尝试在自定义类中使用NTPClient时出现异常ESP8266

问题描述

当我尝试在自定义类RealTimeService中使用NTPClient时，出现异常（请参见下文）。请告知原因以及解决方法。谢谢。

文件RealTimeService.h：

#ifndef RealTimeLib
#define RealTimeLib

#include <NTPClient.h>
#include <WiFiUdp.h>

class RealTimeService {
  private:
    NTPClient _ntp;
    NTPClient _createNtpClient();
    void _update();
  public:
    RealTimeService();
    void begin();
};

#endif

文件RealTimeService.cpp：

#include "RealTimeService.h"

RealTimeService::RealTimeService() : 
  _ntp(_createNtpClient())
{
}

NTPClient RealTimeService::_createNtpClient() {
  WiFiUDP udp;
  NTPClient ntp(udp,"pool.ntp.org",3600,86400000);
  return ntp;
}

void RealTimeService::begin() {
  _update();
}

void RealTimeService::_update() {
  _ntp.begin(); // Throws an exception
  if(_ntp.update()) {
    long time = _ntp.getEpochTime();
  } else {
    Serial.print("Failed to get time from server.\n");
  }
}

文件WebServerSecure.ino：

#include <ESP8266WiFi.h>
#include "RealTimeService.h"


#ifndef STASSID
#define STASSID "Sedmikraska"
#define STAPSK  "38098246"
#endif

const char* ssid = STASSID;
const char* password = STAPSK;

RealTimeService realTime;

void setup(void) {
  Serial.begin(115200);
  WiFi.begin(ssid,password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  realTime.begin();
}

void loop(void) {
  delay(1000);
}

它在_ntp.begin（）行的RealTimeService :: _ update（）函数中引发异常。

User exception (panic/abort/assert)

解码后的堆栈为：

0x4020714a: HardwareSerial::begin(unsigned long,SerialConfig,SerialMode,unsigned char,bool) at C:\Users\user\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\HardwareSerial.cpp line 51
0x4020804c: __unhandled_exception_cpp() at C:\Users\user\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\core_esp8266_main.cpp line 229
0x4020a07c: NTPClient::begin(int) at C:\Users\user\Documents\Arduino\libraries\NTPClient\NTPClient.cpp line 61
0x40202544: NTPClient::begin() at C:\Users\user\Documents\Arduino\libraries\NTPClient\NTPClient.cpp line 53
0x40201028: RealTimeService::_update() at C:\Users\user\AppData\Local\Temp\arduino_build_506039\sketch\RealTimeService.cpp line 20
0x40201b04: ESP8266WiFiSTAClass::status() at C:\Users\user\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\libraries\ESP8266WiFi\src\ESP8266WiFiSTA.cpp line 634
0x40201058: RealTimeService::begin() at C:\Users\user\AppData\Local\Temp\arduino_build_506039\sketch\RealTimeService.cpp line 16
0x4020115c: setup() at C:\Users\user\Documents\Arduino\WebServerSecure/WebServerSecure.ino line 23
0x40208224: loop_wrapper() at C:\Users\user\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\core_esp8266_main.cpp line 194

解决方法

您在udp中定义RealTimeService::_createNtpClient()并将其传递给NTPClient。 NTPClient返回后，RealTimeService::_createNtpClient()将继续需要它，但是udp将变得无效。即使NTPClient复制了它，它的析构函数也会被调用，从而使它使用的资源无效。

您需要将udp更改为实例变量，以便它可以与_ntp一样生存。

class RealTimeService {
  private:
    WiFiUDP _udp;
    NTPClient _ntp;
...

和

NTPClient RealTimeService::_createNtpClient() {
  NTPClient ntp(_udp,"pool.ntp.org",3600,86400000);

您的代码也反复调用_ntp.begin()。您应该确保所使用的NTP库允许这样做；有时，编写库是为了使其begin()方法只能被调用一次。