Fix wrong txn duration in case SDK init is deferred

CHANGELOG.md

@@ -21,6 +21,7 @@
 
 - Send breadcrumbs and client error in `SentryOkHttpEventListener` even without transactions ([#3087](https://github.com/getsentry/sentry-java/pull/3087))
 - Keep `io.sentry.exception.SentryHttpClientException` from obfuscation to display proper issue title on Sentry ([#3093](https://github.com/getsentry/sentry-java/pull/3093))
+- (Android) Fix wrong activity transaction duration in case SDK init is deferred ([#3092](https://github.com/getsentry/sentry-java/pull/3092))
 
 ### Dependencies
 

sentry-android-core/src/main/java/io/sentry/android/core/ActivityLifecycleIntegration.java

@@ -413,6 +413,10 @@ public void onActivityPostResumed(@NonNull Activity activity) {
   public void onActivityPrePaused(@NonNull Activity activity) {
     // only executed if API >= 29 otherwise it happens on onActivityPaused
     if (isAllActivityCallbacksAvailable) {
+      // as the SDK may gets (re-)initialized mid activity lifecycle, ensure we set the flag here as
+      // well
+      // this ensures any newly launched activity will not use the app start timestamp as txn start
+      firstActivityCreated = true;
       if (hub == null) {
         lastPausedTime = AndroidDateUtils.getCurrentSentryDateTime();
       } else {
@@ -425,6 +429,10 @@ public void onActivityPrePaused(@NonNull Activity activity) {
   public synchronized void onActivityPaused(final @NotNull Activity activity) {
     // only executed if API < 29 otherwise it happens on onActivityPrePaused
     if (!isAllActivityCallbacksAvailable) {
+      // as the SDK may gets (re-)initialized mid activity lifecycle, ensure we set the flag here as
+      // well
+      // this ensures any newly launched activity will not use the app start timestamp as txn start
+      firstActivityCreated = true;
       if (hub == null) {
         lastPausedTime = AndroidDateUtils.getCurrentSentryDateTime();
       } else {

sentry-android-core/src/test/java/io/sentry/android/core/ActivityLifecycleIntegrationTest.kt

@@ -20,6 +20,7 @@ import io.sentry.Scope
 import io.sentry.ScopeCallback
 import io.sentry.Sentry
 import io.sentry.SentryDate
+import io.sentry.SentryDateProvider
 import io.sentry.SentryNanotimeDate
 import io.sentry.SentryTracer
 import io.sentry.Span
@@ -1320,6 +1321,34 @@ class ActivityLifecycleIntegrationTest {
         verify(fixture.activityFramesTracker).setMetrics(activity, fixture.transaction.eventId)
     }
 
+    @Test
+    fun `When sentry is initialized mid activity lifecycle, last paused time should be used in favor of app start time`() {
+        val sut = fixture.getSut(importance = RunningAppProcessInfo.IMPORTANCE_FOREGROUND)
+        val now = SentryNanotimeDate(Date(1234), 456)
+
+        fixture.options.tracesSampleRate = 1.0
+        fixture.options.dateProvider = SentryDateProvider { now }
+        sut.register(fixture.hub, fixture.options)
+
+        // usually done by SentryPerformanceProvider
+        val startDate = SentryNanotimeDate(Date(5678), 910)
+        setAppStartTime(startDate)
+        AppStartMetrics.getInstance().appStartType = AppStartType.COLD
+
+        // when activity is paused without being created
+        // indicating a delayed SDK init
+        val oldActivity = mock<Activity>()
+        sut.onActivityPrePaused(oldActivity)
+        sut.onActivityPaused(oldActivity)
+
+        // and the next activity is created
+        val newActivity = mock<Activity>()
+        sut.onActivityCreated(newActivity, null)
+
+        // then the transaction should start with the paused time
+        assertEquals(now.nanoTimestamp(), fixture.transaction.startDate.nanoTimestamp())
+    }
+
     private fun runFirstDraw(view: View) {
         // Removes OnDrawListener in the next OnGlobalLayout after onDraw
         view.viewTreeObserver.dispatchOnDraw()