Use appcompat-v7

app/build.gradle

@@ -1,11 +1,11 @@
 apply plugin: 'com.android.application'
 
 android {
-    compileSdkVersion 26
+    compileSdkVersion 27
     defaultConfig {
         applicationId "xdsopl.robot36"
         minSdkVersion 15
-        targetSdkVersion 26
+        targetSdkVersion 27
         versionCode 36
         versionName "1.35"
         renderscriptTargetApi 18
@@ -21,5 +21,5 @@ android {
 
 dependencies {
     implementation fileTree(include: ['*.jar'], dir: 'libs')
-    implementation 'com.android.support:support-v4:26.1.0'
+    implementation 'com.android.support:appcompat-v7:27.1.1'
 }

app/src/main/AndroidManifest.xml

@@ -8,7 +8,7 @@
         android:allowBackup="true"
         android:icon="@drawable/ic_launcher"
         android:label="@string/app_name"
-        android:theme="@style/AppTheme" >
+        android:theme="@style/Theme.AppCompat.Light" >
         <activity
             android:configChanges="keyboardHidden|orientation|screenSize"
             android:name="xdsopl.robot36.MainActivity"

app/src/main/java/xdsopl/robot36/MainActivity.java

@@ -18,7 +18,6 @@ limitations under the License.
 package xdsopl.robot36;
 
 import android.Manifest;
-import android.app.Activity;
 import android.app.AlertDialog;
 import android.app.NotificationManager;
 import android.app.PendingIntent;
@@ -39,13 +38,15 @@ import android.provider.MediaStore;
 import android.support.v4.app.ActivityCompat;
 import android.support.v4.app.NotificationCompat;
 import android.support.v4.content.ContextCompat;
+import android.support.v4.view.MenuItemCompat;
+import android.support.v7.app.AppCompatActivity;
+import android.support.v7.widget.ShareActionProvider;
 import android.util.Log;
 import android.view.Gravity;
 import android.view.Menu;
 import android.view.MenuItem;
 import android.view.View;
 import android.widget.LinearLayout;
-import android.widget.ShareActionProvider;
 import android.widget.Toast;
 
 import java.io.File;
@@ -56,7 +57,7 @@ import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
 
-public class MainActivity extends Activity {
+public class MainActivity extends AppCompatActivity {
     private Decoder decoder;
     private ImageView image;
     private Bitmap bitmap;
@@ -273,7 +274,8 @@ public class MainActivity extends Activity {
         getMenuInflater().inflate(R.menu.menu_main, menu);
         this.menu = menu;
         updateMenuButtons();
-        share = (ShareActionProvider)menu.findItem(R.id.menu_item_share).getActionProvider();
+        MenuItem item = menu.findItem(R.id.menu_item_share);
+        share = (ShareActionProvider)MenuItemCompat.getActionProvider(item);
         return true;
     }
 

app/src/main/res/menu/menu_main.xml

@@ -1,5 +1,6 @@
 <menu
     xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:support="http://schemas.android.com/apk/res-auto"
     xmlns:tools="http://schemas.android.com/tools"
     tools:context=".MainActivity">
 
@@ -7,26 +8,26 @@
         android:id="@+id/action_toggle_decoder"
         android:title="@string/action_toggle_decoder"
         android:icon="@android:drawable/ic_media_play"
-        android:showAsAction="ifRoom" />
+        support:showAsAction="ifRoom" />
 
     <group android:id="@+id/group_decoder" android:enabled="false">
         <item
             android:id="@+id/menu_item_share"
-            android:showAsAction="always"
+            support:showAsAction="always"
             android:title="@string/action_share"
-            android:actionProviderClass="android.widget.ShareActionProvider" />
+            support:actionProviderClass="android.support.v7.widget.ShareActionProvider" />
 
         <item
             android:id="@+id/action_save_image"
             android:title="@string/action_save_image"
             android:icon="@android:drawable/ic_menu_save"
-            android:showAsAction="ifRoom" />
+            support:showAsAction="ifRoom" />
 
         <item
             android:id="@+id/action_clear_image"
             android:title="@string/action_clear_image"
             android:icon="@android:drawable/ic_menu_close_clear_cancel"
-            android:showAsAction="ifRoom" />
+            support:showAsAction="ifRoom" />
 
         <item android:title="@string/image_sharpness"><menu>
             <item android:id="@+id/action_sharpest_image" android:title="@string/action_sharpest_image" />