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Spectrum 2.4GHz is built for modern Android devices but maintains compatibility back to Android 6.0 (Marshmallow), covering the vast majority of active Android handsets. Before installing or distributing the app, verify that the target device meets the minimum OS and hardware requirements listed below, and ensure users understand which runtime permissions the app will request.

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System Requirements

RequirementValue
Operating SystemAndroid 6.0 (Marshmallow) or higher
Minimum SDK (minSdk)API Level 23
Target SDK (targetSdk)API Level 34 (Android 14)
Compile SDKAPI Level 34
Java VersionJava 8 (source/target compatibility 1.8)
App Version Name1.0
App Version Code1
Package / Application IDcom.spectrum24ghz
HardwareDevice must have a 2.4 GHz capable Wi-Fi adapter
Wi-Fi does not need to be connected — or even enabled — for the app to scan. Android’s “Scan Always Available” mode (found under Settings → Location → Advanced → Wi-Fi scanning) allows the Wi-Fi radio to perform passive scans even while the Wi-Fi switch is off. Spectrum 2.4GHz checks WifiManager.isScanAlwaysAvailable() and will prompt the user to enable this setting if both Wi-Fi and scan-always are disabled.

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Required Permissions

The following permissions are declared in AndroidManifest.xml. The app requests only the permissions needed to perform Wi-Fi scanning and display location-gated results:
PermissionAPI LevelPurpose
ACCESS_WIFI_STATEAllRead current Wi-Fi state and trigger getScanResults()
CHANGE_WIFI_STATEAllCall WifiManager.startScan() to initiate active scans
ACCESS_NETWORK_STATEAllInspect general network connectivity state
ACCESS_COARSE_LOCATIONAll (23+)Required by Android to expose Wi-Fi scan results
ACCESS_FINE_LOCATIONAll (23+)Required for precise BSSID and SSID data in scan results
NEARBY_WIFI_DEVICESAPI 33+ (Android 13)Replaces location permission for Wi-Fi scanning on Tiramisu and above
At runtime, MainActivity.requiredPermissions() builds the permission list dynamically — NEARBY_WIFI_DEVICES is only added on devices running Android 13 or higher: 
private List<String> requiredPermissions() {
    List<String> perms = new ArrayList<>();
    perms.add(Manifest.permission.ACCESS_FINE_LOCATION);
    perms.add(Manifest.permission.ACCESS_COARSE_LOCATION);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
        perms.add(Manifest.permission.NEARBY_WIFI_DEVICES);
    }
    return perms;
}
If any permission is denied, the app shows a dialog explaining the requirement and offers a retry option. The Channels tab remains accessible even without scan permissions, since it displays the pre-built static channel list.

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Android Version Behavior Differences

Spectrum 2.4GHz adjusts its behavior at two specific API-level boundaries:

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Android 10+ (API Level 30)

Signal strength is calculated using the device-reported maximum level via WifiManager.getMaxSignalLevel(), which accounts for vendor-specific signal granularity: 
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R) {
    int max = wifiManager.getMaxSignalLevel();
    return Math.max(0, Math.min(
        WifiManager.calculateSignalLevel(rssi, max + 1) * 100 / max,
        100
    ));
}
// Fallback for API < 30:
return WifiManager.calculateSignalLevel(rssi, 100);

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Android 13+ (API Level 33 — Tiramisu)

Two changes apply on Tiramisu and above:
  1. NEARBY_WIFI_DEVICES permission is required in addition to (or instead of) location permissions for Wi-Fi scanning.
  2. RECEIVER_NOT_EXPORTED flag must be passed when registering the BroadcastReceiver for SCAN_RESULTS_AVAILABLE_ACTION, preventing other apps from sending forged scan-results broadcasts:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU) {
    registerReceiver(scanReceiver, filter, RECEIVER_NOT_EXPORTED);
} else {
    registerReceiver(scanReceiver, filter);
}

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Library Dependencies

All dependencies are sourced from the standard AndroidX and Google Maven repositories. No third-party networking or analytics libraries are included.
LibraryVersionPurpose
androidx.core:core1.12.0Core AndroidX utilities and compatibility helpers
androidx.appcompat:appcompat1.6.1Backward-compatible Activity and UI components
com.google.android.material:material1.11.0Material Design components (dialogs, buttons, theming)
androidx.constraintlayout:constraintlayout2.1.4Flexible constraint-based layout engine
androidx.recyclerview:recyclerview1.3.2Efficient scrolling lists for network and channel views
androidx.coordinatorlayout:coordinatorlayout1.2.0Coordinator layout for scroll-based behaviors
Build configuration uses View Binding (buildFeatures { viewBinding true }), eliminating findViewById calls throughout the codebase. Code minification is disabled in the release build type, so ProGuard rules are not applied by default.

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