Replaced fragment switching functionality in MainActivity.kt with Navigation component, simplifying logic significantly; upgraded to AGP 8.0.1

app/src/main/java/com/denizk0461/studip/activity/MainActivity.kt

@@ -3,15 +3,10 @@ package com.denizk0461.studip.activity
 import android.os.Bundle
 import androidx.core.view.WindowCompat
 import androidx.fragment.app.FragmentActivity
-import androidx.fragment.app.FragmentTransaction
-import androidx.lifecycle.Lifecycle
-import com.denizk0461.studip.R
+import androidx.navigation.fragment.NavHostFragment
+import androidx.navigation.fragment.findNavController
+import androidx.navigation.ui.setupWithNavController
 import com.denizk0461.studip.databinding.ActivityMainBinding
-import com.denizk0461.studip.db.AppRepository
-import com.denizk0461.studip.fragment.EventFragment
-import com.denizk0461.studip.fragment.CanteenFragment
-import com.denizk0461.studip.fragment.SettingsFragment
-import com.denizk0461.studip.model.SettingsPreferences
 
 /**
  * Main activity that handles all common fragments. This is opened on app launch.
@@ -21,91 +16,17 @@ class MainActivity : FragmentActivity() {
     // View binding
     private lateinit var binding: ActivityMainBinding
 
-    /*
-     * Tag for the currently active fragment; set on activity launch to the fragment that will be
-     * shown first.
-     */
-    private var currentFragment: String = "event"
-
     override fun onCreate(savedInstanceState: Bundle?) {
         WindowCompat.setDecorFitsSystemWindows(window, false)
         super.onCreate(savedInstanceState)
 
-        /*
-         * Instantiate repository object that is accessed by the fragments' view models to retrieve
-         * data.
-         */
-//        Dependencies.repo = AppRepository(application)
-
         // Inflate view binding and bind to this activity
         binding = ActivityMainBinding.inflate(layoutInflater)
         setContentView(binding.root)
 
-        // Set up navigation view bar to launch fragments
-        binding.navView.setOnItemSelectedListener { item ->
-            // Launch fragment based on the item that has been clicked
-            loadFragment(when (item.itemId) {
-                R.id.food -> "canteen"
-                R.id.settings -> "settings"
-                else -> "event"
-            })
-        }
-
-        // Set up bottom nav bar and the initial fragment when the app launches
-        if (savedInstanceState == null) {
-            // Open the fragment that the user specified to open on app start
-            if (AppRepository.getRepositoryInstance(application)
-                    .getBooleanPreference(SettingsPreferences.LAUNCH_CANTEEN_ON_START)
-            ) {
-                // Open canteen fragment
-                binding.navView.selectedItemId = R.id.food
-                currentFragment = "canteen"
-            } else {
-                // Open event fragment
-                binding.navView.selectedItemId = R.id.plan
-                currentFragment = "event"
-            }
-
-            // Launch the fragment defined in currentFragment
-            loadFragment(currentFragment)
-        }
-    }
-
-    /**
-     * Loads a given fragment.
-     *
-     * @param type  tag for the fragment that is to be opened
-     * @return      true on success, false if another fragment is currently instantiating
-     */
-    private fun loadFragment(type: String): Boolean {
-
-        // Find the fragment that is to be opened, or create it if it hasn't been instantiated yet
-        val fragment = supportFragmentManager.findFragmentByTag(type) ?: getFragment(type)
-
-        // Don't interrupt the current fragment's lifecycle if it isn't fully initialised
-        if (fragment.lifecycle.currentState != Lifecycle.State.INITIALIZED) {
-            return false
-        }
-
-        // Start the transaction to show the new fragment
-        supportFragmentManager.beginTransaction()
-            .replace(R.id.nav_host_fragment_content_main, fragment, type)
-            .setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE)
-            .commit()
-
-        // Success
-        return true
-    }
-
-    /**
-     * Retrieve fragment by its tag.
-     *
-     * @param type  tag for the corresponding fragment
-     * @return      the corresponding fragment
-     */
-    private fun getFragment(type: String) = when (type) {
-        "canteen" -> CanteenFragment() // CanteenFragment.kt
-        "settings" -> SettingsFragment() // SettingsFragment.kt
-        else -> EventFragment() // on unknown value or "event", launch EventFragment.kt
+        // Set up bottom navigation view to navigate between fragments
+        binding.navView.setupWithNavController(
+            binding.navHostFragmentContentMain.getFragment<NavHostFragment>().findNavController()
+        )
     }
 }