为什么Vector不存储字符串？ Arduino的

编程问答 2022-08-15

问题描述

我正在尝试在Vector上存储SSID的值，在第一个循环中，将存储向量并打印字符串，但是当我退出第一个循环时，Vector不会打印任何内容且未存储字符串，您知道吗为什么？

#include "ESP8266WiFi.h"
#include <Vector.h>
void setup() {
    Serial.begin(115200);
  // put your setup code here,to run once:
 // setup
  WiFi.mode(WIFI_STA);
  WiFi.disconnect();
  delay(100);

  Serial.println("Setup done");
  // scan

  Serial.println("scan start");

  // WiFi.scanNetworks will return the number of networks found
  int n = WiFi.scanNetworks();
  Serial.println("scan done");
  if (n == 0) {
    Serial.println("no networks found");

  } else {
    Serial.print(n);
    Serial.println(" networks found");

    Vector< Vector<String> >  result;
    Vector<String> r[20];
    result.setStorage(r);
    for (int i = 0; i < n; i++) {
      String s [3];
      Vector<String> v;
      v.setStorage(s);
     
      // Print SSID and RSSI for each network found
      /**Serial.println(i + 1);
      Serial.print(": ");
      Serial.print(WiFi.SSID(i));
      Serial.print(" (");
      Serial.print(WiFi.RSSI(i));
      Serial.print(")");
      Serial.println((WiFi.encryptionType(i) == ENC_TYPE_NONE) ? " " : "*");**/
      v.push_back( WiFi.SSID(i));
      result.push_back(v);
      Serial.print("result[i][0] : ");
      Serial.println(result[i][0]);
      //result[i][1] = static_cast<char*>WiFi.RSSI(i);
      //result[i][2] = static_cast<char*>WiFi.encryptionType(i);

      delay(10);
    }
     Serial.print("Second Loop ");
    Serial.println(result.size());
    for(int a = 0; a < result.size(); a++){
          Serial.println(result[a][0]);
     }
  }
}

void loop() {
  // put your main code here,to run repeatedly:
delay(10000);
}

我正在ESP8266上执行此代码，向量库为https://github.com/janelia-arduino/Vector。我粘贴输出

11:29:39.991 -> Setup done
11:29:39.991 -> scan start
11:29:42.177 -> scandone
11:29:42.177 -> scan done
11:29:42.177 -> 14 networks found
11:29:42.177 -> result[i][0] : MiFibra-99F6
11:29:42.177 -> result[i][0] : MiFibra-F5AA
11:29:42.210 -> result[i][0] : Punto_Internet
11:29:42.210 -> result[i][0] : vodafoneF968
11:29:42.210 -> result[i][0] : MikroTik-068214
11:29:42.243 -> result[i][0] : Invitado-99F6
11:29:42.243 -> result[i][0] : MOVISTAR_3860
11:29:42.243 -> result[i][0] : DIGIFIBRA-4XxK
11:29:42.243 -> result[i][0] : Netllar Telecom - 7117
11:29:42.276 -> result[i][0] : DIRECT-51-HP OfficeJet 3830
11:29:42.276 -> result[i][0] : DIGIFIBRA-Agh4
11:29:42.276 -> result[i][0] : vodafoneBAC0
11:29:42.309 -> result[i][0] : Station15
11:29:42.309 -> result[i][0] : MIWIFI_2jpc
11:29:42.309 -> Second Loop 14
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 -> 
11:29:42.309 ->

解决方法

答案是Vector的体系结构。它仅类似于std :: vector，主要区别在于它不分配内存。您必须为此提供C样式的数组。您不提供Vector r [20]的存储空间。

在代码中，您在堆栈上创建一个数组，然后使用push_back将其复制到某个地方。可能在Vector实现中进行了检查，因此您不会真正破坏内存。

Vector< Vector<String>>  result;
Vector<String> r[20]; <--- No storage is provided for this Vector
result.setStorage(r);


for (int i = 0; i < n; i++) {
  String s [3]; <--- This is a C-style array in which Vector will store data
  Vector<String> v;
  v.setStorage(s); <--- This is ok
 
 
  v.push_back( WiFi.SSID(i));
  result.push_back(v); <--- data is copied to non-existing location
  Serial.print("result[i][0] : ");
  Serial.println(result[i][0]);

  delay(10);
}

Serial.print("Second Loop ");
Serial.println(result.size());
for(int a = 0; a < result.size(); a++){
      Serial.println(result[a][0]); <--- The memory result is pointing at is not valid anymore
}
arduinoarduino-esp8266c++storestorevectorvector