From 78421ec79fc8228a93c5945704ce7da9095aed0c Mon Sep 17 00:00:00 2001
From: Johan von Forstner <johan.forstner@gmail.com>
Date: Fri, 24 Apr 2020 20:37:03 +0200
Subject: [PATCH] improve gallery transition and fix crash

---
 .../evmap/fragment/GalleryFragment.kt         | 11 +---------
 .../vonforst/evmap/fragment/MapFragment.kt    | 22 +++++++++++++++++++
 .../res/transition/map_exit_transition.xml    | 12 ++++++++++
 3 files changed, 35 insertions(+), 10 deletions(-)
 create mode 100644 app/src/main/res/transition/map_exit_transition.xml

diff --git a/app/src/main/java/net/vonforst/evmap/fragment/GalleryFragment.kt b/app/src/main/java/net/vonforst/evmap/fragment/GalleryFragment.kt
index 156644ee..7d8d23fb 100644
--- a/app/src/main/java/net/vonforst/evmap/fragment/GalleryFragment.kt
+++ b/app/src/main/java/net/vonforst/evmap/fragment/GalleryFragment.kt
@@ -14,7 +14,6 @@ import com.ortiz.touchview.TouchImageView
 import net.vonforst.evmap.MapsActivity
 import net.vonforst.evmap.R
 import net.vonforst.evmap.adapter.GalleryAdapter
-import net.vonforst.evmap.adapter.galleryTransitionName
 import net.vonforst.evmap.api.goingelectric.ChargerPhoto
 import net.vonforst.evmap.databinding.FragmentGalleryBinding
 import net.vonforst.evmap.viewmodel.GalleryViewModel
@@ -103,15 +102,7 @@ class GalleryFragment : Fragment(), MapsActivity.FragmentCallback {
         ) {
             if (isReturning) {
                 val currentPage = currentPage ?: return
-                val index = binding.gallery.currentItem
-
-                if (startingPosition != currentPosition) {
-                    names.clear()
-                    names.add(galleryTransitionName(index))
-
-                    sharedElements.clear()
-                    sharedElements[galleryTransitionName(index)] = currentPage
-                }
+                sharedElements[names[0]] = currentPage
             }
         }
     }
diff --git a/app/src/main/java/net/vonforst/evmap/fragment/MapFragment.kt b/app/src/main/java/net/vonforst/evmap/fragment/MapFragment.kt
index 22971f2e..93fd2377 100644
--- a/app/src/main/java/net/vonforst/evmap/fragment/MapFragment.kt
+++ b/app/src/main/java/net/vonforst/evmap/fragment/MapFragment.kt
@@ -10,6 +10,7 @@ import android.content.res.Configuration
 import android.os.Bundle
 import android.view.*
 import android.view.inputmethod.InputMethodManager
+import androidx.core.app.SharedElementCallback
 import androidx.core.content.ContextCompat
 import androidx.core.view.updateLayoutParams
 import androidx.databinding.DataBindingUtil
@@ -24,6 +25,7 @@ import androidx.navigation.fragment.findNavController
 import androidx.navigation.ui.setupWithNavController
 import androidx.recyclerview.widget.DividerItemDecoration
 import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.transition.TransitionInflater
 import com.google.android.gms.location.FusedLocationProviderClient
 import com.google.android.gms.location.LocationServices
 import com.google.android.gms.maps.CameraUpdateFactory
@@ -106,6 +108,10 @@ class MapFragment : Fragment(), OnMapReadyCallback, MapsActivity.FragmentCallbac
             insets
         }
 
+        setExitSharedElementCallback(exitElementCallback)
+        exitTransition = TransitionInflater.from(requireContext())
+            .inflateTransition(R.transition.map_exit_transition)
+
         return binding.root
     }
 
@@ -495,4 +501,20 @@ class MapFragment : Fragment(), OnMapReadyCallback, MapsActivity.FragmentCallbac
     override fun getRootView(): View {
         return root
     }
+
+    private val exitElementCallback: SharedElementCallback = object : SharedElementCallback() {
+        override fun onMapSharedElements(
+            names: MutableList<String>,
+            sharedElements: MutableMap<String, View>
+        ) {
+            // Locate the ViewHolder for the clicked position.
+            val position = galleryVm.galleryPosition.value ?: return
+
+            val vh = binding.gallery.findViewHolderForAdapterPosition(position)
+            if (vh?.itemView == null) return
+
+            // Map the first shared element name to the child ImageView.
+            sharedElements[names[0]] = vh.itemView
+        }
+    }
 }
\ No newline at end of file
diff --git a/app/src/main/res/transition/map_exit_transition.xml b/app/src/main/res/transition/map_exit_transition.xml
new file mode 100644
index 00000000..e1e95d71
--- /dev/null
+++ b/app/src/main/res/transition/map_exit_transition.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<transitionSet xmlns:android="http://schemas.android.com/apk/res/android"
+    android:duration="375"
+    android:interpolator="@android:interpolator/fast_out_slow_in"
+    android:startDelay="25">
+    <fade>
+        <targets>
+            <target android:targetId="@id/bottom_sheet" />
+            <target android:targetId="@id/fab_directions" />
+        </targets>
+    </fade>
+</transitionSet>
\ No newline at end of file