Slider (lv_slider)¶

Overview¶

The Slider object looks like a Bar supplemented with a knob. The knob can be dragged to set a value. Just like Bar, Slider can be vertical or horizontal.

Parts and Styles¶

LV_PART_MAIN The background of the slider. Uses all the typical background style properties. padding makes the indicator smaller in the respective direction.
LV_PART_INDICATOR The indicator that shows the current state of the slider. Also uses all the typical background style properties.
LV_PART_KNOB A rectangle (or circle) drawn at the current value. Also uses all the typical background properties to describe the knob(s). By default the knob is square (with a optional corner radius) with side length equal to the smaller side of the slider. The knob can be made larger with the padding values. Padding values can be asymmetric too.

Usage¶

Value and range¶

To set an initial value use lv_slider_set_value(slider, new_value, LV_ANIM_ON/OFF). The animation time is set by the styles' anim_time property.

To specify the range (min, max values), lv_slider_set_range(slider, min , max) can be used.

Modes¶

The slider can be one the following modes:

LV_SLIDER_MODE_NORMAL A normal slider as described above
LV_SLIDER_SYMMETRICAL Draw the indicator form the zero value to current value. Requires negaitve minimum range and positive maximum range.
LV_SLIDER_RANGE Allows setting the start value too by lv_bar_set_start_value(bar, new_value, LV_ANIM_ON/OFF). The start value has to be always smaller than the end value.

The mode can be changed with lv_slider_set_mode(slider, LV_SLIDER_MODE_...)

Knob-only mode¶

Normally, the slider can be adjusted either by dragging the knob, or by clicking on the slider bar. In the latter case the knob moves to the point clicked and slider value changes accordingly. In some cases it is desirable to set the slider to react on dragging the knob only. This feature is enabled by adding the LV_OBJ_FLAG_ADV_HITTEST: lv_obj_add_flag(slider, LV_OBJ_FLAG_ADV_HITTEST).

Events¶

LV_EVENT_VALUE_CHANGED Sent while the slider is being dragged or changed with keys. The event is sent continuously while the slider is dragged and once when released. Use lv_slider_is_dragged to detemine whether the Slider is still being dragged or has just been released.

Learn more about Events.

Keys¶

LV_KEY_UP/RIGHT Increment the slider's value by 1
LV_KEY_DOWN/LEFT Decrement the slider's value by 1

Learn more about Keys.

Example¶

C¶

Simple Slider¶

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

static void slider_event_cb(lv_event_t * e);
static lv_obj_t * slider_label;

/**
 * A default slider with a label displaying the current value
 */
void lv_example_slider_1(void)
{
    /*Create a slider in the center of the display*/
    lv_obj_t * slider = lv_slider_create(lv_scr_act());
    lv_obj_center(slider);
    lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_VALUE_CHANGED, NULL);

    /*Create a label below the slider*/
    slider_label = lv_label_create(lv_scr_act());
    lv_label_set_text(slider_label, "0%");

    lv_obj_align_to(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
}

static void slider_event_cb(lv_event_t * e)
{
    lv_obj_t * slider = lv_event_get_target(e);
    char buf[8];
    lv_snprintf(buf, sizeof(buf), "%d%%", lv_slider_get_value(slider));
    lv_label_set_text(slider_label, buf);
    lv_obj_align_to(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
}

#endif

Slider with custom style¶

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



/**
 * Show how to style a slider.
 */
void lv_example_slider_2(void)
{
    /*Create a transition*/
    static const lv_style_prop_t props[] = {LV_STYLE_BG_COLOR, 0};
    static lv_style_transition_dsc_t transition_dsc;
    lv_style_transition_dsc_init(&transition_dsc, props, lv_anim_path_linear, 300, 0, NULL);

    static lv_style_t style_main;
    static lv_style_t style_indicator;
    static lv_style_t style_knob;
    static lv_style_t style_pressed_color;
    lv_style_init(&style_main);
    lv_style_set_bg_opa(&style_main, LV_OPA_COVER);
    lv_style_set_bg_color(&style_main, lv_color_hex3(0xbbb));
    lv_style_set_radius(&style_main, LV_RADIUS_CIRCLE);
    lv_style_set_pad_ver(&style_main, -2); /*Makes the indicator larger*/

    lv_style_init(&style_indicator);
    lv_style_set_bg_opa(&style_indicator, LV_OPA_COVER);
    lv_style_set_bg_color(&style_indicator, lv_palette_main(LV_PALETTE_CYAN));
    lv_style_set_radius(&style_indicator, LV_RADIUS_CIRCLE);
    lv_style_set_transition(&style_indicator, &transition_dsc);

    lv_style_init(&style_knob);
    lv_style_set_bg_opa(&style_knob, LV_OPA_COVER);
    lv_style_set_bg_color(&style_knob, lv_palette_main(LV_PALETTE_CYAN));
    lv_style_set_border_color(&style_knob, lv_palette_darken(LV_PALETTE_CYAN, 3));
    lv_style_set_border_width(&style_knob, 2);
    lv_style_set_radius(&style_knob, LV_RADIUS_CIRCLE);
    lv_style_set_pad_all(&style_knob, 6); /*Makes the knob larger*/
    lv_style_set_transition(&style_knob, &transition_dsc);

    lv_style_init(&style_pressed_color);
    lv_style_set_bg_color(&style_pressed_color, lv_palette_darken(LV_PALETTE_CYAN, 2));

    /*Create a slider and add the style*/
    lv_obj_t * slider = lv_slider_create(lv_scr_act());
    lv_obj_remove_style_all(slider);        /*Remove the styles coming from the theme*/

    lv_obj_add_style(slider, &style_main, LV_PART_MAIN);
    lv_obj_add_style(slider, &style_indicator, LV_PART_INDICATOR);
    lv_obj_add_style(slider, &style_pressed_color, LV_PART_INDICATOR | LV_STATE_PRESSED);
    lv_obj_add_style(slider, &style_knob, LV_PART_KNOB);
    lv_obj_add_style(slider, &style_pressed_color, LV_PART_KNOB | LV_STATE_PRESSED);

    lv_obj_center(slider);
}

#endif

Slider with extended drawer¶

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

static void slider_event_cb(lv_event_t * e);

/**
 * Show the current value when the slider is pressed by extending the drawer
 *
 */
void lv_example_slider_3(void)
{
    /*Create a slider in the center of the display*/
    lv_obj_t * slider;
    slider = lv_slider_create(lv_scr_act());
    lv_obj_center(slider);

    lv_slider_set_mode(slider, LV_SLIDER_MODE_RANGE);
    lv_slider_set_value(slider, 70, LV_ANIM_OFF);
    lv_slider_set_left_value(slider, 20, LV_ANIM_OFF);

    lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_ALL, NULL);
    lv_obj_refresh_ext_draw_size(slider);
}

static void slider_event_cb(lv_event_t * e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t * obj = lv_event_get_target(e);

    /*Provide some extra space for the value*/
    if(code == LV_EVENT_REFR_EXT_DRAW_SIZE) {
        lv_coord_t * size = lv_event_get_param(e);
        *size = LV_MAX(*size, 50);
    }
    else if(code == LV_EVENT_DRAW_PART_END) {
        lv_obj_draw_part_dsc_t * dsc = lv_event_get_param(e);
        if(dsc->part == LV_PART_INDICATOR) {
            char buf[16];
            lv_snprintf(buf, sizeof(buf), "%d - %d", lv_slider_get_left_value(obj), lv_slider_get_value(obj));

            lv_point_t label_size;
            lv_txt_get_size(&label_size, buf, LV_FONT_DEFAULT, 0, 0, LV_COORD_MAX, 0);
            lv_area_t label_area;
            label_area.x1 = dsc->draw_area->x1 + lv_area_get_width(dsc->draw_area) / 2 - label_size.x / 2;
            label_area.x2 = label_area.x1 + label_size.x;
            label_area.y2 = dsc->draw_area->y1 - 10;
            label_area.y1 = label_area.y2 - label_size.y;

            lv_draw_label_dsc_t label_draw_dsc;
            lv_draw_label_dsc_init(&label_draw_dsc);

            lv_draw_label(&label_area, dsc->clip_area, &label_draw_dsc, buf, NULL);
        }
    }
}

#endif

MicroPython¶

No examples yet.

API¶

Typedefs

typedef uint8_t lv_slider_mode_t¶

Enums

enum [anonymous]¶

Values:

enumerator LV_SLIDER_MODE_NORMAL¶

enumerator LV_SLIDER_MODE_SYMMETRICAL¶

enumerator LV_SLIDER_MODE_RANGE¶

Functions

lv_obj_t *lv_slider_create(lv_obj_t *parent)¶

Create a slider objects

Parameters: parent -- pointer to an object, it will be the parent of the new slider.
Returns: pointer to the created slider

static inline void lv_slider_set_value(lv_obj_t *obj, int32_t value, lv_anim_enable_t anim)¶

Set a new value on the slider

Parameters

obj -- pointer to a slider object
value -- the new value
anim -- LV_ANIM_ON: set the value with an animation; LV_ANIM_OFF: change the value immediately

static inline void lv_slider_set_left_value(lv_obj_t *obj, int32_t value, lv_anim_enable_t anim)¶

Set a new value for the left knob of a slider

Parameters

obj -- pointer to a slider object
value -- new value
anim -- LV_ANIM_ON: set the value with an animation; LV_ANIM_OFF: change the value immediately

static inline void lv_slider_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 slider object
min -- minimum value
max -- maximum value

static inline void lv_slider_set_mode(lv_obj_t *obj, lv_slider_mode_t mode)¶

Set the mode of slider.

Parameters

obj -- pointer to a slider object
mode -- the mode of the slider. See ::lv_slider_mode_t

static inline int32_t lv_slider_get_value(const lv_obj_t *obj)¶

Get the value of the main knob of a slider

Parameters: obj -- pointer to a slider object
Returns: the value of the main knob of the slider

static inline int32_t lv_slider_get_left_value(const lv_obj_t *obj)¶

Get the value of the left knob of a slider

Parameters: obj -- pointer to a slider object
Returns: the value of the left knob of the slider

static inline int32_t lv_slider_get_min_value(const lv_obj_t *obj)¶

Get the minimum value of a slider

Parameters: obj -- pointer to a slider object
Returns: the minimum value of the slider

static inline int32_t lv_slider_get_max_value(const lv_obj_t *obj)¶

Get the maximum value of a slider

Parameters: obj -- pointer to a slider object
Returns: the maximum value of the slider

bool lv_slider_is_dragged(const lv_obj_t *obj)¶

Give the slider is being dragged or not

Parameters: obj -- pointer to a slider object
Returns: true: drag in progress false: not dragged

static inline lv_slider_mode_t lv_slider_get_mode(lv_obj_t *slider)¶

Get the mode of the slider.

Parameters: obj -- pointer to a bar object
Returns: see ::lv_slider_mode_t

Variables

const lv_obj_class_t lv_slider_class¶

struct lv_slider_t¶

Public Members

lv_bar_t bar¶

lv_area_t left_knob_area¶

lv_area_t right_knob_area¶

int32_t *value_to_set¶

uint8_t dragging¶

uint8_t left_knob_focus¶