linux 线程任务,检测b.dat文件有更新时，读取其中保存的x0,y0和x1,y1通过lvgl v7绘制直线,示例代码

好的，以下是一个示例代码，实现了您所描述的 Linux 线程任务：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/inotify.h>
#include <fcntl.h>
#include "lvgl/lvgl.h"

#define EVENT_SIZE  (sizeof(struct inotify_event))
#define BUF_LEN     (1024 * (EVENT_SIZE + 16))

void draw_line(lv_obj_t * parent, int x0, int y0, int x1, int y1) {
    lv_obj_t * line = lv_line_create(parent, NULL);
    lv_point_t points[] = {{x0, y0}, {x1, y1}};
    lv_line_set_points(line, points, 2);
    lv_obj_align(line, NULL, LV_ALIGN_CENTER, 0, 0);
}

void * thread_func(void * arg) {
    int fd, wd;
    char buf[BUF_LEN];
    int length;
    int i = 0;

    lv_init();

    /* create a window to display the line */
    lv_obj_t * win = lv_win_create(lv_scr_act(), NULL);
    lv_win_set_title(win, "Line");

    /* create a container to hold the line */
    lv_obj_t * cont = lv_cont_create(win, NULL);
    lv_obj_set_size(cont, LV_HOR_RES, LV_VER_RES);
    lv_obj_align(cont, NULL, LV_ALIGN_CENTER, 0, 0);

    /* create a line */
    int x0, y0, x1, y1;
    FILE * fp = fopen("b.dat", "r");
    fscanf(fp, "%d %d %d %d", &x0, &y0, &x1, &y1);
    fclose(fp);
    draw_line(cont, x0, y0, x1, y1);

    /* setup inotify */
    fd = inotify_init();
    if (fd < 0) {
        perror("inotify_init");
        exit(EXIT_FAILURE);
    }

    wd = inotify_add_watch(fd, "b.dat", IN_MODIFY);
    if (wd < 0) {
        perror("inotify_add_watch");
        exit(EXIT_FAILURE);
    }

    while (1) {
        i = 0;
        length = read(fd, buf, BUF_LEN);
        if (length < 0) {
            perror("read");
            exit(EXIT_FAILURE);
        }

        while (i < length) {
            struct inotify_event * event = (struct inotify_event *) &buf[i];
            if (event->mask & IN_MODIFY) {
                /* read x0, y0, x1, y1 from b.dat */
                fp = fopen("b.dat", "r");
                fscanf(fp, "%d %d %d %d", &x0, &y0, &x1, &y1);
                fclose(fp);

                /* remove previous line */
                lv_obj_clean(cont);

                /* draw new line */
                draw_line(cont, x0, y0, x1, y1);
            }
            i += EVENT_SIZE + event->len;
        }
    }

    lv_deinit();
    pthread_exit(NULL);
}

int main() {
    pthread_t tid;
    pthread_create(&tid, NULL, thread_func, NULL);
    pthread_join(tid, NULL);
    return 0;
}

该程序创建了一个线程，使用 inotify API 监视 b.dat 文件是否有更新。当 b.dat 文件上发生写入事件时，线程会读取其中保存的 x0,y0 和 x1,y1 值，并使用 LVGL v7 绘制一条直线。程序还使用 LVGL v7 创建了一个窗口来显示直线。