preload for little vGL

• 預加載實現

  void preload_demo(void)
  {
      static lv_style_t style;
      lv_style_copy(&style, &lv_style_plain);
      style.line.width = 10;
      style.line.color = lv_color_hex3(0x258);
  
      style.body.border.color = lv_color_hex3(0xbbb);
      style.body.border.width = 10;
      style.body.padding.left = 0;
  
      /*Create a preloader object*/
      lv_obj_t* preload = lv_preload_create(lv_scr_act(), NULL);
      lv_obj_set_size(preload, 100, 100);
      lv_obj_align(preload, NULL, LV_ALIGN_CENTER, 0, 0);
      lv_preload_set_style(preload,LV_PRELOAD_STYLE_MAIN, &style);
  }

• 調用preload_demo函數，編譯運行