Modernize backhandling to support predictive back handling

ultrasonic/src/main/AndroidManifest.xml

@@ -33,6 +33,7 @@
         android:supportsRtl="false"
         android:preserveLegacyExternalStorage="true"
         tools:ignore="UnusedAttribute">
+        <!-- Add for API 34 android:enableOnBackInvokedCallBack="true" -->
 
         <meta-data android:name="com.google.android.gms.car.application"
             android:resource="@xml/automotive_app_desc"/>

ultrasonic/src/main/kotlin/org/moire/ultrasonic/activity/NavigationActivity.kt

@@ -21,6 +21,7 @@ import android.view.Menu
 import android.view.MenuItem
 import android.view.View
 import android.widget.ImageView
+import androidx.activity.OnBackPressedCallback
 import androidx.appcompat.app.AppCompatActivity
 import androidx.appcompat.widget.Toolbar
 import androidx.core.content.ContextCompat
@@ -51,7 +52,6 @@ import org.moire.ultrasonic.R
 import org.moire.ultrasonic.app.UApp
 import org.moire.ultrasonic.data.ActiveServerProvider
 import org.moire.ultrasonic.data.ServerSettingDao
-import org.moire.ultrasonic.fragment.OnBackPressedHandler
 import org.moire.ultrasonic.model.ServerSettingsModel
 import org.moire.ultrasonic.provider.SearchSuggestionProvider
 import org.moire.ultrasonic.service.MediaPlayerLifecycleSupport
@@ -126,6 +126,8 @@ class NavigationActivity : AppCompatActivity() {
         navigationView = findViewById(R.id.nav_view)
         drawerLayout = findViewById(R.id.drawer_layout)
 
+        setupDrawerLayout(drawerLayout!!)
+
         val toolbar = findViewById<Toolbar>(R.id.toolbar)
         setSupportActionBar(toolbar)
 
@@ -212,6 +214,27 @@ class NavigationActivity : AppCompatActivity() {
         }
     }
 
+    private fun setupDrawerLayout(drawerLayout: DrawerLayout) {
+        onBackPressedDispatcher.addCallback(this, closeNavigationDrawerOnBack)
+        drawerLayout.addDrawerListener(object : DrawerLayout.DrawerListener {
+            override fun onDrawerSlide(drawerView: View, slideOffset: Float) {
+                // Nothing
+            }
+
+            override fun onDrawerOpened(drawerView: View) {
+                closeNavigationDrawerOnBack.isEnabled = true
+            }
+
+            override fun onDrawerClosed(drawerView: View) {
+                closeNavigationDrawerOnBack.isEnabled = false
+            }
+
+            override fun onDrawerStateChanged(newState: Int) {
+                // Nothing
+            }
+        })
+    }
+
     override fun onResume() {
         Timber.d("onResume called")
         super.onResume()
@@ -328,15 +351,11 @@ class NavigationActivity : AppCompatActivity() {
         setupActionBarWithNavController(navController, appBarConfig)
     }
 
-    override fun onBackPressed() {
-        if (drawerLayout?.isDrawerVisible(GravityCompat.START) == true) {
-            this.drawerLayout?.closeDrawer(GravityCompat.START)
-        } else {
-            val currentFragment = host!!.childFragmentManager.fragments.last()
-            if (currentFragment is OnBackPressedHandler) currentFragment.onBackPressed()
-            else super.onBackPressed()
+    private val closeNavigationDrawerOnBack = object : OnBackPressedCallback(true) {
+            override fun handleOnBackPressed() {
+                drawerLayout?.closeDrawer(GravityCompat.START)
+            }
         }
-    }
 
     override fun onCreateOptionsMenu(menu: Menu): Boolean {
         val retValue = super.onCreateOptionsMenu(menu)
@@ -352,17 +371,12 @@ class NavigationActivity : AppCompatActivity() {
             super.onOptionsItemSelected(item)
     }
 
+    // TODO: Why is this needed? Shouldn't it just work by default?
     override fun onSupportNavigateUp(): Boolean {
-        val currentFragment = host!!.childFragmentManager.fragments.last()
-        return if (currentFragment is OnBackPressedHandler) {
-            currentFragment.onBackPressed()
-            true
-        } else {
-            findNavController(R.id.nav_host_fragment).navigateUp(appBarConfiguration)
-        }
+        return findNavController(R.id.nav_host_fragment).navigateUp(appBarConfiguration)
     }
 
-    // TODO Test if this works with external Intents
+    // TODO: Test if this works with external Intents
     // android.intent.action.SEARCH and android.media.action.MEDIA_PLAY_FROM_SEARCH calls here
     override fun onNewIntent(intent: Intent?) {
         super.onNewIntent(intent)

ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/EditServerFragment.kt

@@ -7,12 +7,14 @@
 
 package org.moire.ultrasonic.fragment
 
+import android.content.Context
 import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
 import android.widget.Button
 import android.widget.ImageView
+import androidx.activity.OnBackPressedCallback
 import androidx.appcompat.app.AlertDialog
 import androidx.core.content.ContextCompat
 import androidx.fragment.app.Fragment
@@ -52,7 +54,7 @@ private const val DIALOG_PADDING = 12
 /**
  * Displays a form where server settings can be created / edited
  */
-class EditServerFragment : Fragment(), OnBackPressedHandler {
+class EditServerFragment : Fragment() {
 
     private val serverSettingsModel: ServerSettingsModel by viewModel()
     private val activeServerProvider: ActiveServerProvider by inject()
@@ -82,6 +84,13 @@ class EditServerFragment : Fragment(), OnBackPressedHandler {
         super.onCreate(savedInstanceState)
     }
 
+    override fun onAttach(context: Context) {
+        requireActivity().onBackPressedDispatcher.addCallback(
+            this, confirmCloseCallback
+        )
+        super.onAttach(context)
+    }
+
     override fun onCreateView(
         inflater: LayoutInflater,
         container: ViewGroup?,
@@ -189,11 +198,25 @@ class EditServerFragment : Fragment(), OnBackPressedHandler {
         }
     }
 
+    private val confirmCloseCallback = object : OnBackPressedCallback(
+        true // default to enabled
+    ) {
+        override fun handleOnBackPressed() {
+            finishActivity()
+        }
+    }
+
     override fun onStop() {
         Util.hideKeyboard(activity)
+        confirmCloseCallback.isEnabled = false
         super.onStop()
     }
 
+    override fun onResume() {
+        confirmCloseCallback.isEnabled = true
+        super.onResume()
+    }
+
     private fun correctServerAddress() {
         serverAddressEditText?.editText?.setText(
             serverAddressEditText?.editText?.text?.trim(' ', '/')
@@ -206,11 +229,6 @@ class EditServerFragment : Fragment(), OnBackPressedHandler {
         image?.setTint(currentColor)
         serverColorImageView?.background = image
     }
-
-    override fun onBackPressed() {
-        finishActivity()
-    }
-
     override fun onSaveInstanceState(savedInstanceState: Bundle) {
         savedInstanceState.putString(
             ::serverNameEditText.name, serverNameEditText!!.editText?.text.toString()

ultrasonic/src/main/kotlin/org/moire/ultrasonic/fragment/OnBackPressedHandler.kt

@@ -1,15 +0,0 @@
-/*
- * OnBackPressedHandler.kt
- * Copyright (C) 2009-2022 Ultrasonic developers
- *
- * Distributed under terms of the GNU GPLv3 license.
- */
-
-package org.moire.ultrasonic.fragment
-
-/**
- * Interface for fragments handling their own Back button
- */
-interface OnBackPressedHandler {
-    fun onBackPressed()
-}