add conditional navigation

Author: solygambas

17-fun-facts/README.md

@@ -1,16 +1,22 @@
 # Fun Facts
 
-An app that displays fun facts about Android, using FirebaseUI for authentication.
+An app that displays fun facts about Android, using FirebaseUI Authentication.
 
-<!-- <p align="center">
+<p align="center">
 <img src="screenshot.png" style="width:528px;max-width: 100%;">
-</p> -->
+</p>
 
 ## Features
 
 - adding Firebase to the project.
 - implementing the login feature.
 - adding a custom greeting for users who are logged in.
 - implementing the logout feature.
+- enabling settings screen.
+- redirecting the user to the login screen if necessary.
+- handling navigation after successful login.
 
-Based on [Advanced Android in Kotlin 06.1: Android Login with FirebaseUI](https://developer.android.com/codelabs/advanced-android-kotlin-training-login#0) by Google Codelabs (2022).
+Based on 2 tutorials by Google Codelabs (2022):
+
+- [Android Login with FirebaseUI](https://developer.android.com/codelabs/advanced-android-kotlin-training-login#0)
+- [Android Conditional Navigation with Login](https://codelabs.developers.google.com/codelabs/advanced-android-kotlin-training-login-navigation)

17-fun-facts/app/build.gradle

@@ -16,6 +16,7 @@
 
 apply plugin: 'com.android.application'
 apply plugin: 'kotlin-android'
+apply plugin: "androidx.navigation.safeargs.kotlin"
 
 android {
     compileSdkVersion 29

17-fun-facts/app/src/main/java/com/example/android/firebaseui_login_sample/LoginFragment.kt

@@ -66,6 +66,16 @@ class LoginFragment : Fragment() {
         super.onViewCreated(view, savedInstanceState)
 
         navController = findNavController()
+        requireActivity().onBackPressedDispatcher.addCallback(viewLifecycleOwner) {
+            navController.popBackStack(R.id.mainFragment, false)
+        }
+
+        viewModel.authenticationState.observe(viewLifecycleOwner, Observer { authenticationState ->
+            when (authenticationState) {
+                LoginViewModel.AuthenticationState.AUTHENTICATED -> navController.popBackStack()
+                else -> Log.e(TAG, "Authentication state that doesn't require any UI change $authenticationState")
+            }
+        })
     }
 
     private fun launchSignInFlow() {

17-fun-facts/app/src/main/java/com/example/android/firebaseui_login_sample/MainFragment.kt

@@ -61,6 +61,11 @@ class MainFragment : Fragment() {
         observeAuthenticationState()
 
         binding.authButton.setOnClickListener { launchSignInFlow() }
+
+        binding.settingsButton.setOnClickListener {
+            val action = MainFragmentDirections.actionMainFragmentToSettingsFragment()
+            findNavController().navigate(action)
+        }
     }
 
     override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {

17-fun-facts/app/src/main/java/com/example/android/firebaseui_login_sample/SettingsFragment.kt

@@ -39,5 +39,13 @@ class SettingsFragment : PreferenceFragmentCompat() {
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
+        val navController = findNavController()
+        viewModel.authenticationState.observe(viewLifecycleOwner, Observer { authenticationState ->
+            when (authenticationState) {
+                LoginViewModel.AuthenticationState.AUTHENTICATED -> Log.i(TAG, "Authenticated")
+                LoginViewModel.AuthenticationState.UNAUTHENTICATED -> navController.navigate(R.id.loginFragment)
+                else -> Log.e(TAG, "New $authenticationState doesn't require any UI change")
+            }
+        })
     }
 }

17-fun-facts/app/src/main/res/layout/fragment_main.xml

@@ -36,6 +36,19 @@
                 app:layout_constraintTop_toTopOf="parent"
                 tools:text="@string/login_button_text"/>
 
+        <TextView
+            android:id="@+id/settings_button"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_margin="@dimen/text_margin"
+            android:background="@color/colorAccent"
+            android:padding="@dimen/text_padding"
+            android:textColor="@color/white"
+            android:textSize="@dimen/button_text_size"
+            app:layout_constraintRight_toRightOf="parent"
+            app:layout_constraintTop_toTopOf="parent"
+            android:text="@string/settings_btn"/>
+
         <TextView
                 android:id="@+id/welcome_text"
                 android:layout_width="wrap_content"

17-fun-facts/app/src/main/res/navigation/nav_graph.xml

@@ -22,9 +22,12 @@
             app:startDestination="@id/mainFragment">
 
     <fragment
-            android:id="@+id/mainFragment"
-            android:name="com.example.android.firebaseui_login_sample.MainFragment"
-            android:label="MainFragment">
+        android:id="@+id/mainFragment"
+        android:name="com.example.android.firebaseui_login_sample.MainFragment"
+        android:label="MainFragment">
+        <action
+            android:id="@+id/action_mainFragment_to_settingsFragment"
+            app:destination="@id/settingsFragment"/>
     </fragment>
     <fragment
             android:id="@+id/settingsFragment"

17-fun-facts/build.gradle

@@ -26,6 +26,7 @@ buildscript {
         classpath 'com.android.tools.build:gradle:4.2.0'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         classpath 'com.google.gms:google-services:4.3.0'
+        classpath "androidx.navigation:navigation-safe-args-gradle-plugin:2.0.0"
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files
     }

17-fun-facts/screenshot.png

@@ -20,7 +20,7 @@
 | 14  | [Star Shower](https://github.com/solygambas/kotlin-projects/tree/main/14-star-shower)                     | An app to show how to create property animations, using ObjectAnimator.             |
 | 15  | [Milky Way](https://github.com/solygambas/kotlin-projects/tree/main/15-milky-way)                         | An app to learn how to finely customize an animation, using MotionLayout.           |
 | 16  | [Sports App](https://github.com/solygambas/kotlin-projects/tree/main/16-sports-app)                       | A basic app to introduce to adaptative layouts.                                     |
-| 17  | [Fun Facts](https://github.com/solygambas/kotlin-projects/tree/main/17-fun-facts)                         | An app that displays fun facts about Android, using FirebaseUI for authentication.  |
+| 17  | [Fun Facts](https://github.com/solygambas/kotlin-projects/tree/main/17-fun-facts)                         | An app that displays fun facts about Android, using FirebaseUI Authentication.      |
 
 These projects are adapted from various sources: