Android: UsageStatsManager not returning correct daily results

I agree with what is said in that comment you mentioned about queryUsageStats not being a trusted source. I've been with playing with the UsageStatsManager for a little while and it returns inconsistent results based on the time of day. I have found that using the UsageEvents and manually calculating the necessary info to be much more trustworthy (at least for daily stats), as they are points in time and don't have any weird calculating errors that would produce different outputs for the same input depending on the time of day.

I used @Vishal's proposed solution to come up with my own:

/**
 * Returns the stats for the [date] (defaults to today) 
 */
fun getDailyStats(date: LocalDate = LocalDate.now()): List<Stat> {
    // The timezones we'll need 
    val utc = ZoneId.of("UTC")
    val defaultZone = ZoneId.systemDefault()

    // Set the starting and ending times to be midnight in UTC time
    val startDate = date.atStartOfDay(defaultZone).withZoneSameInstant(utc)
    val start = startDate.toInstant().toEpochMilli()
    val end = startDate.plusDays(1).toInstant().toEpochMilli()

    // This will keep a map of all of the events per package name 
    val sortedEvents = mutableMapOf<String, MutableList<UsageEvents.Event>>()

    // Query the list of events that has happened within that time frame
    val systemEvents = usageManager.queryEvents(start, end)
    while (systemEvents.hasNextEvent()) {
        val event = UsageEvents.Event()
        systemEvents.getNextEvent(event)

        // Get the list of events for the package name, create one if it doesn't exist
        val packageEvents = sortedEvents[event.packageName] ?: mutableListOf()
        packageEvents.add(event)
        sortedEvents[event.packageName] = packageEvents
    }

    // This will keep a list of our final stats
    val stats = mutableListOf<Stat>()

    // Go through the events by package name
    sortedEvents.forEach { packageName, events ->
        // Keep track of the current start and end times
        var startTime = 0L
        var endTime = 0L
        // Keep track of the total usage time for this app
        var totalTime = 0L
        // Keep track of the start times for this app 
        val startTimes = mutableListOf<ZonedDateTime>()
        events.forEach {
            if (it.eventType == UsageEvents.Event.MOVE_TO_FOREGROUND) {
                // App was moved to the foreground: set the start time
                startTime = it.timeStamp
                // Add the start time within this timezone to the list
                startTimes.add(Instant.ofEpochMilli(startTime).atZone(utc)
                        .withZoneSameInstant(defaultZone))
            } else if (it.eventType == UsageEvents.Event.MOVE_TO_BACKGROUND) {
                // App was moved to background: set the end time
                endTime = it.timeStamp
            }

            // If there's an end time with no start time, this might mean that
            //  The app was started on the previous day, so take midnight 
            //  As the start time 
            if (startTime == 0L && endTime != 0L) {
                startTime = start
            }

            // If both start and end are defined, we have a session
            if (startTime != 0L && endTime != 0L) {
                // Add the session time to the total time
                totalTime += endTime - startTime
                // Reset the start/end times to 0
                startTime = 0L
                endTime = 0L
            }
        }

        // If there is a start time without an end time, this might mean that
        //  the app was used past midnight, so take (midnight - 1 second) 
        //  as the end time
        if (startTime != 0L && endTime == 0L) {
            totalTime += end - 1000 - startTime
        }
        stats.add(Stat(packageName, totalTime, startTimes))
    }
    return stats
}

// Helper class to keep track of all of the stats 
class Stat(val packageName: String, val totalTime: Long, val startTimes: List<ZonedDateTime>)

A couple of observations:

• The timestamps that the Events have are in UTC, which is why I convert my start/end query times to UTC from my default time zone, and why I convert the start time back on each event. This one got me for a while...
• This takes into account the edge cases where an app was in the foreground before the beginning of the day (i.e. the user opened an app before midnight) or went to the background after the end of the say (i.e. the user still had an app in the foreground past 11:59 PM on that day). Disclaimer: I haven't actually tested these edge cases yet.
• In the case that the user uses an app past midnight, I opted with using 11:59:59 PM as the end time. You can obviously change this to be 1 millisecond off of midnight, or simply midnight depending on how you choose to calculate this. Simply remove the - 1000 and replace with whatever you want.
• In my use case I needed total foreground time + start times, which is why I collect that information. However, you can tweak the Stat class and the code to capture whatever info you need. You can keep track of end times, or number of times an app was launched in a day if needed for example.
• I am using the Java 8 time library here because it was easier to deal with dates. To use this in Android, I use the ThreeTenABP library.

I hope this helps!

I have quiet the same problem and also opened a issue with Google for this. Please have a look at https://issuetracker.google.com/issues/118564471 if this corresponds to what you are describing.