SoftwareApp
65569e9af2
The same benchmark against 1000, 5000 and 20000 files, changing only the fixture: 12-14 frames, 41 frames, 184 frames. That is roughly linear, which is what a RecyclerView fed a pre-sorted list should do, and it is the shape to keep watching - a superlinear jump would mean per-row work that belongs to the folder. The number worth keeping an eye on is not the median but the maximum at 20000: 598 frames against a median of 184, so one iteration of five stalled at roughly three times the others. At that size the first open is occasionally not just slow but stuttering, which is exactly the case a release should be checked against. PERFORMANCE.md records the cost of the fixture too, because it dwarfs the measurement: 20000 files took about thirty minutes through MIUI's storage layer against four minutes of benchmark, which is an argument for building the fixture once and keeping it. And it records where the jank metric came from, since this phone cannot produce one: the API 35 emulator at the 1000-file point gave frameDurationCpuMs P50 218 ms and frameOverrunMs P50 315 ms, software-rendered and therefore not comparable, but proof that the metric exists.
File Manager
An ad-free, one-time-paid Android file manager. It browses and manages the files on your device — locally, with no ads, no account and no analytics.
Nothing ever leaves the device: the app declares no network permission and contains no advertising or tracking SDKs.
Working title. The display name and the store listing are decided before the first Play upload (see docs/ROADMAP.md, M10). The
applicationIdis already fixed and can never change after the first release.
Status
M15 — favourites: done. A star in any folder's app bar puts that folder on the home screen, above
the libraries, where a folder that has gone is marked not found rather than silently dropped and
the row's own star removes it. Before it: M14 — renaming a batch (selecting several files and
choosing Rename opens a pattern dialog instead of the single-file one: one name, the number to
start at, and a preview of the names
it will produce — and the numbering carries on from the folder's own, so series (1) and
series (2) already there make the next batch start at 3. A batch that cannot be done is refused
before anything moves, naming the file in the way, and the whole batch is one undo step. Before it:
M13 — video thumbnails (a video row shows a frame of the video itself rather than a film icon —
the platform's own retriever, through Coil, with a frame taken a second in and the icon kept as the
fallback when a file cannot be decoded), M12 — duplicate finder (size, then the head of every
candidate, then the survivors in full), M11 — library views (a Libraries section on the
root screen — Images, Videos, Audio, Documents, Archives and Recent — whose rows open
ordinary listings of those files, each carrying a count from the search index), and M10 — store
assets: the app is named Plain Files, the icon and feature graphic come from the app's own
vectors, and docs/STORE_LISTING.md holds length-checked listing copy.
Screenshots exist for 5 phone (1080×2160), 4 on a 7-inch tablet (1200×1920) and 4 on a 10-inch
tablet (2560×1600) — but they predate M11, so the home screen in them is the old volume list and
they will need re-shooting, which the library views make a privacy question as well as a cosmetic one
(docs/STORE_LISTING.md).
Tech stack
| Area | Choice |
|---|---|
| Language | Kotlin 2.4.10 (using AGP 9 built-in Kotlin) |
| UI | Jetpack Compose, BOM 2026.06.01, Material 3 |
| Build | Gradle 9.3.1, Android Gradle Plugin 9.1.0 |
| Storage access | MANAGE_EXTERNAL_STORAGE ("All files access") with a Storage Access Framework fallback |
| Archives | Apache Commons Compress + XZ for Java (both pure Java — no NDK) |
| SDK levels | compileSdk/targetSdk 36, minSdk 26 |
targetSdk is 36 because Google Play requires new apps and updates to target
Android 16 (API 36) from 31 August 2026.
Project layout
app/src/main/java/de/softwareapp_hb/filemanager/
├── core/ Pure-Kotlin engine (no Android imports!) — paths, sorting, formatting,
│ search matching, copy/move planning, conflict policy
├── data/ Storage backends (all-files access + SAF), volumes, shares coming in
│ from other apps, the trash index (SQLite), file operations, archives,
│ deletion
├── domain/ Browser + operation controllers, models, permission state
├── service/ Foreground service for long-running file operations
├── ui/ Compose theme, browser screen, components, ViewModels
└── text/ Domain enum → string-resource mapping
app/src/test/java/… JVM unit tests for the core engine
core/ deliberately has no Android dependencies, so the trickiest logic is
covered by fast JVM tests.
The per-file index — what each file holds, and every test name in the suite — is
docs/CODE_MAP.md, generated from the source by
tools/make-code-map.py (--check fails when it is stale). AGENTS.md is the
one-page briefing for whoever picks the repository up: the commands, the layout and its
dependency direction, the rules that have tests behind them, and the traps worth knowing
before spending an hour on them.
Building
Prerequisites:
- JDK 17+ (JDK 25 verified)
- A JDK 21 as well: detekt 1.23 cannot run on 25, so the analyser is pinned to a 21 toolchain and Gradle will not download one.
- Android SDK with
platforms;android-36andbuild-tools;36.0.0
# Tell Gradle where the SDK lives (this file is git-ignored)
echo "sdk.dir=$HOME/Android/Sdk" > local.properties
./gradlew :app:assembleDebug # debug APK
./gradlew :app:testDebugUnitTest # JVM unit tests for the engine
./gradlew :app:lintDebug # Android Lint
./gradlew :app:bundleRelease # Play upload bundle (.aab)
# Everything the gate requires, in one command — what CI and the pre-push hook run:
./tools/verify.sh
The gate is the code-map check, detekt against a frozen baseline, the unit tests
and Android Lint, cheapest first; --release adds an R8 build. CI
(.github/workflows/verify.yml) runs it on every push and pull request and nightly with --release,
because R8 is the one check that has caught a defect nothing else could. To run it before pushing:
git config core.hooksPath .githooks.
The numbers that do exist — and the ones deliberately still missing — are in docs/PERFORMANCE.md.
Release signing is optional and driven by a git-ignored keystore.properties
(see keystore.properties.example); without it the release build still runs
R8/minification but produces an unsigned artefact.
Tracked in git
- Source, resources and Gradle build files.
docs/— the roadmap, the generated code map and the release documentation.PRIVACY.md,CHANGELOG.md,AGENTS.md, and (from M10)store-assets/.
Not tracked: local.properties, keystore.properties, *.jks, build outputs.
Releasing
Release signing is driven by the git-ignored keystore.properties (see
keystore.properties.example). Without that file the release build still runs R8 and
resource shrinking, but produces an unsigned artefact that cannot be uploaded.
./gradlew :app:bundleRelease # Play upload bundle (.aab)
./gradlew :app:assembleRelease # APK, for local checks
# Audit what is actually shipped — in particular that there is no INTERNET permission:
$ANDROID_HOME/build-tools/36.0.0/aapt2 dump permissions \
app/build/outputs/apk/release/app-release.apk
Read docs/PLAY_RELEASE_CHECKLIST.md before uploading. Step 4 is the one that matters most for this app: a file manager must declare "All files access" through Play's Permissions Declaration Form, and have the core purpose documented in its store description. PRIVACY.md is written to match the shipped permissions.
Localisation
All user-visible text lives in app/src/main/res/values/strings.xml, with real <plurals>
wherever a count can be one, and the screen and the progress notification resolve their
labels through text/TextRes.kt so the two cannot drift apart. English is currently the
only locale.
Adding a language is then a file, not a refactor:
app/src/main/res/values-de/strings.xml # same keys, translated values
Deliberately not localised, and why:
- Byte units ("KB", "MB") — symbols, not words, and every file manager and the system Settings app show them the same way.
- The timestamp pattern (
yyyy-MM-dd HH:mm) — a fixed, sortable format; the zone is passed in explicitly rather than assumed.
Checking that nothing was missed
Two things are easy to get wrong: a literal typed into a composable, and showing an enum
constant directly (FileKind.name puts untranslatable English on screen — the details
sheet used to do exactly that). The mechanical check is the pseudo-locale:
./gradlew :app:assembleDebug
# Settings > System > Languages > English (XA), then launch the debug build.
The debug build type sets isPseudoLocalesEnabled = true, so every string that came from
strings.xml renders accented and bracketed ([Îmàgé]). Anything that looks normal is a
string that never went through resources. The release build is unaffected.
One caveat: Google Play's automatic translation translates your store listing, not the app
UI. Translated UI text has to be supplied in values-<locale>/.
Known limitations
- The trash is a time window, not a bin you manage. A delete stages the item in a hidden
.plainfiles-trashfolder on the same volume and keeps it for 24 hours; the Trash entry in the overflow menu lists what is still there and puts a whole batch back. There is no "empty it now" action — expired batches are swept the next time something is deleted — and a name taken again in the meantime is never overwritten, so a restored item can arrive beside the new one rather than replacing it. - Where a trashed item came from is remembered in the app's own database, not on the volume. The staged files are the truth and the database is only an index, so the two are reconciled in both directions: an entry whose file has gone is not offered back, and a batch folder no entry mentions is swept.
- Sharing a file out only works in the all-files mode. A SAF path is relative to the
granted tree rather than a filesystem path, so it cannot be handed to
FileProvider. Receiving a share and being picked from another app's chooser work either way: the first needs no filesystem path, and the second falls back toRESULT_CANCELEDrather than returning a URI the caller could not read. - RAR, CAB, ISO and WIM are refused, not supported — they need native code, which this project deliberately does not ship. (The Commons Compress jar contains no RAR classes at all.) 7z is different: Commons Compress reads it in pure Java, so it is supported — but the format needs a seekable channel rather than a stream, because its header lives at the end of the file. All-files access can supply one; the SAF fallback cannot, so 7z extraction reports that plainly in folder mode instead of half-working.
- 7z files can be opened but not created — writing stays ZIP-only.
- Archive extraction does not restore original timestamps or permissions, and there is no archive encryption or password support.
- Cancellation happens between entries, so a single very large file finishes before a stop is honoured.
- A batch rename is refused rather than half-done when one of its names is taken, including when
the file holding that name is part of the same batch:
a.txttakinga (1).txtwhilea (1).txtis itself being renamed needs the files shuffled through temporary names, so the dialog names the file in the way instead. Renaming in the other order, or starting the numbering past the block, does what you want. - A library is not restored across process death. The persisted view state holds a path, and a library has none, so a restart returns to the root screen rather than to Images or Recent.
- Long-press multi-select is awkward to script from the host. The gesture that opens the
selection bar (
input swipe x y x y 900) works on the MIUI test device but has also registered as a plain tap, so compress/extract from the UI wants a manual pass (see docs/EDGE_CASE_TESTING.md). - The display name is still the working title — decided before the first upload (M10).
Monetisation
One-time paid: €4.49 base, with a €2.29 launch price for the first 14 days. No ads, no subscription, no in-app purchases, no free tier.
The price lives on the Play listing, not in the build, which is why there is no Billing
client in the dependencies and no com.android.vending.BILLING permission in the APK —
that is what keeps "no network permission, nothing leaves your device" true of the
shipped artefact rather than just the source. Rationale, market anchors, the rejected
alternatives and the Console steps: docs/MONETISATION.md.
⚠️ The price must be set before the first upload — Play allows paid → free but never free → paid.
Competitive context
The category leader is File Manager Plus (AlphaInventor; 100 M+ installs, 4.7–4.8★, free with ads and in-app purchases, and a Data Safety form that shares device IDs with third parties). What it offers, what its users praise, what they complain about, and which of those complaints this app can answer without asking for a single new permission: docs/COMPETITIVE_ANALYSIS.md.
Licence
Proprietary — all rights reserved.