[Platform deprecation][Google] Migrate Android back handling before 2026-08-31

[shai-almog]

Impact summary

Urgency: Critical. Google Play has required new apps and updates to target Android 16 (API level 36) since 2026-08-31. On Android 16+, apps targeting API 36 no longer receive Activity.onBackPressed() or KeyEvent.KEYCODE_BACK; they must migrate to the supported predictive-back APIs or explicitly opt out temporarily.

Codename One still routes the Android system back action exclusively through CodenameOneActivity.onBackPressed(). With API 36 now the framework and cloud-build default, CN1 navigation can fail to receive back events on Android 16 devices. Depending on system fallback, a back gesture can bypass the CN1 form stack and leave/finish the activity instead of invoking the current form's back command.

Official requirement and deadline

• Google Play target API requirement: https://developer.android.com/google/play/requirements/target-sdk
  • Current requirement: starting 2026-08-31, new apps and app updates (except the documented form-factor exceptions) must target Android 16 / API 36 or higher.
• Android 16 target behavior changes: https://developer.android.com/about/versions/16/behavior-changes-16#migration-or-opt-out-required-for-predictive-back
  • Page last updated 2026-08-17 UTC.
  • For apps targeting API 36 and running on Android 16+, predictive back is enabled by default; onBackPressed() is not called and KEYCODE_BACK is not dispatched. Apps must use supported back-navigation APIs or temporarily set android:enableOnBackInvokedCallback="false".

Hard enforcement/submission deadline: 2026-08-31 (already passed).

First affected platform/store combination: apps targeting Android 16 / API 36, running on Android 16+, submitted as new apps or updates to Google Play from 2026-08-31.

Concrete Codename One applicability

Verified against codenameone/CodenameOne master at 134f6ec227792da11b595a77eda6c06d3c0a2b8f:

• maven/codenameone-maven-plugin/src/main/java/com/codename1/builders/AndroidGradleBuilder.java
  • Gradle 8 builds raise the installed platform floor to API 36 (maxPlatformVersionInt = Math.max(36, ...)).
  • The generated app uses that value for targetSdkVersion unless android.targetSDKVersion overrides it.
  • Generated application stubs extend CodenameOneActivity by default (...Stub extends ... CodenameOneActivity).
• Ports/Android/src/com/codename1/impl/android/CodenameOneActivity.java
  • onBackPressed() is the bridge that calls Display.keyPressed() and Display.keyReleased() with DROID_IMPL_KEY_BACK.
• The default branch contains no OnBackInvokedDispatcher, OnBackInvokedCallback, AndroidX back dispatcher, or generated android:enableOnBackInvokedCallback handling.
• codenameone/BuildDaemon master at 09cd713c6abe9455d0574ed0a1ff0776bee84754 generates the cloud-build stub extending CodenameOneActivity, so hosted builds consume the same affected port behavior.

Deduplication performed across open and closed issues/PRs using predictive back, onBackPressed, OnBackInvoked, API 36, the enforcement date, and the official notice name. No specific tracking item exists. The broad Android 16 warning in #4466 was closed with guidance to open a separate issue for concrete regressions; #5451 only changed the compile/target SDK default and did not change back dispatch.

Affected users and failure mode

• All CN1 Android apps using the default API 36 target and running on Android 16+.
• Apps with CN1 form back commands, toolbar back actions mapped to the hardware/system back event, dialogs, side menus, or custom key listeners are at risk.
• Failure mode: the CN1 event is not dispatched, app-level back handling is skipped, predictive animation/navigation uses the activity default, or the activity exits rather than navigating within CN1.

Proposed migration

1. Investigation
   • Reproduce on an Android 16 emulator with a generated API 36 CN1 app containing a two-form navigation stack, a dialog, and an in-place editor/IME case.
   • Confirm the behavior for gesture navigation and three-button navigation, including custom android.customActivity subclasses.
2. Implementation
   • Register a lifecycle-safe OnBackInvokedCallback/dispatcher bridge on supported Android versions and route it through the existing CN1 DROID_IMPL_KEY_BACK pressed/released path.
   • Unregister it with the activity lifecycle and preserve IME/dialog priority semantics.
   • Keep pre-Android-13 behavior on older devices. Use a temporary manifest opt-out only as an emergency compatibility fallback, not the final migration.
   • Mirror any generated-source/build changes in codenameone/BuildDaemon.
3. CI and beta validation
   • Add unit/static checks proving the callback is registered for modern targets and the legacy path remains intact.
   • Add Android 16 emulator UI coverage for form navigation, dialogs, side menus, text editing/IME dismissal, gesture back, and button back.
   • Build through both the Maven local path and hosted BuildDaemon path.
4. Release and communication
   • Ship the port and builder/BuildDaemon halves together.
   • Call out the Android 16 back-navigation fix and any temporary opt-out build hint in release notes; notify users targeting API 36 to rebuild.

Internal target dates

The normal safety checkpoints were 2026-06-02 (90 days), 2026-07-02 (60 days), and 2026-08-01 (30-day release buffer). All are missed because enforcement began before this issue was filed.

Emergency recovery targets:

• Investigation and reproducer: 2026-09-03
• Implementation plus focused tests: 2026-09-04
• Hosted/local beta validation: 2026-09-06
• Release and customer communication: 2026-09-07

Risks, unknowns, and verification plan

• Callback priority must not steal back from the IME, native peer dialogs, or Android-owned surfaces.
• Custom activities may override lifecycle/back methods and need a documented integration seam.
• A callback-only implementation restores semantics but may not provide full progress animations; decide whether OnBackAnimationCallback support is needed after correctness is restored.
• Verify on Android 13-16, gesture and three-button navigation, with a generated release AAB targeting 36. Confirm logcat has no predictive-back warnings and that exactly one CN1 back event is delivered per action.