Slider （滑动条）(lv_slider)

Overview（概述）

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The Slider Widget looks like a Bar （进度条）(lv_bar) supplemented with a knob. The knob can be dragged to set the Slider's value. Like Bar, a Slider can be vertical or horizontal.

滑块部件（Slider Widget）看起来就像是添加了一个旋钮的 Bar （进度条）(lv_bar)。可以拖动旋钮来设置滑块的值。和进度条（Bar）一样，滑块可以是垂直方向的，也可以是水平方向的。

Parts and Styles（零件和样式）

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LV_PART_MAIN The background of the Slider. Uses 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 the typical background style properties.
LV_PART_KNOB A rectangle (or circle) drawn at the current value; also uses the typical background style properties to describe the knob(s). By default, the knob is round (radius-style can modify this) with side length equal to the smaller dimension of the Slider. The knob can be made larger with the padding values. Padding values can be asymmetric as well.

LV_PART_MAIN 滑块的背景。使用:ref:typical background style properties <typical bg props>`典型的背景样式属性。 ``padding` 属性会使指示器在相应方向上变小。
LV_PART_INDICATOR 用于显示滑块当前状态的指示器，同样使用:ref:`typical background style properties <typical bg props>`典型的背景样式属性。
LV_PART_KNOB 在当前值位置绘制的一个矩形（或圆形），也使用:ref:typical background style properties <typical bg props>`典型的背景样式属性来描述旋钮。默认情况下，旋钮是圆形的（半径样式可对此进行修改），其边长等于滑块较小的那个尺寸。可以通过 ``padding` 值使旋钮变大。内边距的值也可以是非对称的。

Usage（用法）

Value, range and orientation(值、范围和方向）

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Once a Slider is created, it has:

value == 0
default range of [0..100],
horizontal orientation, with
default width of approximately 2 inches (according to configured value of LV_DPI_DEF),
default hight of approximately 1/10 inch (according to configured value of LV_DPI_DEF).

To set a different value use:

lv_slider_set_value(slider, new_value, LV_ANIM_ON / OFF) (animation time is set by the styles' anim_time property);
lv_slider_set_range(slider, min, max); and
for orientation, width and height, simply set width and height style properties;
lv_bar_set_orientation(slider, orientation) to override orientation caused by width and height. Valid values for orientation are:
- LV_BAR_ORIENTATION_AUTO,
- LV_BAR_ORIENTATION_HORIZONTAL,
- LV_BAR_ORIENTATION_VERTICAL.

The default drawing direction is from left to right in horizontal orientation and bottom to top in vertical orientation. If the minimum value is set to be greater than the maximum value (e.g. [100..0]), the drawing direction is reversed.

一旦创建了一个滑块（Slider），它具有以下属性：

值（value）等于 0；
默认范围是 [0..100]；
水平方向，且
默认宽度大约为 2 英寸（依据 LV_DPI_DEF（C 语言宏）配置的值而定），
默认高度大约为 1/10 英寸（依据 LV_DPI_DEF（C 语言宏）配置的值而定）。

若要设置不同的值，可使用以下方法：

lv_slider_set_value(slider, new_value, LV_ANIM_ON/OFF)`（动画时间由样式的 ``anim_time` 属性设置）；
lv_slider_set_range(slider, min, max)；以及

对于方向、宽度和高度，只需设置宽度和高度样式属性即可； - lv_bar_set_orientation(slider, orientation)`可覆盖由 ``width` 和 height 所决定的方向。 orientation 的有效值如下：

LV_BAR_ORIENTATION_AUTO,

LV_BAR_ORIENTATION_HORIZONTAL,

LV_BAR_ORIENTATION_VERTICAL.

默认的绘制方向在水平方向上是从左到右，在垂直方向上是从下到上。如果最小值被设置得大于最大值（例如 [100..0]），那么绘制方向将会反转。

Modes（模式）

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The slider can be one of 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 negative 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_...)

与bar类似，滑动条可以是以下模式之一：

LV_SLIDER_MODE_NORMAL 像上面说的普通情况
LV_SLIDER_SYMMETRICAL 这个模式下可以指定负的最小范围。但是只能从零值到当前值绘制指示器。
LV_SLIDER_RANGE 在这个模式下也可以指定负的最小范围。这样滑动条的起始值可以不是0，使用 lv_bar_set_start_value(bar, new_value, LV_ANIM_ON / OFF) 设置起始值。要注意设置的起始值必须小于结束值。

可以使用 lv_slider_set_mode(slider, LV_SLIDER_MODE_...) 更改模式。

Knob-only mode（仅旋钮模式）

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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.

通常，可以通过拖动旋钮或单击滑动条来调整滑动条的值。在后一种情况下，旋钮会移动到单击的点，指示器也会相应更改。在某些情况下，需要将滑动条设置为仅对拖动旋钮做出反应，可以通过添加 LV_OBJ_FLAG_ADV_HITTEST lv_obj_add_flag(slider, LV_OBJ_FLAG_ADV_HITTEST) 来启用此功能。

扩展的单击区域(由 lv_obj_set_ext_click_area(slider, value) 设置)增加到旋钮的单击区域。

Events（事件）

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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.

See the events of the Bar too.

Learn more about Events（事件）.