Refactor the JNI interface to make it more modular and maintainable (#802)

android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/MainActivity.kt

@@ -1,7 +1,11 @@
 package com.k2fsa.sherpa.onnx
 
 import android.content.res.AssetManager
-import android.media.*
+import android.media.AudioAttributes
+import android.media.AudioFormat
+import android.media.AudioManager
+import android.media.AudioTrack
+import android.media.MediaPlayer
 import android.net.Uri
 import android.os.Bundle
 import android.util.Log
@@ -212,7 +216,7 @@ class MainActivity : AppCompatActivity() {
         }
 
         if (dictDir != null) {
-            val newDir = copyDataDir( modelDir!!)
+            val newDir = copyDataDir(modelDir!!)
             modelDir = newDir + "/" + modelDir
             dictDir = modelDir + "/" + "dict"
             ruleFsts = "$modelDir/phone.fst,$modelDir/date.fst,$modelDir/number.fst"
@@ -220,7 +224,9 @@ class MainActivity : AppCompatActivity() {
         }
 
         val config = getOfflineTtsConfig(
-            modelDir = modelDir!!, modelName = modelName!!, lexicon = lexicon ?: "",
+            modelDir = modelDir!!,
+            modelName = modelName!!,
+            lexicon = lexicon ?: "",
             dataDir = dataDir ?: "",
             dictDir = dictDir ?: "",
             ruleFsts = ruleFsts ?: "",
@@ -232,11 +238,11 @@ class MainActivity : AppCompatActivity() {
 
 
     private fun copyDataDir(dataDir: String): String {
-        println("data dir is $dataDir")
+        Log.i(TAG, "data dir is $dataDir")
         copyAssets(dataDir)
 
         val newDataDir = application.getExternalFilesDir(null)!!.absolutePath
-        println("newDataDir: $newDataDir")
+        Log.i(TAG, "newDataDir: $newDataDir")
         return newDataDir
     }
 
@@ -256,7 +262,7 @@ class MainActivity : AppCompatActivity() {
                 }
             }
         } catch (ex: IOException) {
-            Log.e(TAG, "Failed to copy $path. ${ex.toString()}")
+            Log.e(TAG, "Failed to copy $path. $ex")
         }
     }
 
@@ -276,7 +282,7 @@ class MainActivity : AppCompatActivity() {
             ostream.flush()
             ostream.close()
         } catch (ex: Exception) {
-            Log.e(TAG, "Failed to copy $filename, ${ex.toString()}")
+            Log.e(TAG, "Failed to copy $filename, $ex")
         }
     }
 }

android/SherpaOnnxTts/app/src/main/java/com/k2fsa/sherpa/onnx/Tts.kt

@@ -49,10 +49,10 @@ class OfflineTts(
     private var ptr: Long
 
     init {
-        if (assetManager != null) {
-            ptr = newFromAsset(assetManager, config)
+        ptr = if (assetManager != null) {
+            newFromAsset(assetManager, config)
         } else {
-            ptr = newFromFile(config)
+            newFromFile(config)
         }
     }
 
@@ -65,7 +65,7 @@ class OfflineTts(
         sid: Int = 0,
         speed: Float = 1.0f
     ): GeneratedAudio {
-        var objArray = generateImpl(ptr, text = text, sid = sid, speed = speed)
+        val objArray = generateImpl(ptr, text = text, sid = sid, speed = speed)
         return GeneratedAudio(
             samples = objArray[0] as FloatArray,
             sampleRate = objArray[1] as Int
@@ -78,7 +78,13 @@ class OfflineTts(
         speed: Float = 1.0f,
         callback: (samples: FloatArray) -> Unit
     ): GeneratedAudio {
-        var objArray = generateWithCallbackImpl(ptr, text = text, sid = sid, speed = speed, callback=callback)
+        val objArray = generateWithCallbackImpl(
+            ptr,
+            text = text,
+            sid = sid,
+            speed = speed,
+            callback = callback
+        )
         return GeneratedAudio(
             samples = objArray[0] as FloatArray,
             sampleRate = objArray[1] as Int
@@ -87,10 +93,10 @@ class OfflineTts(
 
     fun allocate(assetManager: AssetManager? = null) {
         if (ptr == 0L) {
-            if (assetManager != null) {
-                ptr = newFromAsset(assetManager, config)
+            ptr = if (assetManager != null) {
+                newFromAsset(assetManager, config)
             } else {
-                ptr = newFromFile(config)
+                newFromFile(config)
             }
         }
     }
@@ -103,9 +109,14 @@ class OfflineTts(
     }
 
     protected fun finalize() {
-        delete(ptr)
+        if (ptr != 0L) {
+            delete(ptr)
+            ptr = 0
+        }
     }
 
+    fun release() = finalize()
+
     private external fun newFromAsset(
         assetManager: AssetManager,
         config: OfflineTtsConfig,
@@ -123,14 +134,14 @@ class OfflineTts(
     //  - the first entry is an 1-D float array containing audio samples.
     //    Each sample is normalized to the range [-1, 1]
     //  - the second entry is the sample rate
-    external fun generateImpl(
+    private external fun generateImpl(
         ptr: Long,
         text: String,
         sid: Int = 0,
         speed: Float = 1.0f
     ): Array<Any>
 
-    external fun generateWithCallbackImpl(
+    private external fun generateWithCallbackImpl(
         ptr: Long,
         text: String,
         sid: Int = 0,
@@ -156,7 +167,7 @@ fun getOfflineTtsConfig(
     dictDir: String,
     ruleFsts: String,
     ruleFars: String
-): OfflineTtsConfig? {
+): OfflineTtsConfig {
     return OfflineTtsConfig(
         model = OfflineTtsModelConfig(
             vits = OfflineTtsVitsModelConfig(