diff --git a/.gitignore b/.gitignore
index 7fa9d66d..a50a2934 100644
--- a/.gitignore
+++ b/.gitignore
@@ -39,6 +39,7 @@ contributers.py
 # View hierarchy captures
 captures
 # other
+.directory
 *.odg#
 proguard
 libs
diff --git a/app/build.gradle b/app/build.gradle
index ba1ed1c7..40d70aa3 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -2,14 +2,13 @@ plugins {
     id('com.android.application')
     id 'kotlin-android'
     id 'kotlin-kapt'
+    id 'com.google.devtools.ksp'
     id('com.github.triplet.play') version '3.8.3' apply false
 }
-apply from: "../common.gradle"
-apply from: "../playFlavor.gradle"
 
 android {
     namespace "ac.mdiq.podcini"
-    lint {
+    lintOptions {
         disable 'ObsoleteLintCustomCheck', 'CheckResult', 'UnusedAttribute', 'BatteryLife', 'InflateParams',
                 'RestrictedApi', 'TrustAllX509TrustManager', 'ExportedReceiver', 'AllowBackup', 'VectorDrawableCompat',
                 'StaticFieldLeak', 'UseCompoundDrawables', 'NestedWeights', 'Overdraw', 'UselessParent', 'TextFields',
@@ -22,11 +21,25 @@ android {
         buildConfig true
     }
     defaultConfig {
-        // Version code schema:
+        minSdk 21
+        compileSdk 34
+        targetSdk 34
+
+        kotlinOptions {
+            jvmTarget = '17'
+        }
+
+        vectorDrawables.useSupportLibrary false
+        vectorDrawables.generatedDensities = []
+
+        testApplicationId "ac.mdiq.podcini.tests"
+        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
+
+        // Version code schema (not used):
         // "1.2.3-beta4"    -> 1020304
         // "1.2.3"          -> 1020395
-        versionCode 3020106
-        versionName "4.2.3"
+        versionCode 3020107
+        versionName "4.2.4"
 
         def commit = ""
         try {
@@ -65,33 +78,129 @@ android {
             keyPassword project.getProperties().getOrDefault("releaseKeyPassword", "password")
         }
     }
+
     buildTypes {
         debug {
             applicationIdSuffix ".debug"
+            resValue "string", "app_name", "Podcini Debug"
             resValue "string", "provider_authority", "ac.mdiq.podcini.debug.provider"
         }
         release {
+            proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard.cfg"
+            resValue "string", "app_name", "Podcini"
             resValue "string", "provider_authority", "ac.mdiq.podcini.provider"
             minifyEnabled true
             shrinkResources true
             signingConfig signingConfigs.releaseConfig
         }
     }
-    applicationVariants.all { variant ->
-        variant.outputs.all { output ->
+
+    flavorDimensions += ["market"]
+    productFlavors {
+        free {
+            dimension "market"
+        }
+        play {
+            dimension "market"
+        }
+    }
+
+    applicationVariants.configureEach { variant ->
+        variant.outputs.configureEach { output ->
             def applicationName = "Podcini"
             outputFileName = "${applicationName}_${variant.buildType.name}_${defaultConfig.versionName}.apk"
         }
     }
 
+    packagingOptions {
+        resources {
+            excludes += ["META-INF/LICENSE.txt",
+                         "META-INF/NOTICE.txt",
+                         "META-INF/CHANGES",
+                         "META-INF/README.md"]
+        }
+    }
+
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_17
+        targetCompatibility JavaVersion.VERSION_17
+    }
+
+    testOptions {
+        animationsDisabled = true
+        unitTests {
+            includeAndroidResources = true
+        }
+    }
+
+    lint {
+        disable "GradleDependency"
+        checkDependencies true
+        warningsAsErrors true
+        abortOnError true
+        checkGeneratedSources = true
+    }
+
+    buildFeatures {
+        viewBinding true
+    }
 
     androidResources {
         additionalParameters "--no-version-vectors"
     }
 }
 
+tasks.withType(Test).configureEach {
+    testLogging {
+        exceptionFormat "full"
+        events "skipped", "passed", "failed"
+        showStandardStreams true
+        displayGranularity 2
+    }
+}
+
+gradle.projectsEvaluated {
+    tasks.withType(JavaCompile).tap {
+        configureEach {
+            options.compilerArgs << "-Xlint"
+        }
+    }
+}
+
+apply plugin: 'com.github.spotbugs'
+
+spotbugs {
+    effort = 'max'
+    reportLevel = 'medium'
+    excludeFilter = rootProject.file('config/spotbugs/exclude.xml')
+    ignoreFailures = true // Handled by printing task
+}
+
+gradle.taskGraph.beforeTask { task ->
+    if (task.name.toLowerCase().contains('spotbugs')) {
+        task.doLast {
+            def reportFile = task.project.file("build/reports/spotbugs/playDebug.xml")
+            if (!reportFile.exists()) return
+            def slurped = new groovy.xml.XmlSlurper().parse(reportFile)
+
+            def foundErrors = false
+            slurped['BugInstance'].each { bug ->
+                logger.error "[SpotBugs] ${bug['LongMessage']} [${bug.@'type'}]"
+                bug['SourceLine'].each { line ->
+                    logger.error "[SpotBugs]     ${line['Message']}"
+                    foundErrors = true
+                }
+            }
+            if (foundErrors) {
+                throw new TaskExecutionException(task,
+                        new Exception("SpotBugs violations were found. See output above for details."))
+            }
+        }
+    }
+}
+
 dependencies {
-    implementation "androidx.core:core-ktx:$coreVersion"
+    implementation "androidx.core:core-ktx:1.12.0"
     implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version"
 
     constraints {
@@ -103,83 +212,87 @@ dependencies {
         }
     }
 
-    kapt "androidx.annotation:annotation:$annotationVersion"
+    ksp "androidx.annotation:annotation:1.7.1"
 
-    implementation "androidx.appcompat:appcompat:$appcompatVersion"
+    implementation "androidx.appcompat:appcompat:1.6.1"
     implementation 'androidx.coordinatorlayout:coordinatorlayout:1.2.0'
-    implementation "androidx.fragment:fragment-ktx:$fragmentVersion"
+    implementation "androidx.fragment:fragment-ktx:1.6.2"
     implementation 'androidx.gridlayout:gridlayout:1.0.0'
-    implementation "androidx.media:media:$mediaVersion"
-    implementation "androidx.media3:media3-exoplayer:$media3Version"
-    implementation "androidx.media3:media3-ui:$media3Version"
-    implementation "androidx.media3:media3-datasource-okhttp:$media3Version"
-    implementation "androidx.media3:media3-common:$media3Version"
-    implementation "androidx.palette:palette-ktx:$paletteVersion"
-    implementation "androidx.preference:preference-ktx:$preferenceVersion"
-    implementation "androidx.recyclerview:recyclerview:$recyclerViewVersion"
-    implementation "androidx.viewpager2:viewpager2:$viewPager2Version"
-    implementation "androidx.work:work-runtime:$workManagerVersion"
+    implementation "androidx.media:media:1.7.0"
+    implementation "androidx.media3:media3-exoplayer:1.2.1"
+    implementation "androidx.media3:media3-ui:1.2.1"
+    implementation "androidx.media3:media3-datasource-okhttp:1.2.1"
+    implementation "androidx.media3:media3-common:1.2.1"
+    implementation "androidx.palette:palette-ktx:1.0.0"
+    implementation "androidx.preference:preference-ktx:1.2.1"
+    implementation "androidx.recyclerview:recyclerview:1.3.2"
+    implementation "androidx.viewpager2:viewpager2:1.1.0-beta02"
+    implementation "androidx.work:work-runtime:2.9.0"
     implementation "androidx.core:core-splashscreen:1.0.1"
     implementation 'androidx.documentfile:documentfile:1.0.1'
 
-    implementation "com.google.android.material:material:$googleMaterialVersion"
+    implementation "com.google.android.material:material:1.11.0"
 
-    implementation "org.apache.commons:commons-lang3:$commonslangVersion"
-    implementation "commons-io:commons-io:$commonsioVersion"
-    implementation "org.jsoup:jsoup:$jsoupVersion"
+    implementation "org.apache.commons:commons-lang3:3.14.0"
+    implementation "commons-io:commons-io:2.15.1"
+    implementation "org.jsoup:jsoup:1.17.2"
 
-    implementation "com.github.bumptech.glide:glide:$glideVersion"
-    implementation "com.github.bumptech.glide:okhttp3-integration:$glideVersion@aar"
-    kapt "com.github.bumptech.glide:compiler:$glideVersion"
+    implementation "com.github.bumptech.glide:glide:4.16.0"
+    implementation "com.github.bumptech.glide:okhttp3-integration:4.16.0@aar"
+    ksp "com.github.bumptech.glide:ksp:4.16.0"
 
-    implementation "com.squareup.okhttp3:okhttp:$okhttpVersion"
-    implementation "com.squareup.okhttp3:okhttp-urlconnection:$okhttpVersion"
-    implementation "com.squareup.okio:okio:$okioVersion"
-    implementation "org.greenrobot:eventbus:$eventbusVersion"
-    kapt "org.greenrobot:eventbus-annotation-processor:$eventbusVersion"
-    implementation "io.reactivex.rxjava2:rxandroid:$rxAndroidVersion"
-    implementation "io.reactivex.rxjava2:rxjava:$rxJavaVersion"
+    implementation "com.squareup.okhttp3:okhttp:4.12.0"
+    implementation "com.squareup.okhttp3:okhttp-urlconnection:4.12.0"
 
-    implementation "com.joanzapata.iconify:android-iconify-fontawesome:$iconifyVersion"
-    implementation "com.joanzapata.iconify:android-iconify-material:$iconifyVersion"
-    implementation 'com.leinardi.android:speed-dial:3.2.0'
+    implementation "com.squareup.okio:okio:3.7.0"
+
+    implementation "org.greenrobot:eventbus:3.3.1"
+    kapt "org.greenrobot:eventbus-annotation-processor:3.3.1"
+
+    implementation "io.reactivex.rxjava2:rxandroid:2.1.1"
+    implementation "io.reactivex.rxjava2:rxjava:2.2.21"
+
+    implementation "com.joanzapata.iconify:android-iconify-fontawesome:2.2.2"
+    implementation "com.joanzapata.iconify:android-iconify-material:2.2.2"
+    implementation 'com.leinardi.android:speed-dial:3.3.0'
     implementation 'com.github.ByteHamster:SearchPreference:v2.5.0'
-    implementation 'com.github.skydoves:balloon:1.5.3'
+    implementation 'com.github.skydoves:balloon:1.6.4'
     implementation 'com.github.xabaras:RecyclerViewSwipeDecorator:1.3'
-    implementation "com.annimon:stream:$annimonStreamVersion"
+    implementation "com.annimon:stream:1.2.2"
 
     // Non-free dependencies:
-    playImplementation 'com.google.android.play:core-ktx:1.8.0'
-    compileOnly "com.google.android.wearable:wearable:$wearableSupportVersion"
+    playImplementation 'com.google.android.play:core-ktx:1.8.1'
+    compileOnly "com.google.android.wearable:wearable:2.9.0"
 
+//    this one can not be updated?
     androidTestImplementation 'com.nanohttpd:nanohttpd:2.1.1'
-    androidTestImplementation "androidx.test.espresso:espresso-core:$espressoVersion"
-    androidTestImplementation "androidx.test.espresso:espresso-contrib:$espressoVersion"
-    androidTestImplementation "androidx.test.espresso:espresso-intents:$espressoVersion"
-    androidTestImplementation "androidx.test:runner:$runnerVersion"
-    androidTestImplementation "androidx.test:rules:$rulesVersion"
+    androidTestImplementation "androidx.test.espresso:espresso-core:3.5.1"
+    androidTestImplementation "androidx.test.espresso:espresso-contrib:3.5.1"
+    androidTestImplementation "androidx.test.espresso:espresso-intents:3.5.1"
+    androidTestImplementation "androidx.test:runner:1.5.2"
+    androidTestImplementation "androidx.test:rules:1.5.0"
     androidTestImplementation 'androidx.test.ext:junit:1.1.5'
-    androidTestImplementation "org.awaitility:awaitility:$awaitilityVersion"
+    androidTestImplementation "org.awaitility:awaitility:4.2.0"
 
-    implementation "com.annimon:stream:$annimonStreamVersion"
+    implementation "com.annimon:stream:1.2.2"
     implementation 'com.github.mfietz:fyydlin:v0.5.0'
 
     // Non-free dependencies:
 
-    testImplementation "androidx.test:core:$testCoreVersion"
-    testImplementation "org.awaitility:awaitility:$awaitilityVersion"
-    testImplementation "junit:junit:$junitVersion"
+    testImplementation "androidx.test:core:1.5.0"
+    testImplementation "org.awaitility:awaitility:4.2.0"
+    testImplementation "junit:junit:4.13.2"
     testImplementation 'org.mockito:mockito-inline:5.2.0'
-    testImplementation "org.robolectric:robolectric:$robolectricVersion"
+    testImplementation "org.robolectric:robolectric:4.11.1"
     testImplementation 'javax.inject:javax.inject:1'
 
 
-    playImplementation 'com.google.android.gms:play-services-base:17.5.0'
+    playImplementation 'com.google.android.gms:play-services-base:18.3.0'
     freeImplementation 'org.conscrypt:conscrypt-android:2.5.2'
 
     playApi 'androidx.mediarouter:mediarouter:1.6.0'
-    playApi "com.google.android.support:wearable:$wearableSupportVersion"
-    playApi 'com.google.android.gms:play-services-cast-framework:21.2.0'
+    playApi "com.google.android.support:wearable:2.9.0"
+    playApi 'com.google.android.gms:play-services-cast-framework:21.4.0'
 }
 
 kapt {
diff --git a/app/src/androidTest/java/ac/test/podcini/util/service/download/HTTPBin.kt b/app/src/androidTest/java/ac/test/podcini/util/service/download/HTTPBin.kt
index 1df7e462..41f79be9 100644
--- a/app/src/androidTest/java/ac/test/podcini/util/service/download/HTTPBin.kt
+++ b/app/src/androidTest/java/ac/test/podcini/util/service/download/HTTPBin.kt
@@ -1,8 +1,8 @@
 package de.test.podcini.util.service.download
 
+import ac.mdiq.podcini.BuildConfig
 import android.util.Base64
 import android.util.Log
-import ac.mdiq.podcini.BuildConfig
 import fi.iki.elonen.NanoHTTPD
 import fi.iki.elonen.NanoHTTPD.Response.IStatus
 import org.apache.commons.io.IOUtils
diff --git a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Atom.kt b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Atom.kt
index 83c88ad3..549fd5c5 100644
--- a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Atom.kt
+++ b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Atom.kt
@@ -19,17 +19,17 @@ class Atom : Namespace() {
             state.items.add(state.currentItem!!)
             state.currentItem!!.feed = state.feed
         } else if (localName.matches(isText.toRegex())) {
-            val type = attributes.getValue(TEXT_TYPE)
+            val type: String? = attributes.getValue(TEXT_TYPE)
             return AtomText(localName, this, type)
         } else if (LINK == localName) {
-            val href = attributes.getValue(LINK_HREF)
-            val rel = attributes.getValue(LINK_REL)
+            val href: String? = attributes.getValue(LINK_HREF)
+            val rel: String? = attributes.getValue(LINK_REL)
             val parent = state.tagstack.peek()
             if (parent.name.matches(isFeedItem.toRegex())) {
                 if (rel == null || LINK_REL_ALTERNATE == rel) {
                     state.currentItem!!.link = href
                 } else if (LINK_REL_ENCLOSURE == rel) {
-                    val strSize = attributes.getValue(LINK_LENGTH)
+                    val strSize: String? = attributes.getValue(LINK_LENGTH)
                     var size: Long = 0
                     try {
                         if (strSize != null) {
@@ -38,7 +38,7 @@ class Atom : Namespace() {
                     } catch (e: NumberFormatException) {
                         Log.d(TAG, "Length attribute could not be parsed.")
                     }
-                    val mimeType = getMimeType(attributes.getValue(LINK_TYPE), href)
+                    val mimeType: String? = getMimeType(attributes.getValue(LINK_TYPE), href)
 
                     val currItem = state.currentItem
                     if (isMediaFile(mimeType) && currItem != null && !currItem.hasMedia()) {
@@ -49,7 +49,7 @@ class Atom : Namespace() {
                 }
             } else if (parent.name.matches(isFeed.toRegex())) {
                 if (rel == null || LINK_REL_ALTERNATE == rel) {
-                    val type = attributes.getValue(LINK_TYPE)
+                    val type: String? = attributes.getValue(LINK_TYPE)
                     /*
                      * Use as link if a) no type-attribute is given and
                      * feed-object has no link yet b) type of link is
@@ -60,20 +60,20 @@ class Atom : Namespace() {
                         state.feed.link = href
                     } else if (LINK_TYPE_ATOM == type || LINK_TYPE_RSS == type) {
                         // treat as podlove alternate feed
-                        var title = attributes.getValue(LINK_TITLE)
-                        if (title.isEmpty()) {
-                            title = href
+                        var title: String? = attributes.getValue(LINK_TITLE)
+                        if (title.isNullOrEmpty()) {
+                            title = href?:""
                         }
-                        state.addAlternateFeedUrl(title!!, href)
+                        if (!href.isNullOrEmpty()) state.addAlternateFeedUrl(title, href)
                     }
                 } else if (LINK_REL_ARCHIVES == rel) {
-                    val type = attributes.getValue(LINK_TYPE)
+                    val type: String? = attributes.getValue(LINK_TYPE)
                     if (LINK_TYPE_ATOM == type || LINK_TYPE_RSS == type) {
-                        var title = attributes.getValue(LINK_TITLE)
-                        if (title.isEmpty()) {
-                            title = href
+                        var title: String? = attributes.getValue(LINK_TITLE)
+                        if (title.isNullOrEmpty()) {
+                            title = href?:""
                         }
-                        state.addAlternateFeedUrl(title!!, href)
+                        if (!href.isNullOrEmpty()) state.addAlternateFeedUrl(title, href)
                     } else if (LINK_TYPE_HTML == type || LINK_TYPE_XHTML == type) {
                         //A Link such as to a directory such as iTunes
                     }
@@ -205,7 +205,7 @@ class Atom : Namespace() {
          */
         private const val isText = ("$TITLE|$CONTENT|$SUBTITLE|$SUMMARY")
 
-        private const val isFeed = FEED + "|" + ac.mdiq.podcini.feed.parser.namespace.Rss20.CHANNEL
-        private const val isFeedItem = ENTRY + "|" + ac.mdiq.podcini.feed.parser.namespace.Rss20.ITEM
+        private const val isFeed = FEED + "|" + Rss20.CHANNEL
+        private const val isFeedItem = ENTRY + "|" + Rss20.ITEM
     }
 }
diff --git a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Itunes.kt b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Itunes.kt
index 11d1030c..09e589dc 100644
--- a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Itunes.kt
+++ b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Itunes.kt
@@ -10,14 +10,14 @@ class Itunes : Namespace() {
     override fun handleElementStart(localName: String, state: ac.mdiq.podcini.feed.parser.HandlerState,
                                     attributes: Attributes): SyndElement {
         if (IMAGE == localName) {
-            val url = attributes.getValue(IMAGE_HREF)
+            val url: String? = attributes.getValue(IMAGE_HREF)
 
             if (state.currentItem != null) {
                 state.currentItem!!.imageUrl = url
             } else {
                 // this is the feed image
                 // prefer to all other images
-                if (url.isNotEmpty()) {
+                if (!url.isNullOrEmpty()) {
                     state.feed.imageUrl = url
                 }
             }
diff --git a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Media.kt b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Media.kt
index 6dcecad9..f2ff2066 100644
--- a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Media.kt
+++ b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Media.kt
@@ -15,9 +15,9 @@ import java.util.concurrent.TimeUnit
 class Media : Namespace() {
     override fun handleElementStart(localName: String, state: HandlerState, attributes: Attributes): SyndElement {
         if (CONTENT == localName) {
-            val url = attributes.getValue(DOWNLOAD_URL)
-            val defaultStr = attributes.getValue(DEFAULT)
-            val medium = attributes.getValue(MEDIUM)
+            val url: String? = attributes.getValue(DOWNLOAD_URL)
+            val defaultStr: String? = attributes.getValue(DEFAULT)
+            val medium: String? = attributes.getValue(MEDIUM)
             var validTypeMedia = false
             var validTypeImage = false
             val isDefault = "true" == defaultStr
@@ -44,7 +44,7 @@ class Media : Namespace() {
 
             if (state.currentItem != null && (state.currentItem!!.media == null || isDefault) && url != null && validTypeMedia) {
                 var size: Long = 0
-                val sizeStr = attributes.getValue(SIZE)
+                val sizeStr: String? = attributes.getValue(SIZE)
                 if (!sizeStr.isNullOrEmpty()) {
                     try {
                         size = sizeStr.toLong()
@@ -53,7 +53,7 @@ class Media : Namespace() {
                     }
                 }
                 var durationMs = 0
-                val durationStr = attributes.getValue(DURATION)
+                val durationStr: String? = attributes.getValue(DURATION)
                 if (!durationStr.isNullOrEmpty()) {
                     try {
                         val duration = durationStr.toLong()
@@ -71,7 +71,7 @@ class Media : Namespace() {
                 state.currentItem!!.imageUrl = url
             }
         } else if (IMAGE == localName) {
-            val url = attributes.getValue(IMAGE_URL)
+            val url: String? = attributes.getValue(IMAGE_URL)
             if (url != null) {
                 if (state.currentItem != null) {
                     state.currentItem!!.imageUrl = url
@@ -82,7 +82,7 @@ class Media : Namespace() {
                 }
             }
         } else if (DESCRIPTION == localName) {
-            val type = attributes.getValue(DESCRIPTION_TYPE)
+            val type: String? = attributes.getValue(DESCRIPTION_TYPE)
             return AtomText(localName, this, type)
         }
         return SyndElement(localName, this)
diff --git a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/PodcastIndex.kt b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/PodcastIndex.kt
index 6fad4414..c83aa1e1 100644
--- a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/PodcastIndex.kt
+++ b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/PodcastIndex.kt
@@ -9,13 +9,13 @@ class PodcastIndex : Namespace() {
     override fun handleElementStart(localName: String, state: HandlerState,
                                     attributes: Attributes): SyndElement {
         if (FUNDING == localName) {
-            val href = attributes.getValue(URL)
+            val href: String? = attributes.getValue(URL)
             val funding = FeedFunding(href, "")
             state.currentFunding = funding
             state.feed.addPayment(state.currentFunding!!)
         } else if (CHAPTERS == localName) {
-            val href = attributes.getValue(URL)
-            if (href.isNotEmpty()) {
+            val href: String? = attributes.getValue(URL)
+            if (!href.isNullOrEmpty()) {
                 state.currentItem!!.podcastIndexChapterUrl = href
             }
         }
diff --git a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Rss20.kt b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Rss20.kt
index c18c8464..6a2b5076 100644
--- a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Rss20.kt
+++ b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/Rss20.kt
@@ -22,14 +22,14 @@ class Rss20 : Namespace() {
             state.items.add(state.currentItem!!)
             state.currentItem!!.feed = state.feed
         } else if (ENCLOSURE == localName && ITEM == state.tagstack.peek()?.name) {
-            val url = attributes.getValue(ENC_URL)
-            val mimeType = getMimeType(attributes.getValue(ENC_TYPE), url)
+            val url: String? = attributes.getValue(ENC_URL)
+            val mimeType: String? = getMimeType(attributes.getValue(ENC_TYPE), url)
 
-            val validUrl = url.isNotEmpty()
+            val validUrl = !url.isNullOrBlank()
             if (state.currentItem?.media == null && isMediaFile(mimeType) && validUrl) {
                 var size: Long = 0
                 try {
-                    size = attributes.getValue(ENC_LEN).toLong()
+                    size = attributes.getValue(ENC_LEN)?.toLong() ?: 0
                     if (size < 16384) {
                         // less than 16kb is suspicious, check manually
                         size = 0
diff --git a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/SimpleChapters.kt b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/SimpleChapters.kt
index d2812c29..b44dee29 100644
--- a/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/SimpleChapters.kt
+++ b/app/src/main/java/ac/mdiq/podcini/feed/parser/namespace/SimpleChapters.kt
@@ -12,13 +12,13 @@ class SimpleChapters : Namespace() {
         if (currentItem != null) {
             if (localName == CHAPTERS) {
                 currentItem.chapters = mutableListOf()
-            } else if (localName == CHAPTER && attributes.getValue(START).isNotEmpty()) {
+            } else if (localName == CHAPTER && !attributes.getValue(START).isNullOrEmpty()) {
                 // if the chapter's START is empty, we don't need to do anything
                 try {
-                    val start = parseTimeString(attributes.getValue(START))
-                    val title = attributes.getValue(TITLE)
-                    val link = attributes.getValue(HREF)
-                    val imageUrl = attributes.getValue(IMAGE)
+                    val start= parseTimeString(attributes.getValue(START))
+                    val title: String? = attributes.getValue(TITLE)
+                    val link: String? = attributes.getValue(HREF)
+                    val imageUrl: String? = attributes.getValue(IMAGE)
                     val chapter = Chapter(start, title, link, imageUrl)
                     currentItem.chapters?.add(chapter)
                 } catch (e: NumberFormatException) {
diff --git a/build.gradle b/build.gradle
index c1ce5a19..657f240a 100644
--- a/build.gradle
+++ b/build.gradle
@@ -13,6 +13,10 @@ buildscript {
     }
 }
 
+plugins {
+    id 'com.google.devtools.ksp' version '1.9.22-1.0.17' apply false
+}
+
 allprojects {
     repositories {
         google()
@@ -21,48 +25,6 @@ allprojects {
     }
 }
 
-project.ext {
-    // AndroidX
-    annotationVersion = "1.7.1"
-    appcompatVersion = "1.6.1"
-    coreVersion = "1.12.0"
-    fragmentVersion = "1.6.2"
-    mediaVersion = "1.7.0"
-    paletteVersion = "1.0.0"
-    preferenceVersion = "1.2.1"
-    recyclerViewVersion = "1.3.2"
-    viewPager2Version = "1.1.0-beta02"
-    workManagerVersion = "2.9.0"
-    googleMaterialVersion = "1.11.0"
-
-    // Third-party
-    commonslangVersion = "3.14.0"
-    commonsioVersion = "2.15.1"
-    jsoupVersion = "1.17.2"
-    glideVersion = "4.16.0"
-    okhttpVersion = "4.12.0"
-    okioVersion = "3.7.0"
-    eventbusVersion = "3.3.1"
-    rxAndroidVersion = "2.1.1"
-    rxJavaVersion = "2.2.21"
-    iconifyVersion = "2.2.2"
-    annimonStreamVersion = "1.2.2"
-    media3Version = "1.2.1"
-
-    // Google Play build
-    wearableSupportVersion = "2.6.0"
-
-    //Tests
-    awaitilityVersion = "4.2.0"
-    junitVersion = "4.13.2"
-    junit5Version = "5.10.1"
-    robolectricVersion = "4.11.1"
-    espressoVersion = "3.5.0"
-    runnerVersion = "1.5.2"
-    rulesVersion = "1.5.0"
-    testCoreVersion = "1.5.0"
-}
-
 apply plugin: "checkstyle"
 checkstyle {
     toolVersion '10.3.1'
diff --git a/changelog.md b/changelog.md
index 97cb3e5c..3b670b44 100644
--- a/changelog.md
+++ b/changelog.md
@@ -62,4 +62,10 @@
 * removed info button in FeedItemList header
 * added items count in FeedItemList header
 * fixed bug in FeedItemList when filtered list has no items
-* buildConfig is set in build.gradle instead of gradle.properties
\ No newline at end of file
+* buildConfig is set in build.gradle instead of gradle.properties
+
+## 4.2.4
+
+* fixed the "getValue() can not be null" bug
+* enabled ksp for Kotlin builds
+* cleaned up build.gradle files
\ No newline at end of file
diff --git a/common.gradle b/common.gradle
deleted file mode 100644
index d6a86f9c..00000000
--- a/common.gradle
+++ /dev/null
@@ -1,109 +0,0 @@
-android {
-    defaultConfig {
-        minSdk 21
-        compileSdk 34
-        targetSdk 34
-
-        kotlinOptions {
-            jvmTarget = '17'
-        }
-
-        vectorDrawables.useSupportLibrary false
-        vectorDrawables.generatedDensities = []
-
-        testApplicationId "ac.mdiq.podcini.tests"
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
-    }
-
-    buildTypes {
-        release {
-            proguardFiles getDefaultProguardFile("proguard-android.txt"), "proguard.cfg"
-            resValue "string", "app_name", "Podcini"
-        }
-        debug {
-            resValue "string", "app_name", "Podcini Debug"
-        }
-    }
-
-    packagingOptions {
-        resources {
-            excludes += ["META-INF/LICENSE.txt",
-                         "META-INF/NOTICE.txt",
-                         "META-INF/CHANGES",
-                         "META-INF/README.md"]
-        }
-    }
-
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_17
-        targetCompatibility JavaVersion.VERSION_17
-    }
-
-    testOptions {
-        animationsDisabled = true
-        unitTests {
-            includeAndroidResources = true
-        }
-    }
-
-    lint {
-        disable "GradleDependency"
-        checkDependencies true
-        warningsAsErrors true
-        abortOnError true
-        checkGeneratedSources = true
-    }
-
-    buildFeatures {
-        viewBinding true
-    }
-}
-
-tasks.withType(Test).configureEach {
-    testLogging {
-        exceptionFormat "full"
-        events "skipped", "passed", "failed"
-        showStandardStreams true
-        displayGranularity 2
-    }
-}
-
-gradle.projectsEvaluated {
-    tasks.withType(JavaCompile).tap {
-        configureEach {
-            options.compilerArgs << "-Xlint"
-        }
-    }
-}
-
-apply plugin: 'com.github.spotbugs'
-
-spotbugs {
-    effort = 'max'
-    reportLevel = 'medium'
-    excludeFilter = rootProject.file('config/spotbugs/exclude.xml')
-    ignoreFailures = true // Handled by printing task
-}
-
-gradle.taskGraph.beforeTask { task ->
-    if (task.name.toLowerCase().contains('spotbugs')) {
-        task.doLast {
-            def reportFile = task.project.file("build/reports/spotbugs/playDebug.xml")
-            if (!reportFile.exists()) return
-            def slurped = new groovy.xml.XmlSlurper().parse(reportFile)
-
-            def foundErrors = false
-            slurped['BugInstance'].each { bug ->
-                logger.error "[SpotBugs] ${bug['LongMessage']} [${bug.@'type'}]"
-                bug['SourceLine'].each { line ->
-                    logger.error "[SpotBugs]     ${line['Message']}"
-                    foundErrors = true
-                }
-            }
-            if (foundErrors) {
-                throw new TaskExecutionException(task,
-                        new Exception("SpotBugs violations were found. See output above for details."))
-            }
-        }
-    }
-}
diff --git a/fastlane/metadata/android/en-US/changelogs/3020107.txt b/fastlane/metadata/android/en-US/changelogs/3020107.txt
new file mode 100644
index 00000000..99ab91d9
--- /dev/null
+++ b/fastlane/metadata/android/en-US/changelogs/3020107.txt
@@ -0,0 +1,6 @@
+ 
+Version 4.2.4 brings several changes:
+
+* fixed the "getValue() can not be null" bug
+* enabled ksp for Kotlin builds
+* cleaned up build.gradle files
diff --git a/playFlavor.gradle b/playFlavor.gradle
deleted file mode 100644
index 9f2a3d8d..00000000
--- a/playFlavor.gradle
+++ /dev/null
@@ -1,11 +0,0 @@
-android {
-    flavorDimensions += ["market"]
-    productFlavors {
-        free {
-            dimension "market"
-        }
-        play {
-            dimension "market"
-        }
-    }
-}