Add keepalive service

pretixprint/app/src/main/AndroidManifest.xml

@@ -124,6 +124,12 @@
                 <action android:name="eu.pretix.pretixpos.print.PRINT_RECEIPT" />
             </intent-filter>
         </service>
+        <service
+            android:name=".print.KeepaliveService"
+            android:enabled="true"
+            android:exported="false"
+            android:foregroundServiceType="connectedDevice">
+        </service>
 
         <meta-data android:name="io.sentry.dsn" android:value="${SENTRY_DSN}" />
         <meta-data android:name="io.sentry.auto-session-tracking.enable" android:value="false" />

pretixprint/app/src/main/java/eu/pretix/pretixprint/print/KeepaliveService.kt

@@ -0,0 +1,83 @@
+package eu.pretix.pretixprint.print
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.app.Service
+import android.content.Context
+import android.content.Intent
+import android.os.Build
+import android.os.IBinder
+import androidx.core.app.NotificationCompat
+import eu.pretix.pretixprint.R
+import eu.pretix.pretixprint.ui.SettingsActivity
+
+class KeepaliveService : Service() {
+
+    companion object {
+        val CHANNEL_ID = "pretixprint_keepalive_channel"
+        val ONGOING_NOTIFICATION_ID = 43
+
+        fun start(context: Context) {
+            val intent = Intent(context, KeepaliveService::class.java)
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+                context.startForegroundService(intent)
+            } else {
+                context.startService(intent)
+            }
+        }
+    }
+
+    private fun _startForeground() {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
+            val channel = NotificationChannel(
+                CHANNEL_ID,
+                getString(R.string.notification_channel_keepalive),
+                NotificationManager.IMPORTANCE_LOW
+            )
+            channel.description = getString(R.string.notification_channel_keepalive_description)
+            channel.setSound(null, null)
+            channel.enableVibration(false)
+            getSystemService(NotificationManager::class.java).createNotificationChannel(channel)
+        }
+
+        val startBaseActivity = Intent(this, SettingsActivity::class.java)
+        startBaseActivity.action = Intent.ACTION_MAIN
+        startBaseActivity.addCategory(Intent.CATEGORY_LAUNCHER)
+        startBaseActivity.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
+
+        val keepAliveNotification: Notification =
+            NotificationCompat.Builder(this, CHANNEL_ID)
+                .setContentTitle(getString(R.string.keepalive_notification))
+                .setSmallIcon(R.drawable.ic_stat_print)
+                .setContentIntent(
+                    PendingIntent.getActivity(
+                        this,
+                        0,
+                        startBaseActivity,
+                        if (Build.VERSION.SDK_INT >= 23) {
+                            PendingIntent.FLAG_IMMUTABLE
+                        } else {
+                            0
+                        }
+                    )
+                )
+                .build()
+        this.startForeground(ONGOING_NOTIFICATION_ID, keepAliveNotification)
+    }
+
+    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {
+        _startForeground()
+        return START_NOT_STICKY
+    }
+
+    override fun onBind(p0: Intent?): IBinder? {
+        TODO("Not yet implemented")
+    }
+
+    override fun onCreate() {
+        super.onCreate()
+        _startForeground()
+    }
+}

pretixprint/app/src/main/java/eu/pretix/pretixprint/print/PrintService.kt

@@ -10,6 +10,7 @@ import android.os.Build.VERSION.SDK_INT
 import android.os.Bundle
 import android.os.ResultReceiver
 import android.util.Log
+import androidx.annotation.Keep
 import androidx.core.app.NotificationCompat
 import androidx.core.app.NotificationManagerCompat
 import androidx.preference.PreferenceManager
@@ -38,6 +39,7 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
     }
 
     private fun createNotificationChannel() {
+        Log.i("PrintService", "createNotificationChannel()")
         // Create the NotificationChannel, but only on API 26+ because
         // the NotificationChannel class is new and not in the support library
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
@@ -52,6 +54,7 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
     }
 
     private fun startForegroundNotification() {
+        Log.i("PrintService", "startForegroundNotification()")
         createNotificationChannel()
         val notificationIntent = Intent(this, SettingsActivity::class.java)
         val pendingIntent = PendingIntent.getActivity(this, 0, notificationIntent,
@@ -61,10 +64,12 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
                     .setContentIntent(pendingIntent)
                     .setSmallIcon(R.drawable.ic_stat_print)
                     .build()
+        Log.i("PrintService", "startForeground()")
         startForeground(ONGOING_NOTIFICATION_ID, notification)
     }
 
     private fun logException(e: Throwable) {
+        Log.i("PrintService", "logException()")
         try {
             val log = File.createTempFile("error_", ".log", this.cacheDir)
             val fw = FileWriter(log)
@@ -79,6 +84,7 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
     }
 
     private fun print(intent: Intent, rr: ResultReceiver?) {
+        Log.i("PrintService", "print()")
         val prefs = PreferenceManager.getDefaultSharedPreferences(applicationContext)
         val type = getType(intent.action!!)
 
@@ -296,7 +302,12 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
         }
     }
 
+    override fun onCreate() {
+        super.onCreate()
+    }
+
     override fun onHandleIntent(intent: Intent?) {
+        Log.i("PrintService", "onHandleIntent()")
         var rr: ResultReceiver? = null
         if (intent!!.hasExtra("resultreceiver")) {
             rr = intent.getParcelableExtra<ResultReceiver>("resultreceiver")!! as ResultReceiver
@@ -305,6 +316,7 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
         startForegroundNotification()
 
         if (intent.action == ACTION_STOP_SERVICE) {
+            Log.i("PrintService", "stopForeground()")
             stopForeground(true)
             stopSelf()
             return
@@ -336,6 +348,11 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
         val prefs = PreferenceManager.getDefaultSharedPreferences(applicationContext)
         val type = getType(intent.action!!)
         val connection = prefs.getString("hardware_${type}printer_connection", "network_printer")
+
+        if (prefs.getBoolean("keepalive_service", false)) {
+            KeepaliveService.start(this)
+        }
+
         if (connection == "system") {
             // stop the foreground service, but keep the notification
             if (SDK_INT >= Build.VERSION_CODES.N) {
@@ -344,6 +361,7 @@ abstract class AbstractPrintService(name: String) : IntentService(name) {
                 stopForeground(false)
             }
         } else {
+            Log.i("PrintService", "stopForeground()")
             stopForeground(true)
         }
     }

pretixprint/app/src/main/java/eu/pretix/pretixprint/ui/Settings.kt

@@ -35,6 +35,7 @@ import eu.pretix.pretixprint.R
 import eu.pretix.pretixprint.connections.IMinInternalConnection
 import eu.pretix.pretixprint.connections.SunmiInternalConnection
 import eu.pretix.pretixprint.connections.SystemConnection
+import eu.pretix.pretixprint.print.KeepaliveService
 import eu.pretix.pretixprint.print.testPrint
 import io.sentry.Sentry
 import kotlinx.coroutines.CoroutineScope
@@ -371,6 +372,14 @@ class SettingsActivity : AppCompatActivity() {
             .beginTransaction()
             .replace(R.id.content, SettingsFragment())
             .commit()
+
+        if (prefs.getBoolean("keepalive_service", false)) {
+            try {
+                KeepaliveService.start(this)
+            } catch (e: IllegalStateException) {
+                e.printStackTrace()
+            }
+        }
     }
 
     override fun onRequestPermissionsResult(

pretixprint/app/src/main/res/values/strings.xml

@@ -19,6 +19,11 @@
     <string name="settings_label_driver">Driver</string>
     <string name="settings_label_security">Security</string>
     <string name="dismiss">Close</string>
+    <string name="notification_channel_keepalive">Service is running</string>
+    <string name="notification_channel_keepalive_description">Shows a notification when the service is running</string>
+    <string name="keepalive_notification">pretixPRINT is running</string>
+    <string name="keepalive_service">Run keepalive service</string>
+    <string name="keepalive_service_description">Workaround to avoid the app being killed on low-powered devices.</string>
     <string name="notification_channel_print">Print jobs</string>
     <string name="notification_channel_print_description">Shows a notification during a print job</string>
     <string name="print_now_notification">Print prepared. Touch to open print dialog</string>

pretixprint/app/src/main/res/xml/preferences.xml

@@ -52,6 +52,11 @@
             android:key="pref_pin"
             android:title="@string/pin_protection_pin"
             android:summary="@string/pin_protection_description" />
+        <CheckBoxPreference
+            android:defaultValue="false"
+            android:key="keepalive_service"
+            android:title="@string/keepalive_service"
+            android:summary="@string/keepalive_service_description" />
     </PreferenceCategory>
 
     <PreferenceCategory android:title="@string/settings_label_about">