Retain the image loader through configuration change

Make PreviewViewModel own an image loader instance.
This required ImagePreviewImageLoader to:
 * receive a CoroutineScope instance instead of a Lifecycle as ViewModel
   does not offer an associated Lifecycle;
 * make ImagePreviewImageLoader#loadImage to receive a caller's
   Lifecycle to avoid potential memory (Activity) leak.
With ImagePreviewImageLoader now receiving a scope, the dispatcher
argument is dropped as a scope can be configured with a proper
dispatcher.
As ChooserActivity is no longer responsible for the image loader
instantiation, to facilitate testing, a method hook to create an image
loader is replaced with a method hook to create a preview view model and
all the associated plumbing is done for the tests.

Plus some kfmt complience changes.
ImagePreviewImageLoader (and ImagePreviewImageLoaderTest) is moved into
contentpreview package as it's accessed only from within this package.

Fix: 282029067
Test: manual testing with an injected debug logging
Change-Id: I5dcdee2599714a2c51c3e1b63f5c727e43b26f6a

8 files changed, 139 insertions, 90 deletions

diff --git a/java/src/com/android/intentresolver/ChooserActivity.java b/java/src/com/android/intentresolver/ChooserActivity.java
index 0786e088..014aa2a2 100644
--- a/java/src/com/android/intentresolver/ChooserActivity.java
+++ b/java/src/com/android/intentresolver/ChooserActivity.java
@@ -83,9 +83,9 @@ import com.android.intentresolver.NoCrossProfileEmptyStateProvider.DevicePolicyB
 import com.android.intentresolver.chooser.DisplayResolveInfo;
 import com.android.intentresolver.chooser.MultiDisplayResolveInfo;
 import com.android.intentresolver.chooser.TargetInfo;
+import com.android.intentresolver.contentpreview.BasePreviewViewModel;
 import com.android.intentresolver.contentpreview.ChooserContentPreviewUi;
 import com.android.intentresolver.contentpreview.HeadlineGeneratorImpl;
-import com.android.intentresolver.contentpreview.ImageLoader;
 import com.android.intentresolver.contentpreview.PreviewViewModel;
 import com.android.intentresolver.flags.FeatureFlagRepository;
 import com.android.intentresolver.flags.FeatureFlagRepositoryFactory;
@@ -272,13 +272,14 @@ public class ChooserActivity extends ResolverActivity implements
             }
         });
 
+        BasePreviewViewModel previewViewModel =
+                new ViewModelProvider(this, createPreviewViewModelFactory())
+                        .get(BasePreviewViewModel.class);
         mChooserContentPreviewUi = new ChooserContentPreviewUi(
                 getLifecycle(),
-                new ViewModelProvider(this, PreviewViewModel.Companion.getFactory())
-                        .get(PreviewViewModel.class)
-                        .createOrReuseProvider(mChooserRequest),
+                previewViewModel.createOrReuseProvider(mChooserRequest),
                 mChooserRequest.getTargetIntent(),
-                createPreviewImageLoader(),
+                previewViewModel.createOrReuseImageLoader(),
                 createChooserActionFactory(),
                 mEnterTransitionAnimationDelegate,
                 new HeadlineGeneratorImpl(this));
@@ -1314,14 +1315,8 @@ public class ChooserActivity extends ResolverActivity implements
     }
 
     @VisibleForTesting
-    protected ImageLoader createPreviewImageLoader() {
-        final int cacheSize;
-        float chooserWidth = getResources().getDimension(R.dimen.chooser_width);
-        // imageWidth = imagePreviewHeight * minAspectRatio (see ScrollableImagePreviewView)
-        float imageWidth =
-                getResources().getDimension(R.dimen.chooser_preview_image_height_tall) * 2 / 5;
-        cacheSize = (int) (Math.ceil(chooserWidth / imageWidth) + 2);
-        return new ImagePreviewImageLoader(this, getLifecycle(), cacheSize);
+    protected ViewModelProvider.Factory createPreviewViewModelFactory() {
+        return PreviewViewModel.Companion.getFactory();
     }
 
     private ChooserActionFactory createChooserActionFactory() {
diff --git a/java/src/com/android/intentresolver/contentpreview/BasePreviewViewModel.kt b/java/src/com/android/intentresolver/contentpreview/BasePreviewViewModel.kt
new file mode 100644
index 00000000..103e8bf4
--- /dev/null
+++ b/java/src/com/android/intentresolver/contentpreview/BasePreviewViewModel.kt
@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.intentresolver.contentpreview
+
+import androidx.annotation.MainThread
+import androidx.lifecycle.ViewModel
+import com.android.intentresolver.ChooserRequestParameters
+
+/** A contract for the preview view model. Added for testing. */
+abstract class BasePreviewViewModel : ViewModel() {
+    @MainThread
+    abstract fun createOrReuseProvider(
+        chooserRequest: ChooserRequestParameters
+    ): PreviewDataProvider
+
+    @MainThread abstract fun createOrReuseImageLoader(): ImageLoader
+}
diff --git a/java/src/com/android/intentresolver/contentpreview/ChooserContentPreviewUi.java b/java/src/com/android/intentresolver/contentpreview/ChooserContentPreviewUi.java
index 787af95f..9100b392 100644
--- a/java/src/com/android/intentresolver/contentpreview/ChooserContentPreviewUi.java
+++ b/java/src/com/android/intentresolver/contentpreview/ChooserContentPreviewUi.java
@@ -118,6 +118,7 @@ public final class ChooserContentPreviewUi {
         int previewType = previewData.getPreviewType();
         if (previewType == CONTENT_PREVIEW_TEXT) {
             return createTextPreview(
+                    mLifecycle,
                     targetIntent,
                     actionFactory,
                     imageLoader,
@@ -140,6 +141,7 @@ public final class ChooserContentPreviewUi {
         if (!TextUtils.isEmpty(text)) {
             FilesPlusTextContentPreviewUi previewUi =
                     new FilesPlusTextContentPreviewUi(
+                            mLifecycle,
                             isSingleImageShare,
                             previewData.getUriCount(),
                             targetIntent.getCharSequenceExtra(Intent.EXTRA_TEXT),
@@ -180,6 +182,7 @@ public final class ChooserContentPreviewUi {
     }
 
     private static TextContentPreviewUi createTextPreview(
+            Lifecycle lifecycle,
             Intent targetIntent,
             ChooserContentPreviewUi.ActionFactory actionFactory,
             ImageLoader imageLoader,
@@ -195,6 +198,7 @@ public final class ChooserContentPreviewUi {
             }
         }
         return new TextContentPreviewUi(
+                lifecycle,
                 sharingText,
                 previewTitle,
                 previewThumbnail,
diff --git a/java/src/com/android/intentresolver/contentpreview/FilesPlusTextContentPreviewUi.java b/java/src/com/android/intentresolver/contentpreview/FilesPlusTextContentPreviewUi.java
index 860423c4..e4e33839 100644
--- a/java/src/com/android/intentresolver/contentpreview/FilesPlusTextContentPreviewUi.java
+++ b/java/src/com/android/intentresolver/contentpreview/FilesPlusTextContentPreviewUi.java
@@ -31,6 +31,7 @@ import android.widget.ImageView;
 import android.widget.TextView;
 
 import androidx.annotation.Nullable;
+import androidx.lifecycle.Lifecycle;
 
 import com.android.intentresolver.R;
 import com.android.intentresolver.widget.ActionRow;
@@ -48,6 +49,7 @@ import java.util.function.Consumer;
  * file content).
  */
 class FilesPlusTextContentPreviewUi extends ContentPreviewUi {
+    private final Lifecycle mLifecycle;
     private final CharSequence mText;
     private final ChooserContentPreviewUi.ActionFactory mActionFactory;
     private final ImageLoader mImageLoader;
@@ -63,6 +65,7 @@ class FilesPlusTextContentPreviewUi extends ContentPreviewUi {
     private boolean mAllVideos;
 
     FilesPlusTextContentPreviewUi(
+            Lifecycle lifecycle,
             boolean isSingleImage,
             int fileCount,
             CharSequence text,
@@ -70,6 +73,7 @@ class FilesPlusTextContentPreviewUi extends ContentPreviewUi {
             ImageLoader imageLoader,
             MimeTypeClassifier typeClassifier,
             HeadlineGenerator headlineGenerator) {
+        mLifecycle = lifecycle;
         if (isSingleImage && fileCount != 1) {
             throw new IllegalArgumentException(
                     "fileCount = " + fileCount + " and isSingleImage = true");
@@ -155,13 +159,16 @@ class FilesPlusTextContentPreviewUi extends ContentPreviewUi {
 
         ImageView imagePreview = mContentPreviewView.requireViewById(R.id.image_view);
         if (mIsSingleImage && mFirstFilePreviewUri != null) {
-            mImageLoader.loadImage(mFirstFilePreviewUri, bitmap -> {
-                if (bitmap == null) {
-                    imagePreview.setVisibility(View.GONE);
-                } else {
-                    imagePreview.setImageBitmap(bitmap);
-                }
-            });
+            mImageLoader.loadImage(
+                    mLifecycle,
+                    mFirstFilePreviewUri,
+                    bitmap -> {
+                        if (bitmap == null) {
+                            imagePreview.setVisibility(View.GONE);
+                        } else {
+                            imagePreview.setImageBitmap(bitmap);
+                        }
+                    });
         } else {
             imagePreview.setVisibility(View.GONE);
         }
diff --git a/java/src/com/android/intentresolver/contentpreview/ImageLoader.kt b/java/src/com/android/intentresolver/contentpreview/ImageLoader.kt
index 225807ee..8d0fb84b 100644
--- a/java/src/com/android/intentresolver/contentpreview/ImageLoader.kt
+++ b/java/src/com/android/intentresolver/contentpreview/ImageLoader.kt
@@ -18,32 +18,29 @@ package com.android.intentresolver.contentpreview
 
 import android.graphics.Bitmap
 import android.net.Uri
+import androidx.lifecycle.Lifecycle
 import java.util.function.Consumer
 
-/**
- * A content preview image loader.
- */
+/** A content preview image loader. */
 interface ImageLoader : suspend (Uri) -> Bitmap?, suspend (Uri, Boolean) -> Bitmap? {
     /**
      * Load preview image asynchronously; caching is allowed.
+     *
      * @param uri content URI
      * @param callback a callback that will be invoked with the loaded image or null if loading has
-     * failed.
+     *   failed.
      */
-    fun loadImage(uri: Uri, callback: Consumer<Bitmap?>)
+    fun loadImage(callerLifecycle: Lifecycle, uri: Uri, callback: Consumer<Bitmap?>)
 
-    /**
-     * Prepopulate the image loader cache.
-     */
+    /** Prepopulate the image loader cache. */
     fun prePopulate(uris: List<Uri>)
 
-    /**
-     * Load preview image; caching is allowed.
-     */
+    /** Load preview image; caching is allowed. */
     override suspend fun invoke(uri: Uri) = invoke(uri, true)
 
     /**
      * Load preview image.
+     *
      * @param uri content URI
      * @param caching indicates if the loaded image could be cached.
      */
diff --git a/java/src/com/android/intentresolver/ImagePreviewImageLoader.kt b/java/src/com/android/intentresolver/contentpreview/ImagePreviewImageLoader.kt
index c97efdd1..89b79a0a 100644
--- a/java/src/com/android/intentresolver/ImagePreviewImageLoader.kt
+++ b/java/src/com/android/intentresolver/contentpreview/ImagePreviewImageLoader.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2022 The Android Open Source Project
+ * Copyright (C) 2023 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -14,9 +14,9 @@
  * limitations under the License.
  */
 
-package com.android.intentresolver
+package com.android.intentresolver.contentpreview
 
-import android.content.Context
+import android.content.ContentResolver
 import android.graphics.Bitmap
 import android.net.Uri
 import android.util.Log
@@ -26,12 +26,10 @@ import androidx.annotation.VisibleForTesting
 import androidx.collection.LruCache
 import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.coroutineScope
-import com.android.intentresolver.contentpreview.ImageLoader
 import kotlinx.coroutines.CancellationException
 import kotlinx.coroutines.CompletableDeferred
-import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Deferred
-import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 import java.util.function.Consumer
@@ -42,29 +40,24 @@ private const val TAG = "ImagePreviewImageLoader"
  * Implements preview image loading for the content preview UI. Provides requests deduplication and
  * image caching.
  */
-@VisibleForTesting
-class ImagePreviewImageLoader @JvmOverloads constructor(
-    private val context: Context,
-    private val lifecycle: Lifecycle,
+@VisibleForTesting(otherwise = VisibleForTesting.PACKAGE_PRIVATE)
+class ImagePreviewImageLoader(
+    private val scope: CoroutineScope,
+    thumbnailSize: Int,
+    private val contentResolver: ContentResolver,
     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)
-        }
+    private val thumbnailSize: Size = Size(thumbnailSize, thumbnailSize)
 
     private val lock = Any()
-    @GuardedBy("lock")
-    private val cache = LruCache<Uri, RequestRecord>(cacheSize)
-    @GuardedBy("lock")
-    private val runningRequests = HashMap<Uri, RequestRecord>()
+    @GuardedBy("lock") private val cache = LruCache<Uri, RequestRecord>(cacheSize)
+    @GuardedBy("lock") private val runningRequests = HashMap<Uri, RequestRecord>()
 
     override suspend fun invoke(uri: Uri, caching: Boolean): Bitmap? = loadImageAsync(uri, caching)
 
-    override fun loadImage(uri: Uri, callback: Consumer<Bitmap?>) {
-        lifecycle.coroutineScope.launch {
+    override fun loadImage(callerLifecycle: Lifecycle, uri: Uri, callback: Consumer<Bitmap?>) {
+        callerLifecycle.coroutineScope.launch {
             val image = loadImageAsync(uri, caching = true)
             if (isActive) {
                 callback.accept(image)
@@ -74,28 +67,26 @@ class ImagePreviewImageLoader @JvmOverloads constructor(
 
     override fun prePopulate(uris: List<Uri>) {
         uris.asSequence().take(cache.maxSize()).forEach { uri ->
-            lifecycle.coroutineScope.launch {
-                loadImageAsync(uri, caching = true)
-            }
+            scope.launch { loadImageAsync(uri, caching = true) }
         }
     }
 
     private suspend fun loadImageAsync(uri: Uri, caching: Boolean): Bitmap? {
-        return getRequestDeferred(uri, caching)
-            .await()
+        return getRequestDeferred(uri, caching).await()
     }
 
     private fun getRequestDeferred(uri: Uri, caching: Boolean): Deferred<Bitmap?> {
         var shouldLaunchImageLoading = false
-        val request = synchronized(lock) {
-            cache[uri]
-                ?: runningRequests.getOrPut(uri) {
-                    shouldLaunchImageLoading = true
-                    RequestRecord(uri, CompletableDeferred(), caching)
-                }.apply {
-                    this.caching = this.caching || caching
-                }
-        }
+        val request =
+            synchronized(lock) {
+                cache[uri]
+                    ?: runningRequests
+                        .getOrPut(uri) {
+                            shouldLaunchImageLoading = true
+                            RequestRecord(uri, CompletableDeferred(), caching)
+                        }
+                        .apply { this.caching = this.caching || caching }
+            }
         if (shouldLaunchImageLoading) {
             request.loadBitmapAsync()
         }
@@ -103,22 +94,23 @@ class ImagePreviewImageLoader @JvmOverloads constructor(
     }
 
     private fun RequestRecord.loadBitmapAsync() {
-        lifecycle.coroutineScope.launch(dispatcher) {
-            loadBitmap()
-        }.invokeOnCompletion { cause ->
-            if (cause is CancellationException) {
-                cancel()
+        scope
+            .launch { loadBitmap() }
+            .invokeOnCompletion { cause ->
+                if (cause is CancellationException) {
+                    cancel()
+                }
             }
-        }
     }
 
     private fun RequestRecord.loadBitmap() {
-        val bitmap = try {
-            context.contentResolver.loadThumbnail(uri,  thumbnailSize, null)
-        } catch (t: Throwable) {
-            Log.d(TAG, "failed to load $uri preview", t)
-            null
-        }
+        val bitmap =
+            try {
+                contentResolver.loadThumbnail(uri, thumbnailSize, null)
+            } catch (t: Throwable) {
+                Log.d(TAG, "failed to load $uri preview", t)
+                null
+            }
         complete(bitmap)
     }
 
@@ -144,4 +136,4 @@ class ImagePreviewImageLoader @JvmOverloads constructor(
         val deferred: CompletableDeferred<Bitmap?>,
         @GuardedBy("lock") var caching: Boolean
     )
-}
+}
\ No newline at end of file
diff --git a/java/src/com/android/intentresolver/contentpreview/PreviewViewModel.kt b/java/src/com/android/intentresolver/contentpreview/PreviewViewModel.kt
index 2f4b0211..331b0cb6 100644
--- a/java/src/com/android/intentresolver/contentpreview/PreviewViewModel.kt
+++ b/java/src/com/android/intentresolver/contentpreview/PreviewViewModel.kt
@@ -16,24 +16,45 @@
 
 package com.android.intentresolver.contentpreview
 
-import android.content.ContentResolver
-import android.content.Context
+import android.app.Application
+import androidx.annotation.MainThread
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
 import androidx.lifecycle.ViewModelProvider.AndroidViewModelFactory.Companion.APPLICATION_KEY
+import androidx.lifecycle.viewModelScope
 import androidx.lifecycle.viewmodel.CreationExtras
 import com.android.intentresolver.ChooserRequestParameters
+import com.android.intentresolver.R
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.plus
 
 /** A trivial view model to keep a [PreviewDataProvider] instance over a configuration change */
-class PreviewViewModel(private val contentResolver: ContentResolver) : ViewModel() {
+class PreviewViewModel(private val application: Application) : BasePreviewViewModel() {
     private var previewDataProvider: PreviewDataProvider? = null
+    private var imageLoader: ImagePreviewImageLoader? = null
 
-    fun createOrReuseProvider(chooserRequest: ChooserRequestParameters): PreviewDataProvider {
-        return previewDataProvider
-            ?: PreviewDataProvider(chooserRequest.targetIntent, contentResolver).also {
+    @MainThread
+    override fun createOrReuseProvider(
+        chooserRequest: ChooserRequestParameters
+    ): PreviewDataProvider =
+        previewDataProvider
+            ?: PreviewDataProvider(chooserRequest.targetIntent, application.contentResolver).also {
                 previewDataProvider = it
             }
-    }
+
+    @MainThread
+    override fun createOrReuseImageLoader(): ImageLoader =
+        imageLoader
+            ?: ImagePreviewImageLoader(
+                    viewModelScope + Dispatchers.IO,
+                    thumbnailSize =
+                        application.resources.getDimensionPixelSize(
+                            R.dimen.chooser_preview_image_max_dimen
+                        ),
+                    application.contentResolver,
+                    cacheSize = 16
+                )
+                .also { imageLoader = it }
 
     companion object {
         val Factory: ViewModelProvider.Factory =
@@ -42,10 +63,7 @@ class PreviewViewModel(private val contentResolver: ContentResolver) : ViewModel
                 override fun <T : ViewModel> create(
                     modelClass: Class<T>,
                     extras: CreationExtras
-                ): T =
-                    PreviewViewModel(
-                        (checkNotNull(extras[APPLICATION_KEY]) as Context).contentResolver
-                    ) as T
+                ): T = PreviewViewModel(checkNotNull(extras[APPLICATION_KEY])) as T
             }
     }
 }
diff --git a/java/src/com/android/intentresolver/contentpreview/TextContentPreviewUi.java b/java/src/com/android/intentresolver/contentpreview/TextContentPreviewUi.java
index 3c8a6e48..19fd3bb4 100644
--- a/java/src/com/android/intentresolver/contentpreview/TextContentPreviewUi.java
+++ b/java/src/com/android/intentresolver/contentpreview/TextContentPreviewUi.java
@@ -28,6 +28,7 @@ import android.widget.ImageView;
 import android.widget.TextView;
 
 import androidx.annotation.Nullable;
+import androidx.lifecycle.Lifecycle;
 
 import com.android.intentresolver.R;
 import com.android.intentresolver.widget.ActionRow;
@@ -36,6 +37,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 class TextContentPreviewUi extends ContentPreviewUi {
+    private final Lifecycle mLifecycle;
     @Nullable
     private final CharSequence mSharingText;
     @Nullable
@@ -47,12 +49,14 @@ class TextContentPreviewUi extends ContentPreviewUi {
     private final HeadlineGenerator mHeadlineGenerator;
 
     TextContentPreviewUi(
+            Lifecycle lifecycle,
             @Nullable CharSequence sharingText,
             @Nullable CharSequence previewTitle,
             @Nullable Uri previewThumbnail,
             ChooserContentPreviewUi.ActionFactory actionFactory,
             ImageLoader imageLoader,
             HeadlineGenerator headlineGenerator) {
+        mLifecycle = lifecycle;
         mSharingText = sharingText;
         mPreviewTitle = previewTitle;
         mPreviewThumbnail = previewThumbnail;
@@ -117,6 +121,7 @@ class TextContentPreviewUi extends ContentPreviewUi {
             previewThumbnailView.setVisibility(View.GONE);
         } else {
             mImageLoader.loadImage(
+                    mLifecycle,
                     mPreviewThumbnail,
                     (bitmap) -> updateViewWithImage(
                             contentPreviewLayout.findViewById(