ImageViewer, fix Android rotation (#3007)

examples/imageviewer/shared/build.gradle.kts

@@ -6,6 +6,7 @@ plugins {
     id("com.android.library")
     id("org.jetbrains.compose")
     kotlin("plugin.serialization")
+    id("kotlin-parcelize")
 }
 
 version = "1.0-SNAPSHOT"

examples/imageviewer/shared/src/androidMain/kotlin/example/imageviewer/model/Page.android.kt

@@ -0,0 +1,16 @@
+package example.imageviewer.model
+
+import android.os.Parcelable
+import kotlinx.parcelize.Parcelize
+
+@Parcelize
+actual class MemoryPage actual constructor(actual val pictureIndex: Int) : Page, Parcelable
+
+@Parcelize
+actual class CameraPage : Page, Parcelable
+
+@Parcelize
+actual class FullScreenPage actual constructor(actual val pictureIndex: Int) : Page, Parcelable
+
+@Parcelize
+actual class GalleryPage : Page, Parcelable

examples/imageviewer/shared/src/androidMain/kotlin/example/imageviewer/view/CameraView.android.kt

@@ -15,6 +15,7 @@ import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.material.CircularProgressIndicator
 import androidx.compose.runtime.*
+import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.graphics.Color
@@ -82,7 +83,7 @@ private fun CameraWithGrantedPermission(
     val preview = Preview.Builder().build()
     val previewView = remember { PreviewView(context) }
     val imageCapture: ImageCapture = remember { ImageCapture.Builder().build() }
-    var isFrontCamera by remember { mutableStateOf(false) }
+    var isFrontCamera by rememberSaveable { mutableStateOf(false) }
     val cameraSelector = remember(isFrontCamera) {
         val lensFacing =
             if (isFrontCamera) {

examples/imageviewer/shared/src/commonMain/kotlin/example/imageviewer/ImageViewer.common.kt

@@ -3,6 +3,8 @@ package example.imageviewer
 import androidx.compose.animation.*
 import androidx.compose.animation.core.tween
 import androidx.compose.runtime.*
+import androidx.compose.runtime.saveable.listSaver
+import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.snapshots.SnapshotStateList
 import example.imageviewer.model.*
 import example.imageviewer.view.*
@@ -33,8 +35,17 @@ fun ImageViewerCommon(
 fun ImageViewerWithProvidedDependencies(
     pictures: SnapshotStateList<PictureData>
 ) {
-    val selectedPictureIndex = remember { mutableStateOf(0) }
-    val navigationStack = remember { NavigationStack<Page>(GalleryPage()) }
+    // rememberSaveable is required to properly handle Android configuration changes (such as device rotation)
+    val selectedPictureIndex = rememberSaveable { mutableStateOf(0) }
+    val navigationStack = rememberSaveable(
+        saver = listSaver<NavigationStack<Page>, Page>(
+            restore = { NavigationStack(*it.toTypedArray()) },
+            save = { it.stack },
+        )
+    ) {
+        NavigationStack(GalleryPage())
+    }
+
     val externalEvents = LocalInternalEvents.current
     LaunchedEffect(Unit) {
         externalEvents.collect {
@@ -62,8 +73,8 @@ fun ImageViewerWithProvidedDependencies(
                 GalleryScreen(
                     pictures = pictures,
                     selectedPictureIndex = selectedPictureIndex,
-                    onClickPreviewPicture = { previewPictureId ->
-                        navigationStack.push(MemoryPage(mutableStateOf(previewPictureId)))
+                    onClickPreviewPicture = { previewPictureIndex ->
+                        navigationStack.push(MemoryPage(previewPictureIndex))
                     }
                 ) {
                     navigationStack.push(CameraPage())
@@ -72,7 +83,7 @@ fun ImageViewerWithProvidedDependencies(
 
             is FullScreenPage -> {
                 FullscreenImageScreen(
-                    picture = page.picture,
+                    picture = pictures[page.pictureIndex],
                     back = {
                         navigationStack.back()
                     }
@@ -83,14 +94,19 @@ fun ImageViewerWithProvidedDependencies(
                 MemoryScreen(
                     pictures = pictures,
                     memoryPage = page,
-                    onSelectRelatedMemory = { picture ->
-                        navigationStack.push(MemoryPage(mutableStateOf(picture)))
+                    onSelectRelatedMemory = { pictureIndex ->
+                        navigationStack.push(MemoryPage(pictureIndex))
                     },
-                    onBack = {
-                        navigationStack.back()
+                    onBack = { resetNavigation ->
+                        if (resetNavigation) {
+                            selectedPictureIndex.value = 0
+                            navigationStack.reset()
+                        } else {
+                            navigationStack.back()
+                        }
                     },
-                    onHeaderClick = { galleryId ->
-                        navigationStack.push(FullScreenPage(galleryId))
+                    onHeaderClick = { pictureIndex ->
+                        navigationStack.push(FullScreenPage(pictureIndex))
                     },
                 )
             }

examples/imageviewer/shared/src/commonMain/kotlin/example/imageviewer/model/Page.common.kt

@@ -0,0 +1,15 @@
+package example.imageviewer.model
+
+interface Page
+
+expect class MemoryPage(pictureIndex: Int) : Page {
+    val pictureIndex: Int
+}
+
+expect class CameraPage() : Page
+
+expect class FullScreenPage(pictureIndex: Int) : Page {
+    val pictureIndex: Int
+}
+
+expect class GalleryPage() : Page

examples/imageviewer/shared/src/commonMain/kotlin/example/imageviewer/model/Page.kt

@@ -1,10 +0,0 @@
-package example.imageviewer.model
-
-import androidx.compose.runtime.MutableState
-
-sealed interface Page
-
-class MemoryPage(val pictureState: MutableState<PictureData>) : Page
-class CameraPage : Page
-class FullScreenPage(val picture: PictureData) : Page
-class GalleryPage : Page

examples/imageviewer/shared/src/commonMain/kotlin/example/imageviewer/view/GalleryScreen.kt

@@ -50,7 +50,7 @@ enum class GalleryStyle {
 fun GalleryScreen(
     pictures: SnapshotStateList<PictureData>,
     selectedPictureIndex: MutableState<Int>,
-    onClickPreviewPicture: (PictureData) -> Unit,
+    onClickPreviewPicture: (index: Int) -> Unit,
     onMakeNewMemory: () -> Unit
 ) {
     val imageProvider = LocalImageProvider.current
@@ -113,17 +113,17 @@ fun GalleryScreen(
                 Box(
                     Modifier.fillMaxSize()
                         .clickable {
-                            onClickPreviewPicture(pictures[pagerState.currentPage])
+                            onClickPreviewPicture(pagerState.currentPage)
                         }
                 ) {
-                    HorizontalPager(pictures.size, state = pagerState) { idx ->
-                        val picture = pictures[idx]
+                    HorizontalPager(pictures.size, state = pagerState) { index ->
+                        val picture = pictures[index]
                         var image: ImageBitmap? by remember(picture) { mutableStateOf(null) }
                         LaunchedEffect(picture) {
                             image = imageProvider.getImage(picture)
                         }
                         if (image != null) {
-                            Box(Modifier.fillMaxSize().animatePageChanges(pagerState, idx)) {
+                            Box(Modifier.fillMaxSize().animatePageChanges(pagerState, index)) {
                                 Image(
                                     bitmap = image!!,
                                     contentDescription = null,
@@ -176,7 +176,7 @@ fun GalleryScreen(
 private fun SquaresGalleryView(
     images: List<PictureData>,
     pagerState: PagerState,
-    onSelect: (Int) -> Unit,
+    onSelect: (index: Int) -> Unit,
 ) {
     LazyVerticalGrid(
         modifier = Modifier.padding(top = 4.dp),
@@ -184,11 +184,11 @@ private fun SquaresGalleryView(
         verticalArrangement = Arrangement.spacedBy(1.dp),
         horizontalArrangement = Arrangement.spacedBy(1.dp)
     ) {
-        itemsIndexed(images) { idx, picture ->
+        itemsIndexed(images) { index, picture ->
             SquareThumbnail(
                 picture = picture,
-                onClick = { onSelect(idx) },
-                isHighlighted = pagerState.targetPage == idx
+                onClick = { onSelect(index) },
+                isHighlighted = pagerState.targetPage == index
             )
         }
     }
@@ -244,8 +244,8 @@ fun SquareThumbnail(
 @Composable
 private fun ListGalleryView(
     pictures: List<PictureData>,
-    onSelect: (Int) -> Unit,
-    onFullScreen: (PictureData) -> Unit,
+    onSelect: (index: Int) -> Unit,
+    onFullScreen: (index: Int) -> Unit,
 ) {
     val notification = LocalNotification.current
     ScrollableColumn(
@@ -259,7 +259,7 @@ private fun ListGalleryView(
                     onSelect(p.index)
                 },
                 onClickFullScreen = {
-                    onFullScreen(p.value)
+                    onFullScreen(p.index)
                 },
                 onClickInfo = {
                     notification.notifyImageData(p.value)

examples/imageviewer/shared/src/commonMain/kotlin/example/imageviewer/view/MemoryScreen.kt

@@ -38,20 +38,19 @@ import example.imageviewer.model.*
 import example.imageviewer.shareIcon
 import example.imageviewer.style.ImageviewerColors
 import org.jetbrains.compose.resources.ExperimentalResourceApi
-import org.jetbrains.compose.resources.painterResource
 
 @Composable
 fun MemoryScreen(
     pictures: SnapshotStateList<PictureData>,
     memoryPage: MemoryPage,
-    onSelectRelatedMemory: (PictureData) -> Unit,
-    onBack: () -> Unit,
-    onHeaderClick: (PictureData) -> Unit,
+    onSelectRelatedMemory: (index: Int) -> Unit,
+    onBack: (resetNavigation: Boolean) -> Unit,
+    onHeaderClick: (index: Int) -> Unit,
 ) {
     val imageProvider = LocalImageProvider.current
     val sharePicture = LocalSharePicture.current
     var edit: Boolean by remember { mutableStateOf(false) }
-    val picture = memoryPage.pictureState.value
+    val picture = pictures.getOrNull(memoryPage.pictureIndex) ?: return
     var headerImage: ImageBitmap? by remember(picture) { mutableStateOf(null) }
     val platformContext = getPlatformContext()
     LaunchedEffect(picture) {
@@ -78,7 +77,7 @@ fun MemoryScreen(
                     MemoryHeader(
                         it,
                         picture = picture,
-                        onClick = { onHeaderClick(picture) }
+                        onClick = { onHeaderClick(memoryPage.pictureIndex) }
                     )
                 }
             }
@@ -106,7 +105,7 @@ fun MemoryScreen(
                     Row(Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.SpaceEvenly) {
                         IconWithText(Icons.Default.Delete, "Delete") {
                             imageProvider.delete(picture)
-                            onBack()
+                            onBack(true)
                         }
                         IconWithText(Icons.Default.Edit, "Edit") {
                             edit = true
@@ -123,14 +122,15 @@ fun MemoryScreen(
         }
         TopLayout(
             alignLeftContent = {
-                BackButton(onBack)
+                BackButton {
+                    onBack(false)
+                }
             },
             alignRightContent = {},
         )
         if (edit) {
             EditMemoryDialog(picture.name, picture.description) { name, description ->
-                val edited = imageProvider.edit(picture, name, description)
-                memoryPage.pictureState.value = edited
+                imageProvider.edit(picture, name, description)
                 edit = false
             }
         }
@@ -267,7 +267,7 @@ fun Headliner(s: String) {
 @Composable
 fun RelatedMemoriesVisualizer(
     pictures: List<PictureData>,
-    onSelectRelatedMemory: (PictureData) -> Unit
+    onSelectRelatedMemory: (index: Int) -> Unit
 ) {
     Box(
         modifier = Modifier.padding(10.dp, 0.dp).clip(RoundedCornerShape(10.dp)).fillMaxWidth()
@@ -276,22 +276,14 @@ fun RelatedMemoriesVisualizer(
             modifier = Modifier.fillMaxSize(),
             horizontalArrangement = Arrangement.spacedBy(8.dp)
         ) {
-            itemsIndexed(pictures) { idx, item ->
-                RelatedMemory(item, onSelectRelatedMemory)
+            itemsIndexed(pictures) { index, item ->
+                Box(Modifier.size(130.dp).clip(RoundedCornerShape(8.dp))) {
+                    SquareThumbnail(
+                        picture = item,
+                        isHighlighted = false,
+                        onClick = { onSelectRelatedMemory(index) })
+                }
             }
         }
     }
 }
-
-@Composable
-fun RelatedMemory(
-    galleryEntry: PictureData,
-    onSelectRelatedMemory: (PictureData) -> Unit
-) {
-    Box(Modifier.size(130.dp).clip(RoundedCornerShape(8.dp))) {
-        SquareThumbnail(
-            picture = galleryEntry,
-            isHighlighted = false,
-            onClick = { onSelectRelatedMemory(galleryEntry) })
-    }
-}

examples/imageviewer/shared/src/commonMain/kotlin/example/imageviewer/view/NavigationStack.kt

@@ -2,18 +2,22 @@ package example.imageviewer.view
 
 import androidx.compose.runtime.mutableStateListOf
 
-class NavigationStack<T>(initial: T) {
-    private val stack = mutableStateListOf(initial)
+class NavigationStack<T>(vararg initial: T) {
+    val stack = mutableStateListOf(*initial)
     fun push(t: T) {
         stack.add(t)
     }
 
     fun back() {
-        if(stack.size > 1) {
+        if (stack.size > 1) {
             // Always keep one element on the view stack
             stack.removeLast()
         }
     }
 
+    fun reset() {
+        stack.removeRange(1, stack.size)
+    }
+
     fun lastWithIndex() = stack.withIndex().last()
 }

examples/imageviewer/shared/src/desktopMain/kotlin/example/imageviewer/model/Page.desktop.kt

@@ -0,0 +1,9 @@
+package example.imageviewer.model
+
+actual class MemoryPage actual constructor(actual val pictureIndex: Int) : Page
+
+actual class CameraPage : Page
+
+actual class FullScreenPage actual constructor(actual val pictureIndex: Int) : Page
+
+actual class GalleryPage : Page

examples/imageviewer/shared/src/iosMain/kotlin/example/imageviewer/model/Page.ios.kt

@@ -0,0 +1,9 @@
+package example.imageviewer.model
+
+actual class MemoryPage actual constructor(actual val pictureIndex: Int) : Page
+
+actual class CameraPage : Page
+
+actual class FullScreenPage actual constructor(actual val pictureIndex: Int) : Page
+
+actual class GalleryPage : Page