Keep measuring in the background (opt-in setting)

app/src/androidTest/java/de/rwth_aachen/phyphox/BleCompatConnectTest.java

@@ -116,7 +116,7 @@ public void theDeviceOffersItsExperimentAndItLoads() throws Exception {
                 experiment.experiment.loaded);
 
         assertFalse("the experiment must be left for the host to start, not started here",
-                experiment.measuring);
+                experiment.isMeasuring());
 
         //Instrumentation runs in the app's process: returning kills the remote server the host needs.
         if (holdForHost)

app/src/androidTest/java/de/rwth_aachen/phyphox/ViewBehaviorTest.java

@@ -270,7 +270,7 @@ public void aNanIsReplacedByTheDefault() throws Exception {
             assertBuffer("dropdown_nan", 2);
             assertBuffer("edit_nan", 12);
             assertBuffer("slider_nan", 3);
-            assertTrue("replacing a NaN started the experiment", !activity.measuring);
+            assertTrue("replacing a NaN started the experiment", !activity.isMeasuring());
         } finally {
             FixtureExperiment.close(activity);
         }

app/src/main/AndroidManifest.xml

@@ -20,6 +20,13 @@
     <uses-permission android:name="android.permission.SCHEDULE_EXACT_ALARM" />
     <uses-permission android:name="android.permission.FLASHLIGHT" />
     <uses-permission android:name="android.permission.ACCESS_LOCAL_NETWORK" />
+    <!-- Measuring in the background (MeasurementService): the foreground service, one permission per declared type, and its notification -->
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_SPECIAL_USE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_LOCATION" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_MICROPHONE" />
+    <uses-permission android:name="android.permission.FOREGROUND_SERVICE_CONNECTED_DEVICE" />
+    <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
 
     <uses-feature android:glEsVersion="0x00020000" android:required="true" />
     <uses-feature android:name="android.hardware.camera" android:required="false" />
@@ -121,6 +128,15 @@
                 android:name="autoStoreLocales"
                 android:value="true" />
         </service>
+        <!-- Declares every type a measurement might need; the service only requests the ones the loaded experiment uses -->
+        <service
+            android:name="de.rwth_aachen.phyphox.MeasurementService"
+            android:exported="false"
+            android:foregroundServiceType="specialUse|location|microphone|connectedDevice">
+            <property
+                android:name="android.app.PROPERTY_SPECIAL_USE_FGS_SUBTYPE"
+                android:value="Continue a running sensor measurement of a physics experiment while the app is in the background" />
+        </service>
     </application>
     <queries>
         <!-- Opening web links -->

app/src/main/java/de/rwth_aachen/phyphox/Bluetooth/Bluetooth.kt

@@ -33,6 +33,7 @@ import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.runBlocking
 import java.io.Serializable
+import java.lang.ref.WeakReference
 import java.nio.ByteBuffer
 import java.util.UUID
 import java.util.Vector
@@ -154,6 +155,17 @@ open class Bluetooth(
 
     private val connectedDeviceInformation = ConnectedDeviceInfo()
 
+    //The experiment screen showing this device's battery and signal strength. Weak: a run may outlive its screen.
+    @Transient
+    @JvmField
+    var connectedDeviceDelegate: WeakReference<UpdateConnectedDeviceDelegate>? = null
+
+    //The experiment screen that carries out this device's commands, the one showing its run (not the activity that
+    // loaded it, which may be gone). Weak for the same reason.
+    @Transient
+    @JvmField
+    var commandDelegate: WeakReference<BluetoothCommandDelegate>? = null
+
     @Transient
     private var lastToastShown = 0L
 
@@ -552,7 +564,7 @@ open class Bluetooth(
     private fun updateConnectedDeviceInfo(rssi: Int) {
         connectedDeviceInformation.signalStrength = rssi
         mainHandler.post {
-            Experiment.updateConnectedDeviceDelegate?.updateConnectedDevice(arrayListOf(connectedDeviceInformation))
+            connectedDeviceDelegate?.get()?.updateConnectedDevice(arrayListOf(connectedDeviceInformation))
         }
     }
 
@@ -609,15 +621,15 @@ open class Bluetooth(
             Log.w(TAG, "Could not subscribe to the command characteristic")
     }
 
-    //A notification on the command characteristic. The activity carries the command out like a tap on
+    //A notification on the command characteristic. The screen carries the command out like a tap on
     // the corresponding button; an unknown command is ignored by contract so newer devices stay harmless.
     internal fun handleCommand(data: ByteArray) {
         val command = BluetoothCommand.decode(data)
         if (command == null) {
             Log.d(TAG, "Ignoring unknown command from $deviceName: " + (data.firstOrNull()?.let { "0x%02x".format(it.toInt() and 0xff) } ?: "empty"))
             return
         }
-        (activity as? BluetoothCommandDelegate)?.onBluetoothCommand(command, this)
+        commandDelegate?.get()?.onBluetoothCommand(command, this)
     }
 
     /** Attributes of a characteristic as defined in the phyphox file */