[camerax] Shorten interval for releasing weak references to Dart-wrapped native objects

packages/camera/camera_android_camerax/CHANGELOG.md

@@ -1,3 +1,11 @@
+## 0.6.3
+
+* Shortens default interval that internal Java `InstanceManager` uses to release garbage collected weak references to
+  native objects.
+* Dynamically shortens interval that internal Java `InstanceManager` uses to release garbage collected weak references to
+  native objects when an `ImageAnalysis.Analyzer` is set/removed to account for increased memory usage of analyzing
+  images that may cause a crash.
+
 ## 0.6.2
 
 * Adds support to control video FPS and bitrate. See `CameraController.withSettings`.

packages/camera/camera_android_camerax/android/src/main/java/io/flutter/plugins/camerax/ImageAnalysisHostApiImpl.java

@@ -69,6 +69,14 @@ public void setAnalyzer(@NonNull Long identifier, @NonNull Long analyzerIdentifi
       throw new IllegalStateException("Context must be set to set an Analyzer.");
     }
 
+    // Shorten time interval used to define how often the instanceManager removes garbage
+    // collected weak references to native Android objects that it manages in order to
+    // account for the increased memory usage that comes from analyzing images with an
+    // ImageAnalysis.Analyzer.
+    instanceManager.setClearFinalizedWeakReferencesInterval(
+        InstanceManager.CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL_FOR_IMAGE_ANALYSIS);
+    instanceManager.releaseAllFinalizedInstances();
+
     getImageAnalysisInstance(identifier)
         .setAnalyzer(
             ContextCompat.getMainExecutor(context),
@@ -81,6 +89,13 @@ public void clearAnalyzer(@NonNull Long identifier) {
     ImageAnalysis imageAnalysis =
         (ImageAnalysis) Objects.requireNonNull(instanceManager.getInstance(identifier));
     imageAnalysis.clearAnalyzer();
+
+    // Restore the default time interval used to define how often the instanceManager
+    // removes garbage collected weak references to native Android objects that it
+    // manages since analyzing images with an ImageAnalysis.Analyzer, which involves
+    // increased memory usage, is finished.
+    instanceManager.setClearFinalizedWeakReferencesInterval(
+        InstanceManager.DEFAULT_CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL);
   }
 
   /** Dynamically sets the target rotation of the {@link ImageAnalysis}. */

packages/camera/camera_android_camerax/android/src/main/java/io/flutter/plugins/camerax/InstanceManager.java

@@ -36,9 +36,25 @@ public class InstanceManager {
   // Host uses identifiers >= 2^16 and Dart is expected to use values n where,
   // 0 <= n < 2^16.
   private static final long MIN_HOST_CREATED_IDENTIFIER = 65536;
-  private static final long CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL = 30000;
   private static final String TAG = "InstanceManager";
 
+  /**
+   * The default time interval used to define how often this instance removes garbage collected weak
+   * references to native Android objects that this instance manages.
+   */
+  public static final long DEFAULT_CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL = 3000;
+
+  /**
+   * The time interval used to define how often this instance removes garbage collected weak
+   * references to native Android objects that this instance manages, specifically when an {@code
+   * ImageAnalysis.Analyzer} is set on an {@code ImageAnalysis} instance to support image streaming.
+   *
+   * <p>Streaming images with an {@code ImageAnalysis.Analyzer} involves increased memory usage, so
+   * this interval, which is lower than the default {@link
+   * DEFAULT_CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL} interval, accommodates this fact.
+   */
+  public static final long CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL_FOR_IMAGE_ANALYSIS = 1000;
+
   /** Interface for listening when a weak reference of an instance is removed from the manager. */
   public interface FinalizationListener {
     void onFinalize(long identifier);
@@ -58,6 +74,9 @@ public interface FinalizationListener {
   private long nextIdentifier = MIN_HOST_CREATED_IDENTIFIER;
   private boolean hasFinalizationListenerStopped = false;
 
+  private long clearFinalizedWeakReferencesInterval =
+      DEFAULT_CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL;
+
   /**
    * Instantiate a new manager.
    *
@@ -73,8 +92,7 @@ public static InstanceManager create(@NonNull FinalizationListener finalizationL
 
   private InstanceManager(FinalizationListener finalizationListener) {
     this.finalizationListener = finalizationListener;
-    handler.postDelayed(
-        this::releaseAllFinalizedInstances, CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL);
+    handler.postDelayed(this::releaseAllFinalizedInstances, clearFinalizedWeakReferencesInterval);
   }
 
   /**
@@ -217,7 +235,19 @@ public boolean hasFinalizationListenerStopped() {
     return hasFinalizationListenerStopped;
   }
 
-  private void releaseAllFinalizedInstances() {
+  /**
+   * Modifies the time interval used to define how often this instance removes garbage collected
+   * weak references to native Android objects that this instance was managing.
+   */
+  public void setClearFinalizedWeakReferencesInterval(long interval) {
+    clearFinalizedWeakReferencesInterval = interval;
+  }
+
+  /**
+   * Releases garbage collected weak references to native Android objects that this instance was
+   * managing.
+   */
+  public void releaseAllFinalizedInstances() {
     if (hasFinalizationListenerStopped()) {
       return;
     }
@@ -231,8 +261,7 @@ private void releaseAllFinalizedInstances() {
         finalizationListener.onFinalize(identifier);
       }
     }
-    handler.postDelayed(
-        this::releaseAllFinalizedInstances, CLEAR_FINALIZED_WEAK_REFERENCES_INTERVAL);
+    handler.postDelayed(this::releaseAllFinalizedInstances, clearFinalizedWeakReferencesInterval);
   }
 
   private void addInstance(Object instance, long identifier) {

packages/camera/camera_android_camerax/pubspec.yaml

@@ -2,7 +2,7 @@ name: camera_android_camerax
 description: Android implementation of the camera plugin using the CameraX library.
 repository: https://github.com/flutter/packages/tree/main/packages/camera/camera_android_camerax
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.6.2
+version: 0.6.3
 
 environment:
   sdk: ^3.1.0