fix(gestures): Replace GestureDetectorCompat with lightweight detector to fix ANR by romtsn · Pull Request #5138 · getsentry/sentry-java

romtsn · 2026-03-02T20:05:02Z

Summary

Replace GestureDetectorCompat with a custom lightweight SentryGestureDetector in SentryWindowCallback to fix ANR SDK-CRASHES-JAVA-596 (175K+ occurrences, 574 users)
GestureDetectorCompat internally uses Handler.sendMessage/removeMessages which acquires a synchronized lock on the main thread's MessageQueue, plus recordGestureClassification() triggers IPC/binder calls — both cause contention under load
The new detector only implements click, scroll, and fling detection (the only gestures SentryGestureListener uses), eliminating all Handler scheduling, MessageQueue lock contention, and IPC overhead

Test plan

Added SentryGestureDetectorTest with 7 test cases: tap, no-tap, scroll with deltas, fling, slow release, cancel cleanup, sequential gesture reset
Existing SentryWindowCallbackTest (4 tests) passes
Existing SentryGestureListenerTest suite passes
./gradlew :sentry-android-core:testDebugUnitTest passes
Manual testing on Android device

🤖 Generated with Claude Code

…stureDetector to fix ANR GestureDetectorCompat internally uses Handler.sendMessage/removeMessages which acquires a synchronized lock on the main thread MessageQueue, plus recordGestureClassification triggers IPC calls. This caused ANRs under load (SDK-CRASHES-JAVA-596, 175K+ occurrences). Replace with a minimal custom detector that only detects click, scroll, and fling without any Handler scheduling, MessageQueue contention, or IPC overhead. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

github-actions · 2026-03-02T20:05:41Z

Semver Impact of This PR

🟢 Patch (bug fixes)

📋 Changelog Preview

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Entries from this PR are highlighted with a left border (blockquote style).

New Features ✨

(anr) Profile main thread when ANR and report ANR profiles to Sentry by markushi in #4899

Bug Fixes 🐛

(gestures) Replace GestureDetectorCompat with lightweight detector to fix ANR by romtsn in #5138

Remove the dependency on protobuf-lite for tombstones by supervacuus in #5157

_{🤖 This preview updates automatically when you update the PR.}

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

...droid-core/src/main/java/io/sentry/android/core/internal/gestures/SentryGestureDetector.java

github-actions · 2026-03-02T20:17:20Z

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	308.54 ms	367.34 ms	58.80 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
`ee747ae`	358.21 ms	389.41 ms	31.20 ms
`22f4345`	325.23 ms	454.66 ms	129.43 ms
`fcec2f2`	328.91 ms	387.75 ms	58.84 ms
`a416a65`	333.78 ms	410.37 ms	76.59 ms
`d15471f`	286.65 ms	314.68 ms	28.03 ms
`951caf7`	323.66 ms	392.82 ms	69.16 ms
`17a0955`	372.53 ms	446.70 ms	74.17 ms
`9fbb112`	404.51 ms	475.65 ms	71.14 ms
`dba088c`	333.98 ms	381.16 ms	47.18 ms
`3d205d0`	352.15 ms	432.53 ms	80.38 ms

App size

Revision	Plain	With Sentry	Diff
`ee747ae`	1.58 MiB	2.10 MiB	530.95 KiB
`22f4345`	1.58 MiB	2.29 MiB	719.83 KiB
`fcec2f2`	1.58 MiB	2.12 MiB	551.50 KiB
`a416a65`	1.58 MiB	2.12 MiB	555.26 KiB
`d15471f`	1.58 MiB	2.13 MiB	559.54 KiB
`951caf7`	1.58 MiB	2.13 MiB	558.77 KiB
`17a0955`	1.58 MiB	2.10 MiB	533.20 KiB
`9fbb112`	1.58 MiB	2.11 MiB	539.18 KiB
`dba088c`	1.58 MiB	2.13 MiB	558.99 KiB
`3d205d0`	1.58 MiB	2.10 MiB	532.97 KiB

Previous results on branch: rz/fix/anr-gesture-detector

Startup times

Revision	Plain	With Sentry	Diff
`9adfd0d`	382.98 ms	473.75 ms	90.77 ms
`3c64e61`	338.52 ms	430.68 ms	92.16 ms
`99696ad`	313.46 ms	354.00 ms	40.54 ms

App size

Revision	Plain	With Sentry	Diff
`9adfd0d`	1.58 MiB	2.29 MiB	723.82 KiB
`3c64e61`	1.58 MiB	2.29 MiB	723.86 KiB
`99696ad`	1.58 MiB	2.29 MiB	723.83 KiB

...droid-core/src/main/java/io/sentry/android/core/internal/gestures/SentryGestureDetector.java

…velocity data Matches GestureDetector behavior: if consecutive ACTION_DOWN events arrive without an intervening ACTION_UP/ACTION_CANCEL, stale motion data could bleed into fling detection. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

cursor

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

...ndroid-core/src/main/java/io/sentry/android/core/internal/gestures/SentryWindowCallback.java

…check UserInteractionIntegration gated itself on GestureDetectorCompat being available via classloader check, but SentryGestureDetector only uses Android SDK classes. Remove the check so the integration works without androidx.core. Also remove the stale proguard -keep rule. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sentry · 2026-03-11T13:27:23Z

Sentry Build Distribution

App	Version	Configuration
SDK Size	8.34.1 (1)	release

sentry · 2026-03-11T13:30:10Z

...droid-core/src/main/java/io/sentry/android/core/internal/gestures/SentryGestureDetector.java

+            listener.onScroll(currentDownEvent, event, scrollX, scrollY);
+            isInTapRegion = false;
+            lastX = x;
+            lastY = y;
+          }
+          break;
+        }
+
+      case MotionEvent.ACTION_UP:
+        if (isInTapRegion) {
+          listener.onSingleTapUp(event);


Bug: The SentryGestureDetector doesn't handle multi-touch events, causing it to incorrectly fire onSingleTapUp callbacks during gestures like pinch-to-zoom.
_{Severity: MEDIUM}

Suggested Fix

In the onTouchEvent method, add cases for ACTION_POINTER_DOWN and ACTION_POINTER_UP. In these cases, cancel the tap detection by setting the isInTapRegion flag to false. This will prevent onSingleTapUp from being called when a multi-touch gesture is in progress.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not valid. Location: sentry-android-core/src/main/java/io/sentry/android/core/internal/gestures/SentryGestureDetector.java#L60-L96 Potential issue: The `SentryGestureDetector.onTouchEvent` method does not handle multi-touch events like `ACTION_POINTER_DOWN` or `ACTION_POINTER_UP`. When a user performs a multi-touch gesture (e.g., pinch-to-zoom), the `isInTapRegion` flag remains `true` after the first pointer goes down. When any pointer is lifted, an `ACTION_UP` event is processed while `isInTapRegion` is still true, incorrectly triggering an `onSingleTapUp` callback. This results in spurious click breadcrumbs being generated for multi-touch gestures, leading to inaccurate user interaction telemetry.

romtsn and others added 2 commits March 2, 2026 21:03

test(android): Add unit tests for SentryGestureDetector

664f126

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

romtsn requested review from adinauer, lcian and markushi as code owners March 2, 2026 20:05

changelog

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Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sentry bot reviewed Mar 2, 2026

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...ndroid-core/src/main/java/io/sentry/android/core/internal/gestures/SentryWindowCallback.java Show resolved Hide resolved

romtsn and others added 2 commits March 2, 2026 23:15

Merge branch 'main' into rz/fix/anr-gesture-detector

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sentry bot reviewed Mar 11, 2026

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markushi approved these changes Mar 11, 2026

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fix(gestures): Replace GestureDetectorCompat with lightweight detector to fix ANR#5138

fix(gestures): Replace GestureDetectorCompat with lightweight detector to fix ANR#5138
romtsn wants to merge 6 commits intomainfrom
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romtsn commented Mar 2, 2026

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