Replace Android system TTS engine (#508)

sherpa-onnx/jni/jni.cc

@@ -524,6 +524,8 @@ class SherpaOnnxOfflineTts {
 
   int32_t SampleRate() const { return tts_.SampleRate(); }
 
+  int32_t NumSpeakers() const { return tts_.NumSpeakers(); }
+
  private:
   OfflineTts tts_;
 };
@@ -652,6 +654,13 @@ JNIEXPORT jint JNICALL Java_com_k2fsa_sherpa_onnx_OfflineTts_getSampleRate(
       ->SampleRate();
 }
 
+SHERPA_ONNX_EXTERN_C
+JNIEXPORT jint JNICALL Java_com_k2fsa_sherpa_onnx_OfflineTts_getNumSpeakers(
+    JNIEnv *env, jobject /*obj*/, jlong ptr) {
+  return reinterpret_cast<sherpa_onnx::SherpaOnnxOfflineTts *>(ptr)
+      ->NumSpeakers();
+}
+
 // see
 // https://stackoverflow.com/questions/29043872/android-jni-return-multiple-variables
 static jobject NewInteger(JNIEnv *env, int32_t value) {