fix(export): stream large JSON downloads to a cache file

[TimeToBuildBob]

Why

#229 saved small-bucket blob downloads, but "Export all" / a huge bucket still dies silently on 0.14.2b4. The web UI waits for a fully-buffered JSON body (30s axios timeout + JSON.parse in the WebView).

Fixes #228

Companion PRs:

• fix(export): send HTTP headers before serializing large exports aw-server-rust#721 — stream headers during serialization
• fix(export): stream large bucket exports without JSON.parse aw-webui#993 — blob download + Android bridge

Change

• Intercept /export XHRs in the injected hook and call Android.exportFromUrl
• Native fetch with the dashboard API key streams into a cache file (not a JS string)
• Existing Save-to picker / toast path unchanged

CSV of a huge bucket still materializes events in JS.

Tests

./gradlew :mobile:testStandardDebugUnitTest --tests net.activitywatch.android.fragments.WebUIFragmentTest

[TimeToBuildBob]

Review guide (auto-posted)

Structured warm-up for reviewers — what changed, what to run, where to look.

Key files

• mobile/src/main/java/net/activitywatch/android/fragments/WebUIFragment.kt (+96/-11, Δ107)
• mobile/src/test/java/net/activitywatch/android/fragments/WebUIFragmentTest.kt (+34/-0, Δ34)

Suggested verification

• Run the repo's usual CI-equivalent checks locally

Known risks / watch points

• No automatic high-risk tags; use file list + diff for judgment.

Suggested review focus

• Confirm behavior matches the PR description acceptance criteria.
• Skim the largest diffs first (listed above).
• If CI is green, spot-check the highest-risk paths called out here.

Generated by scripts/github/pr-warmup-review-guide.py for #304.

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; the two lifecycle defects from the previous review are fixed and no new actionable issue was found.

Findings

1.  WebView Access From Bridge Thread ▶
2.  Completed Exports Can Disappear ▶
3.  Required Profiling Evidence Missing ▶

Summary

This PR routes large JSON exports from the embedded dashboard through an authenticated native download that streams directly to a cache file before entering the existing Android save flow. The latest revision:

• Marshals JavaScript bridge work onto the main looper before accessing the WebView.
• Handles download completion independently of the Fragment view and deletes completed files that can no longer be queued.
• Adds unit coverage for streaming, URL resolution, bridge forwarding, and orphaned-cache cleanup.

Diagram

sequenceDiagram
    participant W as Dashboard WebView
    participant B as Android bridge
    participant F as WebUIFragment
    participant S as Local ActivityWatch server
    participant C as Export cache
    participant P as Android save picker
    W->>B: exportFromUrl(url, filename)
    B->>F: Marshal callback to main looper
    F->>F: Resolve and validate loopback URL
    F->>S: Authenticated export request
    S-->>C: Stream response into cache file
    C-->>F: Pending export
    alt Fragment remains added
        F->>P: Queue and launch save picker
    else Fragment detached
        F->>C: Delete orphaned cache file
    end

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_{Reviews (2) · Last reviewed commit: "fix(export): marshal JS-bridge export on..."}

[TimeToBuildBob]

@greptileai review

[TimeToBuildBob]

Erik merged this at 2026-09-23T01:08:14Z as 6484f5c. CI was green (Test, Test E2E 29, Greptile 5/5). All review threads resolved. No further action on this PR.

Companion stack also landed: ActivityWatch/aw-server-rust#721, ActivityWatch/aw-webui#993. #228 stays open until Export-all JSON is confirmed on a ~500k-event device; CSV of a huge bucket is still JS-bound.