Cleanup.

src/main/java/de/dennisguse/opentracks/settings/ActivityTypePreference.java

@@ -24,6 +24,7 @@ import android.widget.ArrayAdapter;
 import android.widget.AutoCompleteTextView;
 import android.widget.ImageView;
 
+import androidx.annotation.NonNull;
 import androidx.preference.DialogPreference;
 import androidx.preference.PreferenceDialogFragmentCompat;
 
@@ -71,7 +72,7 @@ public class ActivityTypePreference extends DialogPreference {
         }
 
         @Override
-        protected void onBindDialogView(View view) {
+        protected void onBindDialogView(@NonNull View view) {
             super.onBindDialogView(view);
 
             final Context context = getActivity();

src/main/java/de/dennisguse/opentracks/settings/DefaultsSettingsFragment.java

@@ -3,6 +3,7 @@ package de.dennisguse.opentracks.settings;
 import android.content.SharedPreferences;
 import android.os.Bundle;
 
+import androidx.annotation.NonNull;
 import androidx.fragment.app.DialogFragment;
 import androidx.preference.ListPreference;
 import androidx.preference.Preference;
@@ -48,7 +49,7 @@ public class DefaultsSettingsFragment extends PreferenceFragmentCompat implement
     }
 
     @Override
-    public void onDisplayPreferenceDialog(Preference preference) {
+    public void onDisplayPreferenceDialog(@NonNull Preference preference) {
         DialogFragment dialogFragment = null;
         if (preference instanceof ActivityTypePreference) {
             activityPreferenceDialog = ActivityTypePreference.ActivityPreferenceDialog.newInstance(preference.getKey());

src/main/java/de/dennisguse/opentracks/settings/bluetooth/BluetoothLeSensorPreference.java

@@ -17,6 +17,7 @@ import android.util.AttributeSet;
 import android.util.Log;
 import android.widget.Toast;
 
+import androidx.annotation.NonNull;
 import androidx.appcompat.app.AlertDialog;
 import androidx.preference.DialogPreference;
 import androidx.preference.PreferenceDialogFragmentCompat;
@@ -234,7 +235,7 @@ public abstract class BluetoothLeSensorPreference extends DialogPreference {
 
         //Behave like ListPreferenceDialogFragmentCompat, but uses a custom listAdapter.
         @Override
-        protected void onPrepareDialogBuilder(AlertDialog.Builder builder) {
+        protected void onPrepareDialogBuilder(@NonNull AlertDialog.Builder builder) {
             super.onPrepareDialogBuilder(builder);
 
             builder.setSingleChoiceItems(listAdapter, selectedEntryIndex,