ui: add predictive back gesture

Rework the back pressed callbacks to support a predictive back gesture.

This completes the trivial Android 13 reworks.

CHANGELOG.md

@@ -5,9 +5,10 @@
 #### What's New
 - Added Android 13 support [#129]
     - Switch to new storage permissions
-    - Add monochrome icon
+    - Add themed icon
     - Fix issue where widget covers would not load
     - Use new media notification panel style
+    - Add predictive back navigation
 
 #### What's Improved
 - Playback bar now has a marquee effect

app/build.gradle

@@ -70,7 +70,7 @@ dependencies {
 
     // General
     implementation "androidx.core:core-ktx:1.8.0"
-    implementation "androidx.activity:activity-ktx:1.5.1"
+    implementation "androidx.activity:activity-ktx:1.6.0-rc01"
     implementation "androidx.fragment:fragment-ktx:1.5.2"
 
     // UI

app/src/main/AndroidManifest.xml

@@ -26,6 +26,7 @@
         android:theme="@style/Theme.Auxio.App"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:appCategory="audio"
+        android:enableOnBackInvokedCallback="true"
         tools:ignore="UnusedAttribute">
 
         <activity

app/src/main/java/org/oxycblt/auxio/MainFragment.kt

@@ -53,9 +53,12 @@ class MainFragment :
     ViewBindingFragment<FragmentMainBinding>(), ViewTreeObserver.OnPreDrawListener {
     private val playbackModel: PlaybackViewModel by androidActivityViewModels()
     private val navModel: NavigationViewModel by activityViewModels()
-    private var callback: DynamicBackPressedCallback? = null
+    private val callback = DynamicBackPressedCallback()
     private var lastInsets: WindowInsets? = null
-    private var elevationNormal = -1f
+
+    private val elevationNormal: Float by lifecycleObject { binding ->
+        binding.context.getDimen(R.dimen.elevation_normal)
+    }
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -69,10 +72,7 @@ class MainFragment :
         // --- UI SETUP ---
         val context = requireActivity()
 
-        context.onBackPressedDispatcher.addCallback(
+        context.onBackPressedDispatcher.addCallback(viewLifecycleOwner, callback)
-            viewLifecycleOwner, DynamicBackPressedCallback().also { callback = it })
-
-        elevationNormal = requireContext().getDimen(R.dimen.elevation_normal)
 
         binding.root.setOnApplyWindowInsetsListener { _, insets ->
             lastInsets = insets
@@ -128,16 +128,6 @@ class MainFragment :
         requireBinding().playbackSheet.viewTreeObserver.addOnPreDrawListener(this)
     }
 
-    override fun onResume() {
-        super.onResume()
-        callback?.isEnabled = true
-    }
-
-    override fun onPause() {
-        super.onPause()
-        callback?.isEnabled = false
-    }
-
     override fun onStop() {
         super.onStop()
         requireBinding().playbackSheet.viewTreeObserver.removeOnPreDrawListener(this)
@@ -209,6 +199,10 @@ class MainFragment :
             tryHideAll()
         }
 
+        // Since the callback is also reliant on the bottom sheets, we must also update it
+        // every frame.
+        callback.updateEnabledState()
+
         return true
     }
 
@@ -322,10 +316,8 @@ class MainFragment :
     private inner class DynamicBackPressedCallback : OnBackPressedCallback(false) {
         override fun handleOnBackPressed() {
             val binding = requireBinding()
-
             val playbackSheetBehavior =
                 binding.playbackSheet.coordinatorLayoutBehavior as PlaybackSheetBehavior
-
             val queueSheetBehavior =
                 binding.queueSheet.coordinatorLayoutBehavior as QueueSheetBehavior?
 
@@ -344,15 +336,29 @@ class MainFragment :
                 return
             }
 
-            // First navigate upwards in the explore graph, then navigate back in the activity.
+            binding.exploreNavHost.findNavController().navigateUp()
-            val navController = binding.exploreNavHost.findNavController()
+        }
-            if (navController.currentDestination?.id == navController.graph.startDestinationId) {
+
-                isEnabled = false
+        fun updateEnabledState() {
-                requireActivity().onBackPressed()
+            val binding = requireBinding()
-                isEnabled = true
+            val playbackSheetBehavior =
-            } else {
+                binding.playbackSheet.coordinatorLayoutBehavior as PlaybackSheetBehavior
-                navController.navigateUp()
+            val queueSheetBehavior =
-            }
+                binding.queueSheet.coordinatorLayoutBehavior as QueueSheetBehavior?
+
+            val exploreNavController = binding.exploreNavHost.findNavController()
+
+            logD(
+                playbackSheetBehavior.state == NeoBottomSheetBehavior.STATE_EXPANDED ||
+                    queueSheetBehavior?.state == NeoBottomSheetBehavior.STATE_EXPANDED ||
+                    exploreNavController.currentDestination?.id !=
+                        exploreNavController.graph.startDestinationId)
+
+            isEnabled =
+                playbackSheetBehavior.state == NeoBottomSheetBehavior.STATE_EXPANDED ||
+                    queueSheetBehavior?.state == NeoBottomSheetBehavior.STATE_EXPANDED ||
+                    exploreNavController.currentDestination?.id !=
+                        exploreNavController.graph.startDestinationId
         }
     }
 }

app/src/main/java/org/oxycblt/auxio/home/HomeFragment.kt

@@ -84,10 +84,9 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
             // Orientation change will wipe whatever transition we were using prior, which will
             // result in no transition when the user navigates back. Make sure we re-initialize
             // our transitions.
-            if (savedInstanceState.getBoolean(KEY_INIT_WITH_SEARCH_TRANSITIONS)) {
+            val axis = savedInstanceState.getInt(KEY_LAST_TRANSITION_AXIS, -1)
-                initSearchTransitions()
+            if (axis > -1) {
-            } else {
+                initAxisTransitions(axis)
-                initDetailTransitions()
             }
         }
     }
@@ -152,7 +151,11 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
     }
 
     override fun onSaveInstanceState(outState: Bundle) {
-        outState.putBoolean(KEY_INIT_WITH_SEARCH_TRANSITIONS, enterTransition is MaterialSharedAxis)
+        val enter = enterTransition
+        if (enter is MaterialSharedAxis) {
+            outState.putInt(KEY_LAST_TRANSITION_AXIS, enter.axis)
+        }
+
         super.onSaveInstanceState(outState)
     }
 
@@ -165,7 +168,7 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
         when (item.itemId) {
             R.id.action_search -> {
                 logD("Navigating to search")
-                initSearchTransitions()
+                initAxisTransitions(MaterialSharedAxis.Z)
                 findNavController().navigate(HomeFragmentDirections.actionShowSearch())
             }
             R.id.action_settings -> {
@@ -376,23 +379,22 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
                 else -> return
             }
 
-        initDetailTransitions()
+        initAxisTransitions(MaterialSharedAxis.X)
 
         findNavController().navigate(action)
     }
 
-    private fun initSearchTransitions() {
+    private fun initAxisTransitions(axis: Int) {
-        enterTransition = MaterialSharedAxis(MaterialSharedAxis.Z, true)
+        // Sanity check
-        returnTransition = MaterialSharedAxis(MaterialSharedAxis.Z, false)
+        if (axis != MaterialSharedAxis.X && axis != MaterialSharedAxis.Z) {
-        exitTransition = MaterialSharedAxis(MaterialSharedAxis.Z, true)
+            logW("Invalid axis provided")
-        reenterTransition = MaterialSharedAxis(MaterialSharedAxis.Z, false)
+            return
-    }
+        }
 
-    private fun initDetailTransitions() {
+        enterTransition = MaterialSharedAxis(axis, true)
-        enterTransition = MaterialSharedAxis(MaterialSharedAxis.X, true)
+        returnTransition = MaterialSharedAxis(axis, false)
-        returnTransition = MaterialSharedAxis(MaterialSharedAxis.X, false)
+        exitTransition = MaterialSharedAxis(axis, true)
-        exitTransition = MaterialSharedAxis(MaterialSharedAxis.X, true)
+        reenterTransition = MaterialSharedAxis(axis, false)
-        reenterTransition = MaterialSharedAxis(MaterialSharedAxis.X, false)
     }
 
     /**
@@ -433,7 +435,7 @@ class HomeFragment : ViewBindingFragment<FragmentHomeBinding>(), Toolbar.OnMenuI
             lazyReflectedField(ViewPager2::class, "mRecyclerView")
         private val VIEW_PAGER_TOUCH_SLOP_FIELD: Field by
             lazyReflectedField(RecyclerView::class, "mTouchSlop")
-        private const val KEY_INIT_WITH_SEARCH_TRANSITIONS =
+        private const val KEY_LAST_TRANSITION_AXIS =
-            BuildConfig.APPLICATION_ID + ".key.INIT_WITH_SEARCH_TRANSITIONS"
+            BuildConfig.APPLICATION_ID + ".key.LAST_TRANSITION_AXIS"
     }
 }

app/src/main/java/org/oxycblt/auxio/playback/AnimatedMaterialButton.kt

@@ -23,8 +23,8 @@ import android.util.AttributeSet
 import com.google.android.material.button.MaterialButton
 
 /**
- * A [MaterialButton] that automatically morphs from a circle to a squircle shape appearance when
+ * A [MaterialButton] that automatically morphs from a circle to a squircle shape appearance when it
- * it is activated.
+ * is activated.
  */
 class AnimatedMaterialButton
 @JvmOverloads