Question

我无法从GET响应中提取我需要的数据我只想记住介于＆＃34; - ＆＃34;之间的charcaters。和＆＃34; - ＆＃34;因为我不需要任何其他东西。我尝试使用while循环，如下所示但它不会工作

谢谢

    String readString;

    while (client.connected() || client.available()) {
      char c = client.read(); //gets byte from ethernet buffer

      while(c != "-"); //this throw error
      readString += c; //places captured byte in readString
    }

    client.stop(); //stop client

    Serial.print(readString);

    String res = readString.substring("-","-"); //throw error
    String val = "happy";

    if(res == val){
      Serial.print(res);
      Serial.println(" happy");
    }else{
      Serial.print(res);
      Serial.println(" sad");
    }

  Serial.println("==================");
  Serial.println();
  readString=""; //clear readString variable

Answer 1

好的，这里有不同的问题。

您无法比较字符（c）和字符串（"-"）。您应该使用'-'与char进行比较。
在你的循环中会阻止程序执行。您应该使用某种状态机（例如使用状态变量）。
如果正确编写阅读功能，则无需使用substring功能。在任何情况下，substring函数都需要INDICES，而不是chars。

这就是说，这段代码适合你的情况：

// state =
// 0 -> waiting for first -
// 1 -> reading the answer and waiting for second -
// 2 -> finished reading
uint8_t state = 0;

while (client.connected() || client.available()) {
    char c = client.read(); //gets byte from ethernet buffer

    if ((c == '-') && (state < 2))
        state++;
    if ((state == 1) && (c != '-'))
        readString += c;
}

client.stop(); //stop client

Serial.print(readString);
String val = "happy";

if(res == val){
    Serial.print(readString);
    Serial.println(" happy");
}else{
    Serial.print(readString);
    Serial.println(" sad");
}

无论如何，我真的不喜欢在arduino中使用变量大小的变量，因为你的内存很少（所以你为什么要浪费它？）。我的建议是始终使用固定大小的字符串（aka char数组）。例如：

// state =
// 0 -> waiting for first -
// 1 -> reading the answer and waiting for second -
// 2 -> finished reading
uint8_t state = 0;

char readString[MAX_SIZE+1];
uint8_t readStringIndex = 0;

while (client.connected() || client.available()) {
    char c = client.read(); //gets byte from ethernet buffer

    if ((c == '-') && (state < 2))
        state++;
    if ((state == 1) && (c != '-'))
    {
        readString[readStringIndex] = c;
        readStringIndex++;
    }
}
readString[readStringIndex] = '\0'; // string terminator

client.stop(); //stop client

Serial.print(readString);

if(strcmp(readString, "happy")){
    Serial.print(readString);
    Serial.println(" happy");
}else{
    Serial.print(readString);
    Serial.println(" sad");
}

修改

OP提到字符串不再由两个' - '分隔，而是包含在'＆lt;'之间和'＆gt;'。

因此，应该以这种方式修改代码：

// state = // 0 -> waiting for first - // 1 -> reading the answer and waiting for second - // 2 -> finished reading uint8_t state = 0; char readString[MAX_SIZE+1]; uint8_t readStringIndex = 0; while (client.connected() || client.available()) { char c = client.read(); //gets byte from ethernet buffer switch (state) { case 0: // Waiting for first char if (c == '<') state = 1; break; case 1: // Reading the answer and waiting for second char if (c == '>') state = 2; else { readString[readStringIndex] = c; readStringIndex++; } break; } } readString[readStringIndex] = '\0'; // string terminator client.stop(); //stop client Serial.print(readString); if(strcmp(readString, "happy")){ Serial.print(readString); Serial.println(" happy"); }else{ Serial.print(readString); Serial.println(" sad"); }

解析GET响应

1 个答案: