Use custom QueryPagingSource (#7321)

* Use custom QueryPagingSource - Adds placeholder to make the list jump around less - Fixes issue where SQLDelight QueryPagingSource would throw IndexOutOfBounds * Review Changes (cherry picked from commit 3fd9e021fa)
2022-06-18 20:55:58 +02:00
parent 3bcec2238d
commit 9a28d42b63
9 changed files with 301 additions and 119 deletions
@@ -0,0 +1,72 @@
+package eu.kanade.data
+
+import androidx.paging.PagingSource
+import androidx.paging.PagingState
+import com.squareup.sqldelight.Query
+import eu.kanade.tachiyomi.Database
+import kotlin.properties.Delegates
+
+class QueryPagingSource<RowType : Any>(
+    val handler: DatabaseHandler,
+    val countQuery: Database.() -> Query<Long>,
+    val queryProvider: Database.(Long, Long) -> Query<RowType>,
+) : PagingSource<Long, RowType>(), Query.Listener {
+
+    override val jumpingSupported: Boolean = true
+
+    private var currentQuery: Query<RowType>? by Delegates.observable(null) { _, old, new ->
+        old?.removeListener(this)
+        new?.addListener(this)
+    }
+
+    init {
+        registerInvalidatedCallback {
+            currentQuery?.removeListener(this)
+            currentQuery = null
+        }
+    }
+
+    override suspend fun load(params: LoadParams<Long>): LoadResult<Long, RowType> {
+        try {
+            val key = params.key ?: 0L
+            val loadSize = params.loadSize
+            val count = handler.awaitOne { countQuery() }
+
+            val (offset, limit) = when (params) {
+                is LoadParams.Prepend -> key - loadSize to loadSize.toLong()
+                else -> key to loadSize.toLong()
+            }
+
+            val data = handler.awaitList {
+                queryProvider(limit, offset)
+                    .also { currentQuery = it }
+            }
+
+            val (prevKey, nextKey) = when (params) {
+                is LoadParams.Append -> { offset - loadSize to offset + loadSize }
+                else -> { offset to offset + loadSize }
+            }
+
+            return LoadResult.Page(
+                data = data,
+                prevKey = if (offset <= 0L || prevKey < 0L) null else prevKey,
+                nextKey = if (offset + loadSize >= count) null else nextKey,
+                itemsBefore = maxOf(0L, offset).toInt(),
+                itemsAfter = maxOf(0L, count - (offset + loadSize)).toInt(),
+            )
+        } catch (e: Exception) {
+            return LoadResult.Error(throwable = e)
+        }
+    }
+
+    override fun getRefreshKey(state: PagingState<Long, RowType>): Long? {
+        return state.anchorPosition?.let { anchorPosition ->
+            val anchorPage = state.closestPageToPosition(anchorPosition)
+            anchorPage?.prevKey ?: anchorPage?.nextKey
+        }
+    }
+
+    override fun queryResultsChanged() {
+        invalidate()
+    }
+}