Удаление юнит-тестов (они пока что не нужны), добавление ActionBar в SettingsActivity (с помощью класса AppCompatPreferenceActivity).

app/build.gradle

@@ -16,7 +16,7 @@ android {
             proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
         }
     }
-    buildToolsVersion '27.0.3'
+    buildToolsVersion '28.0.3'
 }
 
 dependencies {

app/src/androidTest/java/ru/volgorobot/vrcatalog/ExampleInstrumentedTest.java

@@ -1,26 +0,0 @@
-package ru.volgorobot.vrcatalog;
-
-import android.content.Context;
-import android.support.test.InstrumentationRegistry;
-import android.support.test.runner.AndroidJUnit4;
-
-import org.junit.Test;
-import org.junit.runner.RunWith;
-
-import static org.junit.Assert.*;
-
-/**
- * Instrumented test, which will execute on an Android device.
- *
- * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
- */
-@RunWith(AndroidJUnit4.class)
-public class ExampleInstrumentedTest {
-    @Test
-    public void useAppContext() {
-        // Context of the app under test.
-        Context appContext = InstrumentationRegistry.getTargetContext();
-
-        assertEquals("ru.volgorobot.vrcatalog", appContext.getPackageName());
-    }
-}

app/src/main/java/ru/volgorobot/vrcatalog/SettingsActivity.java

@@ -1,23 +1,19 @@
 package ru.volgorobot.vrcatalog;
 
-import android.support.v7.app.AppCompatActivity;
 import android.os.Bundle;
-import android.support.v7.app.AppCompatDelegate;
 import android.view.Menu;
 import android.view.MenuItem;
-import android.preference.PreferenceActivity;
+import ru.volgorobot.vrcatalog.additional.AppCompatPreferenceActivity;
 
-public class SettingsActivity extends PreferenceActivity {
+public class SettingsActivity extends AppCompatPreferenceActivity {
-
-    private AppCompatDelegate mDelegate;
 
     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         addPreferencesFromResource(R.xml.activity_settings);
 
-        //getActionBar().setDisplayHomeAsUpEnabled(true);
+        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
-        //getActionBar().setHomeButtonEnabled(true);
+        getSupportActionBar().setHomeButtonEnabled(true);
     }
 
     @Override

app/src/main/java/ru/volgorobot/vrcatalog/additional/AppCompatPreferenceActivity.java

@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package ru.volgorobot.vrcatalog.additional;
+import android.content.res.Configuration;
+import android.os.Bundle;
+import android.preference.PreferenceActivity;
+import android.support.annotation.LayoutRes;
+import android.support.annotation.Nullable;
+import android.support.v7.app.ActionBar;
+import android.support.v7.app.AppCompatDelegate;
+import android.support.v7.widget.Toolbar;
+import android.view.MenuInflater;
+import android.view.View;
+import android.view.ViewGroup;
+
+/**
+ * A {@link android.preference.PreferenceActivity} which implements and proxies the necessary calls
+ * to be used with AppCompat.
+ *
+ * This technique can be used with an {@link android.app.Activity} class, not just
+ * {@link android.preference.PreferenceActivity}.
+ */
+
+public abstract class AppCompatPreferenceActivity extends PreferenceActivity {
+    private AppCompatDelegate mDelegate;
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        getDelegate().installViewFactory();
+        getDelegate().onCreate(savedInstanceState);
+        super.onCreate(savedInstanceState);
+    }
+
+    @Override
+    protected void onPostCreate(Bundle savedInstanceState) {
+        super.onPostCreate(savedInstanceState);
+        getDelegate().onPostCreate(savedInstanceState);
+    }
+
+    public ActionBar getSupportActionBar() {
+        return getDelegate().getSupportActionBar();
+    }
+
+    public void setSupportActionBar(@Nullable Toolbar toolbar) {
+        getDelegate().setSupportActionBar(toolbar);
+    }
+
+    @Override
+    public MenuInflater getMenuInflater() {
+        return getDelegate().getMenuInflater();
+    }
+
+    @Override
+    public void setContentView(@LayoutRes int layoutResID) {
+        getDelegate().setContentView(layoutResID);
+    }
+
+    @Override
+    public void setContentView(View view) {
+        getDelegate().setContentView(view);
+    }
+
+    @Override
+    public void setContentView(View view, ViewGroup.LayoutParams params) {
+        getDelegate().setContentView(view, params);
+    }
+
+    @Override
+    public void addContentView(View view, ViewGroup.LayoutParams params) {
+        getDelegate().addContentView(view, params);
+    }
+
+    @Override
+    protected void onPostResume() {
+        super.onPostResume();
+        getDelegate().onPostResume();
+    }
+
+    @Override
+    protected void onTitleChanged(CharSequence title, int color) {
+        super.onTitleChanged(title, color);
+        getDelegate().setTitle(title);
+    }
+
+    @Override
+    public void onConfigurationChanged(Configuration newConfig) {
+        super.onConfigurationChanged(newConfig);
+        getDelegate().onConfigurationChanged(newConfig);
+    }
+
+    @Override
+    protected void onStop() {
+        super.onStop();
+        getDelegate().onStop();
+    }
+
+    @Override
+    protected void onDestroy() {
+        super.onDestroy();
+        getDelegate().onDestroy();
+    }
+
+    public void invalidateOptionsMenu() {
+        getDelegate().invalidateOptionsMenu();
+    }
+
+    private AppCompatDelegate getDelegate() {
+        if (mDelegate == null) {
+            mDelegate = AppCompatDelegate.create(this, null);
+        }
+        return mDelegate;
+    }
+}

app/src/test/java/ru/volgorobot/vrcatalog/ExampleUnitTest.java

@@ -1,17 +0,0 @@
-package ru.volgorobot.vrcatalog;
-
-import org.junit.Test;
-
-import static org.junit.Assert.*;
-
-/**
- * Example local unit test, which will execute on the development machine (host).
- *
- * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
- */
-public class ExampleUnitTest {
-    @Test
-    public void addition_isCorrect() {
-        assertEquals(4, 2 + 2);
-    }
-}

build.gradle

@@ -7,7 +7,7 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.1.4'
+        classpath 'com.android.tools.build:gradle:3.2.1'
         
 
         // NOTE: Do not place your application dependencies here; they belong

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
-#Sat Sep 08 16:32:20 MSK 2018
+#Fri Nov 16 14:50:11 MSK 2018
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-4.4-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.6-all.zip