button matrix for little vGL

• 简单的按键矩阵实现

定义按键表，注意最后一个一定是空字符串

static const char* btnm_map[] = 
{
    "1","2","3","4","5","\n",
    "6","7","8","9","0","\n",
    LV_SYMBOL_OK,LV_SYMBOL_BACKSPACE,""
};

按键回调函数实现

static void event_handler_matrix(lv_obj_t* obj, lv_event_t event)
 {
    if (event == LV_EVENT_VALUE_CHANGED)
    {
        const char* txt = lv_btnm_get_active_btn_text(obj);
        printf("%s was pressed,id=%d\n", txt,lv_btnm_get_pressed_btn(obj));
    }
 }

生成矩阵按键

void button_matrix_demo(void) 
{
    lv_obj_t* btnm1 = lv_btnm_create(lv_scr_act(), NULL);
    lv_btnm_set_map(btnm1, btnm_map);
    lv_btnm_set_btn_width(btnm1, 10, 2);
    lv_obj_align(btnm1, NULL, LV_ALIGN_CENTER, 0, 0);
    lv_obj_set_event_cb(btnm1, event_handler_matrix);
}

在main函数调用button_matrix_demo函数，编译运行