如何解决为什么Vector不存储字符串? Arduino的
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
}
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