3.2 KiB
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 an optional corner radius) with side length equal to the smaller side of the slider. The knob can be made larger with thepadding
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 of the following modes:
LV_SLIDER_MODE_NORMAL
A normal slider as described aboveLV_SLIDER_SYMMETRICAL
Draw the indicator form the zero value to current value. Requires negative minimum range and positive maximum range.LV_SLIDER_RANGE
Allows setting the start value too bylv_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)
.
The extended click area (set by lv_obj_set_ext_click_area(slider, value)
) increases to knob's click area.
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 being dragged.LV_EVENT_RELEASED
Sent when the slider has just been released.LV_EVENT_DRAW_PART_BEGIN
andLV_EVENT_DRAW_PART_END
are sent for the following parts.LV_SLIDER_DRAW_PART_KNOB
The main (right) knob of the sliderpart
:LV_PART_KNOB
draw_area
: area of the indicatorrect_dsc
id
: 0
LV_SLIDER_DRAW_PART_KNOB
The left knob of the sliderpart
:LV_PART_KNOB
draw_area
: area of the indicatorrect_dsc
id
: 1
See the events of the Bar too.
Learn more about Events.
Keys
LV_KEY_UP/RIGHT
Increment the slider's value by 1LV_KEY_DOWN/LEFT
Decrement the slider's value by 1
Learn more about Keys.
Example
.. include:: ../../../examples/widgets/slider/index.rst
API
.. doxygenfile:: lv_slider.h
:project: lvgl