diff --git a/app/build.gradle b/app/build.gradle
index 828f781..3d2ba0b 100644
--- a/app/build.gradle
+++ b/app/build.gradle
@@ -17,12 +17,16 @@ android {
             minifyEnabled false
         }
     }
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
 }
 
 dependencies {
-    compile fileTree(dir: 'libs', include: ['*.jar'])
-    compile 'com.android.support:appcompat-v7:25.3.1'
-    compile 'com.github.johnkil.print:print:1.3.1'
-    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
-    compile project(':library')
+    implementation fileTree(include: ['*.jar'], dir: 'libs')
+    implementation 'com.android.support:appcompat-v7:28.0.0'
+    implementation 'com.github.johnkil.print:print:1.3.1'
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
+    implementation project(':library')
 }
diff --git a/app/src/main/java/com/unnamed/b/atv/sample/fragment/CustomViewHolderFragment.kt b/app/src/main/java/com/unnamed/b/atv/sample/fragment/CustomViewHolderFragment.kt
index 188e86b..8df792b 100644
--- a/app/src/main/java/com/unnamed/b/atv/sample/fragment/CustomViewHolderFragment.kt
+++ b/app/src/main/java/com/unnamed/b/atv/sample/fragment/CustomViewHolderFragment.kt
@@ -6,6 +6,7 @@ import android.text.TextUtils
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import android.widget.TextView
 import com.unnamed.b.atv.model.TreeNode
 import com.unnamed.b.atv.sample.R
 import com.unnamed.b.atv.sample.holder.*
@@ -22,21 +23,21 @@ class CustomViewHolderFragment : Fragment() {
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
         val rootView = inflater.inflate(R.layout.fragment_default, container, false)
         val containerView = rootView.findViewById(R.id.container) as ViewGroup
-        rootView.findViewById(R.id.status_bar).visibility = View.GONE
+        rootView.findViewById<TextView>(R.id.status_bar).visibility = View.GONE
 
         val root = TreeNode.root()
 
-        val myProfile = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "My Profile")).setViewHolder(ProfileHolder(activity))
-        val bruce = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "Bruce Wayne")).setViewHolder(ProfileHolder(activity))
-        val clark = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "Clark Kent")).setViewHolder(ProfileHolder(activity))
-        val barry = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "Barry Allen")).setViewHolder(ProfileHolder(activity))
+        val myProfile = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "My Profile")).setViewHolder(ProfileHolder(context!!))
+        val bruce = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "Bruce Wayne")).setViewHolder(ProfileHolder(context!!))
+        val clark = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "Clark Kent")).setViewHolder(ProfileHolder(context!!))
+        val barry = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_person, "Barry Allen")).setViewHolder(ProfileHolder(context!!))
         addProfileData(myProfile)
         addProfileData(clark)
         addProfileData(bruce)
         addProfileData(barry)
         root.addChildren(myProfile, bruce, barry, clark)
 
-        tView = AndroidTreeView(activity, root)
+        tView = AndroidTreeView(context!!, root)
         tView!!.setDefaultAnimation(true)
         tView!!.setDefaultContainerStyle(R.style.TreeNodeStyleDivided, true)
         containerView.addView(tView!!.view)
@@ -52,16 +53,16 @@ class CustomViewHolderFragment : Fragment() {
     }
 
     private fun addProfileData(profile: TreeNode) {
-        val socialNetworks = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_people, "Social")).setViewHolder(HeaderHolder(activity))
-        val places = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_place, "Places")).setViewHolder(HeaderHolder(activity))
+        val socialNetworks = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_people, "Social")).setViewHolder(HeaderHolder(context!!))
+        val places = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_place, "Places")).setViewHolder(HeaderHolder(context!!))
 
-        val facebook = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_facebook)).setViewHolder(SocialViewHolder(activity))
-        val linkedin = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_linkedin)).setViewHolder(SocialViewHolder(activity))
-        val google = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_gplus)).setViewHolder(SocialViewHolder(activity))
-        val twitter = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_twitter)).setViewHolder(SocialViewHolder(activity))
+        val facebook = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_facebook)).setViewHolder(SocialViewHolder(context!!))
+        val linkedin = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_linkedin)).setViewHolder(SocialViewHolder(context!!))
+        val google = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_gplus)).setViewHolder(SocialViewHolder(context!!))
+        val twitter = TreeNode(SocialViewHolder.SocialItem(R.string.ic_post_twitter)).setViewHolder(SocialViewHolder(context!!))
 
-        val lake = TreeNode(PlaceHolderHolder.PlaceItem("A rose garden")).setViewHolder(PlaceHolderHolder(activity))
-        val mountains = TreeNode(PlaceHolderHolder.PlaceItem("The white house")).setViewHolder(PlaceHolderHolder(activity))
+        val lake = TreeNode(PlaceHolderHolder.PlaceItem("A rose garden")).setViewHolder(PlaceHolderHolder(context!!))
+        val mountains = TreeNode(PlaceHolderHolder.PlaceItem("The white house")).setViewHolder(PlaceHolderHolder(context!!))
 
         places.addChildren(lake, mountains)
         socialNetworks.addChildren(facebook, google, twitter, linkedin)
diff --git a/app/src/main/java/com/unnamed/b/atv/sample/fragment/FolderStructureFragment.kt b/app/src/main/java/com/unnamed/b/atv/sample/fragment/FolderStructureFragment.kt
index e2948cd..eb8ca9f 100644
--- a/app/src/main/java/com/unnamed/b/atv/sample/fragment/FolderStructureFragment.kt
+++ b/app/src/main/java/com/unnamed/b/atv/sample/fragment/FolderStructureFragment.kt
@@ -56,7 +56,7 @@ class FolderStructureFragment : Fragment() {
 
         root.addChildren(computerRoot)
 
-        tView = AndroidTreeView(activity, root)
+        tView = AndroidTreeView(context!!, root)
         tView!!.setDefaultAnimation(true)
         tView!!.setDefaultContainerStyle(R.style.TreeNodeStyleCustom)
         tView!!.setDefaultViewHolder(IconTreeItemHolder::class.java)
@@ -109,7 +109,7 @@ class FolderStructureFragment : Fragment() {
     private val nodeLongClickListener = object : TreeNode.TreeNodeLongClickListener {
         override fun onLongClick(node: TreeNode, value: Any): Boolean {
             val item = value as IconTreeItemHolder.IconTreeItem
-            Toast.makeText(activity, "Long click: " + item.text, Toast.LENGTH_SHORT).show()
+            Toast.makeText(context, "Long click: " + item.text, Toast.LENGTH_SHORT).show()
             return true
         }
     }
diff --git a/app/src/main/java/com/unnamed/b/atv/sample/fragment/SelectableTreeFragment.kt b/app/src/main/java/com/unnamed/b/atv/sample/fragment/SelectableTreeFragment.kt
index bfff4f2..cde9596 100644
--- a/app/src/main/java/com/unnamed/b/atv/sample/fragment/SelectableTreeFragment.kt
+++ b/app/src/main/java/com/unnamed/b/atv/sample/fragment/SelectableTreeFragment.kt
@@ -6,7 +6,9 @@ import android.text.TextUtils
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import android.widget.Button
 import android.widget.Toast
+import com.github.johnkil.print.PrintButton
 import com.unnamed.b.atv.model.TreeNode
 import com.unnamed.b.atv.sample.R
 import com.unnamed.b.atv.sample.holder.IconTreeItemHolder
@@ -29,47 +31,47 @@ class SelectableTreeFragment : Fragment() {
         val rootView = inflater.inflate(R.layout.fragment_selectable_nodes, null, false)
         val containerView = rootView.findViewById(R.id.container) as ViewGroup
 
-        val selectionModeButton = rootView.findViewById(R.id.btn_toggleSelection)
+        val selectionModeButton = rootView.findViewById<PrintButton>(R.id.btn_toggleSelection)
         selectionModeButton.setOnClickListener {
             selectionModeEnabled = !selectionModeEnabled
             tView!!.isSelectionModeEnabled = selectionModeEnabled
         }
 
-        val selectAllBtn = rootView.findViewById(R.id.btn_selectAll)
+        val selectAllBtn = rootView.findViewById<Button>(R.id.btn_selectAll)
         selectAllBtn.setOnClickListener {
             if (!selectionModeEnabled) {
-                Toast.makeText(activity, "Enable selection mode first", Toast.LENGTH_SHORT).show()
+                Toast.makeText(context!!, "Enable selection mode first", Toast.LENGTH_SHORT).show()
             }
             tView!!.selectAll(true)
         }
 
-        val deselectAll = rootView.findViewById(R.id.btn_deselectAll)
+        val deselectAll = rootView.findViewById<Button>(R.id.btn_deselectAll)
         deselectAll.setOnClickListener {
             if (!selectionModeEnabled) {
-                Toast.makeText(activity, "Enable selection mode first", Toast.LENGTH_SHORT).show()
+                Toast.makeText(context!!, "Enable selection mode first", Toast.LENGTH_SHORT).show()
             }
             tView!!.deselectAll()
         }
 
-        val check = rootView.findViewById(R.id.btn_checkSelection)
+        val check = rootView.findViewById<Button>(R.id.btn_checkSelection)
         check.setOnClickListener {
             if (!selectionModeEnabled) {
-                Toast.makeText(activity, "Enable selection mode first", Toast.LENGTH_SHORT).show()
+                Toast.makeText(context!!, "Enable selection mode first", Toast.LENGTH_SHORT).show()
             } else {
-                Toast.makeText(activity, tView!!.selected.size.toString() + " selected", Toast.LENGTH_SHORT).show()
+                Toast.makeText(context!!, tView!!.selected.size.toString() + " selected", Toast.LENGTH_SHORT).show()
             }
         }
 
         val root = TreeNode.root()
 
-        val s1 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_sd_storage, "Storage1")).setViewHolder(ProfileHolder(activity))
-        val s2 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_sd_storage, "Storage2")).setViewHolder(ProfileHolder(activity))
+        val s1 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_sd_storage, "Storage1")).setViewHolder(ProfileHolder(context!!))
+        val s2 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_sd_storage, "Storage2")).setViewHolder(ProfileHolder(context!!))
         s1.isSelectable = false
         s2.isSelectable = false
 
-        val folder1 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder 1")).setViewHolder(SelectableHeaderHolder(activity))
-        val folder2 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder 2")).setViewHolder(SelectableHeaderHolder(activity))
-        val folder3 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder 3")).setViewHolder(SelectableHeaderHolder(activity))
+        val folder1 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder 1")).setViewHolder(SelectableHeaderHolder(context!!))
+        val folder2 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder 2")).setViewHolder(SelectableHeaderHolder(context!!))
+        val folder3 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder 3")).setViewHolder(SelectableHeaderHolder(context!!))
 
         fillFolder(folder1)
         fillFolder(folder2)
@@ -80,7 +82,7 @@ class SelectableTreeFragment : Fragment() {
 
         root.addChildren(s1, s2)
 
-        tView = AndroidTreeView(activity, root)
+        tView = AndroidTreeView(context!!, root)
         tView!!.setDefaultAnimation(true)
         containerView.addView(tView!!.view)
 
@@ -94,9 +96,9 @@ class SelectableTreeFragment : Fragment() {
     }
 
     private fun fillFolder(folder: TreeNode) {
-        val file1 = TreeNode("File1").setViewHolder(SelectableItemHolder(activity))
-        val file2 = TreeNode("File2").setViewHolder(SelectableItemHolder(activity))
-        val file3 = TreeNode("File3").setViewHolder(SelectableItemHolder(activity))
+        val file1 = TreeNode("File1").setViewHolder(SelectableItemHolder(context!!))
+        val file2 = TreeNode("File2").setViewHolder(SelectableItemHolder(context!!))
+        val file3 = TreeNode("File3").setViewHolder(SelectableItemHolder(context!!))
         folder.addChildren(file1, file2, file3)
     }
 
diff --git a/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingArrowExpandFragment.kt b/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingArrowExpandFragment.kt
index 00760cb..adb03e0 100644
--- a/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingArrowExpandFragment.kt
+++ b/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingArrowExpandFragment.kt
@@ -6,6 +6,7 @@ import android.text.TextUtils
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import android.widget.LinearLayout
 import android.widget.Toast
 import com.unnamed.b.atv.model.TreeNode
 import com.unnamed.b.atv.sample.R
@@ -23,22 +24,22 @@ class TwoDScrollingArrowExpandFragment : Fragment(), TreeNode.TreeNodeClickListe
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
         val rootView = inflater.inflate(R.layout.fragment_selectable_nodes, null, false)
-        rootView.findViewById(R.id.status).visibility = View.GONE
+        rootView.findViewById<LinearLayout>(R.id.status).visibility = View.GONE
         val containerView = rootView.findViewById(R.id.container) as ViewGroup
 
         val root = TreeNode.root()
 
         val s1 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder with very long name ")).setViewHolder(
-                ArrowExpandSelectableHeaderHolder(activity))
+                ArrowExpandSelectableHeaderHolder(context!!))
         val s2 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Another folder with very long name")).setViewHolder(
-                ArrowExpandSelectableHeaderHolder(activity))
+                ArrowExpandSelectableHeaderHolder(context!!))
 
         fillFolder(s1)
         fillFolder(s2)
 
         root.addChildren(s1, s2)
 
-        tView = AndroidTreeView(activity, root)
+        tView = AndroidTreeView(context!!, root)
         tView!!.setDefaultAnimation(true)
         tView!!.setUse2dScroll(true)
         tView!!.setDefaultContainerStyle(R.style.TreeNodeStyleCustom)
@@ -73,7 +74,7 @@ class TwoDScrollingArrowExpandFragment : Fragment(), TreeNode.TreeNodeClickListe
     }
 
     override fun onClick(node: TreeNode, value: Any) {
-        val toast = Toast.makeText(activity, (value as IconTreeItemHolder.IconTreeItem).text, Toast.LENGTH_SHORT)
+        val toast = Toast.makeText(context!!, (value as IconTreeItemHolder.IconTreeItem).text, Toast.LENGTH_SHORT)
         toast.show()
     }
 
diff --git a/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingFragment.kt b/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingFragment.kt
index eedd4c3..7c11b7a 100644
--- a/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingFragment.kt
+++ b/app/src/main/java/com/unnamed/b/atv/sample/fragment/TwoDScrollingFragment.kt
@@ -6,6 +6,7 @@ import android.text.TextUtils
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import android.widget.LinearLayout
 
 import com.unnamed.b.atv.model.TreeNode
 import com.unnamed.b.atv.sample.R
@@ -22,20 +23,20 @@ class TwoDScrollingFragment : Fragment() {
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
         val rootView = inflater.inflate(R.layout.fragment_selectable_nodes, container, false)
-        rootView.findViewById(R.id.status).visibility = View.GONE
+        rootView.findViewById<LinearLayout>(R.id.status).visibility = View.GONE
         val containerView = rootView.findViewById(R.id.container) as ViewGroup
 
         val root = TreeNode.root()
 
-        val s1 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder with very long name ")).setViewHolder(SelectableHeaderHolder(activity))
-        val s2 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Another folder with very long name")).setViewHolder(SelectableHeaderHolder(activity))
+        val s1 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Folder with very long name ")).setViewHolder(SelectableHeaderHolder(context!!))
+        val s2 = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "Another folder with very long name")).setViewHolder(SelectableHeaderHolder(context!!))
 
         fillFolder(s1)
         fillFolder(s2)
 
         root.addChildren(s1, s2)
 
-        tView = AndroidTreeView(activity, root)
+        tView = AndroidTreeView(context!!, root)
         tView!!.setDefaultAnimation(true)
         tView!!.setUse2dScroll(true)
         tView!!.setDefaultContainerStyle(R.style.TreeNodeStyleCustom)
@@ -55,7 +56,7 @@ class TwoDScrollingFragment : Fragment() {
     private fun fillFolder(folder: TreeNode) {
         var currentNode = folder
         for (i in 0..9) {
-            val file = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, NAME)).setViewHolder(SelectableHeaderHolder(activity))
+            val file = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, NAME)).setViewHolder(SelectableHeaderHolder(context!!))
             currentNode.addChild(file)
             currentNode = file
         }
diff --git a/app/src/main/java/com/unnamed/b/atv/sample/holder/IconTreeItemHolder.kt b/app/src/main/java/com/unnamed/b/atv/sample/holder/IconTreeItemHolder.kt
index e41fcb6..680a129 100644
--- a/app/src/main/java/com/unnamed/b/atv/sample/holder/IconTreeItemHolder.kt
+++ b/app/src/main/java/com/unnamed/b/atv/sample/holder/IconTreeItemHolder.kt
@@ -27,16 +27,16 @@ class IconTreeItemHolder(context: Context) : TreeNode.BaseNodeViewHolder<IconTre
 
         arrowView = view.findViewById(R.id.arrow_icon) as PrintView
 
-        view.findViewById(R.id.btn_addFolder).setOnClickListener {
+        view.findViewById<PrintView>(R.id.btn_addFolder).setOnClickListener {
             val newFolder = TreeNode(IconTreeItemHolder.IconTreeItem(R.string.ic_folder, "New Folder"))
             treeView!!.addNode(node, newFolder)
         }
 
-        view.findViewById(R.id.btn_delete).setOnClickListener { treeView!!.removeNode(node) }
+        view.findViewById<PrintView>(R.id.btn_delete).setOnClickListener { treeView!!.removeNode(node) }
 
         //if My computer
         if (node.level == 1) {
-            view.findViewById(R.id.btn_delete).visibility = View.GONE
+            view.findViewById<PrintView>(R.id.btn_delete).visibility = View.GONE
         }
 
         return view
diff --git a/app/src/main/java/com/unnamed/b/atv/sample/holder/SelectableItemHolder.kt b/app/src/main/java/com/unnamed/b/atv/sample/holder/SelectableItemHolder.kt
index 2e28427..1919ca0 100644
--- a/app/src/main/java/com/unnamed/b/atv/sample/holder/SelectableItemHolder.kt
+++ b/app/src/main/java/com/unnamed/b/atv/sample/holder/SelectableItemHolder.kt
@@ -28,7 +28,7 @@ class SelectableItemHolder(context: Context) : TreeNode.BaseNodeViewHolder<Strin
         nodeSelector!!.isChecked = node.isSelected
 
         if (node.isLastChild) {
-            view.findViewById(R.id.bot_line).visibility = View.INVISIBLE
+            view.findViewById<View>(R.id.bot_line).visibility = View.INVISIBLE
         }
 
         return view
diff --git a/build.gradle b/build.gradle
index 01a6ae9..4290fc3 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,12 +1,13 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 
 buildscript {
-    ext.kotlin_version = '1.1.3-2'
+    ext.kotlin_version = '1.3.30'
     repositories {
         jcenter()
+        google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.3.3'
+        classpath 'com.android.tools.build:gradle:3.3.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
 
         // NOTE: Do not place your application dependencies here; they belong
@@ -24,6 +25,7 @@ allprojects {
 
     repositories {
         jcenter()
+        google()
     }
 }
 
diff --git a/gradle.properties b/gradle.properties
index 3bf73e3..3e9c70d 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -21,10 +21,10 @@ VERSION_NAME=1.3.0
 VERSION_CODE=12
 
 
-ANDROID_BUILD_MIN_SDK_VERSION=11
-ANDROID_BUILD_TARGET_SDK_VERSION=25
-ANDROID_BUILD_SDK_VERSION=25
-ANDROID_BUILD_TOOLS_VERSION=25.0.3
+ANDROID_BUILD_MIN_SDK_VERSION=14
+ANDROID_BUILD_TARGET_SDK_VERSION=28
+ANDROID_BUILD_SDK_VERSION=28
+ANDROID_BUILD_TOOLS_VERSION=28.0.3
 
 GROUP=com.github.bmelnychuk
 POM_DESCRIPTION=Tree View implementation for android
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index e75f47b..013927c 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,6 @@
-#Sun Jul 16 01:41:43 IST 2017
+#Fri Apr 12 13:23:36 MSK 2019
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-3.3-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-4.10.1-all.zip
diff --git a/library/build.gradle b/library/build.gradle
index 7cfd8db..30467bb 100644
--- a/library/build.gradle
+++ b/library/build.gradle
@@ -19,9 +19,9 @@ android {
 }
 
 dependencies {
-    compile fileTree(dir: 'libs', include: ['*.jar'])
-    compile 'com.android.support:appcompat-v7:25.3.1'
-    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
+    implementation fileTree(dir: 'libs', include: ['*.jar'])
+    implementation 'com.android.support:appcompat-v7:28.0.0'
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
 }
 
 apply from: '../maven_push.gradle'
diff --git a/library/src/main/java/com/unnamed/b/atv/model/TreeNode.kt b/library/src/main/java/com/unnamed/b/atv/model/TreeNode.kt
index b4d7510..f2dc307 100644
--- a/library/src/main/java/com/unnamed/b/atv/model/TreeNode.kt
+++ b/library/src/main/java/com/unnamed/b/atv/model/TreeNode.kt
@@ -212,7 +212,7 @@ class TreeNode(val value: Any?) {
             get() = createNodeView(mNode!!, mNode!!.value as E)
 
         open val nodeItemsView: ViewGroup
-            get() = view.findViewById(R.id.node_items) as ViewGroup
+            get() = view.findViewById<ViewGroup>(R.id.node_items) as ViewGroup
 
         val isInitialized: Boolean
             get() = mView != null
diff --git a/library/src/main/java/com/unnamed/b/atv/view/AndroidTreeView.kt b/library/src/main/java/com/unnamed/b/atv/view/AndroidTreeView.kt
index 092ca6d..623c6a0 100644
--- a/library/src/main/java/com/unnamed/b/atv/view/AndroidTreeView.kt
+++ b/library/src/main/java/com/unnamed/b/atv/view/AndroidTreeView.kt
@@ -20,7 +20,7 @@ import java.util.*
  */
 class AndroidTreeView {
 
-    protected var mRoot: TreeNode? = null
+    private var mRoot: TreeNode? = null
     private var mContext: Context? = null
     private var applyForRoot: Boolean = false
     private var containerStyle = 0