Merge pull request #27 from Notalib/fix/scroll-to-location

fix: when loading a chapter in a new file, scrollToLocation didn't work right

Author: ddfreiling

flutter_readium/android/src/main/kotlin/dk/nota/flutter_readium/ReadiumReader.kt

@@ -781,7 +781,7 @@ object ReadiumReader : TimebasedNavigator.TimebasedListener, EpubNavigator.Visua
         return epubNavigator?.isReaderReady() ?: false
     }
 
-    fun epubGo(locator: Locator, animated: Boolean) {
+    suspend fun epubGo(locator: Locator, animated: Boolean) {
         epubNavigator?.go(locator, animated)
     }
 

flutter_readium/android/src/main/kotlin/dk/nota/flutter_readium/ReadiumReaderWidget.kt

@@ -175,7 +175,7 @@ class ReadiumReaderWidget(
     }
 
     override fun onVisualCurrentLocationChanged(locator: Locator) {
-        Log.d(TAG, "::onVisualCurrentLocationChanged $Locator")
+        Log.d(TAG, "::onVisualCurrentLocationChanged $locator")
     }
 
     override fun onVisualReaderIsReady() {

flutter_readium/android/src/main/kotlin/dk/nota/flutter_readium/Utils.kt

@@ -5,6 +5,7 @@ import android.app.Application
 import android.content.Context
 import android.content.ContextWrapper
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.withContext
 import org.json.JSONArray
 import org.json.JSONObject
@@ -79,3 +80,7 @@ fun canScroll(locations: Locator.Locations) =
 ): T {
     return withContext(scope.coroutineContext, block)
 }
+
+fun <T> MutableStateFlow<T>.update(new: T) {
+    if (this.value != new) this.value = new
+}

flutter_readium/android/src/main/kotlin/dk/nota/flutter_readium/fragments/EpubReaderFragment.kt

@@ -130,7 +130,7 @@ class EpubReaderFragment : VisualReaderFragment(), EpubNavigatorFragment.Listene
         Log.d(TAG, "::goRight")
         val navigator = epubNavigator
         if (navigator == null) {
-            Log.d(TAG, "::goLeft. Navigator not ready.")
+            Log.d(TAG, "::goRight. Navigator not ready.")
             return
         }
 
@@ -289,15 +289,16 @@ class EpubReaderFragment : VisualReaderFragment(), EpubNavigatorFragment.Listene
             return
         }
 
-        // DFG: This will be relative to your app's src/main/assets/ folder.
-        // To reference assets from other flutter packages use 'flutter_assets/packages/<package>/assets/.*'
-        // Readium uses WebViewAssetLoader.AssetsPathHandler under the surface.
         val preferences = model.preferences ?: EpubPreferences()
         model.preferences = preferences
         val navigatorFactory = model.navigatorFactory!!
         val fragmentFactory = navigatorFactory.createFragmentFactory(
             configuration = EpubNavigatorFragment.Configuration(
                 shouldApplyInsetsPadding = false,
+
+                // DFG: This will be relative to your app's src/main/assets/ folder.
+                // To reference assets from other flutter packages use 'flutter_assets/packages/<package>/assets/.*'
+                // Readium uses WebViewAssetLoader.AssetsPathHandler under the surface.
                 servedAssets = listOf(
                     "flutter_assets/packages/flutter_readium/assets/.*",
                 )

flutter_readium/android/src/main/kotlin/dk/nota/flutter_readium/navigators/EpubNavigator.kt

@@ -82,9 +82,9 @@ class EpubNavigator : BaseNavigator, EpubReaderFragment.Listener {
     var editor: EpubPreferencesEditor? = null
 
     /*
-     * The initial locations to scroll to when the navigator is ready.
+     * Pending scroll target to be applied when the page is loaded.
      */
-    var initialLocations: Locator.Locations? = null
+    var pendingScrollToLocations: Locator.Locations? = null
 
     val preferences: EpubPreferences?
         get() = editor?.preferences
@@ -105,7 +105,7 @@ class EpubNavigator : BaseNavigator, EpubReaderFragment.Listener {
         }
 
     override suspend fun initNavigator() {
-        initialLocations =
+        pendingScrollToLocations =
             initialLocator?.locations?.let { locations ->
                 if (canScroll(locations)) locations else null
             }
@@ -132,20 +132,23 @@ class EpubNavigator : BaseNavigator, EpubReaderFragment.Listener {
         }
     }
 
-    fun go(locator: Locator, animated: Boolean) {
+    suspend fun go(locator: Locator, animated: Boolean): Boolean {
         val navigator = epubNavigator
         if (navigator == null) {
             Log.d(TAG, "::go - epubNavigator is null!")
-            return
+            return false
         }
 
-        mainScope.launch {
+        return withScope(mainScope) {
             afterFragmentStarted()
-            if (navigator.go(locator, animated)) {
-                Log.d(TAG, "GO returned.")
-            } else {
-                Log.w(TAG, "GO FAILED!")
+            if (!navigator.go(locator, animated)) {
+                Log.w(TAG, "::go -  FAILED!")
+                return@withScope false
             }
+
+            Log.d(TAG, "::go - returned true")
+
+            return@withScope true
         }
     }
 
@@ -217,13 +220,15 @@ class EpubNavigator : BaseNavigator, EpubReaderFragment.Listener {
         Log.d(TAG, "::onPageLoaded")
         visualListener.onPageLoaded()
 
-        val locations = initialLocations
-        if (locations != null) {
-            initialLocations = null
+        pendingScrollToLocations?.let { locations ->
+            Log.d(TAG, "::onPageLoaded - pendingScrollToLocations: $locations")
 
-            mainScope.launch {
+            mainScope.async {
                 scrollToLocations(locations, toStart = true)
             }
+
+            pendingScrollToLocations = null
+
         }
 
         notifyIsReady()
@@ -385,14 +390,14 @@ class EpubNavigator : BaseNavigator, EpubReaderFragment.Listener {
 
             if (shouldGo) {
                 Log.d(TAG, "::goToLocator: Go to $locatorHref from $currentHref")
+                pendingScrollToLocations = locations
                 go(locator, animated)
             } else if (!shouldScroll) {
                 Log.w(TAG, "::goToLocator: Already at $locatorHref, no scroll target, go to start")
                 scrollToLocations(Locator.Locations(progression = 0.0), true)
             } else {
-                Log.d(TAG, "::goToLocator: Don't go to $locatorHref, already there")
-            }
-            if (shouldScroll) {
+                Log.d(TAG, "::goToLocator: Already at $locatorHref, scroll to position")
+
                 scrollToLocations(locations, false)
             }
         }.await()