support reading rule FST for Android TTS (#410)

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

@@ -101,12 +101,14 @@ class MainActivity : AppCompatActivity() {
     fun initTts() {
         var modelDir :String?
         var modelName :String?
+        var ruleFsts: String?
 
         // The purpose of such a design is to make the CI test easier
         // Please see
         // https://github.com/k2-fsa/sherpa-onnx/blob/master/scripts/apk/generate-tts-apk-script.py
         modelDir = null
         modelName = null
+        ruleFsts = null
 
         // Example 1:
         // modelDir = "vits-vctk"
@@ -116,7 +118,12 @@ class MainActivity : AppCompatActivity() {
         // modelDir = "vits-piper-en_US-lessac-medium"
         // modelName = "en_US-lessac-medium.onnx"
 
-        val config = getOfflineTtsConfig(modelDir = modelDir!!, modelName = modelName!!)!!
+        // Example 3:
+        // modelDir = "vits-zh-aishell3"
+        // modelName = "vits-aishell3.onnx"
+        // ruleFsts = "vits-zh-aishell3/rule.fst"
+
+        val config = getOfflineTtsConfig(modelDir = modelDir!!, modelName = modelName!!, ruleFsts = ruleFsts ?: "")!!
         tts = OfflineTts(assetManager = application.assets, config = config)
     }
 }

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

@@ -21,6 +21,7 @@ data class OfflineTtsModelConfig(
 
 data class OfflineTtsConfig(
     var model: OfflineTtsModelConfig,
+    var ruleFsts: String = "",
 )
 
 class GeneratedAudio(
@@ -116,7 +117,7 @@ class OfflineTts(
 // please refer to
 // https://k2-fsa.github.io/sherpa/onnx/tts/pretrained_models/index.html
 // to download models
-fun getOfflineTtsConfig(modelDir: String, modelName: String): OfflineTtsConfig? {
+fun getOfflineTtsConfig(modelDir: String, modelName: String, ruleFsts: String): OfflineTtsConfig? {
     return OfflineTtsConfig(
         model = OfflineTtsModelConfig(
             vits = OfflineTtsVitsModelConfig(
@@ -125,8 +126,9 @@ fun getOfflineTtsConfig(modelDir: String, modelName: String): OfflineTtsConfig?
                 tokens = "$modelDir/tokens.txt"
             ),
             numThreads = 2,
-            debug = false,
+            debug = true,
             provider = "cpu",
-        )
+        ),
+        ruleFsts=ruleFsts,
     )
 }