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59 lines
2.1 KiB
Markdown
59 lines
2.1 KiB
Markdown
2 years ago
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# Roller (lv_roller)
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## Overview
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Roller allows you to simply select one option from a list by scrolling.
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## Parts and Styles
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- `LV_PART_MAIN` The background of the roller uses all the typical background properties and text style properties. `style_text_line_space` adjusts the space between the options.
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When the Roller is scrolled and doesn't stop exactly on an option it will scroll to the nearest valid option automatically in `anim_time` milliseconds as specified in the style.
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- `LV_PART_SELECTED` The selected option in the middle. Besides the typical background properties it uses the text style properties to change the appearance of the text in the selected area.
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## Usage
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### Set options
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Options are passed to the Roller as a string with `lv_roller_set_options(roller, options, LV_ROLLER_MODE_NORMAL/INFINITE)`. The options should be separated by `\n`. For example: `"First\nSecond\nThird"`.
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`LV_ROLLER_MODE_INFINITE` makes the roller circular.
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You can select an option manually with `lv_roller_set_selected(roller, id, LV_ANIM_ON/OFF)`, where *id* is the index of an option.
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### Get selected option
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To get the *index* of the currently selected option use `lv_roller_get_selected(roller)`.
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`lv_roller_get_selected_str(roller, buf, buf_size)` will copy the name of the selected option to `buf`.
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### Visible rows
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The number of visible rows can be adjusted with `lv_roller_set_visible_row_count(roller, num)`.
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This function calculates the height with the current style. If the font, line space, border width, etc. of the roller changes this function needs to be called again.
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## Events
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- `LV_EVENT_VALUE_CHANGED` Sent when a new option is selected.
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See the events of the [Base object](/widgets/obj) too.
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Learn more about [Events](/overview/event).
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## Keys
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- `LV_KEY_RIGHT/DOWN` Select the next option
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- `LV_KEY_LEFT/UP` Select the previous option
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- `LY_KEY_ENTER` Apply the selected option (Send `LV_EVENT_VALUE_CHANGED` event)
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## Example
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```eval_rst
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.. include:: ../../../examples/widgets/roller/index.rst
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```
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## API
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```eval_rst
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.. doxygenfile:: lv_roller.h
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:project: lvgl
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```
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