利用TCP封装HTTP包请求天气信息

Linux还真是逐步熟悉中，现在才了解到Linux即没有原生的GUI，也没有应用层协议栈，所以要实现HTTP应用，必须利用TCP然后自己封装HTTP数据包。本篇即记录封装HTTP数据包，到心知天气请求天气信息的案例实现过程。

1、心知天气API说明
心知天气应该是当下国内使用很普遍的一个天气数据站点。相关注册和使用过程，这里就不再啰嗦了，不清楚的朋友可以自己到官网上查看（https://www.seniverse.com/）。

本例仅测试实时天气数据获取，天气相关数据只有“状态（晴朗之类）”和“气温”，请求接口地址如下：

可以看到请求地址给的是域名，TCP连接需要直接给IP地址，所以用ping来获取其IP为“116.62.81.138”，端口自然是80。

得到IP地址后，先不着急编程，通过网络助手实验一把，具体过程是：选择TCP Client，连接对方IP和端口（116.62.81.138:80），然后将请求地址前加上方法字串“GET”，结尾还要有两个回车换行“\r\n\r\n”。初次测试时，忘记了回车换行符没有成功，加上后就好了。

封装好的数据包是：“GET https://api.thinkpage.cn/v3/weather/now.json?key=yourkey&location=tianjin&language=en&unit=c\r\n\r\n”。

2、JSON分析
请求到的数据是JSON格式，贴到Json.cn（https://www.json.cn/）的在线工具里，可以更清晰的看到其结构。

可以看到请求实时数据（now.json），得到一个JSON对象，包含一个“results”引导的JSON数组，且数组只有一个元素，元素中又包含“location”、“now”和“last_update”三个JSON对象，内部还有键值对。

既然是开发Linux API的C程序，当然利用cJSON库来帮助进行数据解析了。本人使用的库是从网上搜到的一个百度网盘分享。

链接：https://pan.baidu.com/s/1DQynsdlNyIvsVXmf4W5b8Q
提取码：ww4z

3、请求天气案例
具体思路就是建立TCP Client连接心知天气的Server，然后发送请求包，得到响应包，解析并打印出结果，案例比较简单做成单次的——开启即运行到底，代码如下：

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>#include "cJSON.h"#define SERVER_IP      "116.62.81.138"
#define SERVER_PORT    80
#define NOW            "now.json"
#define DAILY          "daily.json"
#define API_KEY        "SK0LJ8FI2TP0L-IsQ"
#define CITY           "tianjin"
#define REQ_PACK       "GET https://api.thinkpage.cn/v3/weather/%s?key=%s&location=%s&language=en&unit=c\r\n\r\n"
#define N              1024
#define errlog(errmsg) do{ perror(errmsg);\printf("----%s----%s----%d----\n", __FILE__, __func__, __LINE__);\return -1;\} while(0)//struct for weather data
typedef struct {char id[16];char name[32];char country[16];char path[64];char timezone[32];char tz_offset[16];char text[16];char code[4];char temp[8];char last_update[32];
} weather_t;//parse function & print weather_t data function
void aita_ParseJsonNow(char *json, weather_t *w);
void aita_PrintWeather(weather_t *w);int main(int argc, const char *argv[]) {int sockfd;struct sockaddr_in serveraddr;socklen_t addrlen = sizeof(serveraddr);char sendbuf[N] = "";char recvbuf[N] = "";weather_t weather = {0};
//create socketif((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {errlog("socket error");}
//connect to server of seniverse.comserveraddr.sin_family = AF_INET;serveraddr.sin_addr.s_addr = inet_addr(SERVER_IP);serveraddr.sin_port = htons(SERVER_PORT);if((connect(sockfd, (struct sockaddr*)&serveraddr, addrlen)) < 0) {errlog("connect error");}
//build & send request packagesprintf(sendbuf, REQ_PACK, NOW, API_KEY, CITY);if(send(sockfd, sendbuf, N, 0) < 0) {errlog("send error");}
//waiting server responseif(recv(sockfd, recvbuf, N, 0) < 0) {errlog("recv error");}printf("recv: %s\n", recvbuf);
//parse & print dataaita_ParseJsonNow(recvbuf, &weather);aita_PrintWeather(&weather);close(sockfd);return 0;
}void aita_ParseJsonNow(char *msg, weather_t *w) {cJSON *json, *ja, *jo, *josub, *item;json = cJSON_Parse(msg); //parse string to cJSON typeif(json == NULL) {printf("json type cast error: %s", cJSON_GetErrorPtr());return;} else {printf("parse now pack\n");if((ja=cJSON_GetObjectItem(json, "results")) != NULL) { //get results arrayif((jo=cJSON_GetArrayItem(ja, 0)) != NULL) {        //get array[0](the only item)//get location objectif((josub=cJSON_GetObjectItem(jo, "location")) != NULL) {if((item=cJSON_GetObjectItem(josub, "id")) != NULL) {memcpy(w->id, item->valuestring, strlen(item->valuestring));}if((item=cJSON_GetObjectItem(josub, "name")) != NULL) {memcpy(w->name, item->valuestring, strlen(item->valuestring));}if((item=cJSON_GetObjectItem(josub, "country")) != NULL) {memcpy(w->country, item->valuestring, strlen(item->valuestring));}if((item=cJSON_GetObjectItem(josub, "path")) != NULL) {memcpy(w->path, item->valuestring, strlen(item->valuestring));}if((item=cJSON_GetObjectItem(josub, "timezone")) != NULL) {memcpy(w->timezone, item->valuestring, strlen(item->valuestring));}if((item=cJSON_GetObjectItem(josub, "timezone_offset")) != NULL) {memcpy(w->tz_offset, item->valuestring, strlen(item->valuestring));}}//get now objectif((josub=cJSON_GetObjectItem(jo, "now")) != NULL) {if((item=cJSON_GetObjectItem(josub, "text")) != NULL) {memcpy(w->text, item->valuestring, strlen(item->valuestring));}if((item=cJSON_GetObjectItem(josub, "code")) != NULL) {memcpy(w->code, item->valuestring, strlen(item->valuestring));}if((item=cJSON_GetObjectItem(josub, "temperature")) != NULL) {memcpy(w->temp, item->valuestring, strlen(item->valuestring));}}//get last_update objectif((josub=cJSON_GetObjectItem(jo, "last_update")) != NULL) {memcpy(w->last_update, josub->valuestring, strlen(josub->valuestring));                 }}}}//delete original json pack free memorycJSON_Delete(json);return;
}void aita_PrintWeather(weather_t *w) {printf("id: %s\n", w->id);printf("name: %s\n", w->name);printf("country: %s\n", w->country);printf("path: %s\n", w->path);printf("timezone: %s\n", w->timezone);printf("timezone_offset: %s\n", w->tz_offset);printf("text: %s\n", w->text);printf("code: %s\n", w->code);printf("temperature: %s\n", w->temp);printf("last_update: %s\n", w->last_update);
}

项目路径中建立了源文件main.c，编写上述代码，并导入cJSON.c和cJSON.h，编译命令为：“riscv64-unknown-linux-gnu-gcc main.c cJSON.c -o weather -lm”。因为cJSON会用到math库，而它需要“-lm”来动态链接。

lvgl显示图片和本地时间

1、lvgl的图片显示
lvgl框架中图片可以是一个文件也可以是一个变量（数组形式的图片码），当然文件还需要初始化lvgl对文件系统的接口，本例暂以变量形式提供。

应用要显示图片，则需要引入一个图片控件，然后设置它的数据源——使用“lv_img_set_src()”函数。示例如下：

lv_obj_t * icon = lv_img_create(lv_scr_act(), NULL);
/*From variable*/
lv_img_set_src(icon, &my_icon_dsc);

上述代码中“icon”是一个lvgl对象指针，通过“lv_img_create()”实例化，则对应图片控件。设置数据源时传入参数“my_icon_dsc”是lvgl中的图片描述符数据结构“lv_img_dsc_t”——本身是一个结构体类型，其定义源码如下：

//in “../lvgl/src/draw/lv_img_buf.h”
typedef struct {uint32_t cf : 5;          /*Color format: See `lv_img_color_format_t`*/uint32_t always_zero : 3; /*It the upper bits of the first byte. Always zero to look like anon-printable character*/uint32_t reserved : 2; /*Reserved to be used later*/uint32_t w : 11; /*Width of the image map*/uint32_t h : 11; /*Height of the image map*/
} lv_img_header_t;typedef struct {lv_img_header_t header; /**< A header describing the basics of the image*/uint32_t data_size;     /**< Size of the image in bytes*/const uint8_t * data;   /**< Pointer to the data of the image*/
} lv_img_dsc_t;

示例代码中，图片描述符变量的定义过程如下代码：

uint8_t my_icon_data[] = {0x00, 0x01, 0x02, ...};static lv_img_dsc_t my_icon_dsc = {![8.png](/assets/uploads/files/1653270047514-8.png) .header.always_zero = 0,.header.w = 80,.header.h = 60,.data_size = 80 * 60 * LV_COLOR_DEPTH / 8,.header.cf = LV_IMG_CF_TRUE_COLOR,          /*Set the color format*/.data = my_icon_data,
};

其中，枚举“LV_IMG_CF_TRUE_COLOR”是色彩格式定义，表示RGB格式。

宏“LV_COLOR_DEPTH”则定义色彩深度，它位于“lv_conf.h”，用户可以自定义。本例中设置为32，即4字节的ARGB8888格式。

2、时间获取
86板的Tina Linux可以通过C time库轻松地获得本地时间等数据。本例使用的API有：time()、localtime()、strftime()以及time_t、struct tm。

3、图片和时间显示案例
本例继续使用线程管理lvgl刷新，创建1s周期的lvgl定时器，在定时器回调中获取本地时间并格式化输出。另外，系统初始时显示一个“天津”的Logo，而且初始即做一次时间获取和输出（如果不做，初始刹那label会显示默认“text”字样）。

图片码通过软件“Img2Lcd”获取，软件配置方式如下图所示。图片生成的数组有72008个字节，被放置到头文件“aita_logo.h”。

/* Includes ------------------------------------------------------- */
#include "lvgl/lvgl.h"
#include "lv_drivers/display/fbdev.h"
#include "lv_drivers/indev/evdev.h"
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <time.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "aita_logo.h"/* Private macro -------------------------------------------------- */
#define AITA_DISP_BUF_SIZE     (128 * 1024)
#define AITA_SCREEN_WIDTH      480
#define AITA_SCREEN_HEIGHT     480
#define AITA_TITLE_STRING      "AITA Weather for LicheeRV with LVGL"
#define SEND_PERIOD            1000
#define errlog(errmsg)         do{ perror(errmsg);\printf("----%s----%s----%d----\n", __FILE__, __func__, __LINE__);\return;\} while(0)/* Global variables ----------------------------------------------- */
lv_indev_t *aita_indev;   //pointer of indev
lv_obj_t *sys_scr;        //pointer of system screen instance
lv_obj_t *head_label;     //pointer of title label instance
lv_obj_t *main_label;     //pointer of main label instance
char main_label_text[32]; //main label text string for datetime
lv_obj_t *logo_img;       //pointer of city logo image instance
lv_timer_t *sec_timer;    //pointer of timer instance for tcp polling
pthread_t lvgl_tid;       //lvgl thread id
pthread_t tcprecv_tid;    //tcp receive thread id
pthread_mutex_t lvgl_mutex;  //mutex for lvgl tick
//image descriptor for logo_img
//ARGB8888 image 180*100 which code array is 'tj_logo' 
lv_img_dsc_t img_dsc_city = {.header.always_zero = 0,.header.w = 180,.header.h = 100,.data_size = 18000 * LV_COLOR_SIZE / 8,.header.cf = LV_IMG_CF_TRUE_COLOR,.data = tj_logo,
};/* Private function prototypes ------------------------------------ */
void aita_InitLVGL(void);
void aita_CreateMainUI(void);
void *thread_lvgl(void *arg);
void sec_timer_cb(lv_timer_t *timer);
void aita_InitTimer(void);
void aita_GetTime(void);/* Private functions ---------------------------------------------- */
int main(void) {void *retval;//by author. initialize lvgl including displaybuffer, device for disp & inputaita_InitLVGL();//by author. initialize and register event device
//these code must be in main(), otherwise the touch will fail.static lv_indev_drv_t indev_drv;lv_indev_drv_init(&indev_drv);indev_drv.type = LV_INDEV_TYPE_POINTER; //by author. choice touchpadindev_drv.read_cb = evdev_read;         //by author. input callbackaita_indev = lv_indev_drv_register(&indev_drv);//by author. create the main view when the demo starts up    aita_CreateMainUI();//by author. create a timeraita_InitTimer();//by author. create mutex for lvglif(pthread_mutex_init(&lvgl_mutex, NULL) != 0) {errlog("initialize mutex error");}//by author. create lvgl threadif(pthread_create(&lvgl_tid, NULL, thread_lvgl, (void *)0) != 0) {errlog("create lvgl thread error");}//by author. wait for thread exit, this demo should never be here.pthread_join(lvgl_tid, &retval);printf("lvgl thread exit, return value: %s\n", (char *)retval);pthread_mutex_destroy(&lvgl_mutex);return 0;
}/*Set in lv_conf.h as `LV_TICK_CUSTOM_SYS_TIME_EXPR`*/
uint32_t custom_tick_get(void)
{static uint64_t start_ms = 0;if(start_ms == 0) {struct timeval tv_start;gettimeofday(&tv_start, NULL);start_ms = (tv_start.tv_sec * 1000000 + tv_start.tv_usec) / 1000;}struct timeval tv_now;gettimeofday(&tv_now, NULL);uint64_t now_ms;now_ms = (tv_now.tv_sec * 1000000 + tv_now.tv_usec) / 1000;uint32_t time_ms = now_ms - start_ms;return time_ms;
}void aita_InitLVGL(void) {/*LittlevGL init*/lv_init();/*Linux frame buffer device init*/fbdev_init(); //by author. initialize framebuffer device for displayevdev_init(); //by author. initialize event device for touchpad/*A small buffer for LittlevGL to draw the screen's content*/static lv_color_t buf[AITA_DISP_BUF_SIZE];/*Initialize a descriptor for the buffer*/static lv_disp_draw_buf_t disp_buf;lv_disp_draw_buf_init(&disp_buf, buf, NULL, AITA_DISP_BUF_SIZE);/*Initialize and register a display driver*/static lv_disp_drv_t disp_drv;lv_disp_drv_init(&disp_drv);disp_drv.draw_buf   = &disp_buf;disp_drv.flush_cb   = fbdev_flush;disp_drv.hor_res    = 480;disp_drv.ver_res    = 480;lv_disp_drv_register(&disp_drv);
}void aita_CreateMainUI(void) {//by author. create system screen which is basic graphic levelsys_scr = lv_obj_create(lv_scr_act());lv_obj_set_size(sys_scr, AITA_SCREEN_WIDTH, AITA_SCREEN_HEIGHT);//by author. create the main title which is just a labelhead_label = lv_label_create(sys_scr);lv_label_set_text(head_label, AITA_TITLE_STRING);lv_obj_align(head_label, LV_ALIGN_TOP_MID, 0, 10);//by author. create the city logo imagelogo_img = lv_img_create(sys_scr);lv_img_set_src(logo_img, &img_dsc_city);lv_obj_align(logo_img, LV_ALIGN_TOP_LEFT, 10, 40);//by author. get local time and show stringaita_GetTime();main_label = lv_label_create(sys_scr);lv_label_set_text(main_label, main_label_text);lv_obj_align(main_label, LV_ALIGN_TOP_LEFT, 200, 40);lv_obj_set_style_text_font(main_label, &lv_font_montserrat_20, 0);
}//by author. lvgl core thread function
void *thread_lvgl(void *arg) {while(1) {pthread_mutex_lock(&lvgl_mutex);lv_task_handler();pthread_mutex_unlock(&lvgl_mutex);usleep(5000); /* sleep for 5 ms */}
}//by author. sec_timer callback which refresh date string
void sec_timer_cb(lv_timer_t *timer) {aita_GetTime();lv_label_set_text(main_label, main_label_text);  
}
//by author. initialize timer for 1s timing
void aita_InitTimer(void) {sec_timer = lv_timer_create(sec_timer_cb, 1000, NULL);lv_timer_set_repeat_count(sec_timer, -1);
}
//by author. get local time string
void aita_GetTime(void) {time_t    tsec;struct tm *tlocal;tsec = time(NULL);tlocal = localtime(&tsec);memset(main_label_text, 0, 32);strftime(main_label_text, 32, "%Y-%m-%d %a %H:%M:%S", tlocal);
}

lvgl日历控件和显示天气

本篇结合本人前两篇的HTTP请求天气数据（通过“心知天气”网站）和lvgl显示图片及时间，在案例主界面上增加了日历显示和实时天气显示，先直接上图。

1、lvgl日历控件
calendar是lvgl提供的“Extra widgets”组件之一，需要注意的是8.0版本后有几个API的传参发生了变化，本例使用8.3版本，设置日期是需要同时传递“年、月、日”三个参数。

本例使用的API有：lv_calendar_create()、lv_canlendar_set_today_date()、lv_calendar_set_showed_date()和lv_calendar_header_arrow_create()。

lv_calendar_create()函数用于实例化calendar控件，传参是控件的父容器指针，本例使用“lv_scr_act()”即系统屏幕。

lv_canlendar_set_today_date()函数用于设置当前日期，本人使用发现lvgl是附带万年历功能的，只要设置好当天的年月日，就可以自动生成正确的日历排布。函数传参分别是控件指针和年月日数据。

关于年月日参数有两点注意事项。一是v7版本中，传参通过lv_calendar_date_t结构体，其包含年月日三个成员。二是如果使用了C time库的struct tm，注意其中年份需要加上“1900”，而月份则需要加“1”。

lv_calendar_set_showed_date()函数用于设置日历当前显示页，也就是设置当前月份。本人实验的效果是当天日期框会自动高亮，如果想设置多个高亮日期，可以使用函数lv_calendar_set_highlighted_dates()。

lv_calendar_header_arrow_create()函数用于向日历控件顶部增加“左、右箭头”两个按钮用于日历翻页（一页是一月）。此外，还有函数lv_calendar_header_dropdown_create()则是设置两个下拉列表分别用于选择年份和月份。这两个函数都只用传递日历控件指针一个参数，且是8.1版本新增API。

2、日历和天气显示案例
本案例的思路是：1）在应用启动时，获取当前时间（上篇中已经实现），然后将时间保存在全局量“struct tm today”中，并利用变量“today”来初始化日历控件的日期数据。2）上篇实现的时间显示案例，通过lvgl定时器，每秒获取本地数据，此处在定时器回调中再增加一个每到正分钟发送“Linux条件变量”。3）同时，应用启动时建立两个线程——lvgl线程和请求天气线程，请求天气线程等待条件变量到来，开启一次天气数据请求过程。

本例代码结合文章上半部分已经给出的案例，这里只给出改变部分。

/* Includes ------------------------------------------------------- */
// 增加头文件，cJSON用于解析JSON格式的天气数据
#include "cJSON.h"/* Private macro -------------------------------------------------- */
// 增加请求天气数据相关的宏定义
#define HTTP_IP                "116.62.81.138"
#define HTTP_PORT              80
#define NOW                    "now.json"
#define API_KEY                "SK0LJ8FI2TP0L-IsQ"
#define CITY                   "tianjin"
#define REQ_PACK               "GET https://api.thinkpage.cn/v3/weather/%s?key=%s&location=%s&language=en&unit=c\r\n\r\n"
#define N                      1024
// struct for weather data 建立结构体存储解析后的天气数据
typedef struct {char id[16];char name[32];char country[16];char path[64];char timezone[32];char tz_offset[16];char text[16];char code[4];char temp[8];char last_update[32];
} weather_t;/* Global variables ----------------------------------------------- */
// 增加显示天气的标签控件定义
lv_obj_t *weather_label;  //pointer of weather label instance
// 增加日历控件定义
lv_obj_t  *calendar;      //pointer of calendar instance
// 定义today变量存储当前日期，用于设置日历
struct tm today;          //
// 请求天气的线程ID
pthread_t reqweather_tid; //request weather thread id
// 请求天气线程等待的条件变量（min_cond）
// Linux中需要互斥量包含条件变量的使用，所以定义cond_mutex
pthread_mutex_t cond_mutex;  //mutex for 1-min cond
pthread_cond_t  min_cond; //1-min cond
/* Private functions ---------------------------------------------- */
int main(void) {
// other code from previous demo
// main()函数中创建互斥量、条件变量、请求天气线程
//by author. create mutex for 1-min condif(pthread_mutex_init(&cond_mutex, NULL) != 0) {errlog("initialize cond mutex error");}//by author. create condition for 1-minif(pthread_cond_init(&min_cond, NULL) != 0) {errlog("initialize 1 minute condition error");}//by author. create request weather threadif(pthread_create(&reqweather_tid, NULL, thread_reqweather, (void *)0) != 0) {errlog("create request weather thread error");}//by author. wait for thread exit, this demo should never be here.pthread_join(lvgl_tid, &retval);printf("lvgl thread exit, return value: %s\n", (char *)retval);pthread_join(reqweather_tid, &retval);printf("request weather thread exit, return value: %s\n", (char *)retval);pthread_mutex_destroy(&lvgl_mutex);pthread_mutex_destroy(&cond_mutex);pthread_cond_destroy(&min_cond);return 0;
}void aita_CreateMainUI(void) {
// other code from previous demo
// aita_CreateMainUI()被main()函数调用，初始化主界面。//by author. create the weather labelweather_label = lv_label_create(sys_scr);lv_label_set_text(weather_label, "         ");lv_obj_align(weather_label, LV_ALIGN_TOP_LEFT, 200, 120);//by author. create the calendarcalendar = lv_calendar_create(sys_scr);lv_obj_set_size(calendar, 235, 235);lv_obj_align(calendar, LV_ALIGN_BOTTOM_LEFT, 10, -50);lv_calendar_set_today_date(calendar, today.tm_year+1900, today.tm_mon+1, today.tm_mday);lv_calendar_set_showed_date(calendar, today.tm_year+1900, today.tm_mon+1);lv_calendar_header_arrow_create(calendar);
}// 增加正分钟发送条件变量
void sec_timer_cb(lv_timer_t *timer) {aita_GetTime();lv_label_set_text(main_label, main_label_text);if(today.tm_sec == 0) {//by author. send condition signal per whole minutepthread_cond_signal(&min_cond);}
}
// 增加对today的赋值
void aita_GetTime(void) {time_t    tsec;struct tm *tlocal;tsec = time(NULL);tlocal = localtime(&tsec);today = *tlocal;memset(main_label_text, 0, 32);strftime(main_label_text, 32, "%Y-%m-%d %a %H:%M:%S", tlocal);
}// 请求天气线程业务逻辑
void *thread_reqweather(void *arg) {int sockfd;struct sockaddr_in serveraddr;socklen_t addrlen = sizeof(serveraddr);char sendbuf[N] = "";char recvbuf[N] = "";weather_t weather = {0};char w_string[64] = "";while(1) {pthread_mutex_lock(&cond_mutex);pthread_cond_wait(&min_cond, &cond_mutex);pthread_mutex_unlock(&cond_mutex);     //create socketif((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {errlog("socket error");}//connect to server of seniverse.comserveraddr.sin_family = AF_INET;serveraddr.sin_addr.s_addr = inet_addr(HTTP_IP);serveraddr.sin_port = htons(HTTP_PORT);if((connect(sockfd, (struct sockaddr*)&serveraddr, addrlen)) < 0) {errlog("connect error");}//build & send request packagememset(sendbuf, 0, N);sprintf(sendbuf, REQ_PACK, NOW, API_KEY, CITY);if(send(sockfd, sendbuf, N, 0) < 0) {errlog("send error");}//waiting server responseif(recv(sockfd, recvbuf, N, 0) < 0) {errlog("recv error");}printf("recv: %s\n", recvbuf);//parse & print data，下面两个函数来自于“十三”案例aita_ParseJsonNow(recvbuf, &weather);aita_PrintWeather(&weather);close(sockfd);memset(recvbuf, 0, N);//show weather stringmemset(w_string, 0, 64);sprintf(w_string, "weather:%s temperatur:%s", weather.text, weather.temp);pthread_mutex_lock(&lvgl_mutex);lv_label_set_text(weather_label, w_string);pthread_mutex_unlock(&lvgl_mutex);       }
}

另外，本例在lvgl工程中增加了cJSON.c和cJSON.h文件，Makefile也做出了调整，具体如下所示。