Add image caching to ImagePreviewImageLoader

ScrollableImagePreviewView being a RecyclerView may reattache its
children multiple times and rely on the ImageLoader to implement any
image retrival optimizations.

Fix: 269797062
Test: manual test, unit tests
Change-Id: I256f4a78a677e939f717fee5dd82492ec572bc65

4 files changed, 51 insertions, 9 deletions

diff --git a/java/src/com/android/intentresolver/ChooserActivity.java b/java/src/com/android/intentresolver/ChooserActivity.java
index 32b10f23..910eb885 100644
--- a/java/src/com/android/intentresolver/ChooserActivity.java
+++ b/java/src/com/android/intentresolver/ChooserActivity.java
@@ -85,6 +85,7 @@ import com.android.intentresolver.chooser.MultiDisplayResolveInfo;
 import com.android.intentresolver.chooser.TargetInfo;
 import com.android.intentresolver.flags.FeatureFlagRepository;
 import com.android.intentresolver.flags.FeatureFlagRepositoryFactory;
+import com.android.intentresolver.flags.Flags;
 import com.android.intentresolver.grid.ChooserGridAdapter;
 import com.android.intentresolver.grid.DirectShareViewHolder;
 import com.android.intentresolver.model.AbstractResolverComparator;
@@ -1338,7 +1339,15 @@ public class ChooserActivity extends ResolverActivity implements
 
     @VisibleForTesting
     protected ImageLoader createPreviewImageLoader() {
-        return new ImagePreviewImageLoader(this, getLifecycle());
+        final int cacheSize;
+        if (mFeatureFlagRepository.isEnabled(Flags.SHARESHEET_SCROLLABLE_IMAGE_PREVIEW)) {
+            float chooserWidth = getResources().getDimension(R.dimen.chooser_width);
+            float imageWidth = getResources().getDimension(R.dimen.chooser_preview_image_width);
+            cacheSize = (int) (Math.ceil(chooserWidth / imageWidth) + 2);
+        } else {
+            cacheSize = 3;
+        }
+        return new ImagePreviewImageLoader(this, getLifecycle(), cacheSize);
     }
 
     private void handleScroll(View view, int x, int y, int oldx, int oldy) {
diff --git a/java/src/com/android/intentresolver/ChooserContentPreviewUi.java b/java/src/com/android/intentresolver/ChooserContentPreviewUi.java
index aa147853..60ea0122 100644
--- a/java/src/com/android/intentresolver/ChooserContentPreviewUi.java
+++ b/java/src/com/android/intentresolver/ChooserContentPreviewUi.java
@@ -17,6 +17,7 @@
 package com.android.intentresolver;
 
 import static android.content.ContentProvider.getUserIdFromUri;
+
 import static java.lang.annotation.RetentionPolicy.SOURCE;
 
 import android.animation.ObjectAnimator;
@@ -413,6 +414,7 @@ public final class ChooserContentPreviewUi {
                 actionFactory);
         imagePreview.setTransitionElementStatusCallback(transitionElementStatusCallback);
         imagePreview.setImages(imageUris, imageLoader);
+        imageLoader.prePopulate(imageUris);
 
         return contentPreviewLayout;
     }
diff --git a/java/src/com/android/intentresolver/ImageLoader.kt b/java/src/com/android/intentresolver/ImageLoader.kt
index 13b1dd9c..0ed8b122 100644
--- a/java/src/com/android/intentresolver/ImageLoader.kt
+++ b/java/src/com/android/intentresolver/ImageLoader.kt
@@ -22,4 +22,5 @@ import java.util.function.Consumer
 
 interface ImageLoader : suspend (Uri) -> Bitmap? {
     fun loadImage(uri: Uri, callback: Consumer<Bitmap?>)
+    fun prePopulate(uris: List<Uri>)
 }
diff --git a/java/src/com/android/intentresolver/ImagePreviewImageLoader.kt b/java/src/com/android/intentresolver/ImagePreviewImageLoader.kt
index 40081c87..7b6651a2 100644
--- a/java/src/com/android/intentresolver/ImagePreviewImageLoader.kt
+++ b/java/src/com/android/intentresolver/ImagePreviewImageLoader.kt
@@ -20,21 +20,34 @@ import android.content.Context
 import android.graphics.Bitmap
 import android.net.Uri
 import android.util.Size
+import androidx.annotation.GuardedBy
+import androidx.annotation.VisibleForTesting
+import androidx.collection.LruCache
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.coroutineScope
+import kotlinx.coroutines.CompletableDeferred
 import kotlinx.coroutines.CoroutineDispatcher
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
-import kotlinx.coroutines.withContext
 import java.util.function.Consumer
 
-internal class ImagePreviewImageLoader @JvmOverloads constructor(
+@VisibleForTesting
+class ImagePreviewImageLoader @JvmOverloads constructor(
     private val context: Context,
     private val lifecycle: Lifecycle,
+    cacheSize: Int,
     private val dispatcher: CoroutineDispatcher = Dispatchers.IO
 ) : ImageLoader {
 
+    private val thumbnailSize: Size =
+        context.resources.getDimensionPixelSize(R.dimen.chooser_preview_image_max_dimen).let {
+            Size(it, it)
+        }
+
+    @GuardedBy("self")
+    private val cache = LruCache<Uri, CompletableDeferred<Bitmap?>>(cacheSize)
+
     override suspend fun invoke(uri: Uri): Bitmap? = loadImageAsync(uri)
 
     override fun loadImage(uri: Uri, callback: Consumer<Bitmap?>) {
@@ -46,12 +59,29 @@ internal class ImagePreviewImageLoader @JvmOverloads constructor(
         }
     }
 
-    private suspend fun loadImageAsync(uri: Uri): Bitmap? {
-        val size = context.resources.getDimensionPixelSize(R.dimen.chooser_preview_image_max_dimen)
-        return withContext(dispatcher) {
-            runCatching {
-                context.contentResolver.loadThumbnail(uri, Size(size, size), null)
-            }.getOrNull()
+    override fun prePopulate(uris: List<Uri>) {
+        uris.asSequence().take(cache.maxSize()).forEach { uri ->
+            lifecycle.coroutineScope.launch {
+                loadImageAsync(uri)
+            }
         }
     }
+
+    private suspend fun loadImageAsync(uri: Uri): Bitmap? {
+        return synchronized(cache) {
+            cache.get(uri) ?: CompletableDeferred<Bitmap?>().also { result ->
+                cache.put(uri, result)
+                lifecycle.coroutineScope.launch(dispatcher) {
+                    result.loadBitmap(uri)
+                }
+            }
+        }.await()
+    }
+
+    private fun CompletableDeferred<Bitmap?>.loadBitmap(uri: Uri) {
+        val bitmap = runCatching {
+            context.contentResolver.loadThumbnail(uri,  thumbnailSize, null)
+        }.getOrNull()
+        complete(bitmap)
+    }
 }