从 API 请求数据

问题描述

this is the error on serial monitor

我使用的是 ESP8266 NodeMcu，IDE 使用的是 Arduino

我不知道该怎么办，现在已经 10 个小时了。

#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <ArduinoJson.h>

//Provide your own WiFi credentials
const char* ssid = "Kyzer";
const char* password = "@kyzer4$";
//String for storing server response
String response = "";
//JSON document
DynamicJsonDocument doc(2048);


void setup() {
  Serial.begin(115200);
  //Initiate WiFi connection
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid,password);
  Serial.println("");

  // Wait for connection
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.print("WiFi connected with IP: ");
  Serial.println(WiFi.localIP());
}

void loop() {
  //Initiate HTTP client
  HTTPClient http;
  //The API URL
  String request = "https://covid-api.mmediagroup.fr/v1/cases?country=Portugal";
  //Start the request
  http.begin(request);
  //Use HTTP GET request
  http.GET();
  //Response from server
  response = http.getString();
  //Parse JSON,read error if any
  DeserializationError error = deserializeJson(doc,response);
  if(error) {
     Serial.print(F("deserializeJson() failed: "));
     Serial.println(error.f_str());
     delay(5000);
     return;
  }
  //Print parsed value on Serial Monitor
  Serial.print("cases: ");
  Serial.println(doc["confirmed"].as<int>());
  Serial.print("recovered: ");
  Serial.println(doc["recovered"].as<int>());
  Serial.print("deaths: ");
  Serial.println(doc["deaths"].as<int>());
  Serial.println("");
  //Close connection  
  http.end();
  //Wait five seconds
  delay(5000);
}

请有人帮我我无法获得我想要的数据并在串行监视器上显示它，可能是什么问题？

解决方法

您尝试解析的 json 对象的结构如下：

  {"All": {
    "confirmed": 378656,"recovered": 304825,"deaths": 6254,"country": "Portugal","population": 10329506,"sq_km_area": 91982,"life_expectancy": "75.8","elevation_in_meters": 372,"continent": "Europe","abbreviation": "PT","location": "Southern Europe","iso": 620,"capital_city": "Lisboa","lat": "39.3999","long": "-8.2245","updated": "2020/12/22 23:22:35+00"
    }
  }

元素confirmed、recovered 和deaths 都在All 元素下，因此您需要通过评估All 或使用{ {1}}，或者创建一个名为 doc["All"]["confirmed"] 的新根 json 对象，以便您可以使用 All 访问它。看例子：

All["confirmed"]