diff --git a/app/build.gradle b/app/build.gradle
index 92682e6c3..08e569987 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -1,7 +1,7 @@
 plugins {
     id('com.android.application')
     id('com.getkeepsafe.dexcount')
-    id('com.github.triplet.play') version '3.4.0' apply false
+    id('com.github.triplet.play') version '3.6.0-agp4.2' apply false
 }
 apply from: "../common.gradle"
 apply from: "../playFlavor.gradle"
@@ -76,9 +76,9 @@ android {
 
             dexcount {
                 if (project.hasProperty("enableDexcountInDebug")) {
-                    runOnEachPackage enableDexcountInDebug.toBoolean()
+                    runOnEachPackage = enableDexcountInDebug.toBoolean()
                 } else { // default to not running dexcount
-                    runOnEachPackage false
+                    runOnEachPackage = false
                 }
             }
         }
diff --git a/app/src/main/java/de/danoeh/antennapod/activity/WidgetConfigActivity.java b/app/src/main/java/de/danoeh/antennapod/activity/WidgetConfigActivity.java
index 3020aba43..674071294 100644
--- a/app/src/main/java/de/danoeh/antennapod/activity/WidgetConfigActivity.java
+++ b/app/src/main/java/de/danoeh/antennapod/activity/WidgetConfigActivity.java
@@ -1,21 +1,14 @@
 package de.danoeh.antennapod.activity;
 
-import android.Manifest;
-import android.app.WallpaperManager;
 import android.appwidget.AppWidgetManager;
 import android.content.Intent;
 import android.content.SharedPreferences;
-import android.content.pm.PackageManager;
-import android.graphics.drawable.Drawable;
-import android.os.Build;
 import android.os.Bundle;
 import android.view.View;
 import android.widget.CheckBox;
-import android.widget.ImageView;
 import android.widget.SeekBar;
 import android.widget.TextView;
 import androidx.appcompat.app.AppCompatActivity;
-import androidx.core.content.ContextCompat;
 import de.danoeh.antennapod.R;
 import de.danoeh.antennapod.core.preferences.UserPreferences;
 import de.danoeh.antennapod.core.receiver.PlayerWidget;
@@ -51,7 +44,6 @@ public class WidgetConfigActivity extends AppCompatActivity {
             finish();
         }
 
-        displayDeviceBackground();
         opacityTextView = findViewById(R.id.widget_opacity_textView);
         opacitySeekBar = findViewById(R.id.widget_opacity_seekBar);
         widgetPreview = findViewById(R.id.widgetLayout);
@@ -102,16 +94,6 @@ public class WidgetConfigActivity extends AppCompatActivity {
         widgetPreview.findViewById(R.id.butRew).setVisibility(ckRewind.isChecked() ? View.VISIBLE : View.GONE);
     }
 
-    private void displayDeviceBackground() {
-        int permission = ContextCompat.checkSelfPermission(this, Manifest.permission.READ_EXTERNAL_STORAGE);
-        if (Build.VERSION.SDK_INT < 27 || permission == PackageManager.PERMISSION_GRANTED) {
-            final WallpaperManager wallpaperManager = WallpaperManager.getInstance(this);
-            final Drawable wallpaperDrawable = wallpaperManager.getDrawable();
-            ImageView background = findViewById(R.id.widget_config_background);
-            background.setImageDrawable(wallpaperDrawable);
-        }
-    }
-
     private void confirmCreateWidget(View v) {
         int backgroundColor = getColorWithAlpha(PlayerWidget.DEFAULT_COLOR, opacitySeekBar.getProgress());
 
diff --git a/build.gradle b/build.gradle
index f6992882c..7271a4650 100644
--- a/build.gradle
+++ b/build.gradle
@@ -6,9 +6,9 @@ buildscript {
         jcenter()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.1.3'
-        classpath 'com.getkeepsafe.dexcount:dexcount-gradle-plugin:1.0.4'
-        classpath 'de.timfreiheit.resourceplaceholders:placeholders:0.3'
+        classpath 'com.android.tools.build:gradle:4.2.2'
+        classpath 'com.getkeepsafe.dexcount:dexcount-gradle-plugin:3.0.0'
+        classpath 'de.timfreiheit.resourceplaceholders:placeholders:0.4'
         classpath "gradle.plugin.com.github.spotbugs.snom:spotbugs-gradle-plugin:4.7.0"
     }
 }
diff --git a/core/lint.xml b/core/lint.xml
index fd9f5eb99..aa2c50677 100644
--- a/core/lint.xml
+++ b/core/lint.xml
@@ -8,4 +8,8 @@
     <issue id="MissingDefaultResource">
         <ignore path="**/values-**/strings.xml" />
     </issue>
+
+    <issue id="UnusedResources" severity="error">
+        <ignore path="**/values-**/strings.xml" />
+    </issue>
 </lint>
diff --git a/core/src/main/java/de/danoeh/antennapod/core/preferences/UserPreferences.java b/core/src/main/java/de/danoeh/antennapod/core/preferences/UserPreferences.java
index 76dfab169..c20666aaa 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/preferences/UserPreferences.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/preferences/UserPreferences.java
@@ -530,7 +530,8 @@ public class UserPreferences {
     private static void setAllowMobileFor(String type, boolean allow) {
         HashSet<String> defaultValue = new HashSet<>();
         defaultValue.add("images");
-        Set<String> allowed = prefs.getStringSet(PREF_MOBILE_UPDATE, defaultValue);
+        final Set<String> getValueStringSet = prefs.getStringSet(PREF_MOBILE_UPDATE, defaultValue);
+        final Set<String> allowed = new HashSet<>(getValueStringSet);
         if (allow) {
             allowed.add(type);
         } else {
diff --git a/core/src/main/java/de/danoeh/antennapod/core/storage/mapper/FeedMediaCursorMapper.java b/core/src/main/java/de/danoeh/antennapod/core/storage/mapper/FeedMediaCursorMapper.java
index 608fce5c4..0dc3dc231 100644
--- a/core/src/main/java/de/danoeh/antennapod/core/storage/mapper/FeedMediaCursorMapper.java
+++ b/core/src/main/java/de/danoeh/antennapod/core/storage/mapper/FeedMediaCursorMapper.java
@@ -36,7 +36,7 @@ public abstract class FeedMediaCursorMapper {
         }
 
         Boolean hasEmbeddedPicture;
-        switch (cursor.getInt(cursor.getColumnIndex(PodDBAdapter.KEY_HAS_EMBEDDED_PICTURE))) {
+        switch (cursor.getInt(cursor.getColumnIndexOrThrow(PodDBAdapter.KEY_HAS_EMBEDDED_PICTURE))) {
             case 1:
                 hasEmbeddedPicture = Boolean.TRUE;
                 break;