widget_rtlsdr

Immersive, gqrx/CubicSDR-inspired widget library for RTL-SDR on Android/Flutter, built on top of core_rtlsdr (source), which is itself built on driver_rtlsdr (source).

core_rtlsdr gives you tuning/streaming/demod/gain/squelch/stereo/RDS/ spectrum/recording/scan/presets as plain ChangeNotifier controllers, but deliberately ships no UI — its own example/ is intentionally minimal Material widgets, just enough to prove the controllers are sufficient on their own. widget_rtlsdr is that UI layer: a big digit frequency readout, an FFT scope and waterfall styled like a real receiver, themed control panels, and a settings navigation that adapts from a phone to a tablet — all driven by the same controllers, so this package never touches driver_rtlsdr or dart:ffi directly either.

What this package provides

• Display widgets: FrequencyReadout (odometer-style digit tuner — drag or scroll a digit to change just that place, carries cascade into neighbors automatically, same interaction as gqrx's tuning display), SpectrumScope (FFT line/fill plot with a bottom frequency axis and a shaded demod-passband overlay around the tuned frequency, tap/drag to retune), WaterfallView (scrolling spectrogram — rendered as a single Canvas.drawVertices mesh regardless of how many bins/rows are on screen, so it stays smooth at the spectrum controller's ~25 fps default), SignalMeter (dBFS bar with a squelch threshold tick), ModeSelector (iterates DemodMode.values, so it stays correct as driver_rtlsdr adds demodulation modes).
• Control panels, one per core_rtlsdr controller — each a self-contained, independently usable RtlSdrPanel section: GainPanel, SquelchPanel, StereoRdsPanel, RecordingPanel, ScanPanel, PresetsPanel, StatsPanel, UsbStatusBanner.
• Theming: RtlSdrTheme/RtlSdrThemeData (.dark/.light) — a near-black "receiver bezel" palette plus a configurable waterfall colormap (defaultWaterfallColormap, a gqrx-style dark-blue→cyan→green→ yellow→red ramp). Every widget falls back to .dark if used without an ancestor RtlSdrTheme.
• RtlSdrImmersiveScreen: the full instrument view — meter, tuner, scope, waterfall — filling the screen.
• Distributed settings navigation — the piece that answers "where do gain/squelch/scan/presets/etc. actually live in my app?": RtlSdrSettingsSection is a plain, navigation-agnostic (id, title, icon, builder) unit. The same section list can be shown:
  1. behind RtlSdrImmersiveScreen's settings button via RtlSdrSettingsScreen — a drill-down list pushing each section as its own full-screen subscreen on a phone, or a master-detail split (list + content, no navigation) on a tablet/wide window, switching automatically at a configurable breakpoint;
  2. as a fixed side panel next to the scope on very wide windows (automatic in RtlSdrImmersiveScreen above sideSettingsBreakpoint);
  3. individually, anywhere in a host app's own navigation/router, via RtlSdrSettingsSection.pageRoute() / RtlSdrSettingSectionScreen.

What this package deliberately does NOT provide

• A DI/state-management framework: every widget takes its controller (RadioController, ScanController, ...) as a plain constructor parameter — wire them up with provider, riverpod, or nothing at all, same stance core_rtlsdr takes on RtlSdrDriver. example/ uses provider, but that's the example's choice, not a requirement.
• FFI or Android-platform code of its own: it depends only on core_rtlsdr's controllers. NativeRtlSdrDriver (the real, Android-only driver) and the UsbState/UsbChannel permission flow are core_rtlsdr/driver_rtlsdr concerns — see their docs.

Installation

dependencies:
  widget_rtlsdr: ^0.0.1

widget_rtlsdr depends on core_rtlsdr (pulled in transitively), which itself depends on driver_rtlsdr, which is Android-only. See core_rtlsdr's README for the two things your app needs beyond pubspec.yaml (a minSdk = 26 bump and a USB auto-open intent filter) — nothing extra is needed for this package on top of that.

Usage

import 'package:core_rtlsdr/core_rtlsdr.dart';
import 'package:widget_rtlsdr/widget_rtlsdr.dart';

Minimal: just the immersive screen

Once you have a RadioController (see core_rtlsdr's README for the USB permission flow + NativeRtlSdrDriver wiring):

RtlSdrTheme(
  data: RtlSdrThemeData.dark(),
  child: RtlSdrImmersiveScreen(radio: radio),
)

With distributed settings

RtlSdrImmersiveScreen(
  radio: radio,
  settingsSections: [
    RtlSdrSettingsSection(
      id: 'gain',
      title: 'Gain',
      icon: Icons.tune,
      builder: (context) => GainPanel(radio: radio),
    ),
    if (radio.demodMode.supportsSquelch)
      RtlSdrSettingsSection(
        id: 'squelch',
        title: 'Squelch',
        icon: Icons.volume_off,
        builder: (context) => SquelchPanel(radio: radio),
      ),
    RtlSdrSettingsSection(
      id: 'scan',
      title: 'Band scan',
      icon: Icons.search,
      builder: (context) => ScanPanel(radio: radio, scan: scan, presets: presets),
    ),
    // ...PresetsPanel, RecordingPanel, StereoRdsPanel, StatsPanel
  ],
)

Resize the window (or run on a tablet vs. a phone) to see the same section list switch between a drill-down list of full-screen subscreens and a side-by-side master-detail split — no extra code either way.

A section on its own, in your app's own navigation

Navigator.of(context).push(gainSection.pageRoute());

See example/ for a complete, runnable app: the same UsbState/ UsbChannel permission flow and NativeRtlSdrDriver composition root as core_rtlsdr's own example, rendered through this package's widgets.

Testing without hardware

Every widget here takes a controller, not a driver — so build/test them against core_rtlsdr's FakeRtlSdrDriver (package:core_rtlsdr/testing.dart) exactly like core_rtlsdr's own test suite does, no dongle/emulator/Android device needed:

final radio = RadioController(FakeRtlSdrDriver());
await tester.pumpWidget(MaterialApp(home: Scaffold(body: GainPanel(radio: radio))));

See this package's own test/ for the full pattern, including UsbStatusBanner exercised against every UsbState/UsbConnectionStatus value (UsbState is plain Dart with no FFI, so it's host-testable too).

License

GPLv2-or-later — see LICENSE. driver_rtlsdr links librtlsdr (GPLv2), which requires any software using it to be distributed under the GPL; this package (and core_rtlsdr) inherit that requirement down the dependency chain.