LVGL 8.2.0之Faded area line chart with custom division lines

绘制事件处理函数

static lv_obj_t* chart1; 
static lv_chart_series_t* ser1;
static lv_chart_series_t* ser2;
static void draw_event_cb(lv_event_t* e)
{
    lv_obj_t* obj = lv_event_get_target(e); //获取事件对象
    /*Add the faded area before the lines are drawn*/
    lv_obj_draw_part_dsc_t* dsc = lv_event_get_draw_part_dsc(e); //得到绘制对象描述符
    if (dsc->part == LV_PART_ITEMS) { //处理ITEM项绘制
        if (!dsc->p1 || !dsc->p2) return; //p1,p2为NULL直接返回
        /*Add a line mask that keeps the area below the line*/
        lv_draw_mask_line_param_t line_mask_param;
        lv_draw_mask_line_points_init(&line_mask_param, dsc->p1->x, dsc->p1->y, dsc->p2->x, dsc->p2->y,
            LV_DRAW_MASK_LINE_SIDE_BOTTOM); // 初时化line_mask_param,底边阴影
        int16_t line_mask_id = lv_draw_mask_add(&line_mask_param, NULL);
        /*Add a fade effect: transparent bottom covering top*/
        lv_coord_t h = lv_obj_get_height(obj); //获取高度
        lv_draw_mask_fade_param_t fade_mask_param;
        lv_draw_mask_fade_init(&fade_mask_param, &obj->coords, LV_OPA_COVER, obj->coords.y1 + h / 8, LV_OPA_TRANSP,
            obj->coords.y2); //初时化fade_mask_param
        int16_t fade_mask_id = lv_draw_mask_add(&fade_mask_param, NULL);
        /*Draw a rectangle that will be affected by the mask*/
        lv_draw_rect_dsc_t draw_rect_dsc;
        lv_draw_rect_dsc_init(&draw_rect_dsc); //初时化draw_rect_dsc
        draw_rect_dsc.bg_opa = LV_OPA_20;
        draw_rect_dsc.bg_color = dsc->line_dsc->color;

        lv_area_t a;
        a.x1 = dsc->p1->x;
        a.x2 = dsc->p2->x - 1;
        a.y1 = LV_MIN(dsc->p1->y, dsc->p2->y); //y取最小值
        a.y2 = obj->coords.y2;
        lv_draw_rect(dsc->draw_ctx, &draw_rect_dsc, &a); //绘制
        /*Remove the masks*/
        lv_draw_mask_free_param(&line_mask_param);
        lv_draw_mask_free_param(&fade_mask_param);

        lv_draw_mask_remove_id(line_mask_id);
        lv_draw_mask_remove_id(fade_mask_id);
    }
    /*Hook the division lines too*/
    else if (dsc->part == LV_PART_MAIN) { //绘制MAIN项
        if (dsc->line_dsc == NULL || dsc->p1 == NULL || dsc->p2 == NULL) return;
        /*Vertical line*/
        if (dsc->p1->x == dsc->p2->x) {
            dsc->line_dsc->color = lv_palette_lighten(LV_PALETTE_GREY, 1);
            if (dsc->id == 3) {
                dsc->line_dsc->width = 2;
                dsc->line_dsc->dash_gap = 0;
                dsc->line_dsc->dash_width = 0;
            }
            else {
                dsc->line_dsc->width = 1;
                dsc->line_dsc->dash_gap = 6;
                dsc->line_dsc->dash_width = 6;
            }
        }
        /*Horizontal line*/
        else {
            if (dsc->id == 2) {
                dsc->line_dsc->width = 2;
                dsc->line_dsc->dash_gap = 0;
                dsc->line_dsc->dash_width = 0;
            }
            else {
                dsc->line_dsc->width = 2;
                dsc->line_dsc->dash_gap = 6;
                dsc->line_dsc->dash_width = 6;
            }
            if (dsc->id == 1 || dsc->id == 3) {
                dsc->line_dsc->color = lv_palette_main(LV_PALETTE_GREEN);
            }
            else {
                dsc->line_dsc->color = lv_palette_lighten(LV_PALETTE_GREY, 1);
            }
        }
    }
}

• 定时器回调函数

static void add_data(lv_timer_t* timer)
{
    LV_UNUSED(timer);
    static uint32_t cnt = 0;
    lv_chart_set_next_value(chart1, ser1, lv_rand(20, 90)); // 使用随机值设置ser1下一个值
    if (cnt % 4 == 0) lv_chart_set_next_value(chart1, ser2, lv_rand(40, 60)); // 每4次设置一次ser2的下一个值
    cnt++;
}

• 创建chat

static void lv_example_chart_2(void)
{
    /*Create a chart1*/
    chart1 = lv_chart_create(lv_scr_act()); //创建chat对象
    lv_obj_set_size(chart1, 200, 150); // 设置大小
    lv_obj_center(chart1);  // 居中对齐
    lv_chart_set_type(chart1, LV_CHART_TYPE_LINE); /*Show lines and points too*/
    lv_chart_set_div_line_count(chart1, 5, 7); // 5x7分格线
    lv_obj_add_event_cb(chart1, draw_event_cb, LV_EVENT_DRAW_PART_BEGIN, NULL); //添加绘制事件
    lv_chart_set_update_mode(chart1, LV_CHART_UPDATE_MODE_CIRCULAR); // 设置更新模式
    /*Add two data series*/
    ser1 = lv_chart_add_series(chart1, lv_palette_main(LV_PALETTE_RED), LV_CHART_AXIS_PRIMARY_Y); // LV_CHART_AXIS_PRIMARY_Y线为红色
    ser2 = lv_chart_add_series(chart1, lv_palette_main(LV_PALETTE_BLUE),  LV_CHART_AXIS_SECONDARY_Y); //LV_CHART_AXIS_SECONDARY_Y线为蓝色
    uint32_t i;
    for (i = 0; i