An AMOLED-black, monochrome binary-clock Android home-screen widget.
It renders the current time and date as a 6×4 grid of dots. Cells that would otherwise go unused carry a couple of small extras: the device alarm state and weather glyphs. A slim battery indicator sits between the minutes and day rows. The aesthetic is deliberately austere — solid dots on true black, no chrome, no colour — so it disappears into an AMOLED wallpaper and sips battery.
Weather is opt-in and off by default: the clock, date, alarm and battery all work out of the box, and the app makes no network or location calls until you turn weather on and point it at a server. See Weather for details.
The widget with weather turned off — no weather glyph, since weather is opt-in:
Configuration — appearance, and turning weather on or off:
The face is a grid of rows (values) and columns (place values):
- Rows encode, top to bottom: hours, minutes, day (of month), month.
- Columns are binary place values: 32 · 16 · 8 · 4 · 2 · 1.
- A lit (solid) dot means that place value is on; an unlit dot is off. Add the lit columns in a row to read that row's number.
For example, a minutes row with the 32, 8, and 2 dots lit reads
32 + 8 + 2 = 42.
The cells not needed by the low-value ends of the shorter rows are reused for a handful of glyphs — the alarm state and three weather readings. Each has a fixed, always-reserved cell:
| Cell | Glyph |
|---|---|
Hours row · leftmost column (the unused 32) |
Alarm state — a lit alarm clock when one is scheduled, an "alarm off" icon otherwise |
Day row · leftmost column (the unused 32) |
Weather now — current conditions, day/night aware |
Month row · leftmost column (the unused 32) |
Weather today — the day's forecast |
Month row · second column (the unused 16) |
Weather tomorrow — the next day's forecast |
Those cells are free because the hours row never needs the 32 place (hours only
reach 23), the day row never needs it (days only reach 31), and the month row
needs only the low four places (months only reach 12) — so a glyph there can
never collide with a lit time/date bit.
The three weather glyphs cluster in the bottom-left: current conditions on the day row, with today's and tomorrow's forecast side-by-side on the month row just below. Only the "now" glyph is day/night aware — its sun becomes a moon after dark; the two forecast glyphs always use their daytime icon. The conditions map to Material Symbols icons — clear, partly cloudy, overcast, fog, drizzle, rain, rain showers, snow, snow showers, and thunderstorm. When weather is off, or no forecast has been fetched yet, those cells are simply empty — no placeholder glyph.
Between the minutes and day rows sits a battery readout that's always on. It has two parts, both in the icon tone:
-
A level gauge spanning the first five columns: a hollow, capsule-shaped track filled left→right in proportion to the charge (a full track is 100%). The track's centre is genuinely transparent, so a translucent-background widget shows the wallpaper through it.
-
A state glyph in the sixth column, which only appears when there's something to say. One glyph at a time:
Glyph Meaning ⚡ bolt Charging (at any level — charging always wins) △ outline triangle Low (default: 20% or less), discharging ▲ filled triangle Very low (default: 10% or less), discharging (empty) Above low threshold and discharging — gauge only
The escalation reads as one shape getting "louder": hollow at low, solid at very low. The bolt is a distinct shape so charging is never confused with a warning. There's deliberately no charging-speed distinction and no colour — see the design notes below.
Configurable thresholds: The low and very-low battery warning thresholds can be adjusted in settings via number steppers (+5% / −5% increments). This lets you customize warnings based on your device and usage patterns — set higher thresholds if you want earlier warnings, or lower if your device has good standby time.
Weather is opt-in and off by default. Until you point the app at a weather server it makes no network or location calls and shows no weather glyphs — the clock, date, alarm and battery all work regardless.
To turn it on, open settings and either tap Use Open-Meteo for the free,
keyless public Open-Meteo service
(https://api.open-meteo.com/), or enter your own Open-Meteo-compatible
endpoint — for example a self-hosted Open-Meteo instance.
Clear the field to turn weather back off.
The endpoint must speak Open-Meteo's API: the app calls /v1/forecast and reads
the WMO weather_code values it returns. Any server mirroring that contract
works; an arbitrary weather API will not. This is why the setting is a server
URL, not a free choice of provider.
Once enabled, weather uses two permissions:
- INTERNET — to reach the weather server you configured.
- Coarse location (
ACCESS_COARSE_LOCATION) — to fetch conditions for where you are. Location is read via the platformLocationManageronly (no fused or Google Play location), and your coordinates are sent only to the server you configured, only while weather is on.
Changes you make in settings (colours, tap actions) apply as soon as you leave the screen — the widget is redrawn on exit. Turning weather on or off is the exception: it changes what the widget fetches rather than how it draws, so the weather glyphs appear or clear on the next refresh tick (below), not the moment you leave settings.
The live signals the widget observes — the alarm state, the battery
indicator (both the gauge and its glyph), and the weather glyphs — update
on the widget's own refresh tick, roughly once a minute. Glance compiles to
RemoteViews, which has no way to react to an event the instant it fires, so
plugging in the charger, or turning weather off, can take up to a refresh cycle
to show. This is expected, not a bug.
The alarm glyph lights whenever the platform reports a scheduled alarm
(AlarmManager.nextAlarmClock() != null) — the same signal that drives the
system status-bar alarm icon. We deliberately do not try to filter it.
Automation and routine features (for example Samsung Modes & Routines)
schedule via setAlarmClock() exactly like a real alarm, so they can light the
glyph even when you didn't set a "real" alarm. It's tempting to filter these out
by the scheduling app's package, but the public API only exposes the soonest
alarm with no way to look past it — so any such filter risks the far worse
failure of hiding a genuine alarm that happens to sit behind a routine one.
Mirroring the OS is the honest best-effort a normal app can make.
Note that an OEM status bar may appear to filter these internally; it has privileged access to the alarm database that third-party apps do not, so its behaviour can't be reliably reproduced through the public API.
The glyph beside the gauge is pure warning semantics — an alert triangle or a charging bolt — never a little battery outline. The gauge already owns the battery metaphor; a mini-battery next to it would just say the same thing twice. So the glyph stays quiet until the charge is low enough to matter, then speaks in warning shapes only.
There's no slow/normal/fast charging distinction: Android can't report charge
rate reliably in a once-a-minute widget (BATTERY_PROPERTY_CURRENT_NOW is noisy
or unsupported on many devices, and plug type is only a coarse proxy), so a
single "charging" bolt is the honest signal. And there's no colour — any hue
would collide with Material You or the user's own colour pick, and the whole face
is deliberately monochrome.
- Kotlin
- Jetpack Glance (
glance-appwidget) for the widget UI - Koin for dependency injection
- DataStore for settings + weather caching
- Retrofit / OkHttp / kotlinx.serialization for networking
- WorkManager for periodic weather refresh
- Open-Meteo as the weather data source (keyless, FOSS-friendly)
BinClockWidget targets F-Droid: it is 100% FOSS and contains no Google Play Services, no Firebase, and no proprietary SDKs. Its one optional network feature is Weather — opt-in, off by default, and backed by the keyless Open-Meteo API or your own self-hosted server.
./gradlew :app:assembleDebugRequirements: JDK 21, Android SDK with platform 37 installed.
- minSdk 26
- compileSdk / targetSdk 37
BinClockWidget is free and open-source software licensed under the GNU General Public License v3.0.
SPDX-License-Identifier: GPL-3.0-or-later
You're free to use, modify, and distribute this software, but any derivative works must also be open source under GPL-3.0-or-later.