LVGL 8.2 Roller

Simple Roller

static void event_handler(lv_event_t* e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t* obj = lv_event_get_target(e);
    if (code == LV_EVENT_VALUE_CHANGED) {
        char buf[32];
        lv_roller_get_selected_str(obj, buf, sizeof(buf));
        LV_LOG_USER("Selected month: %s\n", buf);
    }
}

static void lv_example_roller_1(void)
{
    lv_obj_t* roller1 = lv_roller_create(lv_scr_act());
    lv_roller_set_options(roller1,
        "January\n"
        "February\n"
        "March\n"
        "April\n"
        "May\n"
        "June\n"
        "July\n"
        "August\n"
        "September\n"
        "October\n"
        "November\n"
        "December",
        LV_ROLLER_MODE_INFINITE);
    lv_roller_set_visible_row_count(roller1, 4);
    lv_obj_center(roller1);
    lv_obj_add_event_cb(roller1, event_handler, LV_EVENT_ALL, NULL);
}

• 运行效果
  

Styling the roller

static void event_handler(lv_event_t* e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t* obj = lv_event_get_target(e);
    if (code == LV_EVENT_VALUE_CHANGED) {
        char buf[32];
        lv_roller_get_selected_str(obj, buf, sizeof(buf));
        LV_LOG_USER("Selected value: %s", buf);
    }
}
/**
* Roller with various alignments and larger text in the selected area
*/
static void lv_example_roller_2(void)
{
    /*A style to make the selected option larger*/
    static lv_style_t style_sel;
    lv_style_init(&style_sel);
    lv_style_set_text_font(&style_sel, &lv_font_montserrat_22);
    const char* opts = "1\n2\n3\n4\n5\n6\n7\n8\n9\n10";
    lv_obj_t* roller;
    /*A roller on the left with left aligned text, and custom width*/
    roller = lv_roller_create(lv_scr_act());
    lv_roller_set_options(roller, opts, LV_ROLLER_MODE_NORMAL);
    lv_roller_set_visible_row_count(roller, 2);
    lv_obj_set_width(roller, 100);
    lv_obj_add_style(roller, &style_sel, LV_PART_SELECTED);
    lv_obj_set_style_text_align(roller, LV_TEXT_ALIGN_LEFT, 0);
    lv_obj_align(roller, LV_ALIGN_LEFT_MID, 10, 0);
    lv_obj_add_event_cb(roller, event_handler, LV_EVENT_ALL, NULL);
    lv_roller_set_selected(roller, 2, LV_ANIM_OFF);
    /*A roller on the middle with center aligned text, and auto (default) width*/
    roller = lv_roller_create(lv_scr_act());
    lv_roller_set_options(roller, opts, LV_ROLLER_MODE_NORMAL);
    lv_roller_set_visible_row_count(roller, 3);
    lv_obj_add_style(roller, &style_sel, LV_PART_SELECTED);
    lv_obj_align(roller, LV_ALIGN_CENTER, 0, 0);
    lv_obj_add_event_cb(roller, event_handler, LV_EVENT_ALL, NULL);
    lv_roller_set_selected(roller, 5, LV_ANIM_OFF);
    /*A roller on the right with right aligned text, and custom width*/
    roller = lv_roller_create(lv_scr_act());
    lv_roller_set_options(roller, opts, LV_ROLLER_MODE_NORMAL);
    lv_roller_set_visible_row_count(roller, 4);
    lv_obj_set_width(roller, 80);
    lv_obj_add_style(roller, &style_sel, LV_PART_SELECTED);
    lv_obj_set_style_text_align(roller, LV_TEXT_ALIGN_RIGHT, 0);
    lv_obj_align(roller, LV_ALIGN_RIGHT_MID, -10, 0);
    lv_obj_add_event_cb(roller, event_handler, LV_EVENT_ALL, NULL);
    lv_roller_set_selected(roller, 8, LV_ANIM_OFF);
}

• 运行效果
  

add fade mask to roller

static void mask_event_cb(lv_event_t* e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t* obj = lv_event_get_target(e);
    static int16_t mask_top_id = -1;
    static int16_t mask_bottom_id = -1;
    if (code == LV_EVENT_COVER_CHECK) {
        lv_event_set_cover_res(e, LV_COVER_RES_MASKED);
    }
    else if (code == LV_EVENT_DRAW_MAIN_BEGIN) {
        /* add mask */
        const lv_font_t* font = lv_obj_get_style_text_font(obj, LV_PART_MAIN);
        lv_coord_t line_space = lv_obj_get_style_text_line_space(obj, LV_PART_MAIN);
        lv_coord_t font_h = lv_font_get_line_height(font);
        lv_area_t roller_coords;
        lv_obj_get_coords(obj, &roller_coords);
        lv_area_t rect_area;
        rect_area.x1 = roller_coords.x1;
        rect_area.x2 = roller_coords.x2;
        rect_area.y1 = roller_coords.y1;
        rect_area.y2 = roller_coords.y1 + (lv_obj_get_height(obj) - font_h - line_space) / 2;
        lv_draw_mask_fade_param_t* fade_mask_top = lv_mem_buf_get(sizeof(lv_draw_mask_fade_param_t));
        lv_draw_mask_fade_init(fade_mask_top, &rect_area, LV_OPA_TRANSP, rect_area.y1,LV_OPA_COVER, rect_area.y2);
        mask_top_id = lv_draw_mask_add(fade_mask_top, NULL);
        rect_area.y1 = rect_area.y2 + font_h + line_space - 1;
        rect_area.y2 = roller_coords.y2;
        lv_draw_mask_fade_param_t* fade_mask_bottom = lv_mem_buf_get(sizeof(lv_draw_mask_fade_param_t));
        lv_draw_mask_fade_init(fade_mask_bottom, &rect_area, LV_OPA_COVER, rect_area.y1, LV_OPA_TRANSP, rect_area.y2);
        mask_bottom_id = lv_draw_mask_add(fade_mask_bottom, NULL);
    }
    else if (code == LV_EVENT_DRAW_POST_END) {
        lv_draw_mask_fade_param_t* fade_mask_top = lv_draw_mask_remove_id(mask_top_id);
        lv_draw_mask_fade_param_t* fade_mask_bottom = lv_draw_mask_remove_id(mask_bottom_id);
        lv_draw_mask_free_param(fade_mask_top);
        lv_draw_mask_free_param(fade_mask_bottom);
        lv_mem_buf_release(fade_mask_top);
        lv_mem_buf_release(fade_mask_bottom);
        mask_top_id = -1;
        mask_bottom_id = -1;
    }
}

static void lv_example_roller_3(void)
{
    static lv_style_t style;
    lv_style_init(&style);
    lv_style_set_bg_color(&style, lv_color_black());
    lv_style_set_text_color(&style, lv_color_white());
    lv_style_set_border_width(&style, 0);
    lv_style_set_pad_all(&style, 0);
    lv_obj_add_style(lv_scr_act(), &style, 0);
    lv_obj_t* roller1 = lv_roller_create(lv_scr_act());
    lv_obj_add_style(roller1, &style, 0);
    lv_obj_set_style_bg_opa(roller1, LV_OPA_TRANSP, LV_PART_SELECTED);
#if LV_FONT_MONTSERRAT_22
    lv_obj_set_style_text_font(roller1, &lv_font_montserrat_22, LV_PART_SELECTED);
#endif
    lv_roller_set_options(roller1,
        "January\n"
        "February\n"
        "March\n"
        "April\n"
        "May\n"
        "June\n"
        "July\n"
        "August\n"
        "September\n"
        "October\n"
        "November\n"
        "December",
        LV_ROLLER_MODE_NORMAL);
    lv_obj_center(roller1);
    lv_roller_set_visible_row_count(roller1, 3);
    lv_obj_add_event_cb(roller1, mask_event_cb, LV_EVENT_ALL, NULL);
}

• 运行效果