Enabled Lint for core module

core/build.gradle

@@ -52,6 +52,16 @@ android {
             dimension "market"
         }
     }
+
+    lintOptions {
+        disable "InvalidPeriodicWorkRequestInterval", "ObsoleteLintCustomCheck", "DefaultLocale", "UnusedAttribute",
+                "GradleDependency", "ParcelClassLoader", "Typos", "ExtraTranslation", "ImpliedQuantity",
+                "PluralsCandidate", "UnusedQuantity", "StringFormatCount", "TrustAllX509TrustManager",
+                "StaticFieldLeak", "TypographyEllipsis", "IconDensities", "IconDuplicates"
+
+        warningsAsErrors true
+        abortOnError true
+    }
 }
 
 dependencies {

core/src/main/AndroidManifest.xml

@@ -1,5 +1,5 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="de.danoeh.antennapod.core">
+          xmlns:tools="http://schemas.android.com/tools" package="de.danoeh.antennapod.core">
 
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
@@ -12,15 +12,19 @@
 
     <application
         android:allowBackup="true"
-        android:icon="@mipmap/ic_launcher">
+        android:icon="@mipmap/ic_launcher"
+        android:supportsRtl="true">
 
         <service
             android:name=".service.download.DownloadService"
             android:enabled="true" />
+
         <service android:name=".service.playback.PlaybackService"
             android:label="@string/app_name"
             android:enabled="true"
-            android:exported="true">
+            android:exported="true"
+            tools:ignore="ExportedService">
+
             <intent-filter>
                 <action android:name="android.media.browse.MediaBrowserService"/>
             </intent-filter>
@@ -39,8 +43,8 @@
 
         <receiver android:name=".receiver.FeedUpdateReceiver"
             android:label="@string/feed_update_receiver_name"
-            android:exported="true"> <!-- allow feeds update to be triggered by external apps -->
+            android:exported="true"
-        </receiver>
+            tools:ignore="ExportedReceiver" /> <!-- allow feeds update to be triggered by external apps -->
     </application>
 
 </manifest>

core/src/main/java/de/danoeh/antennapod/core/preferences/UserPreferences.java

@@ -249,7 +249,7 @@ public class UserPreferences {
     public static void setFeedOrder(String selected) {
         prefs.edit()
                 .putString(PREF_DRAWER_FEED_ORDER, selected)
-                .commit();
+                .apply();
     }
 
     public static int getFeedCounterSetting() {
@@ -1054,7 +1054,7 @@ public class UserPreferences {
     public static void setFeedFilter(String value) {
         prefs.edit()
                 .putString(PREF_FILTER_FEED, value)
-                .commit();
+                .apply();
     }
 
 }

core/src/main/java/de/danoeh/antennapod/core/storage/DBTasks.java

@@ -257,7 +257,6 @@ public final class DBTasks {
         EventBus.getDefault().post(new MessageEvent(context.getString(R.string.error_file_not_found)));
     }
 
-    @VisibleForTesting(otherwise = VisibleForTesting.PACKAGE_PRIVATE)
     public static List<? extends FeedItem> enqueueFeedItemsToDownload(final Context context,
                        List<? extends FeedItem> items) throws InterruptedException, ExecutionException {
         List<FeedItem> itemsToEnqueue = new ArrayList<>();

core/src/main/res/layout/player_widget.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:tools="http://schemas.android.com/tools"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:padding="@dimen/widget_margin" >
@@ -8,8 +9,8 @@
         android:id="@+id/widgetLayout"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        android:background="#262C31" >
+        android:background="#262C31"
-
+        tools:ignore="UselessParent">
 
         <ImageButton
             android:id="@+id/butPlay"
@@ -41,6 +42,7 @@
                 android:layout_width="@android:dimen/app_icon_size"
                 android:layout_height="match_parent"
                 android:src="@mipmap/ic_launcher_round"
+                android:importantForAccessibility="no"
                 android:layout_margin="12dp" />
 
             <LinearLayout