Use shared library when libapp.so is found (flutter/engine#9172)

engine/src/flutter/shell/platform/android/io/flutter/view/FlutterMain.java

@@ -188,7 +188,11 @@ public class FlutterMain {
             return;
         }
         try {
-            sResourceExtractor.waitForCompletion();
+            // There are resources to extract. For example, the AOT blobs from the `assets` directory.
+            // `sResourceExtractor` is `null` if there isn't any AOT blob to extract.
+            if (sResourceExtractor != null) {
+                sResourceExtractor.waitForCompletion();
+            }
 
             List<String> shellArgs = new ArrayList<>();
             shellArgs.add("--icu-symbol-prefix=_binary_icudtl_dat");
@@ -309,6 +313,13 @@ public class FlutterMain {
      * This is required by the Dart runtime, so it can read the blobs.
      */
     private static void initResources(@NonNull Context applicationContext) {
+        // When the AOT blobs are contained in the native library directory,
+        // we don't need to extract them manually because they are
+        // extracted by the Android Package Manager automatically.
+        if (!sSnapshotPath.equals(PathUtils.getDataDirectory(applicationContext))) {
+            return;
+        }
+
         new ResourceCleaner(applicationContext).start();
 
         final String dataDirPath = PathUtils.getDataDirectory(applicationContext);
@@ -389,7 +400,9 @@ public class FlutterMain {
      * </ul>
      *
      * <p>When the blobs are contained in the native library directory,
-     * the format <b>`lib_%s.so`</b> is applied to the file name.
+     * this method looks for blobs named <b>`lib_%s.so`</b>.
+     *
+     * The shared library should have the `lib` prefix only. e.g. <b>`libapp.so`</b>.
      *
      * <p>Note: The name of the files can be customized in the app's metadata, but the
      * format is preserved.
@@ -404,7 +417,7 @@ public class FlutterMain {
         String aotVmSnapshotInstrLib = "lib_" + sAotVmSnapshotInstr + ".so";
         String aotIsolateSnapshotDataLib = "lib_" + sAotIsolateSnapshotData + ".so";
         String aotIsolateSnapshotInstrLib = "lib_" + sAotIsolateSnapshotInstr + ".so";
-        String aotSharedLibraryLib = "lib_" + sAotSharedLibraryPath + ".so";
+        String aotSharedLibraryLib = "lib" + sAotSharedLibraryPath;
 
         boolean isPrecompiledBlobInLib = libs
             .containsAll(Arrays.asList(