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[camera_android_camerax] Fixes crash on hot restart caused by stale observers #10529

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[camera_android_camerax] Fixes crash on hot restart caused by stale observers #10529

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[camera_android_camerax] Fixes crash on hot restart caused by stale o…
raju-muliyashiya Nov 27, 2025
dc6ebe9
Code format and address gemini comment
raju-muliyashiya Nov 27, 2025
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4 changes: 4 additions & 0 deletions packages/camera/camera_android_camerax/CHANGELOG.md
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@@ -1,3 +1,7 @@
## 0.6.25+1

* Fixes crash on hot restart caused by stale observers.

## 0.6.25

* Adds support for `MediaSettings.fps` for camera preview, image streaming, and video recording.
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11 changes: 11 additions & 0 deletions ...ra_android_camerax/android/src/main/java/io/flutter/plugins/camerax/ObserverProxyApi.java
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Expand Up @@ -29,6 +29,17 @@ public void onChanged(T t) {
new ProxyApiRegistrar.FlutterMethodRunnable() {
@Override
public void run() {
// Check if this observer instance is still in the instance manager.
// During hot restart, old observers may remain attached to LiveData but
// are no longer tracked in the instance manager.
if (!api.getPigeonRegistrar().getInstanceManager().containsInstance(ObserverImpl.this)) {
android.util.Log.w(
"ObserverProxyApi",
"Ignoring onChanged callback for Observer not in InstanceManager (likely from previous hot restart): "
+ ObserverImpl.this);
return;
}

api.onChanged(
ObserverImpl.this,
t,
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24 changes: 23 additions & 1 deletion ...camera_android_camerax/android/src/test/java/io/flutter/plugins/camerax/ObserverTest.java
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Expand Up @@ -7,6 +7,7 @@
import static org.mockito.Mockito.any;
import static org.mockito.Mockito.eq;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

Expand All @@ -16,13 +17,34 @@ public class ObserverTest {
@Test
public void onChanged_makesExpectedCallToDartCallback() {
final ObserverProxyApi mockApi = mock(ObserverProxyApi.class);
when(mockApi.getPigeonRegistrar()).thenReturn(new TestProxyApiRegistrar());
final TestProxyApiRegistrar registrar = new TestProxyApiRegistrar();
when(mockApi.getPigeonRegistrar()).thenReturn(registrar);

final ObserverProxyApi.ObserverImpl<String> instance =
new ObserverProxyApi.ObserverImpl<>(mockApi);

// Add the observer to the instance manager to simulate normal operation
registrar.getInstanceManager().addDartCreatedInstance(instance, 0);

final String value = "result";
instance.onChanged(value);

verify(mockApi).onChanged(eq(instance), eq(value), any());
}

@Test
public void onChanged_doesNotCallDartCallbackWhenObserverNotInInstanceManager() {
final ObserverProxyApi mockApi = mock(ObserverProxyApi.class);
final TestProxyApiRegistrar registrar = new TestProxyApiRegistrar();
when(mockApi.getPigeonRegistrar()).thenReturn(registrar);

final ObserverProxyApi.ObserverImpl<String> instance =
new ObserverProxyApi.ObserverImpl<>(mockApi);

final String value = "result";
instance.onChanged(value);

// Verify that the Dart callback is NOT invoked for stale observers
verify(mockApi, never()).onChanged(any(), any(), any());
}
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@gemini-code-assist gemini-code-assist bot Nov 27, 2025

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medium

To improve maintainability and reduce code duplication, you can extract the common test setup into a method annotated with @org.junit.Before. This will make the tests cleaner and easier to read by separating setup logic from the test logic itself.

  private ObserverProxyApi mockApi;
  private TestProxyApiRegistrar registrar;
  private ObserverProxyApi.ObserverImpl<String> instance;

  @org.junit.Before
  public void setUp() {
    mockApi = mock(ObserverProxyApi.class);
    registrar = new TestProxyApiRegistrar();
    when(mockApi.getPigeonRegistrar()).thenReturn(registrar);
    instance = new ObserverProxyApi.ObserverImpl<>(mockApi);
  }

  @Test
  public void onChanged_makesExpectedCallToDartCallback() {
    // Add the observer to the instance manager to simulate normal operation
    registrar.getInstanceManager().addDartCreatedInstance(instance, 0);

    final String value = "result";
    instance.onChanged(value);

    verify(mockApi).onChanged(eq(instance), eq(value), any());
  }

  @Test
  public void onChanged_doesNotCallDartCallbackWhenObserverNotInInstanceManager() {
    final String value = "result";
    instance.onChanged(value);

    // Verify that the Dart callback is NOT invoked for stale observers
    verify(mockApi, never()).onChanged(any(), any(), any());
  }

}
2 changes: 1 addition & 1 deletion packages/camera/camera_android_camerax/pubspec.yaml
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Expand Up @@ -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: 0.6.25
version: 0.6.25+1

environment:
sdk: ^3.9.0
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