Barometer: use sensor aggregator.

Part of #1424.

src/main/java/de/dennisguse/opentracks/sensors/GainManager.java

@@ -0,0 +1,46 @@
+package de.dennisguse.opentracks.sensors;
+
+import android.content.Context;
+import android.os.Handler;
+import android.util.Log;
+
+import de.dennisguse.opentracks.data.models.AtmosphericPressure;
+import de.dennisguse.opentracks.sensors.driver.BarometerInternal;
+import de.dennisguse.opentracks.sensors.sensorData.AggregatorBarometer;
+import de.dennisguse.opentracks.sensors.sensorData.Raw;
+
+/**
+ * Estimates the altitude gain and altitude loss using the device's pressure sensor (i.e., barometer).
+ */
+public class GainManager implements SensorConnector {
+
+    private static final String TAG = GainManager.class.getSimpleName();
+
+    private final BarometerInternal driver;
+
+    private final SensorManager.SensorDataChangedObserver listener;
+
+    public GainManager(SensorManager.SensorDataChangedObserver listener) {
+        this.listener = listener;
+        driver = new BarometerInternal();
+    }
+
+    public void start(Context context, Handler handler) {
+        driver.connect(context, handler, this);
+
+        if (driver.isConnected()) {
+            listener.onConnect(new AggregatorBarometer("internal"));
+        }
+    }
+
+    public void stop(Context context) {
+        Log.d(TAG, "Stop");
+
+        driver.disconnect(context);
+        listener.onDisconnect(new AggregatorBarometer("internal"));
+    }
+
+    public void onSensorValueChanged(AtmosphericPressure currentSensorValue) {
+        listener.onChange(new Raw<>(currentSensorValue));
+    }
+}