diff --git a/build.gradle b/build.gradle
index 5bd3880b6b7c2e0bb919a208dff24f7e3ba565ec..d8b3ce813f3e8a3cc88d96e4f5f8d20d301cd698 100644
--- a/build.gradle
+++ b/build.gradle
@@ -18,17 +18,17 @@
 
 buildscript {
     ext {
-        minSdkVersion = 9
-        targetSdkVersion = 25
-        compileSdkVersion = 25
-        buildToolsVersion = "25.0.3"
+        minSdkVersion = 14
+        targetSdkVersion = 26
+        compileSdkVersion = 26
+        buildToolsVersion = "26.0.0"
         androidGradlePluginVersion = "2.3.3"
         androidMavenGradlePluginVersion = "1.5"
         gradleBintrayPluginVersion = "1.6"
         kotlinVersion = "1.1.3"
-        supportLibVersion = "25.3.1"
-        espressoVersion = "2.2.2"
-        testRunnerVersion = "0.5"
+        supportLibVersion = "26.0.0"
+        espressoVersion = "3.0.0"
+        testRunnerVersion = "1.0.0"
         junitVersion = "4.12"
     }
 
diff --git a/circle.yml b/circle.yml
index 7b2d032adb0add9e4bac6381ee44459ffe7f07f8..866fe6ca754f541125ef4361874cdd041fd2f820 100644
--- a/circle.yml
+++ b/circle.yml
@@ -6,7 +6,7 @@ machine:
 
 dependencies:
     pre:
-        - echo y | android update sdk --no-ui --all --filter "android-25,build-tools-25.0.3,tools,platform-tools,extra-android-m2repository"
+        - echo y | android update sdk --no-ui --all --filter "android-26,build-tools-26.0.0,tools,platform-tools,extra-android-m2repository"
     cache_directories:
         - ~/.android
     override:
diff --git a/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatViewHolder.kt b/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatViewHolder.kt
index d2435b2c810889164624b96d06d28a29a36bee94..c56bd3240be9517e0257cca0561f176a9964a2cb 100644
--- a/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatViewHolder.kt
+++ b/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/CatViewHolder.kt
@@ -27,7 +27,7 @@ import com.google.android.flexbox.FlexboxLayoutManager
  */
 internal class CatViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
 
-    private val imageView = itemView.findViewById(R.id.imageview) as ImageView
+    private val imageView: ImageView = itemView.findViewById(R.id.imageview)
 
     internal fun bindTo(@DrawableRes drawableRes: Int) {
         imageView.setImageResource(drawableRes)
diff --git a/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/MainActivity.kt b/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/MainActivity.kt
index 8fefc7ad8126d1faa27008ec004326a741e8b800..fe9b869825e5aab9a840483c22e0348d813703c5 100644
--- a/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/MainActivity.kt
+++ b/demo-cat-gallery/src/main/java/com/google/android/flexbox/apps/catgallery/MainActivity.kt
@@ -38,7 +38,7 @@ class MainActivity : AppCompatActivity() {
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
 
-        val toolbar = findViewById(R.id.toolbar) as Toolbar
+        val toolbar: Toolbar = findViewById(R.id.toolbar)
         setSupportActionBar(toolbar)
 
         val flexboxLayoutManager = FlexboxLayoutManager(this).apply {
@@ -47,7 +47,7 @@ class MainActivity : AppCompatActivity() {
             alignItems = AlignItems.STRETCH
         }
 
-        val recyclerView = findViewById(R.id.recyclerview) as RecyclerView
+        val recyclerView: RecyclerView = findViewById(R.id.recyclerview)
         recyclerView.apply {
             layoutManager = flexboxLayoutManager
             adapter = CatAdapter()
diff --git a/demo-playground/src/main/java/com/google/android/flexbox/FlexItemEditFragment.kt b/demo-playground/src/main/java/com/google/android/flexbox/FlexItemEditFragment.kt
index 1b7ee9ecd4fc26f3347d877ad0fa304a20222d49..7ac4894fb7b96483fc34e29cd3c8057f9a99e50f 100644
--- a/demo-playground/src/main/java/com/google/android/flexbox/FlexItemEditFragment.kt
+++ b/demo-playground/src/main/java/com/google/android/flexbox/FlexItemEditFragment.kt
@@ -94,9 +94,8 @@ internal class FlexItemEditFragment : DialogFragment() {
         dialog.setTitle((viewIndex + 1).toString())
 
         val activity = activity
-        val orderTextInput = view
-                .findViewById(R.id.input_layout_order) as TextInputLayout
-        val orderEdit = view.findViewById(R.id.edit_text_order) as EditText
+        val orderTextInput: TextInputLayout = view.findViewById(R.id.input_layout_order)
+        val orderEdit: EditText = view.findViewById(R.id.edit_text_order)
         orderEdit.setText(flexItem.order.toString())
         orderEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, orderTextInput, IntegerInputValidator(),
@@ -106,26 +105,23 @@ internal class FlexItemEditFragment : DialogFragment() {
             orderEdit.isEnabled = false
         }
 
-        val flexGrowInput = view
-                .findViewById(R.id.input_layout_flex_grow) as TextInputLayout
-        val flexGrowEdit = view.findViewById(R.id.edit_text_flex_grow) as EditText
+        val flexGrowInput: TextInputLayout = view .findViewById(R.id.input_layout_flex_grow)
+        val flexGrowEdit: EditText = view.findViewById(R.id.edit_text_flex_grow)
         flexGrowEdit.setText(flexItem.flexGrow.toString())
         flexGrowEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, flexGrowInput, NonNegativeDecimalInputValidator(),
                         R.string.must_be_non_negative_float))
 
-        val flexShrinkInput = view
-                .findViewById(R.id.input_layout_flex_shrink) as TextInputLayout
-        val flexShrinkEdit = view.findViewById(
-                R.id.edit_text_flex_shrink) as EditText
+        val flexShrinkInput: TextInputLayout = view.findViewById(R.id.input_layout_flex_shrink)
+        val flexShrinkEdit: EditText = view.findViewById(R.id.edit_text_flex_shrink)
         flexShrinkEdit.setText(flexItem.flexShrink.toString())
         flexShrinkEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, flexShrinkInput, NonNegativeDecimalInputValidator(),
                         R.string.must_be_non_negative_float))
 
-        val flexBasisPercentInput = view.findViewById(R.id.input_layout_flex_basis_percent) as TextInputLayout
-        val flexBasisPercentEdit = view.findViewById(
-                R.id.edit_text_flex_basis_percent) as EditText
+        val flexBasisPercentInput: TextInputLayout =
+                view.findViewById(R.id.input_layout_flex_basis_percent)
+        val flexBasisPercentEdit: EditText = view.findViewById(R.id.edit_text_flex_basis_percent)
         if (flexItem.flexBasisPercent != FlexboxLayout.LayoutParams.FLEX_BASIS_PERCENT_DEFAULT) {
             flexBasisPercentEdit
                     .setText(Math.round(flexItem.flexBasisPercent * 100).toString())
@@ -136,52 +132,43 @@ internal class FlexItemEditFragment : DialogFragment() {
                 FlexEditTextWatcher(activity, flexBasisPercentInput, FlexBasisPercentInputValidator(),
                         R.string.must_be_minus_one_or_non_negative_integer))
 
-        val widthInput = view
-                .findViewById(R.id.input_layout_width) as TextInputLayout
-        val widthEdit = view.findViewById(R.id.edit_text_width) as EditText
+        val widthInput: TextInputLayout = view.findViewById(R.id.input_layout_width)
+        val widthEdit: EditText = view.findViewById(R.id.edit_text_width)
         widthEdit.setText(activity.pixelToDp(flexItem.width).toString())
         widthEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, widthInput, DimensionInputValidator(),
                         R.string.must_be_minus_one_or_minus_two_or_non_negative_integer))
 
-        val heightInput = view
-                .findViewById(R.id.input_layout_height) as TextInputLayout
-        val heightEdit = view.findViewById(
-                R.id.edit_text_height) as EditText
+        val heightInput: TextInputLayout = view.findViewById(R.id.input_layout_height)
+        val heightEdit: EditText= view.findViewById(R.id.edit_text_height)
         heightEdit.setText(activity.pixelToDp(flexItem.height).toString())
         heightEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, heightInput, DimensionInputValidator(),
                         R.string.must_be_minus_one_or_minus_two_or_non_negative_integer))
 
-        val minWidthInput = view
-                .findViewById(R.id.input_layout_min_width) as TextInputLayout
-        val minWidthEdit = view.findViewById(R.id.edit_text_min_width) as EditText
+        val minWidthInput: TextInputLayout = view.findViewById(R.id.input_layout_min_width)
+        val minWidthEdit: EditText = view.findViewById(R.id.edit_text_min_width)
         minWidthEdit.setText(activity.pixelToDp(flexItem.minWidth).toString())
         minWidthEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, minWidthInput, FixedDimensionInputValidator(),
                         R.string.must_be_non_negative_integer))
 
-        val minHeightInput = view
-                .findViewById(R.id.input_layout_min_height) as TextInputLayout
-        val minHeightEdit = view.findViewById(
-                R.id.edit_text_min_height) as EditText
+        val minHeightInput: TextInputLayout = view.findViewById(R.id.input_layout_min_height)
+        val minHeightEdit: EditText = view.findViewById(R.id.edit_text_min_height)
         minHeightEdit.setText(activity.pixelToDp(flexItem.minHeight).toString())
         minHeightEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, minHeightInput, FixedDimensionInputValidator(),
                         R.string.must_be_non_negative_integer))
 
-        val maxWidthInput = view
-                .findViewById(R.id.input_layout_max_width) as TextInputLayout
-        val maxWidthEdit = view.findViewById(R.id.edit_text_max_width) as EditText
+        val maxWidthInput: TextInputLayout = view.findViewById(R.id.input_layout_max_width)
+        val maxWidthEdit: EditText = view.findViewById(R.id.edit_text_max_width)
         maxWidthEdit.setText(activity.pixelToDp(flexItem.maxWidth).toString())
         maxWidthEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, maxWidthInput, FixedDimensionInputValidator(),
                         R.string.must_be_non_negative_integer))
 
-        val maxHeightInput = view
-                .findViewById(R.id.input_layout_max_height) as TextInputLayout
-        val maxHeightEdit = view.findViewById(
-                R.id.edit_text_max_height) as EditText
+        val maxHeightInput: TextInputLayout = view.findViewById(R.id.input_layout_max_height)
+        val maxHeightEdit: EditText = view.findViewById(R.id.edit_text_max_height)
         maxHeightEdit.setText(activity.pixelToDp(flexItem.maxHeight).toString())
         maxHeightEdit.addTextChangedListener(
                 FlexEditTextWatcher(activity, maxHeightInput, FixedDimensionInputValidator(),
@@ -190,8 +177,7 @@ internal class FlexItemEditFragment : DialogFragment() {
         setNextFocusesOnEnterDown(orderEdit, flexGrowEdit, flexShrinkEdit, flexBasisPercentEdit,
                 widthEdit, heightEdit, minWidthEdit, minHeightEdit, maxWidthEdit, maxHeightEdit)
 
-        val alignSelfSpinner = view.findViewById(
-                R.id.spinner_align_self) as Spinner
+        val alignSelfSpinner: Spinner = view.findViewById(R.id.spinner_align_self)
         val arrayAdapter = ArrayAdapter.createFromResource(activity,
                 R.array.array_align_self, R.layout.spinner_item)
         alignSelfSpinner.adapter = arrayAdapter
@@ -213,18 +199,18 @@ internal class FlexItemEditFragment : DialogFragment() {
             }
         }
 
-        val wrapBeforeCheckBox = view.findViewById(R.id.checkbox_wrap_before) as CheckBox
+        val wrapBeforeCheckBox: CheckBox = view.findViewById(R.id.checkbox_wrap_before)
         wrapBeforeCheckBox.isChecked = flexItem.isWrapBefore
         wrapBeforeCheckBox.setOnCheckedChangeListener { _, isChecked -> flexItemInEdit.isWrapBefore = isChecked }
         val alignSelfPosition = arrayAdapter
                 .getPosition(alignSelfAsString(flexItem.alignSelf))
         alignSelfSpinner.setSelection(alignSelfPosition)
 
-        view.findViewById(R.id.button_cancel).setOnClickListener {
+        view.findViewById<Button>(R.id.button_cancel).setOnClickListener {
             copyFlexItemValues(flexItem, flexItemInEdit)
             dismiss()
         }
-        val okButton = view.findViewById(R.id.button_ok) as Button
+        val okButton: Button = view.findViewById(R.id.button_ok)
         okButton.setOnClickListener(View.OnClickListener {
             if (orderTextInput.isErrorEnabled || flexGrowInput.isErrorEnabled ||
                     flexBasisPercentInput.isErrorEnabled || widthInput.isErrorEnabled ||
diff --git a/demo-playground/src/main/java/com/google/android/flexbox/FlexItemViewHolder.kt b/demo-playground/src/main/java/com/google/android/flexbox/FlexItemViewHolder.kt
index d319d186878c56ab5b9c38d3ee200aba33fba43b..bc6196198cda74946721fa5e101bbe451899cbfe 100644
--- a/demo-playground/src/main/java/com/google/android/flexbox/FlexItemViewHolder.kt
+++ b/demo-playground/src/main/java/com/google/android/flexbox/FlexItemViewHolder.kt
@@ -27,7 +27,7 @@ import com.google.android.apps.flexbox.R
  */
 class FlexItemViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView) {
 
-    private val textView: TextView = itemView.findViewById(R.id.textview) as TextView
+    private val textView: TextView = itemView.findViewById(R.id.textview)
 
     fun bindTo(params: RecyclerView.LayoutParams) {
         val adapterPosition = adapterPosition
diff --git a/demo-playground/src/main/java/com/google/android/flexbox/FlexboxLayoutFragment.kt b/demo-playground/src/main/java/com/google/android/flexbox/FlexboxLayoutFragment.kt
index 8ee1a90878742026181f2d04a3b454463c73a93f..6fd234b6d222329b630a7b9d6f3c35d140225e8d 100644
--- a/demo-playground/src/main/java/com/google/android/flexbox/FlexboxLayoutFragment.kt
+++ b/demo-playground/src/main/java/com/google/android/flexbox/FlexboxLayoutFragment.kt
@@ -33,7 +33,7 @@ import java.util.*
  */
 class FlexboxLayoutFragment : Fragment() {
 
-    private lateinit var flexContainer: FlexContainer
+    private lateinit var flexContainer: FlexboxLayout
 
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,
                               savedInstanceState: Bundle?): View? {
@@ -42,7 +42,7 @@ class FlexboxLayoutFragment : Fragment() {
 
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         val activity = activity as MainActivity
-        flexContainer = view.findViewById(R.id.flexbox_layout) as FlexboxLayout
+        flexContainer = view.findViewById(R.id.flexbox_layout)
 
         val fragmentHelper = FragmentHelper(activity, flexContainer)
         fragmentHelper.initializeViews()
@@ -64,7 +64,7 @@ class FlexboxLayoutFragment : Fragment() {
             }
         }
 
-        val addFab = activity.findViewById(R.id.add_fab) as FloatingActionButton
+        val addFab: FloatingActionButton = activity.findViewById(R.id.add_fab)
         addFab.setOnClickListener {
             val viewIndex = flexContainer.flexItemCount
             // index starts from 0. New View's index is N if N views ([0, 1, 2, ... N-1])
@@ -79,8 +79,7 @@ class FlexboxLayoutFragment : Fragment() {
                     FlexItemChangedListenerImpl(flexContainer), viewIndex))
             flexContainer.addView(textView)
         }
-        val removeFab = activity.findViewById(
-                R.id.remove_fab) as FloatingActionButton
+        val removeFab: FloatingActionButton = activity.findViewById(R.id.remove_fab)
         removeFab.setOnClickListener(View.OnClickListener {
             if (flexContainer.flexItemCount == 0) {
                 return@OnClickListener
diff --git a/demo-playground/src/main/java/com/google/android/flexbox/FragmentHelper.kt b/demo-playground/src/main/java/com/google/android/flexbox/FragmentHelper.kt
index b7263154ed17fe38ec3222b4c5166a1df24661b6..ebceab9b84b93c1f370b8dbbce86fb8f57289f63 100644
--- a/demo-playground/src/main/java/com/google/android/flexbox/FragmentHelper.kt
+++ b/demo-playground/src/main/java/com/google/android/flexbox/FragmentHelper.kt
@@ -67,7 +67,7 @@ internal class FragmentHelper(private val activity: MainActivity, private val fl
     fun initializeViews() {
         sharedPreferences = PreferenceManager.getDefaultSharedPreferences(activity)
         initializeStringResources()
-        val navigationView = activity.findViewById(R.id.nav_view) as NavigationView
+        val navigationView: NavigationView = activity.findViewById(R.id.nav_view)
         navigationView.setNavigationItemSelectedListener(activity)
         val navigationMenu = navigationView.menu
         initializeFlexDirectionSpinner(navigationMenu)
diff --git a/demo-playground/src/main/java/com/google/android/flexbox/MainActivity.kt b/demo-playground/src/main/java/com/google/android/flexbox/MainActivity.kt
index 6ce51691920cc56969e2f6da206518c1c4ff719a..9f99bd2a1122d83e5d5df6dfabfd2b0ebe69a327 100644
--- a/demo-playground/src/main/java/com/google/android/flexbox/MainActivity.kt
+++ b/demo-playground/src/main/java/com/google/android/flexbox/MainActivity.kt
@@ -35,18 +35,18 @@ class MainActivity : AppCompatActivity(), NavigationView.OnNavigationItemSelecte
         super.onCreate(savedInstanceState)
         setContentView(R.layout.activity_main)
 
-        val toolbar = findViewById(R.id.toolbar) as Toolbar
+        val toolbar: Toolbar = findViewById(R.id.toolbar)
         setSupportActionBar(toolbar)
-        val drawer = findViewById(R.id.drawer_layout) as DrawerLayout
+        val drawer: DrawerLayout = findViewById(R.id.drawer_layout)
         val toggle = ActionBarDrawerToggle(
                 this, drawer, toolbar, R.string.navigation_drawer_open,
                 R.string.navigation_drawer_close)
         drawer.addDrawerListener(toggle)
         toggle.syncState()
 
-        val navigationView = findViewById(R.id.nav_view) as NavigationView
-        val radioGroup = navigationView.getHeaderView(0)
-                .findViewById(R.id.radiogroup_container_implementation) as RadioGroup
+        val navigationView: NavigationView = findViewById(R.id.nav_view)
+        val radioGroup: RadioGroup = navigationView.getHeaderView(0)
+                .findViewById(R.id.radiogroup_container_implementation)
         val fragmentManager = supportFragmentManager
 
         radioGroup.setOnCheckedChangeListener { _, checkedId ->
diff --git a/demo-playground/src/main/java/com/google/android/flexbox/RecyclerViewFragment.kt b/demo-playground/src/main/java/com/google/android/flexbox/RecyclerViewFragment.kt
index 6c5e16ae53c24c2f310bb63e2bbe06c9c1cfded0..ae0432bfc17c493724f0b3e5720573c0f0c38ef7 100644
--- a/demo-playground/src/main/java/com/google/android/flexbox/RecyclerViewFragment.kt
+++ b/demo-playground/src/main/java/com/google/android/flexbox/RecyclerViewFragment.kt
@@ -41,7 +41,7 @@ internal class RecyclerViewFragment : Fragment() {
     override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
         super.onViewCreated(view, savedInstanceState)
 
-        val recyclerView = view.findViewById(R.id.recyclerview) as RecyclerView
+        val recyclerView: RecyclerView = view.findViewById(R.id.recyclerview)
         val activity = activity as MainActivity
         val flexboxLayoutManager = FlexboxLayoutManager(activity)
         recyclerView.layoutManager = flexboxLayoutManager
@@ -60,7 +60,7 @@ internal class RecyclerViewFragment : Fragment() {
         val fragmentHelper = FragmentHelper(activity, flexboxLayoutManager)
         fragmentHelper.initializeViews()
 
-        val addFab = activity.findViewById(R.id.add_fab) as FloatingActionButton
+        val addFab: FloatingActionButton = activity.findViewById(R.id.add_fab)
         addFab.setOnClickListener {
             val lp = FlexboxLayoutManager.LayoutParams(
                     ViewGroup.LayoutParams.WRAP_CONTENT,
@@ -68,7 +68,7 @@ internal class RecyclerViewFragment : Fragment() {
             fragmentHelper.setFlexItemAttributes(lp)
             adapter.addItem(lp)
         }
-        val removeFab = activity.findViewById(R.id.remove_fab) as FloatingActionButton
+        val removeFab: FloatingActionButton = activity.findViewById(R.id.remove_fab)
         removeFab.setOnClickListener(View.OnClickListener {
             if (adapter.itemCount == 0) {
                 return@OnClickListener