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Migrate Camera2 hardcoded snippets - #1134
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barbaralaw
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September 22, 2026 21:32
kkuan2011
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Thanks Barbara! AI review flagged one issue. Can you update and send to Erik for review? Thank you!
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Looks good! Minor nits and some comments to remove appcompat and to replace !! with ?.
Ready for SME review after those are addressed!
kkuan2011
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Sep 30, 2026
Rebase the Camera2 migration onto upstream main after the :camera parent module landed, keeping CameraX sources unchanged and adding the Camera2 samples plus the AppCompat, Fragment, Material, and coroutines dependencies they need.
- Use plain START_EXCLUDE (no silent + hand-written // ...) in CaptureSessionsRequests and the SurfaceView callback snippet. - Keep setRepeatingRequest commented out, matching the DAC page. - Remove all !! in the camera2 snippets: safe calls / elvis defaults, ?: return in zoomExample, checkNotNull where a non-null Size is returned. - Replace the deprecated AsyncTask.SERIAL_EXECUTOR default with a required executor parameter in openDualCamera and createDualCameraSession; the zoom example passes a caller-owned cameraExecutor placeholder. - Use ComponentActivity instead of AppCompatActivity and drop appcompat. - Replace the v.post hop with withContext(Dispatchers.IO) in the screen flash stitch-together snippet.
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Summary
Extracts the Kotlin and XML samples from eight Camera2 guides into
:cameraasregion-tagged source under
com.example.camera.snippets.camera2, so the guidescan import them instead of hardcoding them. CameraX already lives in
:cameraon
main; this PR only adds the Camera2 samples (and the extra dependenciesthey need). CameraX sources are unchanged.
44 snippets across 8 pages. 18 publish exactly what the page shows. 26 differ, every one
listed below with a reason. Line wrapping is not counted as a difference:
spotlessApplyruns before submission and rewraps long calls without changing what a reader reads.
Region tags all begin
android_camera2_; the tables drop that prefix.How to read the "why" column
// ......on its own line (omitted arguments or omitted statements). The region publishes the same ellipsis, either as a// ...line comment or as a plain[START_EXCLUDE]block that DevSite renders as..../* ... */...as the right-hand side of a typedvalthat still has a trailing// from …comment. A line comment would swallow that note, so the region wraps the ellipsis in a block comment on the same line.characteristics.get(KEY)directly (which does not compile) or uses!!. Per review, the region publishes no!!: it uses a safe call (?.), an elvis default or early return (?:), orcheckNotNull(...)where the function must return a non-null value.AsyncTask.SERIAL_EXECUTORdefault, or hopping back to the UI thread withv.postfrom a background coroutine).ListandCompletableDeferred? = nullwithout type arguments. The.md.txtexport of the same blocks is the same: no<Unit>, no<Surface>. So the sample does not compile in either form. Though the HTML file still has the type arguments<Surface>(and<Unit>,<DualCamera>,<OutputConfiguration>), they're unescaped inside the<pre>, so the parser treats them as tags — that is why both the browser and the export lose them. This is not a CSS issue; the page source has to escape those brackets (or stop writing raw<Type>in the block). The proposed migrated regions publish the type arguments the samples need. Listed again under "Live snippet fixes this surfaced".Per page
1. Camera capture sessions and requests
https://developer.android.com/media/camera/camera2/capture-sessions-requests
5 snippets, 0 match as published, 5 differ.
capture_sessions_requests_configure_session[START_EXCLUDE]blocks, 1 standalone ellipsis as a line comment; comment continued as// reasons// ...capture_sessions_requests_single_request/* ... */capture_sessions_requests_capture...kept;CaptureRequest→CaptureRequest.Buildercapture_sessions_requests_repeating_request...kept;CaptureRequest→CaptureRequest.Buildercapture_sessions_requests_interleaved_requests/* ... */createCaptureRequest()returns aCaptureRequest.Builder. The livecaptureandrepeating_requestsamples type that local asCaptureRequestand then call.build().The live repeating sample comments out
session.setRepeatingRequest(...); per review, theregion keeps that line commented out to match the page.
configure_sessionpublishes// reasonsas its own comment line so the file compiles.2. Camera lenses and capabilities
https://developer.android.com/media/camera/camera2/camera-enumeration
3 snippets, 1 match, 2 differ.
camera_enumeration_iterate_cameras// ...camera_enumeration_get_first_camera_id_facingreturn nulladded insidecatchMatching as published:
filter_cameras.The live
get_first_camera_id_facingsample is aString?function whosecatchonly logs.Kotlin requires a return on that path;
nullmatchesfirstOrNull()on the success path.3. Use multiple camera streams simultaneously
https://developer.android.com/media/camera/camera2/multiple-camera-streams-simultaneously
11 snippets, 5 match, 6 differ.
multiple_camera_streams_supported_formats?.outputFormatssafe callmultiple_camera_streams_output_sizes_format?.getOutputSizes(...)safe callmultiple_camera_streams_output_sizes_class?.getOutputSizes(...)safe callmultiple_camera_streams_maximum_output_sizecheckNotNull(...)multiple_camera_streams_preview_output_size!!on the config lookup →checkNotNull(...);"SmartSize(${long}x${short})"→"SmartSize(${long}x$short)"multiple_camera_streams_surfaceview_callback...in theSurfaceHolder.Callbackrendered by a plain[START_EXCLUDE]block around the stub overrides// ...getMaximumOutputSize()andgetPreviewOutputSize()return a non-nullSize, so a safecall would change their signatures;
checkNotNull(...)keeps them intact.Matching as published:
combined_request,hardware_level,get_preview_output_sizes,image_reader_instance,image_reader_listener.4. Screen flash
https://developer.android.com/media/camera/camera2/screen-flash-implementation-guidelines
9 snippets, 5 match, 4 differ.
screen_flash_capture_callback_ae_modeCompletableDeferred<Unit>; page rendersCompletableDeferredscreen_flash_capture_callback_convergence<Unit>type arguments;||moved to line ends past an inline commentscreen_flash_run_precapture_sequenceCompletableDeferred<Unit>screen_flash_stitch_togetherlifecycleScope.launch(Dispatchers.IO) { … v.post { … } }→lifecycleScope.launch { withContext(Dispatchers.IO) { … } … }; unusedv ->dropped; all original step comments kept, two short comments addedMatching as published:
overlay_view(XML),brightness_control,check_ae_mode,enable_disable_ae_mode,setup_repeating_request.The wrapper activity (outside every region) extends
ComponentActivity, so:cameradoesnot depend on
appcompat.5. Camera preview
https://developer.android.com/media/camera/camera2/camera-preview
2 snippets extracted, 1 match, 1 differs.
camera_preview_compute_relative_rotation!!onSENSOR_ORIENTATION→?: 0Matching as published:
surfaceview_onmeasure.Not extracted:
viewfinder_request_surface(CameraViewfinder). The page stilldocuments
CameraViewfinder,requestSurfaceAsync(), aViewfinderSurfaceRequestthat takes
CameraCharacteristics, aListenableFutureofSurface, andmarkSurfaceSafeToRelease(). Those types were deprecated and then removed; theshipping widget is
ViewfinderView, the request is width/height only, and theasync API returns a
ViewfinderSurfaceSessionthat must be closed. Publishingthe live snippet would compile only against local stand-ins, and rewriting it
to the current API is a docs change, not a migration. Recommend DevRel rework
that whole CameraViewfinder section (Kotlin, Java twin, and surrounding prose)
before it is imported.
6. HDR video capture
https://developer.android.com/media/camera/camera2/hdr-video-capture
6 snippets, 3 match, 3 differ.
hdr_video_capture_is_ten_bit_profile_supported!!in theforloop →?: return falseon the capabilities lookuphdr_video_capture_is_hlg_supportedVal→val; stray;afterreturn falsedropped; page's!!→?.getSupportedProfiles()and?.contains(...) ?: falsehdr_video_capture_setup_sessionList<Surface>andMutableList<OutputConfiguration>type argumentsMatching as published:
preview_request,record_request,encode_hdr_stream.7. Multi-camera API
https://developer.android.com/media/camera/camera2/multi-camera
6 snippets, 1 match, 5 differ.
multi_camera_find_dual_camerasMutableList<DualCamera>()→mutableListOf<DualCamera>(); type argument published; page's!!.contains(...)→?.contains(...) ?: falsemulti_camera_open_dual_cameraAsyncTask.SERIAL_EXECUTORdefault and its deprecation comment removed;executor: Executoris now requiredmulti_camera_create_dual_camera_session<Surface>type arguments published;AsyncTask.SERIAL_EXECUTORdefault and comment removed;executor: Executoris now requiredmulti_camera_find_short_long_camera_pairmaxOrNull()!!/minOrNull()!!→?: 0fdefaultsmulti_camera_zoom_examplefindShortLongCameraPair(manager)!!→?: return;createDualCameraSession(...)passesexecutor = cameraExecutor;val cameraExecutor: Executor = ... // owned by your activity / fragmentplaceholder added next to the camera manager placeholderMatching as published:
distortion_correction.MutableListhas no constructor, so the page's line cannot compile as written.The executor is now caller-owned rather than a default argument. Defaulting to a new
executor would create a thread pool per call that nothing shuts down; a required parameter
matches the page's Java
openDualCamera, which already took anExecutor, and theframework's own
openCamera(id, executor, callback).8. Camera2 Extensions API
https://developer.android.com/media/camera/camera2/extensions-api
2 snippets, both match as published:
get_extension_camera_ids,start_extension_session.This page's snippet calls
Snackbar.make(...), so:cameragainsimplementation(libs.google.android.material)and the file importscom.google.android.material.snackbar.Snackbaroutside every region — the publishedsnippet is unchanged. The alternative was a compile-only
Snackbarstand-in and no Gradlechange; that avoids pulling Views Material into the module, but it mocks an API
the page actually documents.
Not extracted
Kotlin only. Every page above except HDR video capture carries a Java twin for each of its
Kotlin blocks; those are left for the page edit that retires them. Camera preview also has a
one-line orientation formula under "Orientation calculation" that is prose, not a compilable
sample.
Camera preview's CameraViewfinder sample (
viewfinder_request_surface) is heldout of this PR on purpose; see §5. The SurfaceView onMeasure and relative-rotation
samples from the same page are in
:camera.Live snippet fixes this surfaced
.md.txtboth yieldList,CompletableDeferred?,mutableListOf()— notList<Surface>/CompletableDeferred<Unit>?/mutableListOf<OutputConfiguration>(). The HTML still contains unescaped<Surface>(etc.) inside the code block; that is markup, not Kotlin, which is why the export is empty of generics too.Val cameraCharacteristics = ...and a stray;afterreturn false.MutableList<DualCamera>()—MutableListis an interface with noconstructor.
ViewfinderViewand the request/surface APIs in the sample no longer exist on the stable viewfinder-view artifact (1.5+). The section needs a rewrite, not an import of the current Kotlin/Java fences.val captureRequest: CaptureRequest = ...then.build()—createCaptureRequest()returnsCaptureRequest.Builder.getFirstCameraIdFacingisString?but the livecatchonly logs, so the function does not compile. The region returnsnullfrom thecatch.val cameraManager: CameraManager = ...but the code below callsfindShortLongCameraPair(manager)andcreateDualCameraSession(manager, ...). The region keeps the page's naming; renaming one side is a small follow-up.Review follow-up (584f960)
[START_EXCLUDE](nosilentplus hand-written// ...) inconfigure_sessionandsurfaceview_callback.setRepeatingRequestkept commented out, matching the page.!!anywhere in the camera2 snippets (see null safety).AsyncTask.SERIAL_EXECUTORdefault replaced with a requiredexecutorparameter.ComponentActivityinstead ofAppCompatActivity;appcompatdependency removed.withContext(Dispatchers.IO)instead ofv.postinstitch_together.Region tags are unchanged by this commit.
Verification
./gradlew :camera:compileDebugKotlin— passes./gradlew :camera:lintDebug— passes./gradlew :camera:spotlessApply— run before pushing; the branch is clean afterwards