Lv_scr_load() not working

Bug (archived)
1

Description

I am trying to load a screen and it is not working properly.

What MCU/Processor/Board and compiler are you using?

nRF52840 but also tried it on Simulator and having the same problem.

What do you experience?

I create and load a screen but screen is showing all black.

What do you expect?

I expect proper screen to be loaded.

Code to reproduce

    lv_obj_t *screen1 = lv_obj_create(NULL, NULL);

	lv_obj_t *heading = lv_label_create(screen1, NULL);

	lv_obj_set_width(heading, LV_HOR_RES - 2);
	lv_label_set_text(heading, "Add Text");
	lv_obj_align(heading, NULL, LV_ALIGN_IN_TOP_MID, 0, 0);

	lv_scr_load(screen1);
2

I’ll test this later today when I get a chance, but in the meantime, maybe you could try calling lv_scr_load before you put the label on screen? Does that work?

3

The function “lv_scr_load” is working well in my simulator. Can you show demo screen by calling “demo_create”? Maybe there are some problems when you porting the GUI, or some issues in your display driver.

4

I have stripped down the problem to this.

This code produces this output.

Code -

	lv_theme_t * th = lv_theme_mono_init(210, NULL);
	lv_theme_set_current(th);

	screen1 = lv_obj_create(NULL, NULL);

	heading = lv_label_create(screen1, NULL);
	ui_heading_create(heading, "Add Text", LV_HOR_RES - 2, LV_ALIGN_IN_TOP_LEFT);

	options = lv_btn_create(screen1, NULL);
	ui_options_create(options);
	lv_obj_set_event_cb(options, NULL);

	back_arrow = lv_btn_create(screen1, NULL);
	ui_back_btn_create(back_arrow);

	lv_scr_load(screen1);

Output -

image

Creating the screen before setting the theme gives correct output.

Code -

	screen1 = lv_obj_create(NULL, NULL);

	lv_theme_t * th = lv_theme_mono_init(210, NULL);
	lv_theme_set_current(th);

	heading = lv_label_create(screen1, NULL);
	ui_heading_create(heading, "Add Text", LV_HOR_RES - 2, LV_ALIGN_IN_TOP_LEFT);

	options = lv_btn_create(screen1, NULL);
	ui_options_create(options);
	lv_obj_set_event_cb(options, NULL);

	back_arrow = lv_btn_create(screen1, NULL);
	ui_back_btn_create(back_arrow);

	lv_scr_load(screen1);

Output -
image

5

If I use lv_scr_act() instead of creating a screen (Code Below). Then it works fine.

Code -

        lv_theme_t * th = lv_theme_mono_init(210, NULL);
        lv_theme_set_current(th);
      
        lv_obj_t *scr = lv_scr_act()

        //Then create buttons and text
6

It’s because the theme will be applied only to the objects created after loading the theme.