Add logic for calibration process to app

Signed-off-by: Severin Kaderli <severin@kaderli.dev>

src/MagSend/app/src/main/java/dev/kaderli/magsend/BaseSensorActivity.kt

@@ -0,0 +1,21 @@
+package dev.kaderli.magsend
+
+import android.content.Context
+import android.hardware.Sensor
+import android.hardware.SensorEventListener
+import android.hardware.SensorManager
+import android.os.Bundle
+
+abstract class BaseSensorActivity : BaseActivity(), SensorEventListener {
+  private lateinit var sensorManager: SensorManager;
+  private lateinit var sensor: Sensor;
+
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+    sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
+    sensor = sensorManager.getDefaultSensor(Sensor.TYPE_MAGNETIC_FIELD);
+    sensorManager.registerListener(this, sensor, SensorManager.SENSOR_DELAY_UI);
+  }
+
+  override fun onAccuracyChanged(sensor: Sensor?, accuracy: Int) {}
+}

src/MagSend/app/src/main/java/dev/kaderli/magsend/CalibrationActivity.kt

@@ -1,7 +1,23 @@
 package dev.kaderli.magsend
 
-class CalibrationActivity : BaseActivity() {
+import android.hardware.SensorEvent
+import android.os.Bundle
+import android.widget.TextView
+
+class CalibrationActivity : BaseSensorActivity() {
+  private lateinit var calibrationValue: TextView
+
+  override fun onCreate(savedInstanceState: Bundle?) {
+    super.onCreate(savedInstanceState)
+    calibrationValue = findViewById(R.id.calibrationValue)
+    calibrationValue.text = getString(R.string.calibration_value, 0f)
+  }
+
   override fun getLayoutId(): Int {
     return R.layout.activity_calibration
   }
+
+  override fun onSensorChanged(event: SensorEvent) {
+    calibrationValue.text = getString(R.string.calibration_value, event.values[0])
+  }
 }

src/MagSend/app/src/main/res/layout/activity_calibration.xml

@@ -22,7 +22,6 @@
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:layout_marginTop="@dimen/component_spacing"
-    android:text="82µT "
     android:textSize="48sp"
     app:layout_constraintEnd_toEndOf="parent"
     app:layout_constraintStart_toStartOf="parent"

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

@@ -10,4 +10,5 @@
   <string name="restart_button_label">Restart</string>
   <string name="calibration_activity_label">Calibration</string>
   <string name="receive_activity_label">Receive</string>
+  <string name="calibration_value">%1$.2f µT</string>
 </resources>