[Android] Evict preloaded checkout under memory pressure

[markmur]

Ports the Swift memory-pressure eviction behaviour to Android. Registers a ComponentCallbacks2 on the application context when preloading starts; on a trim-memory signal at or above TRIM_MEMORY_RUNNING_LOW the single cached preload WebView is evicted and the handle transitions to the new PreloadState.Evicted. A presented checkout is spared — eviction is a no-op while isPresented is true, mirroring the Swift guard.

Eviction fires through the cache's own registered callback, so there's no public entry point; tests drive it via the internal cache. See the two new cases in PreloadObservabilityTest for the idle-evict and presented-spared paths.

Why ship this

• Process survival: a paused checkout WebView is prime reclaimable memory. If we ignore onTrimMemory, Android's low-memory killer reclaims at process granularity and can take the whole host app — voluntarily handing back one WebView is the far cheaper trade. This is the change's main justification.
• Platform contract: ComponentCallbacks2 exists precisely for caches like this. An SDK that holds a heavyweight WebView and ignores trim signals is a memory hog consumers have to work around.
• Bounded and low-risk: the cache is single-slot and TTL-bounded, and eviction is isPresented-guarded, so it can only ever reclaim one idle entry and never a live checkout.
• Completes the lifecycle: [Android] Add preload state observability #451 exposed PreloadState; Evicted closes it so a preload can't silently vanish under pressure with no corresponding state for consumers to observe.

[markmur]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [Android] Evict preloaded checkout under memory pressure #453 👈 (View in Graphite)
• [Swift] Evict preloaded checkout under memory pressure #447
• [Android] Add preload state observability #451 : 1 other dependent PR (#455 )
• main

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[github-actions]

React Native — Coverage Report

Lines	Statements	Branches	Functions
	91.85% (327/356)	87.98% (183/208)	100% (86/86)

[github-actions]

Package Size

Platform	Artifact	Base	Head	Delta
Android	release AAR	257.6 KiB	264.5 KiB	+6.9 KiB

Android file breakdown

File	Base	Head	Delta
classes.jar	273.5 KiB	281.3 KiB	+7.8 KiB
res/layout/checkout_view_content.xml	2.2 KiB	2.2 KiB	0 B
res/layout/checkout_sheet_content.xml	2.0 KiB	2.0 KiB	0 B
res/values/values.xml	1.2 KiB	1.2 KiB	0 B
R.txt	1.1 KiB	1.1 KiB	0 B
proguard.txt	798 B	798 B	0 B
AndroidManifest.xml	578 B	578 B	0 B
res/drawable/close.xml	431 B	431 B	0 B
res/menu/checkout_menu.xml	354 B	354 B	0 B
META-INF/com/android/build/gradle/aar-metadata.properties	157 B	157 B	0 B

Measured from the PR base SHA and PR head SHA. The file breakdown shows uncompressed sizes within each package artifact, so individual files do not sum to the compressed artifact total. This comment reports package artifact sizes only; it is not a final app binary-size report.

[bitrise]

Install this build

Open Tophat, select your target device, then click Install. Links open on the Mac running Tophat.

SDK	Install
Kotlin	Install with Tophat

Checkout Kit E2E results

Status	Suite	Target	Platform	OS version tag	Device
✅	tests/shared/launch-smoke.yaml	kotlin	android	latest	Google Pixel 9 Android 17.0

[kiftio]

terminate seems to not be defined

[kiftio]

should we do MEMORY_RUNNING_CRITICAL too

 @Suppress("DEPRECATION")
  private fun isRunningLowOnMemory(level: Int): Boolean =
      level in ComponentCallbacks2.TRIM_MEMORY_RUNNING_LOW..
          ComponentCallbacks2.TRIM_MEMORY_RUNNING_CRITICAL

  override fun onTrimMemory(level: Int) {
      if (isRunningLowOnMemory(level)) {
          evict(PreloadState.Evicted)
      }
  }

[kiftio]

Probably worth a comment that these levels aren't reported in API level 34+

It looks like we just get notified of things TRIM_MEMORY_BACKGROUND and TRIM_MEMORY_UI_HIDDEN from that API level on

so the eviction wouldn't work on newer devices