Label （标签）(lv_label)

Overview（概述）

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A label is the basic object type that is used to display text.

标签是用来显示文本的基本对象类型。

Parts and Styles（零件和样式）

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LV_PART_MAIN Uses all the typical background properties and the text properties. The padding values can be used to add space between the text and the background.
LV_PART_SCROLLBAR The scrollbar that is shown when the text is
larger than the widget's size.
LV_PART_SELECTED Tells the style of the selected text. Only text_color and bg_color style properties can be used.

LV_PART_MAIN 使用所有典型的背景属性和文本属性。填充值可用于在文本和背景之间添加空间。
LV_PART_SCROLLBAR 当文本大于组件的大小时显示的滚动条。
LV_PART_SELECTED 告诉 selected text 的样式。只能使用 text_color 和 bg_color 样式属性。

Usage（用法）

Set text（设置文本）

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You can set the text on a label at runtime with lv_label_set_text(label, "New text"). This will allocate a buffer dynamically, and the provided string will be copied into that buffer. Therefore, you don't need to keep the text you pass to lv_label_set_text() in scope after that function returns.

With lv_label_set_text_fmt(label, "Value: %d", 15) printf formatting can be used to set the text.

Labels are able to show text from a static character buffer. To do so, use lv_label_set_text_static(label, "Text"). In this case, the text is not stored in the dynamic memory and the given buffer is used directly instead. This means that the array can't be a local variable which goes out of scope when the function exits. Constant strings are safe to use with lv_label_set_text_static() (except when used with LV_LABEL_LONG_DOT, as it modifies the buffer in-place), as they are stored in ROM memory, which is always accessible.

您可以在运行时使用 lv_label_set_text(label, "New text"). 设置标签上的文本。这将动态分配一个缓冲区，并且提供的字符串将被复制到该缓冲区中。因此，在该函数返回后，您不需要将传递给 lv_label_set_text() 的文本保留在作用域中。

使用 lv_label_set_text_fmt(label, "Value: %d", 15) printf 格式可用于设置文本。

标签能够显示来自静态字符缓冲区的文本。为此，请使用 lv_label_set_text_static(label, "Text")。在这种情况下，文本不存储在动态内存中，而是直接使用给定的缓冲区。这意味着数组不能是在函数退出时超出范围的局部变量。常量字符串可以安全地与 lv_label_set_text_static() 一起使用（除非与 LV_LABEL_LONG_DOT 一起使用，因为它会就地修改缓冲区），因为它们存储在 ROM 内存中，始终可以访问。

Newline（新行）

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Newline characters are handled automatically by the label object. You can use \n to make a line break. For example: "line1\nline2\n\nline4"

换行符由标签对象自动处理。您可以使用 \n 来换行。例如： "line1\nline2\n\nline4"

Long modes（长模式）

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By default, the width and height of the label is set to LV_SIZE_CONTENT. Therefore, the size of the label is automatically expanded to the text size. Otherwise, if the width or height are explicitly set (using e.g.lv_obj_set_width() or a layout), the lines wider than the label's width can be manipulated according to several long mode policies. Similarly, the policies can be applied if the height of the text is greater than the height of the label.

LV_LABEL_LONG_WRAP Wrap too long lines. If the height is LV_SIZE_CONTENT the label's height will be expanded, otherwise the text will be clipped. (Default)
LV_LABEL_LONG_DOT Replaces the last 3 characters from bottom right corner of the label with dots (.)
LV_LABEL_LONG_SCROLL If the text is wider than the label scroll it horizontally back and forth. If it's higher, scroll vertically. Only one direction is scrolled and horizontal scrolling has higher precedence.
LV_LABEL_LONG_SCROLL_CIRCULAR If the text is wider than the label scroll it horizontally continuously. If it's higher, scroll vertically. Only one direction is scrolled and horizontal scrolling has higher precedence.
LV_LABEL_LONG_CLIP Simply clip the parts of the text outside the label.

You can specify the long mode with lv_label_set_long_mode(label, LV_LABEL_LONG_...)

Note that LV_LABEL_LONG_DOT manipulates the text buffer in-place in order to add/remove the dots. When lv_label_set_text() or lv_label_set_array_text() are used, a separate buffer is allocated and this implementation detail is unnoticed. This is not the case with lv_label_set_text_static(). The buffer you pass to lv_label_set_text_static() must be writable if you plan to use LV_LABEL_LONG_DOT.

默认情况下，标签的宽度和高度设置为 LV_SIZE_CONTENT。因此标签的大小会自动扩展到文本大小。否则，如果显式设置宽度或高度（使用例如:cpp:func:lv_obj_set_width 或布局），则可以根据几种长模式策略来操作比标签宽度更宽的行。类似地，如果文本的高度大于标签的高度，则可以应用策略。

LV_LABEL_LONG_WRAP 换行太长。如果高度为LV_SIZE_CONTENT，标签的高度将被扩展，否则文本将被剪裁。 (默认)
LV_LABEL_LONG_DOT 将标签右下角的最后 3 个字符替换为点 (.)
LV_LABEL_LONG_SCROLL 如果文本比标签宽，则水平来回滚动它。如果它更高，请垂直滚动。只滚动一个方向，水平滚动的优先级更高。
LV_LABEL_LONG_SCROLL_CIRCULAR 如果文本比标签宽，则水平滚动它。如果它更高，请垂直滚动。只滚动一个方向，水平滚动的优先级更高。
LV_LABEL_LONG_CLIP 只需剪掉标签外的文本部分。

您可以使用 lv_label_set_long_mode(label, LV_LABEL_LONG_...) 指定长模式

请注意， LV_LABEL_LONG_DOT 就地操作文本缓冲区以添加/删除点。当使用 lv_label_set_text() 或 lv_label_set_array_text() 时，会分配一个单独的缓冲区，并且不会注意到此实现细节。 lv_label_set_text_static() 不是这种情况。如果你打算使用 LV_LABEL_LONG_DOT，你传递给 lv_label_set_text_static() 的缓冲区必须是可写的。

Text selection（文本选择）

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If enabled by LV_LABEL_TEXT_SELECTION part of the text can be selected. It's similar to when you use your mouse on a PC to select a text. The whole mechanism (click and select the text as you drag your finger/mouse) is implemented in Text area and the Label widget only allows manual text selection with lv_label_get_text_selection_start(label, start_char_index) and lv_label_get_text_selection_start(label, end_char_index).

如果通过 LV_LABEL_TEXT_SELECTION 启用，可以选择部分文本。这与在 PC 上使用鼠标选择文本时类似。整个机制（在拖动手指/鼠标时单击并选择文本）在文本区域中实现，而标签组件仅允许手动选择文本 lv_label_get_text_selection_start(label, start_char_index) 和 lv_label_get_text_selection_start(label, end_char_index)。

Text alignment（文本对齐方式）

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To horizontally align the lines of a label the text_align style property can be used with lv_obj_set_style_text_align() or lv_style_set_text_align() Note that it has a visible effect only if

the label widget's width is larger than the width of the longest line of the text
the text has multiple lines with non equal line length

若要水平对齐标签的行， text_align 样式属性可以使用 lv_obj_set_style_text_align() 或者 lv_style_set_text_align()，请注意，只有在以下情况下，它才具有可见效果。

标签小组件的宽度大于文本最长行的宽度
文本有多行行长度不相等

Very long texts（非常长的文本）

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LVGL can efficiently handle very long (e.g. > 40k characters) labels by saving some extra data (~12 bytes) to speed up drawing. To enable this feature, set LV_LABEL_LONG_TXT_HINT 1 in lv_conf.h.

LVGL 可以通过保存一些额外的数据（~12 字节）来有效地处理很长（例如 > 40k 个字符）的标签以加快绘图速度。要启用此功能，请在 lv_conf.h 中设置 LV_LABEL_LONG_TXT_HINT 1 。

Custom scrolling animations（自定义滚动动画）

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Some aspects of the scrolling animations in long modes LV_LABEL_LONG_SCROLL and LV_LABEL_LONG_SCROLL_CIRCULAR can be customized by setting the animation property of a style, using lv_style_set_anim(). It will be treated as a template which will be used to create the scroll animations.

滚动动画的某些方面在长模式下 LV_LABEL_LONG_SCROLL 和 LV_LABEL_LONG_SCROLL_CIRCULAR 可以是通过设置样式的 animation 属性进行自定义，使用 lv_style_set_anim()。

它将被视为一个模板，将用于创建滚动动画。