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HMG_QLine/CHANGES_EXPLANATION.md

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Changes Explanation - App Background Issue & Clinic Prefix Feature

Problem Statement

The app was going to background after 48-60 hours of continuous running, affecting some screens randomly.

Actual Issue Found (March 1, 2026)

From Log Analysis:

  • App started around midnight Feb 26
  • Health checks ran successfully until 8:36 AM Feb 27 (~14 hours uptime)
  • App stopped logging completely after 8:36 AM
  • No crash logs, no lifecycle events - just silent death
  • User had to manually restart app on March 1

Root Cause: Android OS killed the app due to:

  1. No foreground service - Android aggressively kills background apps
  2. Battery optimization - OS prioritizes battery over app persistence
  3. Incorrect uptime tracking - Previous code calculated time wrong, hiding the issue
  4. No automatic recovery - Once killed, app stayed dead

Root Causes Identified

1. Critical Android OS Issues

  • App running as background service without foreground notification
  • Battery optimization killing app after 12-24 hours
  • No keep-screen-on flags at native level
  • App lifecycle not properly managed

2. Monitoring Issues

  • BUG: Uptime calculation was wrong (used lastChecked instead of appStartTime)
  • No crash detection or recovery mechanism
  • Missing lifecycle event tracking
  • No consecutive failure detection

3. Connection Stability

  • SignalR reconnection logic was basic
  • No exponential backoff for retries
  • Missing health monitoring with failure tracking

Solutions Implemented

1. Android Native Layer Hardening (MainActivity.kt & AndroidManifest.xml)

Changes Made:

MainActivity.kt:

  • Keep Screen On: Added FLAG_KEEP_SCREEN_ON at window level
  • Show When Locked: Added FLAG_SHOW_WHEN_LOCKED
  • Turn Screen On: Added FLAG_TURN_SCREEN_ON
  • Battery Optimization Bypass: Auto-request exemption from battery optimization
  • Power Manager Check: Verify app is not being optimized

AndroidManifest.xml:

  • New Permission: REQUEST_IGNORE_BATTERY_OPTIMIZATIONS
  • New Permission: FOREGROUND_SERVICE_SPECIAL_USE
  • Activity Flags: android:keepScreenOn="true" and android:screenOrientation="portrait"
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    
    // Keep screen on at all times
    window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
    window.addFlags(WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED)
    window.addFlags(WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON)
    
    // Request battery optimization exemption
    requestBatteryOptimizationExemption()
}

private fun requestBatteryOptimizationExemption() {
    val pm = getSystemService(Context.POWER_SERVICE) as PowerManager
    if (!pm.isIgnoringBatteryOptimizations(packageName)) {
        val intent = Intent().apply {
            action = Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS
            data = Uri.parse("package:$packageName")
        }
        startActivity(intent)
    }
}

Why This Helps:

  • Prevents OS Kill: Battery optimization exemption keeps app alive
  • Screen Always On: Prevents doze mode and standby
  • Native Level Protection: Android can't kill app as easily
  • Auto-Request: User doesn't need to manually configure settings

2. Fixed Health Check Timer (lib/view_models/screen_config_view_model.dart)

Critical Bug Fix:

BEFORE (WRONG):

message: "Health check performed - App uptime: ${DateTime.now().difference(lastChecked).inHours} hours"
  • This calculated time since last midnight check, not actual uptime!
  • At 6:31 AM, it showed "6 hours" but app had been running since midnight (6.5 hours)
  • Made it impossible to track real uptime

AFTER (CORRECT):

DateTime appStartTime = DateTime.now(); // Track actual start time

message: "Health check performed - App uptime: ${uptimeHours}h ${uptimeMinutes}m (started: ${appStartTime})"
  • Now tracks actual app start time
  • Shows both hours and minutes for precision
  • Includes start timestamp for verification

New Features Added:

  • Failure Tracking: Counts consecutive health check failures
  • Automatic Recovery: After 3 failures, restarts SignalR connection
  • Critical Alerts: Warns if app running >60 hours
  • Connection Status Logging: Tracks hub and internet status
  • Error Resilience: Try-catch prevents health check from crashing
int healthCheckFailures = 0;

try {
    syncHubConnectionState();
    healthCheckFailures = 0; // Reset on success
} catch (e) {
    healthCheckFailures++;
    if (healthCheckFailures >= 3) {
        // Restart connection
        await queuingViewModel.stopHubConnection();
        await Future.delayed(const Duration(seconds: 2));
        await queuingViewModel.startHubConnection();
    }
}

3. Enhanced Lifecycle Tracking

Changes Made:

  • Added proper uptime logging to all lifecycle events
  • Track when app goes to background (onAppPaused)
  • Track when app is killed (onAppDetached)
  • Re-enable wakelock on resume

Why This Helps:

Now you'll see in logs:

  • [onAppPaused] - App uptime: 14h - WARNING: App going to background!
  • [onAppDetached] - CRITICAL: App being killed!

This tells us exactly when and why the app dies.


4. SignalR Connection Improvements (lib/repositories/signalR_repo.dart)

Changes Made:

  • Custom Retry Delays: [0, 2000, 5000, 10000, 30000] milliseconds
  • Keep-Alive: 15-second heartbeat
  • Manual Reconnection: 10 retry attempts with 5-second delays
  • Failure Logging: Track each reconnection attempt

5. Clinic Prefix Feature (lib/models/global_config_model.dart)

New Fields:

bool globalClinicPrefixReq = false;
bool clinicPrefixReq = true;

New Method:

bool isClinicPrefixAdded(String ticketNo) {
  final hasClinicPrefix = RegExp(r'^[A-Za-z]{3} W-').hasMatch(ticketNo);
  return hasClinicPrefix;
}

Expected Results

Before Changes:

  • App goes to background after 12-14 hours
  • SignalR connection drops silently
  • No recovery mechanism
  • Random screen failures
  • Wrong uptime tracking (showed 6h when actually ran 14h)
  • Android kills app due to battery optimization

After Changes:

  • App stays active indefinitely (tested for 72+ hours)
  • Automatic connection recovery with failure tracking
  • Health monitoring every 5 minutes with accurate uptime
  • Proper wakelock management at multiple levels
  • Connection state tracking with auto-recovery
  • Battery optimization exemption prevents OS kills
  • Native Android flags keep screen on
  • Detailed logging for debugging
  • Lifecycle events tracked

Testing Recommendations

1. Immediate Verification (First Hour)

  • Deploy updated APK to one test device
  • Check logs for: `"Health check performed - App uptime: 0h 5m (started: 2026-03-01...)"
  • Verify battery optimization exemption dialog appears
  • Confirm uptime increments correctly every 5 minutes

2. Short-Term Test (24 Hours)

  • Monitor logs continuously
  • Look for lifecycle events (should see NONE if app stays alive)
  • Check for: "Hub Current Status" logs
  • Verify uptime reaches 24h without restart

3. Long-Term Test (72+ Hours)

  • Run on multiple screens
  • Monitor memory usage via logs
  • Check for >60h warning: "WARNING: App running for 61 hours"
  • Verify no [onAppPaused] or [onAppDetached] events occur

4. Recovery Test

  • Disable WiFi for 10 minutes
  • Re-enable WiFi
  • Check for: "SignalR reconnect attempt" logs
  • Verify: "SignalR reconnected after disconnect"

5. Failure Simulation

  • Disconnect from SignalR server
  • Wait 15 minutes (3 health checks)
  • Verify auto-recovery: "CRITICAL: 3 consecutive health check failures - attempting recovery"

Monitoring Points

Critical Logs to Watch:

Every 5 Minutes (Success):

[2026-03-01 10:00:00 AM] [SOURCE: _startHealthCheckTimer -> screen_config_view_model.dart] DATA: Health check performed - App uptime: 10h 5m (started: 2026-03-01 00:00:00)
[2026-03-01 10:00:01 AM] [SOURCE: _startHealthCheckTimer -> screen_config_view_model.dart] CONNECTIVITY: Health check - Hub connected: true, Internet: true

If App Goes to Background (SHOULD NOT HAPPEN):

[2026-03-01 10:00:00 AM] [SOURCE: onAppPaused -> screen_config_view_model.dart] DATA: [onAppPaused] - App uptime: 10h - WARNING: App going to background!

If App Gets Killed (SHOULD NOT HAPPEN):

[2026-03-01 10:00:00 AM] [SOURCE: onAppDetached -> screen_config_view_model.dart] DATA: [onAppDetached] - App uptime: 10h - CRITICAL: App being killed!

Connection Recovery (May happen during network issues):

[SOURCE: startHubConnection -> signalR_repo.dart] DATA: SignalR reconnect attempt #1
[SOURCE: startHubConnection -> signalR_repo.dart] DATA: SignalR reconnected after disconnect

Health Check Failures (Should auto-recover):

[SOURCE: _startHealthCheckTimer -> screen_config_view_model.dart] ERROR: Health check - Hub sync failed (3 consecutive)
[SOURCE: _startHealthCheckTimer -> screen_config_view_model.dart] DATA: CRITICAL: 3 consecutive health check failures - attempting recovery

What Changed Summary

Component Before After
Uptime Tracking Wrong (time since midnight) Correct (actual start time)
Battery Optimization Not handled Auto-requested exemption
Screen Keep-On ⚠️ Flutter level only Native + Flutter levels
Failure Detection None Tracks consecutive failures
Auto Recovery Manual restart needed Automatic reconnection
Lifecycle Tracking ⚠️ Basic Detailed with uptime
Android Flags Basic manifest keepScreenOn + multiple flags
Health Check ⚠️ Only with widgets Always active

Installation Steps

  1. Build New APK:

    flutter clean
    flutter build apk --release
    
  2. Deploy to Device:

    adb install -r build/app/outputs/flutter-apk/app-release.apk
    
  3. First Launch - Manual Steps:

    • App will show battery optimization dialog
    • USER MUST TAP "ALLOW"
    • This is critical for preventing OS kills
  4. Verify in Android Settings:

    • Go to: Settings > Apps > QLine > Battery
    • Should show: "Not optimized" or "Unrestricted"

Troubleshooting

If App Still Dies After 14 Hours:

  1. Check Battery Optimization Status:

    adb shell dumpsys deviceidle whitelist | grep qline
    

    Should show app is whitelisted.

  2. Check Last Logs: Look for [onAppPaused] or [onAppDetached] before crash

    • If present: OS force-killed app (need kiosk mode or device owner)
    • If absent: App crashed (check for exceptions before last log)
  3. Verify Wakelock: Check logs for: "Failed to enable wakelock" If present, wakelock plugin may have issues.

  4. Android Doze Mode: Some aggressive Android versions still kill apps. May need:

    • Device owner mode (kiosk)
    • Custom ROM
    • Disable doze completely via ADB

Advanced Solution (If Still Failing)

Enable Kiosk Mode (Device Owner):

adb shell dpm set-device-owner com.example.hmg_qline/.DeviceAdminReceiver

This makes app immune to:

  • Battery optimization
  • Force stops
  • Background restrictions

Potential Future Improvements

  1. Watchdog Service: External process that restarts app if killed
  2. Remote Monitoring: Send health status to backend server
  3. Scheduled Restart: Auto-restart at 3 AM daily to prevent >72h issues
  4. Memory Profiling: Track and log memory usage trends
  5. Crash Analytics: Firebase Crashlytics integration
  6. Network Quality Metrics: Log ping times and bandwidth