Bar (lv_bar)

Overview

The bar object has a background and an indicator on it. The width of the indicator is set according to the current value of the bar.

Vertical bars can be created if the width of the object is smaller than its height.

Not only the end, but also the start value of the bar can be set, which changes the start position of the indicator.

Parts and Styles

  • LV_PART_MAIN The background of the bar and it uses the typical background style properties. Adding padding makes the indicator smaller or larger. The anim_time style property sets the animation time if the values set with LV_ANIM_ON.

  • LV_PART_INDICATOR The indicator itself; also uses all the typical background properties.

Usage

Value and range

A new value can be set by lv_bar_set_value(bar, new_value, LV_ANIM_ON/OFF). The value is interpreted in a range (minimum and maximum values) which can be modified with lv_bar_set_range(bar, min, max). The default range is 0..100.

The new value in lv_bar_set_value can be set with or without an animation depending on the last parameter (LV_ANIM_ON/OFF).

Modes

The bar can be one of the following modes:

  • LV_BAR_MODE_NORMAL A normal bar as described above

  • LV_BAR_SYMMETRICAL Draw the indicator from the zero value to current value. Requires a negative minimum range and positive maximum range.

  • LV_BAR_RANGE Allows setting the start value too by lv_bar_set_start_value(bar, new_value, LV_ANIM_ON/OFF). The start value always has to be smaller than the end value.

Events

  • LV_EVENT_DRAW_PART_BEGIN and LV_EVENT_DRAW_PART_END are sent for the following parts:

    • LV_BAR_DRAW_PART_INDICATOR The indicator of the bar

      • part: LV_PART_INDICATOR

      • draw_area: area of the indicator

      • rect_dsc

See the events of the Base object too.

Learn more about Events.

Keys

No Keys are processed by the object type.

Learn more about Keys.

Example

Simple Bar

C code  

 GitHub
#include "../../lv_examples.h"
#if LV_USE_BAR && LV_BUILD_EXAMPLES

void lv_example_bar_1(void)
{
    lv_obj_t * bar1 = lv_bar_create(lv_scr_act());
    lv_obj_set_size(bar1, 200, 20);
    lv_obj_center(bar1);
    lv_bar_set_value(bar1, 70, LV_ANIM_OFF);
}

#endif

MicroPython code  

 GitHub Simulator
bar1 = lv.bar(lv.scr_act())
bar1.set_size(200, 20)
bar1.center()
bar1.set_value(70, lv.ANIM.OFF)


Styling a bar

C code  

 GitHub
#include "../../lv_examples.h"
#if LV_USE_BAR && LV_BUILD_EXAMPLES

/**
 * Example of styling the bar
 */
void lv_example_bar_2(void)
{
    static lv_style_t style_bg;
    static lv_style_t style_indic;

    lv_style_init(&style_bg);
    lv_style_set_border_color(&style_bg, lv_palette_main(LV_PALETTE_BLUE));
    lv_style_set_border_width(&style_bg, 2);
    lv_style_set_pad_all(&style_bg, 6); /*To make the indicator smaller*/
    lv_style_set_radius(&style_bg, 6);
    lv_style_set_anim_time(&style_bg, 1000);

    lv_style_init(&style_indic);
    lv_style_set_bg_opa(&style_indic, LV_OPA_COVER);
    lv_style_set_bg_color(&style_indic, lv_palette_main(LV_PALETTE_BLUE));
    lv_style_set_radius(&style_indic, 3);

    lv_obj_t * bar = lv_bar_create(lv_scr_act());
    lv_obj_remove_style_all(bar);  /*To have a clean start*/
    lv_obj_add_style(bar, &style_bg, 0);
    lv_obj_add_style(bar, &style_indic, LV_PART_INDICATOR);

    lv_obj_set_size(bar, 200, 20);
    lv_obj_center(bar);
    lv_bar_set_value(bar, 100, LV_ANIM_ON);
}

#endif

MicroPython code  

 GitHub Simulator
#
# Example of styling the bar
#
style_bg = lv.style_t()
style_indic = lv.style_t()

style_bg.init()
style_bg.set_border_color(lv.palette_main(lv.PALETTE.BLUE))
style_bg.set_border_width(2)
style_bg.set_pad_all(6)            # To make the indicator smaller
style_bg.set_radius(6)
style_bg.set_anim_time(1000)

style_indic.init()
style_indic.set_bg_opa(lv.OPA.COVER)
style_indic.set_bg_color(lv.palette_main(lv.PALETTE.BLUE))
style_indic.set_radius(3)

bar = lv.bar(lv.scr_act())
bar.remove_style_all()   # To have a clean start
bar.add_style(style_bg, 0)
bar.add_style(style_indic, lv.PART.INDICATOR)

bar.set_size(200, 20)
bar.center()
bar.set_value(100, lv.ANIM.ON)


Temperature meter

C code  

 GitHub
#include "../../lv_examples.h"
#if LV_USE_BAR && LV_BUILD_EXAMPLES

static void set_temp(void * bar, int32_t temp)
{
    lv_bar_set_value(bar, temp, LV_ANIM_ON);
}

/**
 * A temperature meter example
 */
void lv_example_bar_3(void)
{
    static lv_style_t style_indic;

    lv_style_init(&style_indic);
    lv_style_set_bg_opa(&style_indic, LV_OPA_COVER);
    lv_style_set_bg_color(&style_indic, lv_palette_main(LV_PALETTE_RED));
    lv_style_set_bg_grad_color(&style_indic, lv_palette_main(LV_PALETTE_BLUE));
    lv_style_set_bg_grad_dir(&style_indic, LV_GRAD_DIR_VER);

    lv_obj_t * bar = lv_bar_create(lv_scr_act());
    lv_obj_add_style(bar, &style_indic, LV_PART_INDICATOR);
    lv_obj_set_size(bar, 20, 200);
    lv_obj_center(bar);
    lv_bar_set_range(bar, -20, 40);

    lv_anim_t a;
    lv_anim_init(&a);
    lv_anim_set_exec_cb(&a, set_temp);
    lv_anim_set_time(&a, 3000);
    lv_anim_set_playback_time(&a, 3000);
    lv_anim_set_var(&a, bar);
    lv_anim_set_values(&a, -20, 40);
    lv_anim_set_repeat_count(&a, LV_ANIM_REPEAT_INFINITE);
    lv_anim_start(&a);
}


#endif

MicroPython code  

 GitHub Simulator
def set_temp(bar, temp):
    bar.set_value(temp, lv.ANIM.ON)

#
# A temperature meter example
#


style_indic = lv.style_t()

style_indic.init()
style_indic.set_bg_opa(lv.OPA.COVER)
style_indic.set_bg_color(lv.palette_main(lv.PALETTE.RED))
style_indic.set_bg_grad_color(lv.palette_main(lv.PALETTE.BLUE))
style_indic.set_bg_grad_dir(lv.GRAD_DIR.VER)

bar = lv.bar(lv.scr_act())
bar.add_style(style_indic, lv.PART.INDICATOR)
bar.set_size(20, 200)
bar.center()
bar.set_range(-20, 40)

a = lv.anim_t()
a.init()
a.set_time(3000)
a.set_playback_time(3000)
a.set_var(bar)
a.set_values(-20, 40)
a.set_repeat_count(lv.ANIM_REPEAT.INFINITE)
a.set_custom_exec_cb(lambda a, val: set_temp(bar,val))
lv.anim_t.start(a)


Stripe pattern and range value

C code  

 GitHub
#include "../../lv_examples.h"
#if LV_USE_BAR && LV_BUILD_EXAMPLES

/**
 * Bar with stripe pattern and ranged value
 */
void lv_example_bar_4(void)
{
    LV_IMG_DECLARE(img_skew_strip);
    static lv_style_t style_indic;

    lv_style_init(&style_indic);
    lv_style_set_bg_img_src(&style_indic, &img_skew_strip);
    lv_style_set_bg_img_tiled(&style_indic, true);
    lv_style_set_bg_img_opa(&style_indic, LV_OPA_30);

    lv_obj_t * bar = lv_bar_create(lv_scr_act());
    lv_obj_add_style(bar, &style_indic, LV_PART_INDICATOR);

    lv_obj_set_size(bar, 260, 20);
    lv_obj_center(bar);
    lv_bar_set_mode(bar, LV_BAR_MODE_RANGE);
    lv_bar_set_value(bar, 90, LV_ANIM_OFF);
    lv_bar_set_start_value(bar, 20, LV_ANIM_OFF);
}

#endif

MicroPython code  

 GitHub Simulator
#
# get an icon
#
def get_icon(filename,xres,yres):
    try:
        sdl_filename = "../../assets/" + filename + "_" + str(xres) + "x" + str(yres) + "_argb8888.fnt"
        print("file name: ", sdl_filename)
        with open(sdl_filename,'rb') as f:
            icon_data = f.read()
    except:
        print("Could not find image file: " + filename) 
        return None
    
    icon_dsc = lv.img_dsc_t(
        {
            "header": {"always_zero": 0, "w": xres, "h": yres, "cf": lv.img.CF.TRUE_COLOR_ALPHA},
            "data": icon_data,
            "data_size": len(icon_data),
        }
    )
    return icon_dsc

#
# Bar with stripe pattern and ranged value
#

img_skew_strip_dsc = get_icon("img_skew_strip",80,20)
style_indic =  lv.style_t()

style_indic.init()
style_indic.set_bg_img_src(img_skew_strip_dsc)
style_indic.set_bg_img_tiled(True);
style_indic.set_bg_img_opa(lv.OPA._30)

bar = lv.bar(lv.scr_act())
bar.add_style(style_indic, lv.PART.INDICATOR)

bar.set_size(260, 20)
bar.center()
bar.set_mode(lv.bar.MODE.RANGE)
bar.set_value(90, lv.ANIM.OFF)
bar.set_start_value(20, lv.ANIM.OFF)


    

Bar with LTR and RTL base direction

C code  

 GitHub
#include "../../lv_examples.h"
#if LV_USE_BAR && LV_BUILD_EXAMPLES

/**
 * Bar with LTR and RTL base direction
 */
void lv_example_bar_5(void)
{
    lv_obj_t * label;


    lv_obj_t * bar_ltr = lv_bar_create(lv_scr_act());
    lv_obj_set_size(bar_ltr, 200, 20);
    lv_bar_set_value(bar_ltr, 70, LV_ANIM_OFF);
    lv_obj_align(bar_ltr, LV_ALIGN_CENTER, 0, -30);

    label = lv_label_create(lv_scr_act());
    lv_label_set_text(label, "Left to Right base direction");
    lv_obj_align_to(label, bar_ltr, LV_ALIGN_OUT_TOP_MID, 0, -5);

    lv_obj_t * bar_rtl = lv_bar_create(lv_scr_act());
    lv_obj_set_style_base_dir(bar_rtl, LV_BASE_DIR_RTL, 0);
    lv_obj_set_size(bar_rtl, 200, 20);
    lv_bar_set_value(bar_rtl, 70, LV_ANIM_OFF);
    lv_obj_align(bar_rtl, LV_ALIGN_CENTER, 0, 30);

    label = lv_label_create(lv_scr_act());
    lv_label_set_text(label, "Right to Left base direction");
    lv_obj_align_to(label, bar_rtl, LV_ALIGN_OUT_TOP_MID, 0, -5);
}

#endif

MicroPython code  

 GitHub Simulator
#
# Bar with LTR and RTL base direction
#

bar_ltr = lv.bar(lv.scr_act())
bar_ltr.set_size(200, 20)
bar_ltr.set_value(70, lv.ANIM.OFF)
bar_ltr.align(lv.ALIGN.CENTER, 0, -30)

label = lv.label(lv.scr_act())
label.set_text("Left to Right base direction")
label.align_to(bar_ltr, lv.ALIGN.OUT_TOP_MID, 0, -5)

bar_rtl = lv.bar(lv.scr_act())
bar_rtl.set_style_base_dir(lv.BASE_DIR.RTL,0)
bar_rtl.set_size(200, 20)
bar_rtl.set_value(70, lv.ANIM.OFF)
bar_rtl.align(lv.ALIGN.CENTER, 0, 30)

label = lv.label(lv.scr_act())
label.set_text("Right to Left base direction")
label.align_to(bar_rtl, lv.ALIGN.OUT_TOP_MID, 0, -5)

Custom drawer to show the current value

C code  

 GitHub
#include "../../lv_examples.h"
#if LV_USE_BAR && LV_BUILD_EXAMPLES

static void set_value(void *bar, int32_t v)
{
    lv_bar_set_value(bar, v, LV_ANIM_OFF);
}

static void event_cb(lv_event_t * e)
{
    lv_obj_draw_part_dsc_t * dsc = lv_event_get_param(e);
    if(dsc->part != LV_PART_INDICATOR) return;

    lv_obj_t * obj= lv_event_get_target(e);

    lv_draw_label_dsc_t label_dsc;
    lv_draw_label_dsc_init(&label_dsc);
    label_dsc.font = LV_FONT_DEFAULT;

    char buf[8];
    lv_snprintf(buf, sizeof(buf), "%d", (int)lv_bar_get_value(obj));

    lv_point_t txt_size;
    lv_txt_get_size(&txt_size, buf, label_dsc.font, label_dsc.letter_space, label_dsc.line_space, LV_COORD_MAX, label_dsc.flag);

    lv_area_t txt_area;
    /*If the indicator is long enough put the text inside on the right*/
    if(lv_area_get_width(dsc->draw_area) > txt_size.x + 20) {
        txt_area.x2 = dsc->draw_area->x2 - 5;
        txt_area.x1 = txt_area.x2 - txt_size.x + 1;
        label_dsc.color = lv_color_white();
    }
    /*If the indicator is still short put the text out of it on the right*/
    else {
        txt_area.x1 = dsc->draw_area->x2 + 5;
        txt_area.x2 = txt_area.x1 + txt_size.x - 1;
        label_dsc.color = lv_color_black();
    }

    txt_area.y1 = dsc->draw_area->y1 + (lv_area_get_height(dsc->draw_area) - txt_size.y) / 2;
    txt_area.y2 = txt_area.y1 + txt_size.y - 1;

    lv_draw_label(&txt_area, dsc->clip_area, &label_dsc, buf, NULL);
}

/**
 * Custom drawer on the bar to display the current value
 */
void lv_example_bar_6(void)
{
    lv_obj_t * bar = lv_bar_create(lv_scr_act());
    lv_obj_add_event_cb(bar, event_cb, LV_EVENT_DRAW_PART_END, NULL);
    lv_obj_set_size(bar, 200, 20);
    lv_obj_center(bar);

    lv_anim_t a;
    lv_anim_init(&a);
    lv_anim_set_var(&a, bar);
    lv_anim_set_values(&a, 0, 100);
    lv_anim_set_exec_cb(&a, set_value);
    lv_anim_set_time(&a, 2000);
    lv_anim_set_playback_time(&a, 2000);
    lv_anim_set_repeat_count(&a, LV_ANIM_REPEAT_INFINITE);
    lv_anim_start(&a);

}

#endif

MicroPython code  

 GitHub Simulator
def set_value(bar, v):
    bar.set_value(v, lv.ANIM.OFF)

def event_cb(e):
    dsc = lv.obj_draw_part_dsc_t.__cast__(e.get_param())
    if dsc.part != lv.PART.INDICATOR:
        return

    obj= e.get_target()

    label_dsc = lv.draw_label_dsc_t()
    label_dsc.init()
    # label_dsc.font = LV_FONT_DEFAULT;

    value_txt = str(obj.get_value())
    txt_size = lv.point_t()
    lv.txt_get_size(txt_size, value_txt, label_dsc.font, label_dsc.letter_space, label_dsc.line_space, lv.COORD.MAX, label_dsc.flag)

    txt_area = lv.area_t()
    # If the indicator is long enough put the text inside on the right
    if dsc.draw_area.get_width() > txt_size.x + 20:
        txt_area.x2 = dsc.draw_area.x2 - 5
        txt_area.x1 = txt_area.x2 - txt_size.x + 1
        label_dsc.color = lv.color_white()
    # If the indicator is still short put the text out of it on the right*/
    else:
        txt_area.x1 = dsc.draw_area.x2 + 5
        txt_area.x2 = txt_area.x1 + txt_size.x - 1
        label_dsc.color = lv.color_black()

    txt_area.y1 = dsc.draw_area.y1 + (dsc.draw_area.get_height() - txt_size.y) // 2
    txt_area.y2 = txt_area.y1 + txt_size.y - 1

    lv.draw_label(txt_area, dsc.clip_area, label_dsc, value_txt, None)

#
# Custom drawer on the bar to display the current value
#

bar = lv.bar(lv.scr_act())
bar.add_event_cb(event_cb, lv.EVENT.DRAW_PART_END, None)
bar.set_size(200, 20)
bar.center()

a = lv.anim_t()
a.init()
a.set_var(bar)
a.set_values(0, 100)
a.set_custom_exec_cb(lambda a,val: set_value(bar,val))
a.set_time(2000)
a.set_playback_time(2000)
a.set_repeat_count(lv.ANIM_REPEAT.INFINITE)
lv.anim_t.start(a)


API

Typedefs

typedef uint8_t lv_bar_mode_t

Enums

enum [anonymous]

Values:

enumerator LV_BAR_MODE_NORMAL
enumerator LV_BAR_MODE_SYMMETRICAL
enumerator LV_BAR_MODE_RANGE
enum lv_bar_draw_part_type_t

type field in lv_obj_draw_part_dsc_t if class_p = lv_bar_class Used in LV_EVENT_DRAW_PART_BEGIN and LV_EVENT_DRAW_PART_END

Values:

enumerator LV_BAR_DRAW_PART_INDICATOR

The indicator

Functions

lv_obj_t *lv_bar_create(lv_obj_t *parent)

Create a bar object

Parameters

parent -- pointer to an object, it will be the parent of the new bar

Returns

pointer to the created bar

void lv_bar_set_value(lv_obj_t *obj, int32_t value, lv_anim_enable_t anim)

Set a new value on the bar

Parameters
  • bar -- pointer to a bar object

  • value -- new value

  • anim -- LV_ANIM_ON: set the value with an animation; LV_ANIM_OFF: change the value immediately

void lv_bar_set_start_value(lv_obj_t *obj, int32_t start_value, lv_anim_enable_t anim)

Set a new start value on the bar

Parameters
  • obj -- pointer to a bar object

  • value -- new start value

  • anim -- LV_ANIM_ON: set the value with an animation; LV_ANIM_OFF: change the value immediately

void lv_bar_set_range(lv_obj_t *obj, int32_t min, int32_t max)

Set minimum and the maximum values of a bar

Parameters
  • obj -- pointer to the bar object

  • min -- minimum value

  • max -- maximum value

void lv_bar_set_mode(lv_obj_t *obj, lv_bar_mode_t mode)

Set the type of bar.

Parameters
  • obj -- pointer to bar object

  • mode -- bar type from ::lv_bar_mode_t

int32_t lv_bar_get_value(const lv_obj_t *obj)

Get the value of a bar

Parameters

obj -- pointer to a bar object

Returns

the value of the bar

int32_t lv_bar_get_start_value(const lv_obj_t *obj)

Get the start value of a bar

Parameters

obj -- pointer to a bar object

Returns

the start value of the bar

int32_t lv_bar_get_min_value(const lv_obj_t *obj)

Get the minimum value of a bar

Parameters

obj -- pointer to a bar object

Returns

the minimum value of the bar

int32_t lv_bar_get_max_value(const lv_obj_t *obj)

Get the maximum value of a bar

Parameters

obj -- pointer to a bar object

Returns

the maximum value of the bar

lv_bar_mode_t lv_bar_get_mode(lv_obj_t *obj)

Get the type of bar.

Parameters

obj -- pointer to bar object

Returns

bar type from ::lv_bar_mode_t

Variables

const lv_obj_class_t lv_bar_class
struct _lv_bar_anim_t

Public Members

lv_obj_t *bar
int32_t anim_start
int32_t anim_end
int32_t anim_state
struct lv_bar_t

Public Members

lv_obj_t obj
int32_t cur_value

Current value of the bar

int32_t min_value

Minimum value of the bar

int32_t max_value

Maximum value of the bar

int32_t start_value

Start value of the bar

lv_area_t indic_area

Save the indicator area. Might be used by derived types

_lv_bar_anim_t cur_value_anim
_lv_bar_anim_t start_value_anim
lv_bar_mode_t mode

Type of bar