我试图为节点MCU esp-12e制作一个arduino程序，我想用当前连接的客户端列表更新esp，所以我制作了一个函数，替换断开连接的客户端，并将新客户端添加到名为clients的WiFiClients列表中，我已将其设置为null。我使用的代码可以在这里看到：
/* ============================================
I2Cdev device library code is placed under the MIT license
Copyright (c) 2012 Jeff Rowberg
==============================
GY-521 NodeMCU
MPU6050 devkit 1.0
board Lolin Description
======= ========== ====================================================
VCC VU (5V USB) Not available on all boards so use 3.3V if needed.
GND G Ground
SCL D1 (GPIO05) I2C clock
SDA D2 (GPIO04) I2C data
XDA not connected
XCL not connected
AD0 not connected
INT D8 (GPIO15) Interrupt pin
*/
// I2Cdev and MPU6050 must be installed as libraries, or else the .cpp/.h files
// for both classes must be in the include path of your project
#include "I2Cdev.h"
#include <ESP8266WiFi.h>
#include "MPU6050_6Axis_MotionApps20.h"
//#include "MPU6050.h" // not necessary if using MotionApps include file
// Arduino Wire library is required if I2Cdev I2CDEV_ARDUINO_WIRE implementation
// is used in I2Cdev.h
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
#include "Wire.h"
#endif
// class default I2C address is 0x68
// specific I2C addresses may be passed as a parameter here
// AD0 low = 0x68 (default for SparkFun breakout and InvenSense evaluation board)
// AD0 high = 0x69
MPU6050 mpu;
//MPU6050 mpu(0x69); // <-- use for AD0 high
// MPU control/status vars
bool dmpReady = false; // set true if DMP init was successful
uint8_t mpuIntStatus; // holds actual interrupt status byte from MPU
uint8_t devStatus; // return status after each device operation (0 = success, !0 = error)
uint16_t packetSize; // expected DMP packet size (default is 42 bytes)
uint16_t fifoCount; // count of all bytes currently in FIFO
uint8_t fifoBuffer[64]; // FIFO storage buffer
// uncomment "OUTPUT_READABLE_QUATERNION" if you want to see the actual
// quaternion components in a [w, x, y, z] format (not best for parsing
// on a remote host such as Processing or something though)
#define OUTPUT_READABLE_QUATERNION
// uncomment "OUTPUT_READABLE_EULER" if you want to see Euler angles
// (in degrees) calculated from the quaternions coming from the FIFO.
// Note that Euler angles suffer from gimbal lock (for more info, see
// http://en.wikipedia.org/wiki/Gimbal_lock)
//#define OUTPUT_READABLE_EULER
// uncomment "OUTPUT_READABLE_YAWPITCHROLL" if you want to see the yaw/
// pitch/roll angles (in degrees) calculated from the quaternions coming
// from the FIFO. Note this also requires gravity vector calculations.
// Also note that yaw/pitch/roll angles suffer from gimbal lock (for
// more info, see: http://en.wikipedia.org/wiki/Gimbal_lock)
//#define OUTPUT_READABLE_YAWPITCHROLL
// uncomment "OUTPUT_READABLE_REALACCEL" if you want to see acceleration
// components with gravity removed. This acceleration reference frame is
// not compensated for orientation, so +X is always +X according to the
// sensor, just without the effects of gravity. If you want acceleration
// compensated for orientation, us OUTPUT_READABLE_WORLDACCEL instead.
//#define OUTPUT_READABLE_REALACCEL
// uncomment "OUTPUT_READABLE_WORLDACCEL" if you want to see acceleration
// components with gravity removed and adjusted for the world frame of
// reference (yaw is relative to initial orientation, since no magnetometer
// is present in this case). Could be quite handy in some cases.
#define OUTPUT_READABLE_WORLDACCEL
// orientation/motion vars
Quaternion q; // [w, x, y, z] quaternion container
VectorInt16 aa; // [x, y, z] accel sensor measurements
VectorInt16 aaReal; // [x, y, z] gravity-free accel sensor measurements
VectorInt16 aaWorld; // [x, y, z] world-frame accel sensor measurements
VectorFloat gravity; // [x, y, z] gravity vector
#ifdef OUTPUT_READABLE_EULER
float euler[3]; // [psi, theta, phi] Euler angle container
#endif
#ifdef OUTPUT_READABLE_YAWPITCHROLL
float ypr[3]; // [yaw, pitch, roll] yaw/pitch/roll container and gravity vector
#endif
#define INTERRUPT_PIN 15 // use pin 15 on ESP8266
#define CLIENT_COUNT 5 // amount of clients allowed on server
const char DEVICE_NAME[] = "mpu6050";
// ================================================================
// === INTERRUPT DETECTION ROUTINE ===
// ================================================================
volatile bool mpuInterrupt = false; // indicates whether MPU interrupt pin has gone high
void ICACHE_RAM_ATTR dmpDataReady() {
mpuInterrupt = true;
}
void mpu_setup()
{
// join I2C bus (I2Cdev library doesn't do this automatically)
#if I2CDEV_IMPLEMENTATION == I2CDEV_ARDUINO_WIRE
Wire.begin();
Wire.setClock(400000); // 400kHz I2C clock. Comment this line if having compilation difficulties
#elif I2CDEV_IMPLEMENTATION == I2CDEV_BUILTIN_FASTWIRE
Fastwire::setup(400, true);
#endif
// initialize device
Serial.println(F("Initializing I2C devices..."));
mpu.initialize();
pinMode(INTERRUPT_PIN, INPUT);
// verify connection
Serial.println(F("Testing device connections..."));
Serial.println(mpu.testConnection() ? F("MPU6050 connection successful") : F("MPU6050 connection failed"));
// load and configure the DMP
Serial.println(F("Initializing DMP..."));
devStatus = mpu.dmpInitialize();
// supply your own gyro offsets here, scaled for min sensitivity
mpu.setXGyroOffset(220);
mpu.setYGyroOffset(76);
mpu.setZGyroOffset(-85);
mpu.setZAccelOffset(1788); // 1688 factory default for my test chip
// make sure it worked (returns 0 if so)
if (devStatus == 0) {
// turn on the DMP, now that it's ready
Serial.println(F("Enabling DMP..."));
mpu.setDMPEnabled(true);
// enable Arduino interrupt detection
Serial.println(F("Enabling interrupt detection (Arduino external interrupt 0)..."));
attachInterrupt(digitalPinToInterrupt(INTERRUPT_PIN), dmpDataReady, RISING);
mpuIntStatus = mpu.getIntStatus();
// set our DMP Ready flag so the main loop() function knows it's okay to use it
Serial.println(F("DMP ready! Waiting for first interrupt..."));
dmpReady = true;
// get expected DMP packet size for later comparison
packetSize = mpu.dmpGetFIFOPacketSize();
} else {
// ERROR!
// 1 = initial memory load failed
// 2 = DMP configuration updates failed
// (if it's going to break, usually the code will be 1)
Serial.print(F("DMP Initialization failed (code "));
Serial.print(devStatus);
Serial.println(F(")"));
}
}
//push buttons
int aButtonPin = 12;//6
int bButtonPin = 13;//7
int aVal = 0;
int bVal = 0;
bool aDown = false;
bool bDown = false;
String message;
//wifi config
WiFiServer server(5001);
IPAddress IP(192,168,4,15);
IPAddress mask = (255, 255, 255, 255);
WiFiClient clients[CLIENT_COUNT] = {NULL};
const char* ssid = "VRControllers";
const char* password = "VRControllers";
void setup()
{
Serial.begin(9600);
delay(10);
//setup the access point
WiFi.mode(WIFI_AP);
WiFi.softAP(ssid, password);
bool result = WiFi.softAPConfig(IP, IP, mask);
server.begin();
Serial.println(result ? "Server started." : "Server failed to start");
//set up buttons
pinMode(aButtonPin, INPUT);
pinMode(bButtonPin, INPUT);
//set up accelerometer
mpu_setup();
}
void mpu_loop()
{
// if programming failed, don't try to do anything
if (!dmpReady) return;
// wait for MPU interrupt or extra packet(s) available
if (!mpuInterrupt && fifoCount < packetSize) return;
// reset interrupt flag and get INT_STATUS byte
mpuInterrupt = false;
mpuIntStatus = mpu.getIntStatus();
// get current FIFO count
fifoCount = mpu.getFIFOCount();
// check for overflow (this should never happen unless our code is too inefficient)
if ((mpuIntStatus & 0x10) || fifoCount == 1024) {
// reset so we can continue cleanly
mpu.resetFIFO();
Serial.println(F("FIFO overflow!"));
// otherwise, check for DMP data ready interrupt (this should happen frequently)
} else if (mpuIntStatus & 0x02) {
// wait for correct available data length, should be a VERY short wait
while (fifoCount < packetSize) fifoCount = mpu.getFIFOCount();
// read a packet from FIFO
mpu.getFIFOBytes(fifoBuffer, packetSize);
// track FIFO count here in case there is > 1 packet available
// (this lets us immediately read more without waiting for an interrupt)
fifoCount -= packetSize;
#ifdef OUTPUT_READABLE_YAWPITCHROLL
// display Euler angles in degrees
mpu.dmpGetQuaternion(&q, fifoBuffer);
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetYawPitchRoll(ypr, &q, &gravity);
String x = String(ypr[0] * 180/M_PI);
String y = String(ypr[1] * 180/M_PI);
String z = String(ypr[2] * 180/M_PI);
delay(100);
mpu.resetFIFO();
message = x + "," + y + "," + z;
Serial.println(message);
msgAllClients(message);
#endif
#ifdef OUTPUT_READABLE_QUATERNION
// display quaternion values in easy matrix form: w x y z
mpu.dmpGetQuaternion(&q, fifoBuffer);
delay(100);
mpu.resetFIFO();
message = String(q.w) + "," + String(q.x) + "," + String(q.y) + "," + String(q.z);
Serial.println(message);
msgAllClients(message);
#endif
#ifdef OUTPUT_READABLE_EULER
// display Euler angles in degrees
mpu.dmpGetQuaternion(&q, fifoBuffer);
mpu.dmpGetEuler(euler, &q);
String x = String(euler[0] * 180/M_PI);
String y = String(euler[1] * 180/M_PI);
String z = String(euler[2] * 180/M_PI);
delay(100);
mpu.resetFIFO();
message = x + "," + y + "," + z;
Serial.println(message);
msgAllClients(message);
#endif
#ifdef OUTPUT_READABLE_REALACCEL
// display real acceleration, adjusted to remove gravity
mpu.dmpGetQuaternion(&q, fifoBuffer);
mpu.dmpGetAccel(&aa, fifoBuffer);
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetLinearAccel(&aaReal, &aa, &gravity);
delay(100);
mpu.resetFIFO();
message = String(aaReal.x) + "," + String(aaReal.y) + "," + String(aaReal.z);
Serial.println(message);
msgAllClients(message);
#endif
#ifdef OUTPUT_READABLE_WORLDACCEL
// display initial world-frame acceleration, adjusted to remove gravity
// and rotated based on known orientation from quaternion
mpu.dmpGetQuaternion(&q, fifoBuffer);
mpu.dmpGetAccel(&aa, fifoBuffer);
mpu.dmpGetGravity(&gravity, &q);
mpu.dmpGetLinearAccel(&aaReal, &aa, &gravity);
mpu.dmpGetLinearAccelInWorld(&aaWorld, &aaReal, &q);
delay(100);
mpu.resetFIFO();
message = String(aaWorld.x) + "," + String(aaWorld.y) + "," + String(aaWorld.z);
Serial.println(message);
msgAllClients(message);
#endif
}
}
void updateClients(){
WiFiClient newClient = server.available();
bool present = false;
int openIndex = CLIENT_COUNT + 1;
for(int i = 0; i < CLIENT_COUNT; i++){
if(clients[i] != NULL){
if(!clients[i].connected()){
clients[i].stop();
clients[i] = NULL;
openIndex = i < openIndex ? i : openIndex;
continue;
}
present = newClient.remoteIP() == clients[i].remoteIP() ? true : present;
}
else{
openIndex = i < openIndex ? i : openIndex;
}
}
if(!present && openIndex < CLIENT_COUNT){
clients[openIndex] = newClient;
}
}
void msgAllClients(String message){
for(int j = 0; j < CLIENT_COUNT; j++){
if(clients[j] != NULL){
clients[j].println(message);
}
}
}
void buttonLoop(){
aVal = digitalRead(aButtonPin);
if (aVal == HIGH && aDown) {
aDown = false;
Serial.println("A_DOWN");
msgAllClients("A_DOWN");;
} else if (aVal == LOW && !aDown) {
aDown = true;
Serial.println("A_UP");
msgAllClients("A_UP");
}
bVal = digitalRead(bButtonPin);
if (bVal == HIGH && bDown) {
bDown = false;
Serial.println("B_DOWN");
msgAllClients("B_DOWN");
} else if (bVal == LOW && !bDown) {
bDown = true;
Serial.println("B_UP");
msgAllClients("B_UP");
}
}
void loop()
{
updateClients();
mpu_loop();
buttonLoop();
}
然而，当我运行它时，我收到了错误：
Arduino: 1.8.12 (Windows 10), Board: "NodeMCU 1.0 (ESP-12E Module), 80 MHz, Flash, Legacy (new can return nullptr), All SSL ciphers (most compatible), 4MB (FS:2MB OTA:~1019KB), 2, v2 Lower Memory, Disabled, None, Only Sketch, 115200"
In file included from C:UsersmlfreAppDataLocalArduino15packagesesp8266hardwareesp82662.6.3librariesESP8266WiFisrc/ESP8266WiFi.h:39:0,
from C:UsersmlfreOneDriveDesktoppacketHandlerpacketHandler.ino:23:
C:UsersmlfreAppDataLocalArduino15packagesesp8266hardwareesp82662.6.3librariesESP8266WiFisrc/WiFiClient.h:47:3: error: 'WiFiClient::WiFiClient(ClientContext*)' is protected
WiFiClient(ClientContext* client);
^
packetHandler:181:41: error: within this context
WiFiClient clients[CLIENT_COUNT] = {NULL};
^
In file included from C:UsersmlfreAppDataLocalArduino15packagesesp8266hardwareesp82662.6.3librariesESP8266WiFisrc/ESP8266WiFi.h:39:0,
from C:UsersmlfreOneDriveDesktoppacketHandlerpacketHandler.ino:23:
C:UsersmlfreAppDataLocalArduino15packagesesp8266hardwareesp82662.6.3librariesESP8266WiFisrc/WiFiClient.h: In function 'void updateClients()':
C:UsersmlfreAppDataLocalArduino15packagesesp8266hardwareesp82662.6.3librariesESP8266WiFisrc/WiFiClient.h:47:3: error: 'WiFiClient::WiFiClient(ClientContext*)' is protected
WiFiClient(ClientContext* client);
^
packetHandler:322:20: error: within this context
clients[i] = NULL;
^
exit status 1
within this context
由于这个问题似乎是特定于上下文的，谷歌在解决我的问题时效率低下，这就是为什么我转向了栈溢出的好社区。我一开始使用python，后来逐渐转向c++，你们中的一些人可能会从我的编码方式中看出这一点，所以请放心，哈哈。如果需要，我可以提供更多信息。提前谢谢
(我不知道这个问题的上下文，但会尝试猜测问题是什么以及解决方案可能是什么。(
首先要注意，WiFiClient::WiFiClient(ClientContext*)是一个受保护的构造函数。编译器选择该构造函数以将NULL转换为WiFiClient(在做出该选择之后执行访问检查(。
当你写
WiFiClient clients[CLIENT_COUNT] = {NULL};
创建一个数组clients，使其第一个(不是全部！(元素通过受保护的WiFiClient(ClientContext*)构造函数构造，其余元素通过公共WiFiClient()构造函数构造。此行失败，因为受保护的构造函数在此处是不可访问的。
你想要的可能只是这个：
WiFiClient clients[CLIENT_COUNT];
现在，所有元素都是通过WiFiClient()构建的。您可以添加= {}，但在这里它不会改变任何内容。
也会发生同样的情况
clients[i] = NULL;
编译器尝试使用受保护的构造函数将NULL转换为WiFiClient。要使用公共WiFiClient()构造函数，请编写
clients[i] = {};
(这应该是编译的，但我不知道这个赋值是否有语义意义。它看起来很可疑。(
我将如何预先准备一个相等测试，以确保那里有一个元素，例如
clients[i] != NULL？
有了WiFiClient clients[CLIENT_COUNT]，元素总是存在的。NULL或nullptr不表示"无元素"状态。如果需要"可为null"的元素，则应更改数组元素类型。您有几个选项：WiFiClient*、std::unique_ptr<WiFiClient>和std::optional<WiFiClient>。
如果Arduino编译器支持std::unique_ptr(C++11(或std::optional(C++17(，则首选它们而不是原始指针类型。对于原始指针，您应该手动delete对象以避免内存泄漏，而std::unique_ptr将自动执行，并且std::optional根本不在堆上分配对象，而是将它们保留在自己内部。在所有情况下，"无元素"状态的测试仅为if (!clients[i]) ...，元素访问通过*clients[i]或clients[i]->完成。