feat(gallery): pagination

app/src/main/java/com/nextcloud/client/database/dao/FileDao.kt

@@ -65,6 +65,23 @@ interface FileDao {
     )
     suspend fun getGalleryItemsSuspended(startDate: Long, endDate: Long, fileOwner: String): List<FileEntity>
 
+    @Query(
+        "SELECT * FROM filelist" +
+            " WHERE (content_type LIKE 'image/%' OR content_type LIKE 'video/%')" +
+            " AND file_owner = :fileOwner" +
+            " AND path LIKE :pathPrefix || '%'" +
+            " AND (:mimeFilter IS NULL OR content_type LIKE :mimeFilter)" +
+            " ORDER BY modified DESC" +
+            " LIMIT :limit OFFSET :offset"
+    )
+    suspend fun getGalleryItemsPageSuspended(
+        fileOwner: String,
+        pathPrefix: String,
+        mimeFilter: String?,
+        limit: Int,
+        offset: Int
+    ): List<FileEntity>
+
     @Query("SELECT * FROM filelist WHERE file_owner = :fileOwner ORDER BY ${ProviderTableMeta.FILE_DEFAULT_SORT_ORDER}")
     fun getAllFiles(fileOwner: String): List<FileEntity>
 

app/src/main/java/com/nextcloud/utils/extensions/FileDataStorageManagerExtensions.kt

@@ -25,9 +25,33 @@ suspend fun FileDataStorageManager.saveShares(shares: List<OCShare>, accountName
     }
 }
 
-suspend fun FileDataStorageManager.getAllGalleryItemsSuspended(): List<OCFile> {
-    val fileEntities = fileDao.getGalleryItemsSuspended(0, Long.MAX_VALUE, user.accountName)
-    return fileEntities.map { createFileInstance(it) }
+private const val GALLERY_DB_CHUNK_SIZE = 500
+
+suspend fun FileDataStorageManager.getGalleryItemsPageSuspended(
+    pathPrefix: String,
+    mimeFilter: String?,
+    limit: Int
+): List<OCFile> {
+    val result = ArrayList<OCFile>(minOf(limit, GALLERY_DB_CHUNK_SIZE))
+    var offset = 0
+
+    while (offset < limit) {
+        val chunkLimit = minOf(GALLERY_DB_CHUNK_SIZE, limit - offset)
+        val entities = fileDao.getGalleryItemsPageSuspended(
+            user.accountName,
+            pathPrefix,
+            mimeFilter,
+            chunkLimit,
+            offset
+        )
+
+        entities.mapTo(result) { createFileInstance(it) }
+        offset += entities.size
+
+        if (entities.size < chunkLimit) break
+    }
+
+    return result
 }
 
 fun FileDataStorageManager.searchFilesByName(file: OCFile, accountName: String, query: String): List<OCFile> =

app/src/main/java/com/owncloud/android/ui/activity/DrawerActivity.java

@@ -331,7 +331,7 @@ private void openFavoritesTab() {
     }
 
     private void openMediaTab(int menuItemId) {
-        GalleryFragment.Companion.setLastMediaItemPosition(null);
+        GalleryFragment.Companion.clearSavedScrollState();
         resetOnlyPersonalAndOnDevice();
         setupToolbar();
         startPhotoSearch(menuItemId);

app/src/main/java/com/owncloud/android/ui/adapter/OCFileListDelegate.kt

@@ -31,7 +31,6 @@ import com.owncloud.android.datamodel.ThumbnailsCacheManager
 import com.owncloud.android.lib.common.utils.Log_OC
 import com.owncloud.android.ui.activity.ComponentsGetter
 import com.owncloud.android.ui.activity.FolderPickerActivity
-import com.owncloud.android.ui.fragment.GalleryFragment
 import com.owncloud.android.ui.fragment.SearchType
 import com.owncloud.android.ui.interfaces.OCFileListFragmentInterface
 import com.owncloud.android.utils.DisplayUtils
@@ -166,7 +165,6 @@ class OCFileListDelegate(
 
         imageView.setOnClickListener {
             ocFileListFragmentInterface.onItemClicked(file)
-            GalleryFragment.setLastMediaItemPosition(galleryRowHolder.absoluteAdapterPosition)
         }
 
         if (!hideItemOptions) {

app/src/main/java/com/owncloud/android/ui/fragment/GalleryFragment.kt

@@ -1,6 +1,7 @@
 /*
  * Nextcloud - Android Client
  *
+ * SPDX-FileCopyrightText: 2023 Alper Ozturk <alper.ozturk@nextcloud.com>
  * SPDX-FileCopyrightText: 2023 TSI-mc
  * SPDX-FileCopyrightText: 2019 Tobias Kaminsky <tobias@kaminsky.me>
  * SPDX-FileCopyrightText: 2019 Nextcloud GmbH
@@ -14,6 +15,7 @@ import android.content.Intent
 import android.content.IntentFilter
 import android.content.res.Configuration
 import android.os.Bundle
+import android.os.Parcelable
 import android.view.LayoutInflater
 import android.view.Menu
 import android.view.MenuInflater
@@ -28,7 +30,7 @@ import androidx.lifecycle.lifecycleScope
 import androidx.localbroadcastmanager.content.LocalBroadcastManager
 import androidx.recyclerview.widget.GridLayoutManager
 import androidx.recyclerview.widget.RecyclerView
-import com.nextcloud.utils.extensions.getAllGalleryItemsSuspended
+import com.nextcloud.utils.extensions.getGalleryItemsPageSuspended
 import com.nextcloud.utils.extensions.getParcelableArgument
 import kotlinx.coroutines.Job
 import com.nextcloud.utils.extensions.getTypedActivity
@@ -47,7 +49,6 @@ import com.owncloud.android.ui.adapter.GalleryAdapter
 import com.owncloud.android.ui.asynctasks.GallerySearchTask
 import com.owncloud.android.ui.events.ChangeMenuEvent
 import com.owncloud.android.ui.fragment.GalleryFragmentBottomSheetDialog.MediaState
-import com.owncloud.android.utils.MimeTypeUtil
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.withContext
@@ -61,6 +62,8 @@ class GalleryFragment :
     private var showGalleryJob: Job? = null
     private var endDate: Long = 0
     private val limit = 150
+    private var loadedItemCount = INITIAL_GALLERY_WINDOW
+    private var restoreScrollPending = false
     private var adapter: GalleryAdapter? = null
 
     private var bottomSheet: GalleryFragmentBottomSheetDialog? = null
@@ -148,6 +151,8 @@ class GalleryFragment :
     override fun onPause() {
         super.onPause()
         photoSearchTask?.cancel()
+        savedScrollState = recyclerView?.layoutManager?.onSaveInstanceState()
+        savedLoadedItemCount = loadedItemCount
     }
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
@@ -173,6 +178,10 @@ class GalleryFragment :
 
         updateSubtitle(bottomSheet?.currMediaState)
 
+        // Restore the previously loaded window so a saved scroll position still resolves to a valid item.
+        loadedItemCount = savedLoadedItemCount ?: INITIAL_GALLERY_WINDOW
+        restoreScrollPending = savedScrollState != null
+
         handleSearchEvent()
     }
 
@@ -198,11 +207,6 @@ class GalleryFragment :
         val layoutManager = GridLayoutManager(context, 1)
         adapter?.setLayoutManager(layoutManager)
         recyclerView?.setLayoutManager(layoutManager)
-        recyclerView?.post {
-            lastMediaItemPosition?.let { position ->
-                recyclerView?.layoutManager?.scrollToPosition(position)
-            }
-        }
     }
 
     override fun onConfigurationChanged(newConfig: Configuration) {
@@ -308,6 +312,9 @@ class GalleryFragment :
 
     private fun searchAndDisplayAfterChangingFolder() {
         // TODO: Fix folder change, it seems it doesn't work at all
+        loadedItemCount = INITIAL_GALLERY_WINDOW
+        restoreScrollPending = false
+        clearSavedScrollState()
         endDate = System.currentTimeMillis() / 1000
         isPhotoSearchQueryRunning = true
         runGallerySearchTask()
@@ -367,44 +374,56 @@ class GalleryFragment :
                 Log_OC.d(this, "Gallery swipe: retrieve items because end of gallery display")
             }
 
-            // Almost reached the end, continue to load new photos
+            // Almost reached the end, widen the display window and continue to load new photos
             endDate = lastItemTimestamp
+            loadedItemCount += GALLERY_WINDOW_INCREMENT
+            showAllGalleryItems()
             isPhotoSearchQueryRunning = true
             runGallerySearchTask()
         }
     }
 
     override fun updateMediaContent(mediaState: MediaState) {
+        loadedItemCount = INITIAL_GALLERY_WINDOW
+        restoreScrollPending = false
+        clearSavedScrollState()
         showAllGalleryItems()
     }
 
     fun showAllGalleryItems() {
         val mediaState = bottomSheet?.currMediaState ?: return
 
+        val mimeFilter = when (mediaState) {
+            MediaState.MEDIA_STATE_PHOTOS_ONLY -> IMAGE_MIME_FILTER
+            MediaState.MEDIA_STATE_VIDEOS_ONLY -> VIDEO_MIME_FILTER
+            else -> null
+        }
+
         showGalleryJob?.cancel()
         showGalleryJob = lifecycleScope.launch(Dispatchers.Default) {
             val remotePath = preferences.getLastSelectedMediaFolder()
-            val items = mContainerActivity.storageManager.getAllGalleryItemsSuspended()
-
-            val isPhotosOnly = mediaState == MediaState.MEDIA_STATE_PHOTOS_ONLY
-            val isVideosOnly = mediaState == MediaState.MEDIA_STATE_VIDEOS_ONLY
+            val items = mContainerActivity.storageManager.getGalleryItemsPageSuspended(
+                remotePath,
+                mimeFilter,
+                loadedItemCount
+            )
 
-            val filteredItems = items.filter {
-                if (!it.remotePath.startsWith(remotePath)) return@filter false
-                if (isPhotosOnly) return@filter MimeTypeUtil.isImage(it.mimeType)
-                if (isVideosOnly) return@filter MimeTypeUtil.isVideo(it.mimeType)
-                true
-            }
-
-            val galleryItems =
-                filteredItems.toGalleryItems(columnsCount, ThumbnailsCacheManager.getThumbnailDimension())
+            val galleryItems = items.toGalleryItems(columnsCount, ThumbnailsCacheManager.getThumbnailDimension())
 
             withContext(Dispatchers.Main) {
                 if (galleryItems.isEmpty()) {
                     setEmptyListMessage(SearchType.GALLERY_SEARCH)
                 }
                 adapter?.updateList(galleryItems)
                 updateSubtitle(mediaState)
+
+                if (restoreScrollPending && galleryItems.isNotEmpty()) {
+                    restoreScrollPending = false
+                    savedScrollState?.let { state ->
+                        savedScrollState = null
+                        recyclerView?.layoutManager?.onRestoreInstanceState(state)
+                    }
+                }
             }
         }
     }
@@ -448,14 +467,24 @@ class GalleryFragment :
         private const val MAX_ITEMS_PER_ROW = 10
         private const val FRAGMENT_TAG_BOTTOM_SHEET = "data"
 
-        private var lastMediaItemPosition: Int? = null
+        private const val INITIAL_GALLERY_WINDOW = 500
+        private const val GALLERY_WINDOW_INCREMENT = 500
+        private const val IMAGE_MIME_FILTER = "image/%"
+        private const val VIDEO_MIME_FILTER = "video/%"
+
         const val REFRESH_SEARCH_EVENT_RECEIVER: String = "refreshSearchEventReceiver"
 
         private const val MAX_LANDSCAPE_COLUMN_SIZE = 5
         private const val MAX_PORTRAIT_COLUMN_SIZE = 2
 
-        fun setLastMediaItemPosition(position: Int?) {
-            lastMediaItemPosition = position
+        // Kept across the activity recreation that happens when returning from the media preview,
+        // so the grid reopens at the same scroll position and with the same loaded window.
+        private var savedScrollState: Parcelable? = null
+        private var savedLoadedItemCount: Int? = null
+
+        fun clearSavedScrollState() {
+            savedScrollState = null
+            savedLoadedItemCount = null
         }
     }
 }

app/src/main/java/com/owncloud/android/ui/fragment/OCFileListFragment.java

@@ -154,6 +154,7 @@
 import static com.owncloud.android.ui.dialog.setupEncryption.SetupEncryptionDialogFragment.SETUP_ENCRYPTION_DIALOG_TAG;
 import static com.owncloud.android.ui.fragment.SearchType.FAVORITE_SEARCH;
 import static com.owncloud.android.ui.fragment.SearchType.FILE_SEARCH;
+import static com.owncloud.android.ui.fragment.SearchType.GALLERY_SEARCH;
 import static com.owncloud.android.ui.fragment.SearchType.NO_SEARCH;
 import static com.owncloud.android.ui.fragment.SearchType.RECENT_FILES_SEARCH;
 import static com.owncloud.android.ui.fragment.SearchType.SHARED_FILTER;
@@ -1196,7 +1197,7 @@ private void fileOnItemClick(OCFile file) {
             return;
         }
 
-        if (PreviewImageFragment.canBePreviewed(file) && mContainerActivity instanceof FileDisplayActivity fda) {
+        if (canPreviewInVirtualFolderPager(file) && mContainerActivity instanceof FileDisplayActivity fda) {
             fda.previewImageWithSearchContext(file, searchFragment, currentSearchType);
         } else if (file.isDown() && mContainerActivity instanceof FileDisplayActivity fda) {
             fda.previewFile(file, this::setFabVisible);
@@ -1205,6 +1206,20 @@ private void fileOnItemClick(OCFile file) {
         }
     }
 
+    /**
+     * In a gallery or favorites search the preview pager is built from the whole virtual folder, so a directly
+     * tapped video must open through the same pager as the images.
+     */
+    private boolean canPreviewInVirtualFolderPager(OCFile file) {
+        if (PreviewImageFragment.canBePreviewed(file)) {
+            return true;
+        }
+
+        boolean virtualFolderSearch = searchFragment
+            && (currentSearchType == GALLERY_SEARCH || currentSearchType == FAVORITE_SEARCH);
+        return virtualFolderSearch && MimeTypeUtil.isVideo(file);
+    }
+
     private void handlePendingDownloadFile(OCFile file) {
         if (!isAccountManagerInitialized()) {
             Log_OC.e(TAG, "AccountManager not yet initialized");