Optimize page loading

app/src/main/java/org/koitharu/kotatsu/ui/reader/PageLoader.kt

@@ -16,7 +16,7 @@ import kotlin.coroutines.CoroutineContext
 class PageLoader : KoinComponent, CoroutineScope, DisposableHandle {
 
 	private val job = SupervisorJob()
-	private val tasks = HashMap<String, Job>()
+	private val tasks = HashMap<String, Deferred<File>>()
 	private val okHttp by inject<OkHttpClient>()
 	private val cache by inject<PagesCache>()
 
@@ -30,8 +30,13 @@ class PageLoader : KoinComponent, CoroutineScope, DisposableHandle {
 				return it
 			}
 		}
+		val task = tasks[url]?.takeUnless { it.isCancelled }
+		return (task ?: loadAsync(url).also { tasks[url] = it }).await()
+	}
+
+	private fun loadAsync(url: String) = async(Dispatchers.IO) {
 		val uri = Uri.parse(url)
-		return if (uri.scheme == "cbz") {
+		if (uri.scheme == "cbz") {
 			val zip = ZipFile(uri.schemeSpecificPart)
 			val entry = zip.getEntry(uri.fragment)
 			zip.getInputStream(entry).use {
@@ -60,5 +65,6 @@ class PageLoader : KoinComponent, CoroutineScope, DisposableHandle {
 
 	override fun dispose() {
 		coroutineContext.cancel()
+		tasks.clear()
 	}
 }

app/src/main/java/org/koitharu/kotatsu/utils/ext/CommonExt.kt

@@ -1,6 +1,7 @@
 package org.koitharu.kotatsu.utils.ext
 
 import android.content.res.Resources
+import android.util.Log
 import kotlinx.coroutines.delay
 import org.koitharu.kotatsu.BuildConfig
 import org.koitharu.kotatsu.R
@@ -44,3 +45,11 @@ fun Throwable.getDisplayMessage(resources: Resources) = when (this) {
 		resources.getString(R.string.error_occurred)
 	}
 }
+
+inline fun <T> measured(tag: String, block: () -> T): T {
+	val time = System.currentTimeMillis()
+	val res = block()
+	val spent = System.currentTimeMillis() - time
+	Log.d("measured", "$tag ${spent.format(1)} ms")
+	return res
+}

app/src/main/res/layout/item_page.xml

@@ -2,6 +2,7 @@
 <FrameLayout
 	xmlns:android="http://schemas.android.com/apk/res/android"
 	xmlns:tools="http://schemas.android.com/tools"
+	android:background="?android:windowBackground"
 	android:layout_width="match_parent"
 	android:layout_height="match_parent">