Fix unattended boot auto-launch
Plain startActivity() from BootReceiver (and even from a foreground service) gets blocked as a background activity start and the process gets reclaimed before becoming visible. Switch to a full-screen-intent notification (the mechanism alarm/call apps use), which needs USE_FULL_SCREEN_INTENT + POST_NOTIFICATIONS granted, plus setShowWhenLocked/setTurnScreenOn on MainActivity so it displays over the lock screen. Confirmed working on an untouched real-device reboot.
This commit is contained in:
@@ -22,11 +22,19 @@ targetSdk 37.
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- `SettingsActivity.kt` — countdown seconds + command line, persisted in
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`SharedPreferences` (`slocker_launcher_prefs`), defaults `60` /
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`sleep 180`.
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- `BootReceiver.kt` — on `BOOT_COMPLETED`, starts `KioskBootService`
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(**not** `startActivity()` directly — see Known issues).
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- `KioskBootService.kt` — minimal foreground service
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(`foregroundServiceType="specialUse"`) that calls `startForeground()`
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then launches `MainActivity`, then `stopSelf()`.
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- `BootReceiver.kt` — on `BOOT_COMPLETED`, starts `KioskBootService`.
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- `KioskBootService.kt` — foreground service
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(`foregroundServiceType="specialUse"`) that posts a full-screen-intent
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notification (`IMPORTANCE_HIGH` channel) targeting `MainActivity`, then
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`stopSelf()`s after a short delay. This is deliberately **not** a plain
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`startActivity()` call from the receiver/service — see the note below
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on why.
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- `MainActivity.onCreate()` also calls `setShowWhenLocked(true)` +
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`setTurnScreenOn(true)` (API 27+) so it can display over the lock
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screen, and opportunistically requests `POST_NOTIFICATIONS` at runtime
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(needed for the full-screen intent above to fire on API 33+; can only
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be requested from an Activity, so this only takes effect starting the
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*next* boot after a manual open grants it).
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## Build & install
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@@ -48,16 +56,26 @@ Debug-signed APK is fine for sideloading; no release signing config exists.
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Magisk) — the actual deployment target. Full pipeline (boot → kiosk →
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`su` via Magisk → `bwrap` → `tmux` → `sshd`) verified working here.
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## Known issues
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## Why boot-launch works the way it does
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- **Boot auto-launch stalls behind the lock screen.** On a genuinely
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untouched reboot, `MainActivity` starts but stays paused/unresumed
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(`onResume()`, where the countdown starts, never fires) until the user
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manually unlocks and switches to it. Likely needs
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`Activity.setShowWhenLocked(true)` + `setTurnScreenOn(true)` in
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`onCreate()` so it displays and resumes over the lock screen. Diagnosed,
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not yet fixed.
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- Manifest declares `POST_NOTIFICATIONS` but nothing requests it at
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runtime; `KioskBootService`'s notification may silently not display on
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API 33+ without it (the foreground-service priority itself still
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applies regardless).
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Getting auto-launch to actually run unattended after a real (not
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manually-touched) reboot took three iterations, each diagnosed from
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`adb logcat -d | grep -i slockerlauncher` after an untouched reboot —
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worth reading before changing this path:
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1. Calling `startActivity()` straight from `BootReceiver` gets logged by
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`ActivityTaskManager` as a blocked "Background activity start" and the
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process gets killed by `lmkd` ~2s later, before ever becoming visible.
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2. Routing through a foreground service (`KioskBootService`) is
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**necessary but not sufficient** — on this device/OS,
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`startActivity()` from a genuinely-`FOREGROUND_SERVICE` process was
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*still* logged as a blocked background start.
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3. The mechanism Android actually exempts for this is a
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**full-screen-intent notification** (same one alarm/call apps use) —
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needs `USE_FULL_SCREEN_INTENT` (manifest, normal/auto-granted) *and*
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`POST_NOTIFICATIONS` (runtime, API 33+) both granted, or the intent
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silently never fires.
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Confirmed working end to end on the real device (Galaxy A71, Android 13):
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untouched reboot → full-screen-intent notification → `MainActivity`
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resumes on its own → kiosk black screen → configured `su -c` command.
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@@ -6,6 +6,7 @@
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<uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
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<uses-permission android:name="android.permission.FOREGROUND_SERVICE_SPECIAL_USE" />
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<uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
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<uses-permission android:name="android.permission.USE_FULL_SCREEN_INTENT" />
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<application
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android:allowBackup="true"
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@@ -1,20 +1,33 @@
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package ro.ceamac.slockerlauncher
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import android.app.Notification
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import android.app.NotificationChannel
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import android.app.NotificationManager
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import android.app.PendingIntent
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import android.app.Service
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import android.content.Intent
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import android.os.Build
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import android.os.Handler
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import android.os.IBinder
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import android.os.Looper
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import androidx.core.app.NotificationCompat
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import androidx.core.app.NotificationManagerCompat
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/**
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* A boot-triggered launch of MainActivity directly from BroadcastReceiver.onReceive()
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* was logged by ActivityTaskManager as a "Background activity start" and the process
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* was killed by lmkd ~2s later (oom_score_adj 925, i.e. still treated as background)
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* before ever becoming visible. Routing through a foreground service first gives the
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* process foreground priority and is a documented exemption for starting an activity
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* from the background.
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* was killed by lmkd ~2s later before ever becoming visible.
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*
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* Routing through a foreground service alone was NOT enough on this device (Samsung,
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* Android 13): logcat showed the startActivity() call still logged as a blocked
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* "Background activity start" (allowBackgroundActivityStart: false) even while the
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* calling process was genuinely in FOREGROUND_SERVICE state. The mechanism Android
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* actually exempts for "show full-screen UI immediately, even from background/locked"
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* is a full-screen-intent notification (what alarm/incoming-call apps use) — that goes
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* through a different code path in ActivityTaskManager than a plain startActivity().
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*
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* Needs POST_NOTIFICATIONS granted (requested at runtime from MainActivity) — without
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* it, notify() is silently dropped and the full-screen intent never fires.
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*/
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class KioskBootService : Service() {
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@@ -22,31 +35,61 @@ class KioskBootService : Service() {
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override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
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val channel = NotificationChannel(
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CHANNEL_ID,
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getString(R.string.app_name),
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NotificationManager.IMPORTANCE_LOW
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val nm = getSystemService(NotificationManager::class.java)
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nm.createNotificationChannel(
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NotificationChannel(
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FOREGROUND_CHANNEL_ID,
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getString(R.string.app_name),
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NotificationManager.IMPORTANCE_LOW
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)
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)
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// Full-screen intents require an IMPORTANCE_HIGH channel to actually fire.
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nm.createNotificationChannel(
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NotificationChannel(
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FULLSCREEN_CHANNEL_ID,
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getString(R.string.app_name),
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NotificationManager.IMPORTANCE_HIGH
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)
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)
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getSystemService(NotificationManager::class.java).createNotificationChannel(channel)
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}
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val notification = NotificationCompat.Builder(this, CHANNEL_ID)
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.setContentTitle(getString(R.string.app_name))
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.setContentText("Starting…")
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.setSmallIcon(android.R.drawable.ic_lock_idle_lock)
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.setPriority(NotificationCompat.PRIORITY_LOW)
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.build()
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startForeground(NOTIFICATION_ID, notification)
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startForeground(
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FOREGROUND_NOTIFICATION_ID,
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NotificationCompat.Builder(this, FOREGROUND_CHANNEL_ID)
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.setContentTitle(getString(R.string.app_name))
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.setContentText("Starting…")
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.setSmallIcon(android.R.drawable.ic_lock_idle_lock)
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.setPriority(NotificationCompat.PRIORITY_LOW)
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.build()
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)
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val launchIntent = Intent(this, MainActivity::class.java)
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.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
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startActivity(launchIntent)
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val pendingIntent = PendingIntent.getActivity(
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this, 0, launchIntent, PendingIntent.FLAG_UPDATE_CURRENT or PendingIntent.FLAG_IMMUTABLE
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)
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val fullScreenNotification = NotificationCompat.Builder(this, FULLSCREEN_CHANNEL_ID)
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.setContentTitle(getString(R.string.app_name))
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.setContentText("Starting…")
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.setSmallIcon(android.R.drawable.ic_lock_idle_lock)
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.setPriority(NotificationCompat.PRIORITY_HIGH)
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.setCategory(Notification.CATEGORY_ALARM)
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.setFullScreenIntent(pendingIntent, true)
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.setContentIntent(pendingIntent)
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.setAutoCancel(true)
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.build()
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NotificationManagerCompat.from(this).notify(FULLSCREEN_NOTIFICATION_ID, fullScreenNotification)
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stopSelf()
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// Keep the foreground-service protection window open briefly so the process
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// doesn't get reclaimed before the full-screen intent actually lands.
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Handler(Looper.getMainLooper()).postDelayed({ stopSelf() }, 2000L)
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return START_NOT_STICKY
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}
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companion object {
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const val CHANNEL_ID = "slocker_launcher_boot"
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const val NOTIFICATION_ID = 1
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const val FOREGROUND_CHANNEL_ID = "slocker_launcher_boot"
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const val FULLSCREEN_CHANNEL_ID = "slocker_launcher_fullscreen"
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const val FOREGROUND_NOTIFICATION_ID = 1
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const val FULLSCREEN_NOTIFICATION_ID = 2
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}
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}
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@@ -1,12 +1,17 @@
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package ro.ceamac.slockerlauncher
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import android.Manifest
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import android.content.Intent
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import android.content.SharedPreferences
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import android.content.pm.PackageManager
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import android.os.Build
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import android.os.Bundle
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import android.os.CountDownTimer
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import android.view.View
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import android.view.WindowManager
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import androidx.appcompat.app.AppCompatActivity
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import androidx.core.app.ActivityCompat
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import androidx.core.content.ContextCompat
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import androidx.core.view.WindowCompat
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import androidx.core.view.WindowInsetsCompat
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import androidx.core.view.WindowInsetsControllerCompat
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@@ -23,6 +28,18 @@ class MainActivity : AppCompatActivity() {
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override fun onCreate(savedInstanceState: Bundle?) {
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super.onCreate(savedInstanceState)
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// Boot-launched via KioskBootService: without this, the activity is created
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// but stays behind the lock screen (never resumed, countdown never starts)
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// until the user manually unlocks and switches to it.
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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O_MR1) {
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setShowWhenLocked(true)
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setTurnScreenOn(true)
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} else {
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window.addFlags(
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WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED or
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WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON
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)
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}
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binding = ActivityMainBinding.inflate(layoutInflater)
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setContentView(binding.root)
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prefs = getSharedPreferences(PREFS_NAME, MODE_PRIVATE)
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@@ -32,6 +49,18 @@ class MainActivity : AppCompatActivity() {
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startActivity(Intent(this, SettingsActivity::class.java))
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}
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binding.exitButton.setOnClickListener { finishAndRemoveTask() }
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// Needed for KioskBootService's full-screen-intent boot notification to fire on
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// API 33+; can only be requested from an Activity, not a receiver/service, so this
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// opportunistic ask (once, on manual open) is what makes the next auto-boot work.
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if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.TIRAMISU &&
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ContextCompat.checkSelfPermission(this, Manifest.permission.POST_NOTIFICATIONS)
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!= PackageManager.PERMISSION_GRANTED
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) {
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ActivityCompat.requestPermissions(
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this, arrayOf(Manifest.permission.POST_NOTIFICATIONS), 1
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)
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}
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}
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override fun onResume() {
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Reference in New Issue
Block a user