public class CustomApplication extends Application{
  public static CustomApplication instance;
  
  public void onCreate() {
    ...
    instance = this;
    AuthEntity entity = new AuthEntity("appId","appKey","secretKey");
    baiduTextToSpeech = BaiduTextToSpeech.getInstance(this,entity);
  }
  
  public CustomApplication getInstance(){
    return instance;
  }

  public BaiduTextToSpeech getBaiduTextToSpeech() {
      return baiduTextToSpeech;
  }
}

CustomApplication.getInstance().getBaiduTextToSpeech().speak("欢迎使用百度语音合成"));