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, and the default drawing direction is from left to right in horizontal mode and bottom to top in vertical mode. If the minimum value is greater than the maximum value, like 100..0, the drawing direction changes to the opposite direction.

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_MODE_SYMMETRICAL Draw the indicator from the zero value to current value. Requires a negative minimum range and positive maximum range.
LV_BAR_MODE_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

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

#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_screen_active());
    lv_obj_set_size(bar1, 200, 20);
    lv_obj_center(bar1);
    lv_bar_set_value(bar1, 70, LV_ANIM_OFF);
}

#endif

Styling a bar

#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_duration(&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_screen_active());
    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

Temperature meter

#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_screen_active());
    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_duration(&a, 3000);
    lv_anim_set_playback_duration(&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

Stripe pattern and range value

#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_IMAGE_DECLARE(img_skew_strip);
    static lv_style_t style_indic;

    lv_style_init(&style_indic);
    lv_style_set_bg_image_src(&style_indic, &img_skew_strip);
    lv_style_set_bg_image_tiled(&style_indic, true);
    lv_style_set_bg_image_opa(&style_indic, LV_OPA_30);

    lv_obj_t * bar = lv_bar_create(lv_screen_active());
    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

Bar with LTR and RTL base direction

#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_screen_active());
    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_screen_active());
    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_screen_active());
    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_screen_active());
    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

Custom drawer to show the current value

#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_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_text_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;
    txt_area.x1 = 0;
    txt_area.x2 = txt_size.x - 1;
    txt_area.y1 = 0;
    txt_area.y2 = txt_size.y - 1;

    lv_bar_t * bar = (lv_bar_t *) obj;
    const lv_area_t * indic_area = &bar->indic_area;

    /*If the indicator is long enough put the text inside on the right*/
    if(lv_area_get_width(indic_area) > txt_size.x + 20) {
        lv_area_align(indic_area, &txt_area, LV_ALIGN_RIGHT_MID, -10, 0);
        label_dsc.color = lv_color_white();
    }
    /*If the indicator is still short put the text out of it on the right*/
    else {
        lv_area_align(indic_area, &txt_area, LV_ALIGN_OUT_RIGHT_MID, 10, 0);
        label_dsc.color = lv_color_black();
    }
    label_dsc.text = buf;
    label_dsc.text_local = true;
    lv_layer_t * layer = lv_event_get_layer(e);
    lv_draw_label(layer, &label_dsc, &txt_area);
}

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

    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_duration(&a, 4000);
    lv_anim_set_playback_duration(&a, 4000);
    lv_anim_set_repeat_count(&a, LV_ANIM_REPEAT_INFINITE);
    lv_anim_start(&a);

}

#endif

Bar with opposite direction

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

/**
 * Bar with opposite direction
 */
void lv_example_bar_7(void)
{
    lv_obj_t * label;

    lv_obj_t * bar_tob = lv_bar_create(lv_screen_active());
    lv_obj_set_size(bar_tob, 20, 200);
    lv_bar_set_range(bar_tob, 100, 0);
    lv_bar_set_value(bar_tob, 70, LV_ANIM_OFF);
    lv_obj_align(bar_tob, LV_ALIGN_CENTER, 0, -30);

    label = lv_label_create(lv_screen_active());
    lv_label_set_text(label, "From top to bottom");
    lv_obj_align_to(label, bar_tob, LV_ALIGN_OUT_TOP_MID, 0, -5);
}

#endif

API

lv_bar.h