fix(android-fragment): support detach/attach navigation in fragment tracing by romtsn · Pull Request #5660 · getsentry/sentry-java

romtsn · 2026-06-29T20:11:42Z

Summary

Fixes a silent data quality issue where detach/attach tab navigation (and similar patterns) left ui.load spans open until the 30-second activity transaction deadline, producing badly inflated performance data.

Root cause

SentryFragmentLifecycleCallbacks started spans in onFragmentCreated and stopped them in onFragmentStarted (a concession to ViewPager2 which locks background fragments to STARTED). For detach/attach navigation — manual tab switching (transaction.detach(current).attach(next).commit()), ViewPager v1 with FragmentPagerAdapter, and custom navigation frameworks that preserve fragment state — onFragmentCreated is never called for off-screen fragments. Spans would hang silently until the deadline.

Fix

Three targeted changes, all leveraging the fact that startTracing / stopTracing are already idempotent:

Hook	Change	Why
`onFragmentViewCreated`	+`startTracing`	Enables narrower `viewCreated → resumed` span for detach/attach paths. No-op if `onFragmentCreated` already started a span.
`onFragmentResumed`	+`stopTracing`	Ends the span on the detach/attach path where `onFragmentStarted` may not fire. No-op for the normal path where `onFragmentStarted` already closed the span.
`onFragmentViewDestroyed`	+`stopTracing`	Failsafe: closes any span for a fragment whose view is destroyed before reaching STARTED or RESUMED.

The normal lifecycle path (onFragmentCreated → onFragmentViewCreated → onFragmentStarted → onFragmentResumed) is completely unaffected — still produces exactly one ui.load span, closed at onFragmentStarted.

What's new for customers

Apps using detach/attach navigation will now see correct, narrower ui.load spans (viewCreated → resumed) instead of timeout-inflated spans.

Tests

Five new unit tests covering:

Detach/attach path: onFragmentViewCreated starts a span when tracing enabled
Normal path: onFragmentViewCreated is a no-op when span already running
Detach/attach path: onFragmentResumed stops the span
Normal path: onFragmentResumed does not double-finish after onFragmentStarted
Failsafe: onFragmentViewDestroyed stops a span that never reached STARTED/RESUMED

Example trace: https://sentry-sdks.sentry.io/explore/traces/trace/edb7de2bba454d70a4c13eee5bce660c/

As you can see TabFragmentB now correctly shows up after re-attaching (but wouldn't have without this fix):

Not verified

./gradlew spotlessApply apiDump could not run (no JDK in sandbox) — CI will apply formatting and regenerate .api files if needed.

…racing For detach/attach tab navigation (manual tab switching, ViewPager v1 with FragmentPagerAdapter, custom navigation frameworks), onFragmentCreated is skipped for off-screen fragments that are re-attached. Previously this left ui.load spans open until the 30s activity transaction deadline, producing inflated performance data. Fix by calling startTracing in onFragmentViewCreated as well as onFragmentCreated. startTracing is idempotent (no-op if a span is already running), so the normal onFragmentCreated -> onFragmentViewCreated path is unaffected. Add matching stopTracing calls in onFragmentResumed (covers the detach/attach path where onFragmentStarted may be skipped) and onFragmentViewDestroyed (failsafe for fragments destroyed before reaching STARTED or RESUMED). stopTracing is also idempotent, so the normal path is unaffected. Co-Authored-By: sentry-junior[bot] <264270552+sentry-junior[bot]@users.noreply.github.com>

sentry · 2026-06-29T20:13:25Z

📲 Install Builds

Android

🔗 App Name	App ID	Version	Configuration
SDK Size	io.sentry.tests.size	8.46.0 (1)	release

⚙️ sentry-android Build Distribution Settings

github-actions · 2026-06-29T20:19:23Z

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	364.04 ms	473.08 ms	109.04 ms
Size	0 B	0 B	0 B

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
`abfcc92`	337.38 ms	427.39 ms	90.00 ms
`4e3e79d`	369.55 ms	418.39 ms	48.83 ms
`9054d65`	330.94 ms	403.24 ms	72.30 ms
`a416a65`	316.52 ms	359.67 ms	43.15 ms
`d15471f`	315.61 ms	360.22 ms	44.61 ms
`22f4345`	325.23 ms	454.66 ms	129.43 ms
`6b019b7`	403.90 ms	546.09 ms	142.19 ms
`d217708`	409.83 ms	474.72 ms	64.89 ms
`52feca7`	314.77 ms	378.67 ms	63.90 ms
`f634d01`	375.06 ms	420.04 ms	44.98 ms

App size

Revision	Plain	With Sentry	Diff
`abfcc92`	1.58 MiB	2.13 MiB	557.31 KiB
`4e3e79d`	0 B	0 B	0 B
`9054d65`	1.58 MiB	2.29 MiB	723.38 KiB
`a416a65`	1.58 MiB	2.12 MiB	555.26 KiB
`d15471f`	1.58 MiB	2.13 MiB	559.54 KiB
`22f4345`	1.58 MiB	2.29 MiB	719.83 KiB
`6b019b7`	0 B	0 B	0 B
`d217708`	1.58 MiB	2.10 MiB	532.97 KiB
`52feca7`	0 B	0 B	0 B
`f634d01`	1.58 MiB	2.10 MiB	533.40 KiB

Previous results on branch: fix/fragment-detach-attach-tracing

Startup times

Revision	Plain	With Sentry	Diff
`c53e6fb`	312.80 ms	372.79 ms	59.99 ms
`be2bf5f`	314.90 ms	364.90 ms	50.00 ms
`7966377`	324.00 ms	379.38 ms	55.38 ms

App size

Revision	Plain	With Sentry	Diff
`c53e6fb`	0 B	0 B	0 B
`be2bf5f`	0 B	0 B	0 B
`7966377`	0 B	0 B	0 B

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

…ment onFragmentCreated is skipped during detach/attach navigation, so the screen name was never updated for re-attached fragments. Mirror the screen tracking into onFragmentViewCreated to cover that path. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

0xadam-brown

Nice! A few quick comments; otherwise lgtm 👍

0xadam-brown · 2026-07-01T07:26:09Z

+    // off-screen fragments that are re-attached. Starting here enables a narrower
+    // "view created -> resumed" span for those paths. startTracing is idempotent, so for the
+    // normal onFragmentCreated -> onFragmentViewCreated path this is a no-op.
+    if (fragment.isAdded) {


l: We could internalize the if (fragment.isAdded) {... checks inside startTracing() since they protect the integrity of ui.load initiation + we always apply them.

would it also make sense to add the scopes.options.isEnableScreenTracking inside there too?

0xadam-brown · 2026-07-01T07:30:33Z

+import androidx.fragment.app.Fragment
+import androidx.fragment.app.commit
+
+class DetachAttachTabsActivity : AppCompatActivity(R.layout.activity_detach_attach_tabs) {


Thanks for the sample 💯

m: Unfortunately I'm not able to see or click the tabs on my emulator (Pixel 10, API 36.1):

...seems they're being rendered under the action bar.

runningcode

Fragments are so confusing! Thanks for the fix.

Format code

d861925

romtsn and others added 3 commits June 30, 2026 15:52

Add changelog entry and detach/attach sample

a783845

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Merge branch 'main' into fix/fragment-detach-attach-tracing

af34cb1

Remove duplicate test methods in fragment lifecycle test

0412cb7

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

romtsn marked this pull request as ready for review June 30, 2026 15:26

romtsn requested review from 0xadam-brown, adinauer, markushi and runningcode as code owners June 30, 2026 15:26

sentry Bot reviewed Jun 30, 2026

View reviewed changes

Comment thread ...ndroid-fragment/src/main/java/io/sentry/android/fragment/SentryFragmentLifecycleCallbacks.kt

romtsn and others added 2 commits June 30, 2026 19:25

Format code

27d39bd

0xadam-brown reviewed Jul 1, 2026

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runningcode approved these changes Jul 1, 2026

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fix(android-fragment): support detach/attach navigation in fragment tracing#5660

fix(android-fragment): support detach/attach navigation in fragment tracing#5660
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fix/fragment-detach-attach-tracing

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Baseline results on branch: main

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romtsn commented Jun 29, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Root cause

Fix

What's new for customers

Tests

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📲 Install Builds

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