diff --git a/.idea/codeStyles/Project.xml b/.idea/codeStyles/Project.xml
index 36c5e5cc..e4bcaecd 100644
--- a/.idea/codeStyles/Project.xml
+++ b/.idea/codeStyles/Project.xml
@@ -3,7 +3,7 @@
     <JetCodeStyleSettings>
       <option name="PACKAGES_TO_USE_STAR_IMPORTS">
         <value>
-          <package name="kotlinx.android.synthetic" withSubpackages="true" static="false" />
+          <package name="kotlinx.android.synthetic" alias="false" withSubpackages="true" />
         </value>
       </option>
       <option name="NAME_COUNT_TO_USE_STAR_IMPORT" value="2147483647" />
diff --git a/CHANGELOG.md b/CHANGELOG.md
index e9543e9a..c811bc89 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 - `Security` in case of vulnerabilities.
 
 ## [unreleased x.x.x] -
+## [2.3.1] - 01/04/21
+### Changed
+- Added "fun" for all Kotlin interfaces when possible [#102] https://github.com/CanHub/Android-Image-Cropper/issues/102
+
 ## [2.3.0] - 30/03/21
 ### Changed
 - CropOverlayView to Kotlin [#38](https://github.com/CanHub/Android-Image-Cropper/issues/38)
diff --git a/cropper/build.gradle b/cropper/build.gradle
index e42c598e..89ea9d05 100644
--- a/cropper/build.gradle
+++ b/cropper/build.gradle
@@ -22,7 +22,7 @@ android {
         abortOnError false
     }
     buildFeatures {
-        viewBinding = true
+        viewBinding true
     }
 }
 
diff --git a/cropper/src/main/java/com/canhub/cropper/CropImageView.kt b/cropper/src/main/java/com/canhub/cropper/CropImageView.kt
index daa8e599..86daa8a5 100644
--- a/cropper/src/main/java/com/canhub/cropper/CropImageView.kt
+++ b/cropper/src/main/java/com/canhub/cropper/CropImageView.kt
@@ -1575,7 +1575,7 @@ class CropImageView @JvmOverloads constructor(context: Context, attrs: Attribute
     }
 
     /** Interface definition for a callback to be invoked when the crop overlay is released.  */
-    interface OnSetCropOverlayReleasedListener {
+    fun interface OnSetCropOverlayReleasedListener {
 
         /**
          * Called when the crop overlay changed listener is called and inProgress is false.
@@ -1586,7 +1586,7 @@ class CropImageView @JvmOverloads constructor(context: Context, attrs: Attribute
     }
 
     /** Interface definition for a callback to be invoked when the crop overlay is released.  */
-    interface OnSetCropOverlayMovedListener {
+    fun interface OnSetCropOverlayMovedListener {
 
         /**
          * Called when the crop overlay is moved
@@ -1597,14 +1597,14 @@ class CropImageView @JvmOverloads constructor(context: Context, attrs: Attribute
     }
 
     /** Interface definition for a callback to be invoked when the crop overlay is released.  */
-    interface OnSetCropWindowChangeListener {
+    fun interface OnSetCropWindowChangeListener {
 
         /** Called when the crop window is changed  */
         fun onCropWindowChanged()
     }
 
     /** Interface definition for a callback to be invoked when image async loading is complete.  */
-    interface OnSetImageUriCompleteListener {
+    fun interface OnSetImageUriCompleteListener {
 
         /**
          * Called when a crop image view has completed loading image for cropping.<br></br>
@@ -1618,7 +1618,7 @@ class CropImageView @JvmOverloads constructor(context: Context, attrs: Attribute
     }
 
     /** Interface definition for a callback to be invoked when image async crop is complete.  */
-    interface OnCropImageCompleteListener {
+    fun interface OnCropImageCompleteListener {
 
         /**
          * Called when a crop image view has completed cropping image.<br></br>
diff --git a/cropper/src/main/java/com/canhub/cropper/CropOverlayView.kt b/cropper/src/main/java/com/canhub/cropper/CropOverlayView.kt
index 73b8bba1..bb8f0bfc 100644
--- a/cropper/src/main/java/com/canhub/cropper/CropOverlayView.kt
+++ b/cropper/src/main/java/com/canhub/cropper/CropOverlayView.kt
@@ -987,7 +987,7 @@ class CropOverlayView
     }
 
     /** Interface definition for a callback to be invoked when crop window rectangle is changing.  */
-    interface CropWindowChangeListener {
+    fun interface CropWindowChangeListener {
 
         /**
          * Called after a change in crop window rectangle.
diff --git a/sample/build.gradle b/sample/build.gradle
index a565344e..c0f44595 100644
--- a/sample/build.gradle
+++ b/sample/build.gradle
@@ -22,7 +22,7 @@ android {
         freeCompilerArgs = ["-Xinline-classes"]
     }
     buildFeatures {
-        viewBinding = true
+        viewBinding true
     }
 }
 
diff --git a/sample/src/main/java/com/canhub/cropper/sample/crop_image_view/domain/SCropImageViewContract.kt b/sample/src/main/java/com/canhub/cropper/sample/crop_image_view/domain/SCropImageViewContract.kt
index 38fdc0ec..910db09e 100644
--- a/sample/src/main/java/com/canhub/cropper/sample/crop_image_view/domain/SCropImageViewContract.kt
+++ b/sample/src/main/java/com/canhub/cropper/sample/crop_image_view/domain/SCropImageViewContract.kt
@@ -3,17 +3,13 @@ package com.canhub.cropper.sample.crop_image_view.domain
 import com.canhub.cropper.sample.options_dialog.domain.SOptionsDomain
 
 internal interface SCropImageViewContract {
-
-    interface View {
-
+    fun interface View {
         fun setOptions(options: SOptionsDomain)
     }
 
     interface Presenter {
-
         fun bind(view: View)
         fun unbind()
-
         fun onViewCreated()
     }
 }
diff --git a/sample/src/main/java/com/canhub/cropper/sample/extend_activity/domain/SExtendContract.kt b/sample/src/main/java/com/canhub/cropper/sample/extend_activity/domain/SExtendContract.kt
index 42751d02..3079194f 100644
--- a/sample/src/main/java/com/canhub/cropper/sample/extend_activity/domain/SExtendContract.kt
+++ b/sample/src/main/java/com/canhub/cropper/sample/extend_activity/domain/SExtendContract.kt
@@ -1,15 +1,12 @@
 package com.canhub.cropper.sample.extend_activity.domain
 
 internal interface SExtendContract {
-
     interface View {
-
         fun updateRotationCounter(counter: String)
         fun rotate(counter: Int)
     }
 
     interface Presenter {
-
         fun bindView(view: View)
         fun unbindView()
         fun onRotateClick()
diff --git a/sample/src/main/java/com/canhub/cropper/sample/options_dialog/app/SOptionsDialogBottomSheet.kt b/sample/src/main/java/com/canhub/cropper/sample/options_dialog/app/SOptionsDialogBottomSheet.kt
index d3badf9a..4b9d47ef 100644
--- a/sample/src/main/java/com/canhub/cropper/sample/options_dialog/app/SOptionsDialogBottomSheet.kt
+++ b/sample/src/main/java/com/canhub/cropper/sample/options_dialog/app/SOptionsDialogBottomSheet.kt
@@ -14,8 +14,7 @@ import com.example.croppersample.databinding.FragmentOptionsBinding
 import com.google.android.material.bottomsheet.BottomSheetDialogFragment
 
 internal class SOptionsDialogBottomSheet : BottomSheetDialogFragment(), SOptionsContract.View {
-
-    interface Listener {
+    fun interface Listener {
 
         fun onOptionsApplySelected(options: SOptionsDomain)
     }
@@ -189,8 +188,10 @@ internal class SOptionsDialogBottomSheet : BottomSheetDialogFragment(), SOptions
         when (options.cropShape) {
             CropImageView.CropShape.RECTANGLE -> binding.cropShape.chipRectangle.isChecked = true
             CropImageView.CropShape.OVAL -> binding.cropShape.chipOval.isChecked = true
-            CropImageView.CropShape.RECTANGLE_VERTICAL_ONLY -> binding.cropShape.chipRectangleVerticalOnly.isChecked = true
-            CropImageView.CropShape.RECTANGLE_HORIZONTAL_ONLY -> binding.cropShape.chipRectangleHorizontalOnly.isChecked = true
+            CropImageView.CropShape.RECTANGLE_VERTICAL_ONLY ->
+                binding.cropShape.chipRectangleVerticalOnly.isChecked = true
+            CropImageView.CropShape.RECTANGLE_HORIZONTAL_ONLY ->
+                binding.cropShape.chipRectangleHorizontalOnly.isChecked = true
         }
 
         when (options.guidelines) {
diff --git a/sample/src/main/java/com/canhub/cropper/sample/options_dialog/domain/SOptionsContract.kt b/sample/src/main/java/com/canhub/cropper/sample/options_dialog/domain/SOptionsContract.kt
index 47374da7..f2914e24 100644
--- a/sample/src/main/java/com/canhub/cropper/sample/options_dialog/domain/SOptionsContract.kt
+++ b/sample/src/main/java/com/canhub/cropper/sample/options_dialog/domain/SOptionsContract.kt
@@ -7,18 +7,15 @@ import com.canhub.cropper.CropImageView.ScaleType
 internal interface SOptionsContract {
 
     interface View {
-
         fun updateOptions(options: SOptionsDomain)
         fun closeWithResult(options: SOptionsDomain)
     }
 
     interface Presenter {
-
         fun bind(view: View)
         fun unbind()
         fun onViewCreated(options: SOptionsDomain?)
         fun onDismiss()
-
         fun onScaleTypeSelect(scaleType: ScaleType)
         fun onCropShapeSelect(cropShape: CropShape)
         fun onGuidelinesSelect(guidelines: Guidelines)
diff --git a/versions.gradle b/versions.gradle
index 3556da9f..a524126c 100644
--- a/versions.gradle
+++ b/versions.gradle
@@ -1,7 +1,7 @@
 ext {
 
     // Project
-    libVersion = "2.3.0"
+    libVersion = "2.3.1"
     compileSdkVersion = 30
     targetSdkVersion = 30
     minSdkVersion = 14
@@ -19,9 +19,9 @@ ext {
     materialVersion = '1.4.0-alpha01'
 
     // AndroidX
-    androidXAppCompatVersionSample = '1.3.0-beta01'
+    androidXAppCompatVersionSample = '1.3.0-rc01'
     androidXAppCompatVersionCropper = '1.2.0'  // Used to avoid not release stable versions on the lib
     androidXExifVersion = '1.3.2'
     androidXCoreKtxVersion = '1.3.2'
-    androidXLifeCycleVersion = '2.3.0'
-}
\ No newline at end of file
+    androidXLifeCycleVersion = '2.3.1'
+}