ESP32蓝牙连扬声器触发提醒报错：is_connected()未声明

初学者求助：
我想要实现ESP32蓝牙连接到扬声器时触发提醒。在loop中尝试相关代码时，出现“is_connected()未声明”的错误。
我已关联BluetoothA2DPSource.h和cpp文件，在其中找到了以下相关内容，但不确定如何使用。
virtual bool is_connected(); // 在BluetoothA2DPSource.h文件中找到
bool BluetoothA2DPSource::is_connected(){ // 在BluetoothA2DPSource.cpp文件中找到
return s_a2d_state == APP_AV_STATE_CONNECTED;}

你遇到的问题核心是：is_connected()是BluetoothA2DPSource类的成员函数，不是全局函数，不能直接在loop里调用，必须通过你代码中已经创建的BluetoothA2DPSource实例（也就是a2dp对象）来访问。

修正方案 #

修改loop中的代码，通过实例调用成员函数，同时可以补充断开连接时的逻辑：

void loop() {
  // 通过a2dp实例调用is_connected()获取连接状态
  if (a2dp.is_connected()) {
    digitalWrite(led, HIGH); // 连接时点亮LED提醒
  } else {
    digitalWrite(led, LOW);  // 断开时熄灭LED
  }

  player.copy();
}

关键说明 #

• 类的非静态成员函数必须通过类的对象实例调用，格式为实例名.成员函数()
• 你代码中已经声明了BluetoothA2DPSource a2dp;，直接用这个对象调用is_connected()就能正确获取蓝牙连接状态

修改后的完整代码 #

/**
   @file base-player-a2dp.ino
   @author Phil Schatzmann
   @brief Sketch which uses the A2DP callback to provide data from the AudioPlayer via a Queue

   @version 0.1
   @date 2022-12-04

   @copyright Copyright (c) 2022

*/

#include "AudioTools.h"
#include "AudioLibs/AudioA2DP.h"
#include "AudioLibs/AudioSourceSDFAT.h"
#include "AudioCodecs/CodecMP3Helix.h"
#include "AudioLibs/AudioKit.h"



const int led = 5;


int buffer_count = 30;
int buffer_size = 512;
const char *startFilePath = "/";
const char* ext = "mp3";
AudioSourceSDFAT source(startFilePath, ext, PIN_AUDIO_KIT_SD_CARD_CS);
MP3DecoderHelix decoder;
//Setup of synchronized buffer
SynchronizedNBuffer<uint8_t> buffer(buffer_size, buffer_count, portMAX_DELAY, 10);
QueueStream<uint8_t> out(buffer); // convert Buffer to Stream
AudioPlayer player(source, out, decoder);
BluetoothA2DPSource a2dp;

// Provide data to A2DP
int32_t get_data(uint8_t *data, int32_t bytes) {
  size_t result_bytes = buffer.readArray(data, bytes);
  //LOGI("get_data_channels %d -> %d of (%d)", bytes, result_bytes , buffer.available());
  return result_bytes;
}


void setup() {
  Serial.begin(115200);
  AudioLogger::instance().begin(Serial, AudioLogger::Warning);

  pinMode(led, OUTPUT);

  // sd_active is setting up SPI with the right SD pins by calling
  SPI.begin(PIN_AUDIO_KIT_SD_CARD_CLK, PIN_AUDIO_KIT_SD_CARD_MISO, PIN_AUDIO_KIT_SD_CARD_MOSI, PIN_AUDIO_KIT_SD_CARD_CS);
  
  // start QueueStream
  out.begin();

  // setup player
  player.setDelayIfOutputFull(0);
  player.setVolume(0.6);
  player.begin();

  // fill buffer with some data
  player.getStreamCopy().copyN(5);

  // start a2dp source
  Serial.println("starting A2DP...");
  a2dp.start_raw("HW2-915",  get_data);
  Serial.println("Started!");

}

void loop() {
  // 修正：通过a2dp实例调用成员函数is_connected()
  if (a2dp.is_connected()) {
    digitalWrite(led, HIGH);
  } else {
    digitalWrite(led, LOW);
  }

  player.copy();
}

内容的提问来源于stack exchange，提问作者dinghy