PFG – Lectura del LOG y aplicación final de Android

Para finalizar la aplicación Android, deben sustituirse los controles de la interfaz por unos nuevos que reflejen el estado de los sensores y el valor de los parámetros de la Raspberry Pi. Para ello se rediseñan los dos fragments de la aplicación:

Fragment principal

• TextView para la temperatura.
• TextView para la humedad.
• TextView para el sensor de lluvia.
• TextView para el pronóstico.
• TextView para ver el estado del actuador que regula el riego.
• TextView para el Timestamp.
• Botón para leer los últimos valores del LOG.
• Botón para solicitar una actualización de los valores mediante la apertura del semáforo con nombre.

Fragment de parámetros avanzados

• EditText para mostrar la tasa de refresco de las variables de los sensores y un botón para guardar cualquier modificación.
• EditText para mostrar la tasa de solicitud del pronóstico meteorológico y un botón para guardar cualquier modificación.
• EditText para mostrar la ubicación del sistema utilizada para hallar el pronóstico meteorológico y un botón para guardarla.
• Botón para leer los valores de los parámetros del sistema.

 

 Script de lectura de los valores del LOG (read_log.cgi)

Para el funcionamiento de los botones definidos es necesario crear un script que lea estos valores de los sensores recogidos en el fichero LOG.

El script abre en primer lugar el LOG, ubicado en vars/VARS, lee la primera línea (el header que contiene el nombre de las variables) y elimina el último carácter (salto de carro \n). A continuación lee todo el fichero hasta llegar a la última fija (EOF) y la guarda (los valores más actualizados de los sensores). Elimina nuevamente el último carácter y cierra el archivo. Ahora separa los nombres de las variables y los valores mediante la función strtok al estar almacenados en formato CSV. Guarda estos pares de valores en un objeto JSON y lo devuelve por la salida estándar.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "functions.h"
#include "json-builder.h"

#define RUTA "vars/VARS"

int main() {

    FILE * f;
    char * header;
    char data[80];
    char * vars[99];
    char * values[99];

    int nelements;
    int i;

    size_t len = 0;

    json_value * json_obj = json_object_new(0);

    printf("Content-Type: application/json\n\n");

    // Abrimos el LOG
    f = fopen(RUTA, "r");

    if (f == NULL)
        exit(EXIT_FAILURE);    

    // Leemos el header
    getline(&header, &len, f);

    // Eliminamos el último caracter
    header[strlen(header) - 1] = '\0';
 
    // Buscamos la última línea del archivo y la leemos
    int num_lineas;
    int ch;
    while (fgets(data, 80, f) != NULL) {
        if (ch = fgetc(f) == EOF)
            break;
        else {
            fseek(f, -1, SEEK_CUR);
            num_lineas ++;
        }
    }

    // Eliminamos el último caracter
    data[strlen(data) - 1] = '\0';

    // Cerramos el archivo
    fclose(f);

    // Parseamos el header (vars)
    i=0;
    vars[0] = (char *) strtok(header,",");

    while (vars[i] != NULL) {
        i++;
        vars[i] = (char *) strtok(NULL,",");
    }

    // Parsemos los datos (values)
    i=0;
    values[0] = (char *) strtok(data,",");

    while (values[i] != NULL) {
        i++;
        values[i] = (char *) strtok(NULL,",");
    }
    nelements = i;

    // Convertimos a objeto JSON e imprimimos
        for (i=0; i<nelements; i++) {
        json_object_push(json_obj, (json_char *) vars[i], json_string_new(values[i]));
    }

    char * buf = malloc(json_measure(json_obj));
    json_serialize(buf, json_obj);

    printf("%s\n", buf);
}

Compilamos con:

> gcc -o read_log.cgi read_log.c json-builder.c -lm

Y lo probamos:

 

Modificación de los scripts y programa principal de la Raspberry Pi

read.cgi

Al tener que leer un campo de texto que puede contener espacios, se cambia la instrucción fscanf por fgets, la cual lee una línea entera.

#include <stdio.h>
#include <stdlib.h>
#include "functions.h"
#include "json-builder.h"

int main() {

    FILE * f;
    char * data;
    char * pch[99];
    char * vars[99];
    char * values[99];
    char * nombre_fichero;
    json_value * json_obj = json_object_new(0);

    printf("Content-Type: application/json\n\n");

    data = (char *) getenv("QUERY_STRING");

    if (data != NULL) {

        int i=0;
        pch[0] = (char *) strtok(data,"&");

        while (pch[i] != NULL) {
            i++;
            pch[i] = (char *) strtok(NULL,"&");
        }

        int nelements=i;

        for (i=0; i<nelements; i++) {
            sscanf(pch[i],"var=%s", &vars[i]);
            nombre_fichero = ruta((char *) &vars[i]);
            f = fopen((char *) nombre_fichero,"r");

            if (f != NULL) {
                fgets((char *)&values[i], 100, f);
                
                fclose(f);
            }
            
            json_object_push(json_obj, (json_char *) &vars[i], json_string_new((char *)&values[i]));
        }

        char * buf = malloc(json_measure(json_obj));
        json_serialize(buf, json_obj);

        printf("%s\n", buf);
    }
}

 

write.cgi

Se utilizaba la instrucción fscanf para separar la variable y el valor de la URL (write.cgi?REFRESH_RATE=10). Al tener un campo que incluye texto y una coma, se facilita este proceso usando la instrucción strtok.

#include <stdio.h>
#include <stdlib.h>
#include "functions.h"

int main() {

    FILE *f;
    char *data;
    char * pch[99];
    char * nombre_fichero;

    printf("Content-Type: application/json\n\n");

    data = getenv("QUERY_STRING");

    if (data != NULL) {

        int i=0;
        pch[0] = (char *) strtok(data,"=");

        while (pch[i] != NULL) {
            i++;
            pch[i] = (char *) strtok(NULL,"=");
        }

    }

    nombre_fichero = ruta(pch[0]);

    f = fopen(nombre_fichero,"w");

    if (f != NULL) {
        fprintf(f, "%s", pch[1]);
        fclose(f);
        printf("Success");
    }
}

 

main.c

Con motivo de dar forma a la aplicación final de android se añade la variable lógica actuator que indicará si el actuador que controla el riego está encendido o no. Más adelante se propone un algoritmo que controle esta señal.

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <fcntl.h> // O_CREAT
#include <semaphore.h>
#include "functions.h"

#define ARDUINO 0x04
#define TI 0x08

#define TAG_REFRESH_RATE "REFRESH_RATE"
#define TAG_FORECAST "FORECAST"
#define TAG_TIMESTAMP "TIMESTAMP"
#define TAG_TEMP "TEMP"
#define TAG_RAIN "RAIN"
#define TAG_HUM "HUMIDITY"
#define TAG_ACTUATOR "ACTUATOR"

int main() {
    char * buf;

    int refresh_rate;

    char * timestamp;

    uint nBytesTAG_TEMP = sizeof(TAG_TEMP)-1; // no enviamos el caracter '\0'
    uint nBytesTAG_RAIN = sizeof(TAG_RAIN)-1;
    uint nBytesTAG_HUM = sizeof(TAG_HUM)-1;
    uint nBytesTEMP = 4;
    uint nBytesRAIN = 1;
    uint nBytesHUM = 3;

    float temperature;
    uint rain;
    uint humidity;
    int forecast;
    uint actuator;

    char temperature_char[] = {0};
    char rain_char[] = {0};
    char humidity_char[] = {0};
    char forecast_char[] = {0};
    char actuator_char[] = {0};

    int pid, status;

    sem_t * sem;

    char sem_name[] = "miSemaforo";
    char shm_path[] = "/dev/shm/sem.";
    char sem_path[20];
    strcpy(sem_path, shm_path);
    strcat(sem_path, sem_name);

    sem = sem_open(sem_name, O_CREAT, 0666, 0);

    chmod(sem_path, 0666);

    static struct timespec time_to_wait = {0, 0};

    // Creamos el proceso hijo y le indicamos que ejecute el script para obtener la predicción meteorológica
    pid = fork();

    if (pid == 0) {
        execlp("python", "python", "weather_forecast.py", NULL);
        exit(0);
    }

    // Proceso padre
    else {

        for(;;) {

            // Leemos la tasa de refresco
            buf = readVar(TAG_REFRESH_RATE);
            refresh_rate = atoi((char *) &buf);
            printf("%s: %d\n", TAG_REFRESH_RATE, refresh_rate);

            // Ajustamos el valor del semáforo con nombre
            time_to_wait.tv_sec = time(NULL) + refresh_rate;
        
            // Leemos los valores se los sensores
            temperature = readSensor(TI, TAG_TEMP, nBytesTAG_TEMP, nBytesTEMP) / 100.00;
            usleep(50000);
            rain = readSensor(TI, TAG_RAIN, nBytesTAG_RAIN, nBytesRAIN);
            usleep(50000);
            humidity = readSensor(TI, TAG_HUM, nBytesTAG_HUM, nBytesHUM);

            // Obtenemos el timestamp
            timestamp = getTime();

            // Leemos el pronóstico del fichero
            buf = readVar(TAG_FORECAST);
            forecast = atoi((char *) &buf);

            // Algoritmo para el encendido del sistema de riego
            actuator = 0;

            // Convertimos los valores a char*
            sprintf(temperature_char, "%.2f", temperature);
            sprintf(rain_char, "%d", rain);
            sprintf(humidity_char, "%d", humidity);
            sprintf(forecast_char, "%d", forecast);
            sprintf(actuator_char, "%d", actuator);

            // Creamos los char** que cotienen variables y vectores
            char * variables_array[] = {TAG_TIMESTAMP, TAG_TEMP, TAG_RAIN, TAG_HUM, TAG_FORECAST, TAG_ACTUATOR, NULL};
            char * values_array[] = {timestamp, temperature_char, rain_char, humidity_char, forecast_char, actuator_char, NULL};

            printf("%s: %s\n", TAG_TEMP, temperature_char);
            printf("%s: %s\n", TAG_RAIN, rain_char);
            printf("%s: %s\n", TAG_HUM, humidity_char);
            printf("%s: %s\n", TAG_FORECAST, forecast_char);
            printf("%s: %s\n", TAG_ACTUATOR, actuator_char);
            printf("%s\n", timestamp);

            // Guardamos en el log los valores
            writeVar(variables_array, values_array);

            sem_timedwait(sem, &time_to_wait);
        }

        sem_close(sem);
        sem_unlink(sem_name);
    }

    return 0;
}

 

 

Aplicación Android

Se rediseñan los fragments para mostrar la información indicada anteriormente. También se añade a los fragments la funcionalidad de que al cargarse en la Activity realice la petición de leer los datos que debe mostrar en ese fragment de forma automática.

 

main_variables_fragment.xml

<RelativeLayout

    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:id="@+id/layout">

    <!-- Temperature Label -->
    <TextView
        android:id="@+id/temperatureLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/temperature_label"
        android:textStyle="bold"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="20dp" />

    <!-- Temperature Value -->
    <TextView
        android:id="@+id/temperature"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"
        android:layout_marginStart="5dp"
        android:text=""
        android:layout_alignBottom="@id/temperatureLabel"
        android:layout_toRightOf="@id/temperatureLabel"
        android:layout_toEndOf="@id/temperatureLabel" />

    <!-- Humidity Label -->
    <TextView
        android:id="@+id/humidityLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/humidity_label"
        android:textStyle="bold"
        android:layout_below="@+id/temperatureLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="20dp"/>

    <!-- Humidity Value -->
    <TextView
        android:id="@+id/humidity"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"
        android:layout_marginStart="5dp"
        android:text=""
        android:layout_alignTop="@id/humidityLabel"
        android:layout_toRightOf="@id/humidityLabel"
        android:layout_toEndOf="@id/humidityLabel" />

    <!-- Rain Label -->
    <TextView
        android:id="@+id/rainLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/rain_label"
        android:textStyle="bold"
        android:layout_below="@+id/humidityLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="20dp"/>

    <!-- Rain Value -->
    <TextView
        android:id="@+id/rain"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="5dp"
        android:layout_marginStart="5dp"
        android:text=""
        android:layout_alignTop="@id/rainLabel"
        android:layout_toRightOf="@id/rainLabel"
        android:layout_toEndOf="@id/rainLabel" />

    <!-- forecast Label -->
    <TextView
        android:id="@+id/forecastLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/forecast_label"
        android:textStyle="bold"
        android:layout_below="@+id/rainLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="20dp"/>

    <!-- forecast Value -->
    <TextView
        android:id="@+id/forecast"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:layout_marginTop="5dp"
        android:layout_below="@+id/forecastLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp" />

    <!-- actuator Label -->
    <TextView
        android:id="@+id/actuatorLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/actuator_label"
        android:textStyle="bold"
        android:layout_below="@+id/forecast"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="20dp"/>

    <!-- actuator Value -->
    <TextView
        android:id="@+id/actuator"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:layout_marginTop="5dp"
        android:layout_below="@+id/actuatorLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp" />

    <!-- timestamp Label -->
    <TextView
        android:id="@+id/timestampLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/timestamp_label"
        android:textStyle="bold"
        android:layout_below="@+id/actuator"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="20dp"/>

    <!-- timestamp Value -->
    <TextView
        android:id="@+id/timestamp"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""
        android:layout_marginTop="5dp"
        android:layout_below="@+id/timestampLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp" />

    <!-- Request new values button -->
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_refresh"
        android:textSize="14sp"
        android:layout_marginTop="10dp"
        android:id="@+id/buttonRequest"
        android:layout_below="@+id/buttonGet"
        android:layout_centerHorizontal="true" />

    <!-- Get button -->
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_refresh_variables"
        android:textSize="14sp"
        android:id="@+id/buttonGet"
        android:layout_marginTop="10dp"
        android:layout_below="@+id/timestamp"
        android:layout_centerHorizontal="true" />


</RelativeLayout>

 

advanced_variables_fragment.xml

<RelativeLayout

    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:id="@+id/layout">

    <!-- sensors refresh rate Label -->
    <TextView
        android:id="@+id/refreshRateLabel"
        android:layout_width="170dp"
        android:layout_height="wrap_content"
        android:text="@string/refreshRate_label"
        android:lines="3"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="20dp" />

    <!-- sensors refresh rate -->
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="numberDecimal"
        android:ems="5"
        android:textSize="14sp"
        android:id="@+id/refreshRate"
        android:layout_alignBottom="@id/refreshRateLabel"
        android:layout_toRightOf="@id/refreshRateLabel"
        android:layout_toEndOf="@id/refreshRateLabel"
        android:layout_marginLeft="5dp"
        android:layout_marginStart="5dp"/>

    <!-- save refresh rate button -->
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/save_button"
        android:textSize="14sp"
        android:id="@+id/refreshRateSend"
        android:layout_alignBottom="@+id/refreshRate"
        android:layout_toRightOf="@+id/refreshRate"
        android:layout_toEndOf="@+id/refreshRate"/>

    <!-- forecast refresh rate Label -->
    <TextView
        android:id="@+id/refreshForecastRateLabel"
        android:layout_width="170dp"
        android:layout_height="wrap_content"
        android:text="@string/refreshForecastRate_label"
        android:lines="3"
        android:layout_below="@+id/refreshRate"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="20dp" />

    <!-- forecast refresh rate -->
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="numberDecimal"
        android:textSize="14sp"
        android:ems="5"
        android:id="@+id/refreshForecastRate"
        android:layout_alignBottom="@id/refreshForecastRateLabel"
        android:layout_toRightOf="@id/refreshForecastRateLabel"
        android:layout_toEndOf="@id/refreshForecastRateLabel"
        android:layout_marginLeft="5dp"
        android:layout_marginStart="5dp"/>

    <!-- save weather refresh rate button -->
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/save_button"
        android:textSize="14sp"
        android:id="@+id/refreshWeatherRateSend"
        android:layout_alignBottom="@+id/refreshForecastRate"
        android:layout_toRightOf="@+id/refreshForecastRate"
        android:layout_toEndOf="@+id/refreshForecastRate"/>

    <!-- location Label -->
    <TextView
        android:id="@+id/locationLabel"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/location_label"
        android:lines="2"
        android:layout_below="@+id/refreshForecastRateLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginRight="10dp"
        android:layout_marginTop="20dp" />

    <!-- location -->
    <EditText
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:inputType="text"
        android:text=""
        android:ems="15"
        android:id="@+id/location"
        android:textSize="14sp"
        android:layout_below="@+id/locationLabel"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_marginTop="15dp"
        android:layout_marginLeft="10dp"
        android:layout_marginStart="10dp"
        android:layout_marginRight="10dp" />

    <!-- save location button -->
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/save_button"
        android:textSize="14sp"
        android:id="@+id/locationSend"
        android:layout_alignBottom="@+id/location"
        android:layout_toRightOf="@+id/location"
        android:layout_toEndOf="@+id/location" />

    <!-- Refresh button -->
    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_refresh_params"
        android:textSize="14sp"
        android:id="@+id/buttonGet"
        android:layout_below="@id/location"
        android:layout_marginTop="20dp"
        android:layout_centerHorizontal="true" />

</RelativeLayout>

 

MainVariablesFragment.java

Se crean las referencias a los controles de la interfaz y y asocian los listeners a cada uno de los botones que aparecen. El botón Obtener últimos valores a la función readLogVariables, que ejecuta el script read_log.cgi y el botón Solicitad nuevos valores, que ejecuta openSemaphore y 500ms después (espera manejada mediante un Handler) invoca readLogVariables para obtener los nuevos valores que se han solicitado.

package net.eodos.controlderiego;

import android.app.AlertDialog;
import android.app.Fragment;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;

public class MainVariablesFragment extends Fragment {

    private static final String DEBUG_TAG = "HttpDebug";

    public TextView tempField;
    public TextView rainField;
    public TextView humidityField;
    public TextView forecastField;
    public TextView timestampField;
    public TextView actuatorField;
    public Button buttonGet;
    public Button buttonRequest;

    // JSON Node names
    private static final String TAG_TEMP = "TEMP";
    private static final String TAG_RAIN = "RAIN";
    private static final String TAG_HUMIDITY = "HUMIDITY";
    private static final String TAG_FORECAST = "FORECAST";
    private static final String TAG_TIMESTAMP = "TIMESTAMP";
    private static final String TAG_ACTUATOR = "ACTUATOR";

    // Hashmap for ListView
    HashMap<String, String> data;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.main_variables_fragment, container, false);

        // Creamos el array de variables de lectura
        data = new HashMap<>(); // <string, string>

        //Referencia a controles de la interfaz
        tempField = (TextView) view.findViewById(R.id.temperature);
        rainField = (TextView) view.findViewById(R.id.rain);
        humidityField = (TextView) view.findViewById(R.id.humidity);
        forecastField = (TextView) view.findViewById(R.id.forecast);
        timestampField = (TextView) view.findViewById(R.id.timestamp);
        actuatorField = (TextView) view.findViewById(R.id.actuator);
        buttonGet = (Button) view.findViewById(R.id.buttonGet);
        buttonRequest = (Button) view.findViewById(R.id.buttonRequest);

        buttonGet.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                readLogVariables();
            }
        });

        buttonRequest.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                openSemaphore();

                // Wait 500 ms
                Handler handler = new Handler();
                handler.postDelayed(new Runnable() {
                    public void run() {
                        readLogVariables();
                    }
                }, 500);


            }
        });

        return view;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); }

    @Override
    public void onActivityCreated(Bundle state) {
        super.onActivityCreated(state);
        readLogVariables();
    }

    // When user clicks button, calls AsyncTask.
    // Before attempting to fetch the URL, makes sure that there is a network connection.
    public void readLogVariables() {
        String URL = "http://192.168.2.200/cgi-bin/read_log.cgi";
        if (checkConnection()) {
            Log.d(DEBUG_TAG, "Connecting to: " + URL);
            new downloadVariablesTask().execute(URL);
        }
    }

    public void openSemaphore() {
        String URL = "http://192.168.2.200/cgi-bin/open_semaphore.cgi";
        if (checkConnection()) {
            Log.d(DEBUG_TAG, "Connecting to: " + URL);
            new downloadVariablesTask().execute(URL);
        }
    }

    public boolean checkConnection() {
        ConnectivityManager connMgr = (ConnectivityManager)
                getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
        if (networkInfo != null && networkInfo.isConnected()) {
            return true;
        } else {
            showWifiDialog();
            return false;
        }
    }

    // Uses AsyncTask to create a task away from the main UI thread. This task takes a
    // URL string and uses it to create an HttpUrlConnection. Once the connection
    // has been established, the AsyncTask downloads the contents of the webpage as
    // an InputStream. Finally, the InputStream is converted into a string, which is
    // displayed in the UI by the AsyncTask's onPostExecute method.
    public class downloadVariablesTask extends AsyncTask<String, Void, HashMap> {
        @Override
        protected HashMap doInBackground(String... params) {
            // params comes from the execute() call: params[0] is the url.
            try {
                return downloadUrl(params[0],true);
            } catch (IOException e) {
                getActivity().runOnUiThread(new Runnable() {
                    public void run() {
                        showUnableToConnectDialog();
                    }
                });
                return null;
            }
        }
        // onPostExecute displays the results of the AsyncTask.
        @Override
        protected void onPostExecute(HashMap data) {
            if (data != null) {
                // Show toast
                getActivity().runOnUiThread(new Runnable() {
                    public void run() {
                        showSuccessToast();
                    }
                });

                String temperature = (String) data.get(TAG_TEMP);
                String rain = (String) data.get(TAG_RAIN);
                String humidity = (String) data.get(TAG_HUMIDITY);
                String forecast = (String) data.get(TAG_FORECAST);
                String timestamp = (String) data.get(TAG_TIMESTAMP);
                String actuator = (String) data.get(TAG_ACTUATOR);
                tempField.setText(temperature);
                rainField.setText(rain);
                humidityField.setText(humidity);
                forecastField.setText(forecast);
                actuatorField.setText(actuator);
                timestampField.setText(timestamp);
            }
        }
    }

    // Given a URL, establishes an HttpUrlConnection and retrieves
    // the web page content as a InputStream, which it returns as
    // a string./*
    public HashMap downloadUrl(String myurl, boolean read) throws IOException {
        InputStream is = null;

        try {
            URL url = new URL(myurl);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(3000);
            conn.setConnectTimeout(5000);
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            // Starts the query
            conn.connect();
            int response = conn.getResponseCode();
            Log.d(DEBUG_TAG, "The response is: " + response);

            is = conn.getInputStream();

            if (read) {
                // Convert the InputStream into a HashMap
                return parseJSON(is);
            }

            else {
                return null;
            }

            // Makes sure that the InputStream is closed after the app is
            // finished using it.
        } finally {
            if (is != null) {
                is.close();
            }
        }
    }

    public HashMap parseJSON(InputStream stream) throws IOException {

        try {
            // Convert InputStream to a String
            BufferedReader r = new BufferedReader(new InputStreamReader(stream));
            StringBuilder result = new StringBuilder();
            String line;
            while ((line = r.readLine()) != null) {
                result.append(line);
            }

            // Convert the String to a HashMap object
            JSONObject serverJSON = new JSONObject(result.toString());
            String temp = serverJSON.getString(TAG_TEMP) + " " + (char)186 + "C";
            String rain = serverJSON.getString(TAG_RAIN);
            if (Integer.parseInt(rain) == 0) rain = "No";
            else if (Integer.parseInt(rain) == 1) rain = "Si";
            String humidity = serverJSON.getString(TAG_HUMIDITY) + "% HR";
            String forecast = serverJSON.getString(TAG_FORECAST);
            if (Integer.parseInt(forecast) == 0) forecast = "Hoy";
            else if (Integer.parseInt(forecast) == 1) forecast = "Ma" + (char)241 + "ana";
            else if (Integer.parseInt(forecast) == 2) forecast = "Dentro de dos d" + (char)237 + "as";
            else if (Integer.parseInt(forecast) == 3) forecast = "Dentro de tres d" + (char)237 + "as";
            else if (Integer.parseInt(forecast) == -1) forecast = "No hay precipitaciones previstas en tres d" + (char)237 + "as";
            String actuator = serverJSON.getString(TAG_ACTUATOR);
            if (Integer.parseInt(actuator) == 0) actuator = "No";
            else if (Integer.parseInt(actuator) == 1) actuator = "S" + (char)237;
            String timestamp = serverJSON.getString(TAG_TIMESTAMP);

            // New temp HashMap
            HashMap<String, String> data = new HashMap<>();

            // Adding each child node to Hashmap key => value
            data.put(TAG_TEMP, temp);
            data.put(TAG_RAIN, rain);
            data.put(TAG_HUMIDITY, humidity);
            data.put(TAG_FORECAST, forecast);
            data.put(TAG_ACTUATOR, actuator);
            data.put(TAG_TIMESTAMP, timestamp);

            // Return the Hashmap
            return data;

        } catch (JSONException e) {
            e.printStackTrace();
            return null;
        }
    }

    public void showWifiDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(getString(R.string.missingWifi))
                .setCancelable(false)
                .setNegativeButton(getString(R.string.ok), new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    public void showUnableToConnectDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(getString(R.string.unabletoconnect))
                .setCancelable(false)
                .setNegativeButton(getString(R.string.ok), new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    private void showSuccessToast() {
        Context context = getActivity().getApplicationContext();
        CharSequence text = context.getString(R.string.success);
        int duration = Toast.LENGTH_SHORT;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }
}

 

AdvancedVariablesFragment.java

Se crean los controles a la interfaz y se crean los listeners. A los botones Guardar se le asocia la invocación de la función writeVariable(String var, editText EditText) que ejecuta el script write.cgi y al botón Obtener parámetros la función readVariables() que ejecuta el script read.cgi.

También se crea un nuevo Toast con el mensaje Guardado que aparece cuando se guarda correctamente un parámetro en la Raspberry Pi.

package net.eodos.controlderiego;

import android.app.AlertDialog;
import android.app.Fragment;
import android.content.Context;
import android.content.DialogInterface;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;

public class AdvancedVariablesFragment extends Fragment {

    private static final String DEBUG_TAG = "HttpDebug";

    public TextView refreshField;
    public TextView forecastField;
    public TextView locationField;

    public Button buttonGet;
    public Button buttonRefreshRate;
    public Button buttonForecastRate;
    public Button buttonLocation;

    // JSON Node names
    private static final String TAG_REFRESH_RATE = "REFRESH_RATE";
    private static final String TAG_FORECAST_RATE = "FORECAST_RATE";
    private static final String TAG_LOCATION = "LOCATION";

    // Hashmap for ListView
    HashMap<String, String> data;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.advanced_variables_fragment, container, false);

        // Creamos el array de variables de lectura
        data = new HashMap<>(); // <string, string>

        //Referencia a controles de la interfaz
        refreshField = (TextView) view.findViewById(R.id.refreshRate);
        forecastField = (TextView) view.findViewById(R.id.refreshForecastRate);
        locationField = (TextView) view.findViewById(R.id.location);
        buttonGet = (Button) view.findViewById(R.id.buttonGet);
        buttonRefreshRate = (Button) view.findViewById(R.id.refreshRateSend);
        buttonForecastRate = (Button) view.findViewById(R.id.refreshWeatherRateSend);
        buttonLocation = (Button) view.findViewById(R.id.locationSend);

        buttonGet.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                readVariables();
            }
        });

        buttonRefreshRate.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                writeVariable(TAG_REFRESH_RATE, refreshField);
            }
        });

        buttonForecastRate.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                writeVariable(TAG_FORECAST_RATE, forecastField);
            }
        });

        buttonLocation.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                writeVariable(TAG_LOCATION, locationField);
            }
        });

        return view;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) { super.onSaveInstanceState(outState); }

    @Override
    public void onActivityCreated(Bundle state) {
        super.onActivityCreated(state);
        readVariables();
    }

    // When user clicks button, calls AsyncTask.
    // Before attempting to fetch the URL, makes sure that there is a network connection.
   public void readVariables() {
        String[] vars = {TAG_REFRESH_RATE, TAG_FORECAST_RATE, TAG_LOCATION};
        String URL = composeReadURL(vars);
        if (checkConnection()) {
            Log.d(DEBUG_TAG, "Connecting to: " + URL);
            new downloadVariablesTask().execute(URL);
        }
    }

    public void writeVariable(String var, TextView textView) {
        String value = textView.getText().toString();
        String URL = composeWriteURL(var, value);
        if (checkConnection()) {
            Log.d(DEBUG_TAG, "Connecting to: " + URL);
            new writeVariableTask().execute(URL);
        }
    }

    public String composeReadURL(String[] vars) {
        String URL = "http://192.168.2.200/cgi-bin/read.cgi?";
        for (int i=0; i<vars.length; i++) {
            if (i==0) {
                URL = URL + "var=" + vars[i];
            }
            else {
                URL = URL + "&var=" + vars[i];
            }
        }
        return URL;
    }

    public String composeWriteURL(String var, String value) {
        return "http://192.168.2.200/cgi-bin/write.cgi?"+var+"="+value;
    }

    public boolean checkConnection() {
        ConnectivityManager connMgr = (ConnectivityManager)
                getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);
        NetworkInfo networkInfo = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI);
        if (networkInfo != null && networkInfo.isConnected()) {
            return true;
        } else {
            showWifiDialog();
            return false;
        }
    }

    // Uses AsyncTask to create a task away from the main UI thread. This task takes a
    // URL string and uses it to create an HttpUrlConnection. Once the connection
    // has been established, the AsyncTask downloads the contents of the webpage as
    // an InputStream. Finally, the InputStream is converted into a string, which is
    // displayed in the UI by the AsyncTask's onPostExecute method.
    public class downloadVariablesTask extends AsyncTask<String, Void, HashMap> {
        @Override
        protected HashMap doInBackground(String... params) {
            // params comes from the execute() call: params[0] is the url.
            try {
                return downloadUrl(params[0],true);
            } catch (IOException e) {
                getActivity().runOnUiThread(new Runnable() {
                    public void run() {
                        showUnableToConnectDialog();
                    }
                });
                return null;
            }
        }
        // onPostExecute displays the results of the AsyncTask.
        @Override
        protected void onPostExecute(HashMap data) {

            if (data != null) {

                // Show toast
                getActivity().runOnUiThread(new Runnable() {
                    public void run() {
                        showSuccessToast();
                    }
                });

                String refresh_rate = (String) data.get(TAG_REFRESH_RATE);
                String forecast_rate = (String) data.get(TAG_FORECAST_RATE);
                String location = (String) data.get(TAG_LOCATION);
                refreshField.setText(refresh_rate);
                forecastField.setText(forecast_rate);
                locationField.setText(location);
            }
        }
    }

    public class writeVariableTask extends AsyncTask<String, Void, HashMap> {
        @Override
        protected HashMap doInBackground(String... params) {
            // params comes from the execute() call: params[0] is the url.
            try {
                return downloadUrl(params[0],false);
            } catch (IOException e) {
                getActivity().runOnUiThread(new Runnable() {
                    public void run() {
                        showUnableToConnectDialog();
                    }
                });
                return null;
            }
        }

        // onPostExecute displays the results of the AsyncTask.
        @Override
        protected void onPostExecute(HashMap data) {

            // Show toast
            getActivity().runOnUiThread(new Runnable() {
                public void run() {
                    showSavedToast();
                }
            });
        }
    }

    // Given a URL, establishes an HttpUrlConnection and retrieves
    // the web page content as a InputStream, which it returns as
    // a string./*
    public HashMap downloadUrl(String myurl, boolean read) throws IOException {
        InputStream is = null;

        try {
            URL url = new URL(myurl);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(3000);
            conn.setConnectTimeout(5000);
            conn.setRequestMethod("GET");
            conn.setDoInput(true);
            // Starts the query
            conn.connect();
            int response = conn.getResponseCode();
            Log.d(DEBUG_TAG, "The response is: " + response);

            is = conn.getInputStream();

            if (read) {
                // Convert the InputStream into a HashMap
                return parseJSON(is);
            }

            else {
                return null;
            }

            // Makes sure that the InputStream is closed after the app is
            // finished using it.
        } finally {
            if (is != null) {
                is.close();
            }
        }
    }

    public HashMap parseJSON(InputStream stream) throws IOException {

        try {
            // Convert InputStream to a String
            BufferedReader r = new BufferedReader(new InputStreamReader(stream));
            StringBuilder result = new StringBuilder();
            String line;
            while ((line = r.readLine()) != null) {
                result.append(line);
            }

            // Convert the String to a HashMap object
            JSONObject serverJSON = new JSONObject(result.toString());
            String refresh_rate = serverJSON.getString(TAG_REFRESH_RATE);
            String forecast_rate = serverJSON.getString(TAG_FORECAST_RATE);
            String location = serverJSON.getString(TAG_LOCATION);

            // New temp HashMap
            HashMap<String, String> data = new HashMap<>();

            // Adding each child node to Hashmap key => value
            data.put(TAG_REFRESH_RATE, refresh_rate);
            data.put(TAG_FORECAST_RATE, forecast_rate);
            data.put(TAG_LOCATION, location);

            // Return the Hashmap
            return data;

        } catch (JSONException e) {
            e.printStackTrace();
            return null;
        }
    }

    public void showWifiDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(getString(R.string.missingWifi))
                .setCancelable(false)
                .setNegativeButton(getString(R.string.ok), new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    public void showUnableToConnectDialog() {
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(getString(R.string.unabletoconnect))
                .setCancelable(false)
                .setNegativeButton(getString(R.string.ok), new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        dialog.cancel();
                    }
                });
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    private void showSuccessToast() {
        Context context = getActivity().getApplicationContext();
        CharSequence text = context.getString(R.string.success);
        int duration = Toast.LENGTH_SHORT;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }
    private void showSavedToast() {
        Context context = getActivity().getApplicationContext();
        CharSequence text = context.getString(R.string.saved);
        int duration = Toast.LENGTH_SHORT;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();
    }
}

 

Referencias

[1] Handler class.