behave nicely (no foreground service by default) if app is built with targetSdk <26

build.gradle

@@ -64,7 +64,7 @@ android {
 
     defaultConfig {
         minSdkVersion 19
-        targetSdkVersion 28
+        targetSdkVersion 25
         versionCode 285
         versionName "2.3.0-beta.2"
         archivesBaseName += "-$versionName"

src/main/java/eu/siacs/conversations/services/EventReceiver.java

@@ -8,6 +8,7 @@ import android.support.v4.content.ContextCompat;
 import android.util.Log;
 
 import eu.siacs.conversations.Config;
+import eu.siacs.conversations.utils.Compatibility;
 
 public class EventReceiver extends BroadcastReceiver {
 
@@ -24,7 +25,11 @@ public class EventReceiver extends BroadcastReceiver {
 		final String action = originalIntent.getAction();
 		if (action.equals("ui") || hasEnabledAccounts(context)) {
 			try {
-				ContextCompat.startForegroundService(context, intentForService);
+				if (Compatibility.runsAndTargetsTwentySix(context)) {
+					ContextCompat.startForegroundService(context, intentForService);
+				} else {
+					context.startService(intentForService);
+				}
 			} catch (RuntimeException e) {
 				Log.d(Config.LOGTAG,"EventReceiver was unable to start service");
 			}

src/main/java/eu/siacs/conversations/services/NotificationService.java

@@ -831,7 +831,7 @@ public class NotificationService {
     public Notification createForegroundNotification() {
         final Notification.Builder mBuilder = new Notification.Builder(mXmppConnectionService);
         mBuilder.setContentTitle(mXmppConnectionService.getString(R.string.conversations_foreground_service));
-        if (Compatibility.twentySix() || Config.SHOW_CONNECTED_ACCOUNTS) {
+        if (Compatibility.runsAndTargetsTwentySix(mXmppConnectionService) || Config.SHOW_CONNECTED_ACCOUNTS) {
             List<Account> accounts = mXmppConnectionService.getAccounts();
             int enabled = 0;
             int connected = 0;
@@ -852,7 +852,7 @@ public class NotificationService {
         mBuilder.setPriority(Notification.PRIORITY_LOW);
         mBuilder.setSmallIcon(R.drawable.ic_link_white_24dp);
 
-        if (Compatibility.twentySix()) {
+        if (Compatibility.runsTwentySix()) {
             mBuilder.setChannelId("foreground");
         }
 
@@ -907,7 +907,7 @@ public class NotificationService {
                 145,
                 new Intent(mXmppConnectionService, ManageAccountActivity.class),
                 PendingIntent.FLAG_UPDATE_CURRENT));
-        if (Compatibility.twentySix()) {
+        if (Compatibility.runsTwentySix()) {
             mBuilder.setChannelId("error");
         }
         notify(ERROR_NOTIFICATION_ID, mBuilder.build());
@@ -920,7 +920,7 @@ public class NotificationService {
         mBuilder.setSmallIcon(R.drawable.ic_hourglass_empty_white_24dp);
         mBuilder.setContentIntent(createContentIntent(message.getConversation()));
         mBuilder.setOngoing(true);
-        if (Compatibility.twentySix()) {
+        if (Compatibility.runsTwentySix()) {
             mBuilder.setChannelId("compression");
         }
         Notification notification = mBuilder.build();

src/main/java/eu/siacs/conversations/services/XmppConnectionService.java

@@ -108,7 +108,6 @@ import eu.siacs.conversations.ui.UiCallback;
 import eu.siacs.conversations.ui.interfaces.OnAvatarPublication;
 import eu.siacs.conversations.ui.interfaces.OnMediaLoaded;
 import eu.siacs.conversations.ui.interfaces.OnSearchResultsAvailable;
-import eu.siacs.conversations.ui.util.Attachment;
 import eu.siacs.conversations.utils.Compatibility;
 import eu.siacs.conversations.utils.ConversationsFileObserver;
 import eu.siacs.conversations.utils.CryptoHelper;
@@ -960,7 +959,7 @@ public class XmppConnectionService extends Service {
         Resolver.init(this);
         this.mRandom = new SecureRandom();
         updateMemorizingTrustmanager();
-        if (Compatibility.twentySix()) {
+        if (Compatibility.runsTwentySix()) {
             mNotificationService.initializeChannels();
         }
         final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);

src/main/java/eu/siacs/conversations/utils/Compatibility.java

@@ -2,11 +2,11 @@ package eu.siacs.conversations.utils;
 
 import android.content.Context;
 import android.content.SharedPreferences;
+import android.content.pm.ApplicationInfo;
 import android.content.pm.PackageManager;
 import android.os.Build;
 import android.preference.Preference;
 import android.preference.PreferenceCategory;
-import android.preference.PreferenceGroup;
 import android.preference.PreferenceManager;
 import android.support.annotation.BoolRes;
 import android.support.v4.content.ContextCompat;
@@ -22,7 +22,6 @@ import eu.siacs.conversations.ui.SettingsFragment;
 public class Compatibility {
 
     private static final List<String> UNUSED_SETTINGS_POST_TWENTYSIX = Arrays.asList(
-            SettingsActivity.KEEP_FOREGROUND_SERVICE,
             "led",
             "notification_ringtone",
             "notification_headsup",
@@ -34,7 +33,7 @@ public class Compatibility {
         return Build.VERSION.SDK_INT < Build.VERSION_CODES.M || ContextCompat.checkSelfPermission(context, android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED;
     }
 
-    public static boolean twentySix() {
+    public static boolean runsTwentySix() {
         return Build.VERSION.SDK_INT >= Build.VERSION_CODES.O;
     }
 
@@ -50,15 +49,29 @@ public class Compatibility {
         return PreferenceManager.getDefaultSharedPreferences(context);
     }
 
+    private static boolean targetsTwentySix(Context context) {
+        try {
+            final PackageManager packageManager = context.getPackageManager();
+            final ApplicationInfo applicationInfo = packageManager.getApplicationInfo(context.getPackageName(), 0);
+            return applicationInfo == null || applicationInfo.targetSdkVersion >= 26;
+        } catch (PackageManager.NameNotFoundException e) {
+            return true; //when in doubt…
+        }
+    }
+
+    public static boolean runsAndTargetsTwentySix(Context context) {
+        return runsTwentySix() && targetsTwentySix(context);
+    }
+
     public static boolean keepForegroundService(Context context) {
-        return twentySix() || getBooleanPreference(context, SettingsActivity.KEEP_FOREGROUND_SERVICE, R.bool.enable_foreground_service);
+        return runsAndTargetsTwentySix(context) || getBooleanPreference(context, SettingsActivity.KEEP_FOREGROUND_SERVICE, R.bool.enable_foreground_service);
     }
 
     public static void removeUnusedPreferences(SettingsFragment settingsFragment) {
         List<PreferenceCategory> categories = Arrays.asList(
                 (PreferenceCategory) settingsFragment.findPreference("notification_category"),
                 (PreferenceCategory) settingsFragment.findPreference("other_expert_category"));
-        for (String key : (twentySix() ? UNUSED_SETTINGS_POST_TWENTYSIX : UNUESD_SETTINGS_PRE_TWENTYSIX)) {
+        for (String key : (runsTwentySix() ? UNUSED_SETTINGS_POST_TWENTYSIX : UNUESD_SETTINGS_PRE_TWENTYSIX)) {
             Preference preference = settingsFragment.findPreference(key);
             if (preference != null) {
                 for (PreferenceCategory category : categories) {
@@ -68,5 +81,17 @@ public class Compatibility {
                 }
             }
         }
+        if (Compatibility.runsTwentySix()) {
+            if (targetsTwentySix(settingsFragment.getContext())) {
+                Preference preference = settingsFragment.findPreference(SettingsActivity.KEEP_FOREGROUND_SERVICE);
+                if (preference != null) {
+                    for (PreferenceCategory category : categories) {
+                        if (category != null) {
+                            category.removePreference(preference);
+                        }
+                    }
+                }
+            }
+        }
     }
 }