_binding = FragmentDetailsBinding.inflate(inflater, container, false)
return binding.root
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
binding.buttonBackToHome.setOnClickListener {
findNavController().navigateUp()
}
}
override fun onDestroyView() {
super.onDestroyView()
_binding = null
}
}
// navigation/nav_graph.xml
<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/nav_graph"
app:startDestination="@id/homeFragment">
<fragment
android:id="@+id/homeFragment"
android:name="com.example.navigationflow.HomeFragment"
android:label="Home Screen">
<action
android:id="@+id/action_homeFragment_to_detailsFragment"
app:destination="@id/detailsFragment" />
</fragment>
<fragment
android:id="@+id/detailsFragment"
android:name="com.example.navigationflow.DetailsFragment"
android:label="Details Screen" />
</navigation>
// layout/activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<fragment
android:id="@+id/nav_host_fragment"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="0dp"
android:layout_height="0dp"
app:defaultNavHost="true"
app:navGraph="@navigation/nav_graph"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintEnd_toEndOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>
// layout/fragment_home.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:gravity="center"
android:padding="16dp">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Home Screen"
android:textSize="24sp"
android:layout_marginBottom="24dp" />
<Button
android:id="@+id/buttonGoToDetails"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Go to Details" />
</LinearLayout>
// layout/fragment_details.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:gravity="center"
android:padding="16dp">
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Details Screen"
android:textSize="24sp"
android:layout_marginBottom="24dp" />
<Button
android:id="@+id/buttonBackToHome"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Back to Home" />
</LinearLayout>This app uses the Android Navigation Component to manage the flow between two screens: Home and Details.
The NavHostFragment in the main activity hosts the navigation graph, which defines the start screen and possible navigation paths.
In HomeFragment, a button triggers navigation to DetailsFragment using findNavController().navigate(). In DetailsFragment, the back button uses navigateUp() to return to Home.
This setup shows how navigation manages app flow by controlling which screen is shown and how users move between them, keeping the app organized and easy to follow.
