如何将 this 指针传递给 class 中的任务？

Question

我正在创建一个库来管理我们在许多 ESP32 设备上的 wifi 网络连接。

在我的库中，我有一个循环任务，暂停 1 秒，从我的 .begin() 函数中的 xTaskCreate 开始。问题是，如果我没有在我的 .h 文件中将其设为静态，我将无法启动该任务。因此，一旦任务被声明为静态，我就无法访问该任务中的 this-> 指针。无论如何我可以在我的任务中发送 this-> 指针，比如在参数或类似的东西中？

这是一些代码：

class EraWiFi{
    public:
        EraWiFi();
        /*!
        * @brief Initialize WiFi
        * @return Returns true if successful
        */

        bool begin(fs::FS &fs);
        /*!
        * @brief Start EraWiFi service
        * @return Returns true if successful
        */

        void downloadWiFi();

    private:
        static void wifiTask(void * parameter);
};


bool EraWiFi::begin(fs::FS &fs){
    File file = fs.open("/WiFi.json", FILE_READ);
    if(file){
        DynamicJsonDocument wifi(2048);
        DeserializationError error = deserializeJson(wifi, file);
        file.close();
        if (!error){
            Serial.println("We have a VALID WiFi.json configurations file!");
            Serial.println("Adding wifi networks:");
            for (JsonArray arr : wifi.as<JsonArray>()){
                Serial.print("SSID: ");
                Serial.print(arr[0].as<char*>());
                Serial.print(", KEY: ");
                Serial.println(arr[1].as<char*>());
                wifiMulti.addAP(arr[0].as<char*>(), arr[1].as<char*>());
            }
        }else{
            Serial.println("We don't have a VALID WiFi.json configurations file!");
        }
    }else{
        Serial.println("There is no WiFi.json configurations file!");
    }
    wifiMulti.addAP("Testing", "1234");
    xTaskCreate(
        this->wifiTask,    // Function that should be called
        "WiFiTask",   // Name of the task (for debugging)
        10000,            // Stack size (bytes)
        (void*)&this,            // Parameter to pass
        1,               // Task priority
        NULL   // Task handle
    );
    return true;
}



void EraWiFi::downloadWiFi(){
    Serial.println("Downloading WiFi.json from ErabliTEK Server.");
    HTTPClient http;
    // Send request
    http.useHTTP10(true);
    String url = "https://testing.testing.com/wifis/getWiFi/";
    http.begin(url);
    int httpResponseCode =  http.GET();
    if(httpResponseCode == HTTP_CODE_OK){
        // Parse response
        DynamicJsonDocument doc(2048);
        DeserializationError error = deserializeJson(doc, http.getStream());
        // Disconnect
        http.end();
        if (!error){
        File file = fs.open("/WiFi.json", FILE_WRITE);
        if(file){
            // Serialize JSON to file
            if (serializeJson(doc, file) == 0) {
            Serial.println("Error saving WiFi.json!");
            Serial.println(http.getString());
            }else{
            Serial.println("Succesfully saved WiFi.json!");
            }
        }
        // Close the file
        file.close();
        }else{
        Serial.println("Error downloading WiFi.json");
        }
    }else{
        Serial.println("Problem connecting to " + url + " with http code: " + String(httpResponseCode));
    }
}



void EraWiFi::wifiTask(void * parameters){
    bool wifiConnected = false;
    for(;;){
        uint8_t wifiStatus = wifiMulti.run();
        if((wifiStatus != WL_CONNECTED) and wifiConnected) {
            wifiConnected = false;
            Serial.println("WiFi not connected!");
        }else if((wifiStatus == WL_CONNECTED) and !wifiConnected){
            wifiConnected = true;
            Serial.println("WiFi Connected.");
            Serial.print("SSID: ");
            Serial.println(WiFi.SSID());
            Serial.print("KEY: ");
            Serial.println(WiFi.psk());
            Serial.print("IP Address: ");
            Serial.println(WiFi.localIP());
            EraWiFi::downloadWiFi();
        }
        vTaskDelay(1000 / portTICK_PERIOD_MS);
    }
}

Answer 1

您已经在这样做了，只是您没有意识到而已。看一下 FreeRTOS documentation on xTaskCreate()，它解释了第四个参数 pvParameters 是如何作为其（唯一的）输入参数传递给新任务的空指针。

此处的注释行表示您正在获取 EraWiFi 对象的地址并将其传递给任务：

    xTaskCreate(
        this->wifiTask,
        "WiFiTask",
        10000,
        (void*)&this,  //< Pointer gets forwarded to the task
        1,
        NULL
    );

要在您的任务中使用指针，您只需将其从 void*:

转换回来

void EraWiFi::wifiTask(void * parameters){
    EraWifi* p = static_cast<EraWifi*>(parameters); //< That's the same pointer
    p->someMethod();
...

PS。另请注意（在您从不同线程访问同一对象之前，可能会导致难以发现的错误）FreeRTOS 提供了出色的线程间通信工具 - queues and task notifications often being the most useful ones. Check out their tutorial/book 进行了解释。

如何将 this 指针传递给 class 中的任务？

How to pass the this pointer to a task inside a class?

arduino

wifi

esp32

multitasking