|
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： https://api.seniverse.com/v3/weather/now.json?key=your_api_key&location=beijing&language=zh-Hans&unit=c 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 datatypedef 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 functionvoid 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 socket if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) { errlog("socket error"); }//connect to server of seniverse.com serveraddr.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 package sprintf(sendbuf, REQ_PACK, NOW, API_KEY, CITY); if(send(sockfd, sendbuf, N, 0) < 0) { errlog("send error"); }//waiting server response if(recv(sockfd, recvbuf, N, 0) < 0) { errlog("recv error"); } printf("recv: %s\n", recvbuf);//parse & print data aita_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 type if(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 array if((jo=cJSON_GetArrayItem(ja, 0)) != NULL) { //get array[0](the only item) //get location object if((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 object if((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 object if((josub=cJSON_GetObjectItem(jo, "last_update")) != NULL) { memcpy(w->last_update, josub->valuestring, strlen(josub->valuestring)); } } } } //delete original json pack free memory cJSON_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 a non-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 = { .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**，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_**.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_**.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 indevlv_obj_t *sys_scr; //pointer of system screen instancelv_obj_t *head_label; //pointer of title label instancelv_obj_t *main_label; //pointer of main label instancechar main_label_text[32]; //main label text string for datetimelv_obj_t ***_img; //pointer of city ** image instancelv_timer_t *sec_timer; //pointer of timer instance for tcp pollingpthread_t lvgl_tid; //lvgl thread idpthread_t tcprecv_tid; //tcp receive thread idpthread_mutex_t lvgl_mutex; //mutex for lvgl tick//image descriptor for **_img//ARGB8888 image 180*100 which code array is 'tj_**' 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_**,}; /* 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 & input aita_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 touchpad indev_drv.read_cb = evdev_read; //by author. input callback aita_indev = lv_indev_drv_register(&indev_drv); //by author. create the main view when the demo starts up aita_CreateMainUI(); //by author. create a timer aita_InitTimer(); //by author. create mutex for lvgl if(pthread_mutex_init(&lvgl_mutex, NULL) != 0) { errlog("initialize mutex error"); } //by author. create lvgl thread if(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 display evdev_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 level sys_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 label head_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 ** image **_img = lv_img_create(sys_scr); lv_img_set_src(**_img, &img_dsc_city); lv_obj_align(**_img, LV_ALIGN_TOP_LEFT, 10, 40); //by author. get local time and show string aita_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 functionvoid *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 stringvoid sec_timer_cb(lv_timer_t *timer) { aita_GetTime(); lv_label_set_text(main_label, main_label_text); }//by author. initialize timer for 1s timingvoid 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 stringvoid 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IDpthread_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_mutexpthread_mutex_t cond_mutex; //mutex for 1-min condpthread_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 cond if(pthread_mutex_init(&cond_mutex, NULL) != 0) { errlog("initialize cond mutex error"); } //by author. create condition for 1-min if(pthread_cond_init(&min_cond, NULL) != 0) { errlog("initialize 1 minute condition error"); } //by author. create request weather thread if(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 label weather_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 calendar calendar = 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 minute pthread_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 socket if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) { errlog("socket error"); } //connect to server of seniverse.com serveraddr.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 package memset(sendbuf, 0, N); sprintf(sendbuf, REQ_PACK, NOW, API_KEY, CITY); if(send(sockfd, sendbuf, N, 0) < 0) { errlog("send error"); } //waiting server response if(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 string memset(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。
|
楼主
标题置顶
标题高亮
