diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5f7dc04..0d15a59 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 0.3.1
+* Upgrade gradle & kotlin version.
+
 ## 0.3.0+1
 
 * Update readme.
diff --git a/android/build.gradle b/android/build.gradle
index 02a6175..529c567 100644
--- a/android/build.gradle
+++ b/android/build.gradle
@@ -2,14 +2,14 @@ group 'com.codevalop.raw_sound'
 version '1.0-SNAPSHOT'
 
 buildscript {
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.7.20'
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.5.0'
+        classpath 'com.android.tools.build:gradle:7.4.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
@@ -17,7 +17,7 @@ buildscript {
 rootProject.allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }
 
@@ -25,7 +25,7 @@ apply plugin: 'com.android.library'
 apply plugin: 'kotlin-android'
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 33
 
     sourceSets {
         main.java.srcDirs += 'src/main/kotlin'
@@ -39,7 +39,7 @@ android {
 }
 
 dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
     implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.4.2'
     implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.4.2'
     implementation 'androidx.annotation:annotation:1.1.0'
diff --git a/android/gradle/wrapper/gradle-wrapper.properties b/android/gradle/wrapper/gradle-wrapper.properties
index 01a286e..ae04661 100644
--- a/android/gradle/wrapper/gradle-wrapper.properties
+++ b/android/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.5.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.2-all.zip
diff --git a/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlayer.kt b/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlayer.kt
index 59efaba..f5ed7e6 100644
--- a/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlayer.kt
+++ b/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlayer.kt
@@ -5,7 +5,6 @@ import android.media.AudioAttributes
 import android.media.AudioFormat
 import android.media.AudioManager
 import android.media.AudioTrack
-import androidx.annotation.NonNull
 import io.flutter.Log
 import kotlinx.coroutines.*
 import kotlinx.coroutines.sync.Mutex
@@ -26,8 +25,8 @@ enum class PCMType {
 }
 
 /** RawSoundPlayer */
-class RawSoundPlayer(@NonNull androidContext: Context, @NonNull bufferSize: Int,
-                     @NonNull sampleRate: Int, @NonNull nChannels: Int, @NonNull pcmType: PCMType) {
+class RawSoundPlayer(androidContext: Context, bufferSize: Int,
+                     sampleRate: Int, nChannels: Int, pcmType: PCMType) {
     companion object {
         const val TAG = "RawSoundPlayer"
     }
@@ -81,6 +80,7 @@ class RawSoundPlayer(@NonNull androidContext: Context, @NonNull bufferSize: Int,
         }
     }
 
+    @OptIn(DelicateCoroutinesApi::class)
     fun play(): Boolean {
         try {
             audioTrack.play()
@@ -90,7 +90,7 @@ class RawSoundPlayer(@NonNull androidContext: Context, @NonNull bufferSize: Int,
         }
 
         GlobalScope.launch(Dispatchers.IO) {
-            Log.d(TAG, "--> queUseBuffer")
+            Log.d(/* tag = */ TAG, /* message = */ "--> queUseBuffer")
             semUseBufferIdled.withPermit {
 
                 val n = buffersCacheSize - getBuffersCount()
@@ -141,8 +141,8 @@ class RawSoundPlayer(@NonNull androidContext: Context, @NonNull bufferSize: Int,
         }
         runBlocking {
             clearBuffers()
-            resetSemBufferUsed();
-            resetSemBufferAdded();
+            resetSemBufferUsed()
+            resetSemBufferAdded()
         }
         return r
     }
@@ -168,7 +168,8 @@ class RawSoundPlayer(@NonNull androidContext: Context, @NonNull bufferSize: Int,
         }
     }
 
-    fun feed(@NonNull data: ByteArray, onDone: (r: Boolean) -> Unit) {
+    @OptIn(DelicateCoroutinesApi::class)
+    fun feed(data: ByteArray, onDone: (r: Boolean) -> Unit) {
         if (audioTrack.playState != AudioTrack.PLAYSTATE_PLAYING) {
             Log.e(TAG, "Player is not playing")
             onDone(true)
@@ -195,7 +196,7 @@ class RawSoundPlayer(@NonNull androidContext: Context, @NonNull bufferSize: Int,
         // Log.d(TAG, "underrun count: ${audioTrack.underrunCount}")
     }
 
-    fun setVolume(@NonNull volume: Float): Boolean {
+    fun setVolume(volume: Float): Boolean {
         val r = audioTrack.setVolume(volume)
         if (r == AudioTrack.SUCCESS) {
             return true
diff --git a/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlugin.kt b/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlugin.kt
index 970c97f..cbe8de3 100644
--- a/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlugin.kt
+++ b/android/src/main/kotlin/com/codevalop/raw_sound/RawSoundPlugin.kt
@@ -3,8 +3,6 @@ package com.codevalop.raw_sound
 import android.content.Context
 import android.os.Handler
 import android.os.Looper
-import androidx.annotation.NonNull
-import androidx.annotation.Nullable
 import io.flutter.Log
 import io.flutter.embedding.engine.plugins.FlutterPlugin
 import io.flutter.plugin.common.MethodCall
@@ -29,13 +27,13 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
 
     private var players: MutableList<RawSoundPlayer> = mutableListOf()
 
-    override fun onAttachedToEngine(@NonNull flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
+    override fun onAttachedToEngine(flutterPluginBinding: FlutterPlugin.FlutterPluginBinding) {
         channel = MethodChannel(flutterPluginBinding.binaryMessenger, "codevalop.com/raw_sound")
         channel.setMethodCallHandler(this)
         androidContext = flutterPluginBinding.applicationContext
     }
 
-    override fun onMethodCall(@NonNull call: MethodCall, @NonNull result: Result) {
+    override fun onMethodCall(call: MethodCall, result: Result) {
         var playerNo: Int = -1
 
         if (call.method != "initialize") {
@@ -88,32 +86,31 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
         }
     }
 
-    override fun onDetachedFromEngine(@NonNull binding: FlutterPlugin.FlutterPluginBinding) {
+    override fun onDetachedFromEngine(binding: FlutterPlugin.FlutterPluginBinding) {
         channel.setMethodCallHandler(null)
     }
 
-    private fun sendResultError(@NonNull errorCode: String, @Nullable errorMessage: String,
-                                @Nullable errorDetails: Any?, @NonNull result: Result) {
+    private fun sendResultError(errorCode: String, errorMessage: String, errorDetails: Any?, result: Result) {
         Handler(Looper.getMainLooper()).post {
             result.error(errorCode, errorMessage, errorDetails)
         }
     }
 
-    private fun sendResultInt(@NonNull playState: Int, @NonNull result: Result) {
+    private fun sendResultInt(playState: Int, result: Result) {
         Handler(Looper.getMainLooper()).post {
             result.success(playState)
         }
     }
 
-    private fun initialize(@NonNull bufferSize: Int, @NonNull sampleRate: Int,
-                           @NonNull nChannels: Int, @NonNull pcmType: PCMType,
-                           @NonNull result: Result) {
+    private fun initialize(bufferSize: Int, sampleRate: Int,
+                           nChannels: Int, pcmType: PCMType,
+                           result: Result) {
         val player = RawSoundPlayer(androidContext, bufferSize, sampleRate, nChannels, pcmType)
         players.add(player)
         sendResultInt(players.lastIndex, result)
     }
 
-    private fun release(@NonNull playerNo: Int, @NonNull result: Result) {
+    private fun release(playerNo: Int, result: Result) {
         val player = players[playerNo]
         if (player.release()) {
             players.removeAt(playerNo)
@@ -124,7 +121,7 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
         }
     }
 
-    private fun play(@NonNull playerNo: Int, @NonNull result: Result) {
+    private fun play(playerNo: Int, result: Result) {
         val player = players[playerNo]
         if (player.play()) {
             sendResultInt(player.getPlayState(), result)
@@ -134,7 +131,7 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
         }
     }
 
-    private fun stop(@NonNull playerNo: Int, @NonNull result: Result) {
+    private fun stop(playerNo: Int, result: Result) {
         val player = players[playerNo]
         if (player.stop()) {
             sendResultInt(player.getPlayState(), result)
@@ -144,7 +141,7 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
         }
     }
 
-    private fun resume(@NonNull playerNo: Int, @NonNull result: Result) {
+    private fun resume(playerNo: Int, result: Result) {
         val player = players[playerNo]
         if (player.resume()) {
             sendResultInt(player.getPlayState(), result)
@@ -154,7 +151,7 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
         }
     }
 
-    private fun pause(@NonNull playerNo: Int, @NonNull result: Result) {
+    private fun pause(playerNo: Int, result: Result) {
         val player = players[playerNo]
         if (player.pause()) {
             sendResultInt(player.getPlayState(), result)
@@ -164,7 +161,7 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
         }
     }
 
-    private fun feed(@NonNull playerNo: Int, @NonNull data: ByteArray, @NonNull result: Result) {
+    private fun feed(playerNo: Int, data: ByteArray, result: Result) {
         val player = players[playerNo]
         player.feed(
                 data
@@ -178,7 +175,7 @@ class RawSoundPlugin : FlutterPlugin, MethodCallHandler {
         }
     }
 
-    private fun setVolume(@NonNull playerNo: Int, @NonNull volume: Float, @NonNull result: Result) {
+    private fun setVolume(playerNo: Int, volume: Float, result: Result) {
         val player = players[playerNo]
         if (player.setVolume(volume)) {
             sendResultInt(player.getPlayState(), result)
diff --git a/example/android/app/build.gradle b/example/android/app/build.gradle
index 0ef057f..4ccd0a2 100644
--- a/example/android/app/build.gradle
+++ b/example/android/app/build.gradle
@@ -26,7 +26,7 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 33
 
     sourceSets {
         main.java.srcDirs += 'src/main/kotlin'
@@ -58,5 +58,5 @@ flutter {
 }
 
 dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8:$kotlin_version"
 }
diff --git a/example/android/app/src/main/AndroidManifest.xml b/example/android/app/src/main/AndroidManifest.xml
index 62b415a..7e7013b 100644
--- a/example/android/app/src/main/AndroidManifest.xml
+++ b/example/android/app/src/main/AndroidManifest.xml
@@ -6,7 +6,7 @@
          additional functionality it is fine to subclass or reimplement
          FlutterApplication and put your custom class here. -->
     <application
-        android:name="io.flutter.app.FlutterApplication"
+        android:name="${applicationName}"
         android:label="raw_sound_example"
         android:icon="@mipmap/ic_launcher">
         <activity
diff --git a/example/android/app/src/main/kotlin/com/codevalop/raw_sound_example/MainActivity.kt b/example/android/app/src/main/kotlin/com/codevalop/raw_sound_example/MainActivity.kt
index 96e951d..38a9768 100644
--- a/example/android/app/src/main/kotlin/com/codevalop/raw_sound_example/MainActivity.kt
+++ b/example/android/app/src/main/kotlin/com/codevalop/raw_sound_example/MainActivity.kt
@@ -3,4 +3,4 @@ package com.codevalop.raw_sound_example
 import io.flutter.embedding.android.FlutterActivity
 
 class MainActivity: FlutterActivity() {
-}
+}
\ No newline at end of file
diff --git a/example/android/build.gradle b/example/android/build.gradle
index 59baba0..376dab6 100644
--- a/example/android/build.gradle
+++ b/example/android/build.gradle
@@ -1,12 +1,12 @@
 buildscript {
-    ext.kotlin_version = '1.3.50'
+    ext.kotlin_version = '1.7.20'
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:4.1.1'
+        classpath 'com.android.tools.build:gradle:7.4.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
@@ -14,7 +14,7 @@ buildscript {
 allprojects {
     repositories {
         google()
-        jcenter()
+        mavenCentral()
     }
 }
 
diff --git a/example/android/gradle/wrapper/gradle-wrapper.properties b/example/android/gradle/wrapper/gradle-wrapper.properties
index 4eed4fd..ae04661 100644
--- a/example/android/gradle/wrapper/gradle-wrapper.properties
+++ b/example/android/gradle/wrapper/gradle-wrapper.properties
@@ -1,6 +1,5 @@
-#Tue Dec 22 16:27:58 CST 2020
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.5.1-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.5-all.zip
diff --git a/pubspec.yaml b/pubspec.yaml
index d4e3d0b..55d26ad 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,6 +1,6 @@
 name: raw_sound
 description: A flutter plugin for playing raw PCM audio data (16-bit integer and 32-bit float).
-version: 0.3.0+1
+version: 0.3.1
 homepage: https://github.com/8fdafs2/flutter_raw_sound
 repository: https://github.com/8fdafs2/flutter_raw_sound