diff --git a/.travis/build.sh b/.travis/build.sh
index d0c376befa..049fd015be 100755
--- a/.travis/build.sh
+++ b/.travis/build.sh
@@ -12,7 +12,7 @@ if [ -z "$TRAVIS_TAG" ]; then
 else
     ./gradlew clean assembleStandardRelease
 
-    TOOLS="${ANDROID_HOME}/build-tools/26.0.1"
+    TOOLS="$(ls -d ${ANDROID_HOME}/build-tools/* | tail -1)"
     export ARTIFACT="tachiyomi-${TRAVIS_TAG}.apk"
 
     ${TOOLS}/zipalign -v -p 4 app/build/outputs/apk/standard/release/app-standard-release-unsigned.apk app-aligned.apk
diff --git a/app/build.gradle b/app/build.gradle
index 4994c07550..b8dbf6ea5f 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -30,7 +30,7 @@ ext {
 
 android {
     compileSdkVersion 26
-    buildToolsVersion "26.0.2"
+    buildToolsVersion "27.0.1"
     publishNonDefault true
 
     defaultConfig {
@@ -106,7 +106,7 @@ dependencies {
     implementation 'com.github.inorichi:junrar-android:634c1f5'
 
     // Android support library
-    final support_library_version = '26.1.0'
+    final support_library_version = '27.0.1'
     implementation "com.android.support:support-v4:$support_library_version"
     implementation "com.android.support:appcompat-v7:$support_library_version"
     implementation "com.android.support:cardview-v7:$support_library_version"
@@ -122,13 +122,13 @@ dependencies {
 
     // ReactiveX
     implementation 'io.reactivex:rxandroid:1.2.1'
-    implementation 'io.reactivex:rxjava:1.3.3'
+    implementation 'io.reactivex:rxjava:1.3.4'
     implementation 'com.jakewharton.rxrelay:rxrelay:1.2.0'
     implementation 'com.f2prateek.rx.preferences:rx-preferences:1.0.2'
     implementation 'com.github.pwittchen:reactivenetwork:0.7.0'
 
     // Network client
-    implementation "com.squareup.okhttp3:okhttp:3.9.0"
+    implementation "com.squareup.okhttp3:okhttp:3.9.1"
     implementation 'com.squareup.okio:okio:1.13.0'
 
     // REST
@@ -232,7 +232,7 @@ dependencies {
 }
 
 buildscript {
-    ext.kotlin_version = '1.1.51'
+    ext.kotlin_version = '1.1.61'
     repositories {
         mavenCentral()
     }
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryAdapter.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryAdapter.kt
index ae19c08ad2..247b113ba0 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryAdapter.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryAdapter.kt
@@ -79,7 +79,7 @@ class LibraryAdapter(private val controller: LibraryController) : RecyclerViewPa
     /**
      * Returns the position of the view.
      */
-    override fun getItemPosition(obj: Any?): Int {
+    override fun getItemPosition(obj: Any): Int {
         val view = obj as? LibraryCategoryView ?: return POSITION_NONE
         val index = categories.indexOfFirst { it.id == view.category.id }
         return if (index == -1) POSITION_NONE else index
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderCustomFilterDialog.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderCustomFilterDialog.kt
index 7e3ac10038..d76a5156f8 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderCustomFilterDialog.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderCustomFilterDialog.kt
@@ -64,7 +64,7 @@ class ReaderCustomFilterDialog : DialogFragment() {
      * @param savedState The last saved instance state of the Fragment.
      */
     override fun onCreateDialog(savedState: Bundle?): Dialog {
-        val dialog = MaterialDialog.Builder(activity)
+        val dialog = MaterialDialog.Builder(activity!!)
                 .customView(R.layout.reader_custom_filter_dialog, false)
                 .positiveText(android.R.string.ok)
                 .build()
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderSettingsDialog.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderSettingsDialog.kt
index fa09cc120a..8927ad4fe3 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderSettingsDialog.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderSettingsDialog.kt
@@ -24,7 +24,7 @@ class ReaderSettingsDialog : DialogFragment() {
     private lateinit var subscriptions: CompositeSubscription
 
     override fun onCreateDialog(savedState: Bundle?): Dialog {
-        val dialog = MaterialDialog.Builder(activity)
+        val dialog = MaterialDialog.Builder(activity!!)
                 .title(R.string.label_settings)
                 .customView(R.layout.reader_settings_dialog, true)
                 .positiveText(android.R.string.ok)
@@ -40,8 +40,11 @@ class ReaderSettingsDialog : DialogFragment() {
         viewer.onItemSelectedListener = IgnoreFirstSpinnerListener { position ->
             subscriptions += Observable.timer(250, MILLISECONDS, AndroidSchedulers.mainThread())
                     .subscribe {
-                        (activity as ReaderActivity).presenter.updateMangaViewer(position)
-                        activity.recreate()
+                        val readerActivity = activity as? ReaderActivity
+                        if (readerActivity != null) {
+                            readerActivity.presenter.updateMangaViewer(position)
+                            readerActivity.recreate()
+                        }
                     }
         }
         viewer.setSelection((activity as ReaderActivity).presenter.manga.viewer, false)
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerReader.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerReader.kt
index ab12c872a2..a5a4e71d49 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerReader.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/PagerReader.kt
@@ -100,12 +100,12 @@ abstract class PagerReader : BaseReader() {
     /**
      * Text color for black theme.
      */
-    val whiteColor by lazy { ContextCompat.getColor(context, R.color.textColorSecondaryDark) }
+    val whiteColor by lazy { ContextCompat.getColor(context!!, R.color.textColorSecondaryDark) }
 
     /**
      * Text color for white theme.
      */
-    val blackColor by lazy { ContextCompat.getColor(context, R.color.textColorSecondaryLight) }
+    val blackColor by lazy { ContextCompat.getColor(context!!, R.color.textColorSecondaryLight) }
 
     /**
      * Initializes the pager.
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/HorizontalPager.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/HorizontalPager.kt
index e12f773a75..e359b7fbf2 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/HorizontalPager.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/HorizontalPager.kt
@@ -24,7 +24,7 @@ class HorizontalPager(context: Context) : ViewPager(context), Pager {
     override fun onInterceptTouchEvent(ev: MotionEvent): Boolean {
         try {
             if (ev.action and MotionEvent.ACTION_MASK == MotionEvent.ACTION_DOWN) {
-                if (currentItem == 0 || currentItem == adapter.count - 1) {
+                if (currentItem == 0 || currentItem == adapter!!.count - 1) {
                     startDragX = ev.x
                 }
             }
@@ -50,7 +50,7 @@ class HorizontalPager(context: Context) : ViewPager(context), Pager {
 
                         startDragX = 0f
                     }
-                } else if (currentItem == adapter.count - 1) {
+                } else if (currentItem == adapter!!.count - 1) {
                     if (ev.action and MotionEvent.ACTION_MASK == MotionEvent.ACTION_UP) {
                         val displacement = startDragX - ev.x
 
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/LeftToRightReader.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/LeftToRightReader.kt
index 39f533c3f7..28d170deb1 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/LeftToRightReader.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/LeftToRightReader.kt
@@ -13,7 +13,7 @@ import eu.kanade.tachiyomi.ui.reader.viewer.pager.PagerReader
 class LeftToRightReader : PagerReader() {
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedState: Bundle?): View? {
-        return HorizontalPager(activity).apply { initializePager(this) }
+        return HorizontalPager(activity!!).apply { initializePager(this) }
     }
 
 }
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/RightToLeftReader.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/RightToLeftReader.kt
index 7815bc66b4..ab866cbd68 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/RightToLeftReader.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/horizontal/RightToLeftReader.kt
@@ -13,7 +13,7 @@ import eu.kanade.tachiyomi.ui.reader.viewer.pager.PagerReader
 class RightToLeftReader : PagerReader() {
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedState: Bundle?): View? {
-        return HorizontalPager(activity).apply {
+        return HorizontalPager(activity!!).apply {
             rotation = 180f
             initializePager(this)
         }
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalReader.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalReader.kt
index 3a5716025a..028e9b1872 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalReader.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalReader.kt
@@ -13,7 +13,7 @@ import eu.kanade.tachiyomi.ui.reader.viewer.pager.PagerReader
 class VerticalReader : PagerReader() {
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedState: Bundle?): View? {
-        return VerticalPager(activity).apply { initializePager(this) }
+        return VerticalPager(activity!!).apply { initializePager(this) }
     }
 
 }
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalViewPagerImpl.java b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalViewPagerImpl.java
index d435dd24ea..d9174ff3dd 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalViewPagerImpl.java
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/pager/vertical/VerticalViewPagerImpl.java
@@ -33,7 +33,6 @@ import android.support.annotation.DrawableRes;
 import android.support.v4.os.ParcelableCompat;
 import android.support.v4.os.ParcelableCompatCreatorCallbacks;
 import android.support.v4.view.AccessibilityDelegateCompat;
-import android.support.v4.view.KeyEventCompat;
 import android.support.v4.view.MotionEventCompat;
 import android.support.v4.view.PagerAdapter;
 import android.support.v4.view.VelocityTrackerCompat;
@@ -2598,14 +2597,10 @@ public class VerticalViewPagerImpl extends ViewGroup {
                     handled = arrowScroll(FOCUS_RIGHT);
                     break;
                 case KeyEvent.KEYCODE_TAB:
-                    if (Build.VERSION.SDK_INT >= 11) {
-                        // The focus finder had a bug handling FOCUS_FORWARD and FOCUS_BACKWARD
-                        // before Android 3.0. Ignore the tab key on those devices.
-                        if (KeyEventCompat.hasNoModifiers(event)) {
-                            handled = arrowScroll(FOCUS_FORWARD);
-                        } else if (KeyEventCompat.hasModifiers(event, KeyEvent.META_SHIFT_ON)) {
-                            handled = arrowScroll(FOCUS_BACKWARD);
-                        }
+                    if (event.hasNoModifiers()) {
+                        handled = arrowScroll(FOCUS_FORWARD);
+                    } else if (event.hasModifiers(KeyEvent.META_SHIFT_ON)) {
+                        handled = arrowScroll(FOCUS_BACKWARD);
                     }
                     break;
                 default:
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonReader.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonReader.kt
index d10cb41b1d..83d3f88df3 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonReader.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/reader/viewer/webtoon/WebtoonReader.kt
@@ -73,7 +73,7 @@ class WebtoonReader : BaseReader() {
     private var scrollDistance: Int = 0
 
     val screenHeight by lazy {
-        val display = activity.windowManager.defaultDisplay
+        val display = activity!!.windowManager.defaultDisplay
 
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1) {
             val metrics = DisplayMetrics()
@@ -91,7 +91,7 @@ class WebtoonReader : BaseReader() {
         val screenHeight = resources.displayMetrics.heightPixels
         scrollDistance = screenHeight * 3 / 4
 
-        layoutManager = PreCachingLayoutManager(activity)
+        layoutManager = PreCachingLayoutManager(activity!!)
         layoutManager.extraLayoutSpace = screenHeight / 2
 
         recycler = RecyclerView(activity).apply {
diff --git a/app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsDownloadController.kt b/app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsDownloadController.kt
index 39485d6ece..04ec17f605 100644
--- a/app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsDownloadController.kt
+++ b/app/src/main/java/eu/kanade/tachiyomi/ui/setting/SettingsDownloadController.kt
@@ -194,7 +194,7 @@ class SettingsDownloadController : SettingsController() {
                     File.separator + "downloads"
 
             return mutableListOf(File(defaultDir)) +
-                    ContextCompat.getExternalFilesDirs(activity, "").filterNotNull()
+                    ContextCompat.getExternalFilesDirs(activity!!, "").filterNotNull()
         }
     }
 
diff --git a/build.gradle b/build.gradle
index 1115873b6d..7bdf0497e7 100644
--- a/build.gradle
+++ b/build.gradle
@@ -7,7 +7,7 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.0.0'
+        classpath 'com.android.tools.build:gradle:3.0.1'
         classpath 'com.github.ben-manes:gradle-versions-plugin:0.17.0'
         classpath 'com.github.zellius:android-shortcut-gradle-plugin:0.1.1'
         // NOTE: Do not place your application dependencies here; they belong