fix(camera_android_camerax): Add missing androidx.concurrent:concurrent-futures dependency

[0xfe10]

Description

Fixes build failure when compiling with CameraX 1.5.2:
error: Cannot attach type annotations @org.jspecify.annotations.NonNull
class file for androidx.concurrent.futures.CallbackToFutureAdapter not found

The androidx.camera:camera-core:1.5.2 library internally uses CallbackToFutureAdapter from androidx.concurrent.futures, but this dependency was not explicitly declared in build.gradle.

This fix adds the missing androidx.concurrent:concurrent-futures:1.2.0 dependency to resolve the compilation error.

Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

List which issues are fixed by this PR. You must list at least one issue.

Root Cause

When camera plugin upgraded to use camera_android_camerax as the default Android implementation (in camera 0.11.0), projects using CameraX 1.5.2+ started experiencing compilation failures because the transitive dependency on androidx.concurrent.futures was not explicitly declared.

Changes

• Added implementation("androidx.concurrent:concurrent-futures:1.2.0") to android/build.gradle dependencies

Testing

• Verified build succeeds with AGP 8.9.1, Gradle 9.3.0, and compileSdk 35
• Confirmed no runtime issues with camera functionality

Related Issue

This PR fixes build failures reported by users upgrading to camera 0.11.0+

Pre-Review Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter.
• I signed the CLA.
• The title of the PR starts with the name of the package surrounded by square brackets: [camera_android_camerax]
• I linked to at least one issue that this PR fixes in the description above. (No existing issue found - this is a build configuration fix)
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy. (Version bump not required - build dependency fix only)
• I updated CHANGELOG.md to add a description of the change. (CHANGELOG update not required - internal build dependency fix)
• I updated/added any relevant documentation (doc comments with ///). (No API changes - documentation not required)
• I added new tests to check the change I am making. (Test exemption - build dependency fix, no behavioral changes)
• All existing and new tests are passing.

Exemption Justification: This PR only adds a missing build dependency declaration that should have been present. It does not change any API, behavior, or user-facing functionality. The dependency was already being used transitively but not explicitly declared, causing build failures in certain configurations.

continue for #10906

[0xfe10]

continue for #10906

camera_android_camerax: build failure due to missing concurrent-futures dependency

Description

After upgrading my project to Flutter 3.38.7 with AGP 8.9.1 and Gradle 9.3.0,
the Android build started failing as soon as I added the camera plugin.

I tracked it down to a missing explicit dependency declaration for concurrent-futures
in camera_android_camerax's build.gradle. Adding that one line brought the build back.

I'm submitting this PR hoping upstream can include the same declaration.
I understand your example app runs fine — below is a full reproduction and root cause
analysis explaining why this failure is inevitable on Gradle 9.x.

---

Error

Running ./gradlew assembleDebug produces:

error: cannot access CallbackToFutureAdapter
  class file for androidx.concurrent.futures.CallbackToFutureAdapter not found

or

error: Cannot attach type annotations @org.jspecify.annotations.NonNull
  class file for androidx.concurrent.futures.CallbackToFutureAdapter not found

---

Reproduction

I've prepared a minimal reproduction project that demonstrates the issue out of the box:

Repo: https://github.com/justshowcode/flutter_packages_camerax_repro

git clone https://github.com/justshowcode/flutter_packages_camerax_repro
cd flutter_packages_camerax_repro
flutter pub get
cd android && ./gradlew assembleDebug

Environment:

	Version
Flutter	3.41.4 (stable)
camera	0.11.3
camera_android_camerax	0.6.30 (camera-core:1.5.3)
AGP	8.9.1
Gradle	9.3.0
compileSdk	35
Java	17

No code changes needed — just clone and run to reproduce.

---

Root Cause

I checked the Maven POM for camera-core. Both 1.5.2 and the latest 1.5.3 declare
concurrent-futures as runtime scope:

<!-- https://dl.google.com/dl/android/maven2/androidx/camera/camera-core/1.5.3/camera-core-1.5.3.pom -->
<dependency>
  <groupId>androidx.concurrent</groupId>
  <artifactId>concurrent-futures</artifactId>
  <version>1.1.0</version>
  <scope>runtime</scope>
</dependency>

runtime scope means the dependency is not on the compile classpath — it's only
available at runtime.

• Gradle 8.x — promotes transitive runtime dependencies onto the compile classpath,
  so the build passes
• Gradle 9.x — enforces strict classpath isolation and no longer does this promotion,
  so CallbackToFutureAdapter is invisible to the compiler

This is why your example works — it's still on Gradle 8.x.
The POM declaration itself is arguably wrong: concurrent-futures is used at compile time
and should be compile scope, not runtime.

---

Fix

Explicitly declare the dependency in camera_android_camerax/android/build.gradle:

dependencies {
    def camerax_version = "1.5.3"
    implementation("androidx.camera:camera-core:${camerax_version}")
+   implementation("androidx.concurrent:concurrent-futures:1.2.0")
    // ...
}

This does not introduce any new dependency — concurrent-futures is already pulled in
transitively by camera-core. The explicit declaration simply ensures Gradle 9.x places
it on the compile classpath.

[gemini-code-assist]

Code Review

This pull request adds the androidx.concurrent:concurrent-futures:1.2.0 dependency to the camera_android_camerax package's build.gradle file. This change is intended to resolve a build failure. My review includes one suggestion to define the new dependency's version in a variable to improve code consistency and maintainability.

[gemini-code-assist]

For better maintainability and consistency, it's good practice to extract dependency versions into variables and group them at the top of the dependencies block.

    def camerax_version = "1.5.3"
    def concurrentFuturesVersion = "1.2.0"
    implementation("androidx.camera:camera-core:${camerax_version}")
    implementation("androidx.concurrent:concurrent-futures:${concurrentFuturesVersion}")