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_MAINUses 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_SCROLLBARThe scrollbar that is shown when the text islarger than the widget's size.
LV_PART_SELECTEDTells the style of the selected text. Onlytext_colorandbg_colorstyle 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）
显示原文
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_WRAPWrap too long lines. If the height isLV_SIZE_CONTENTthe label's height will be expanded, otherwise the text will be clipped. (Default)LV_LABEL_LONG_DOTReplaces the last 3 characters from bottom right corner of the label with dots (.)LV_LABEL_LONG_SCROLLIf 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_CIRCULARIf 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_CLIPSimply 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）
显示原文
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。
Symbols（符号）
显示原文
The labels can display symbols alongside letters (or on their own). Read the Fonts（字体） section to learn more about the symbols.
标签可以在字母旁边显示符号（或单独显示）。 阅读 Fonts（字体） 部分以了解有关符号的更多信息。
Events（事件）
显示原文
No special events are sent by the Label.
See the events of the Base object too.
Learn more about Events（事件）.
标签不发送特殊事件。
另请参阅 基本对象 的事件。
详细了解更多 Events（事件）。
Keys（按键）
对象类型不处理 按键 。
了解有关 Keys（按键） 的更多信息。
Example
Line wrap, recoloring and scrolling
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_BUILD_EXAMPLES
/**
* Show line wrap, re-color, line align and text scrolling.
*/
void lv_example_label_1(void)
{
lv_obj_t * label1 = lv_label_create(lv_screen_active());
lv_label_set_long_mode(label1, LV_LABEL_LONG_WRAP); /*Break the long lines*/
lv_label_set_text(label1, "Recolor is not supported for v9 now.");
lv_obj_set_width(label1, 150); /*Set smaller width to make the lines wrap*/
lv_obj_set_style_text_align(label1, LV_TEXT_ALIGN_CENTER, 0);
lv_obj_align(label1, LV_ALIGN_CENTER, 0, -40);
lv_obj_t * label2 = lv_label_create(lv_screen_active());
lv_label_set_long_mode(label2, LV_LABEL_LONG_SCROLL_CIRCULAR); /*Circular scroll*/
lv_obj_set_width(label2, 150);
lv_label_set_text(label2, "It is a circularly scrolling text. ");
lv_obj_align(label2, LV_ALIGN_CENTER, 0, 40);
}
#endif
Text shadow
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_BUILD_EXAMPLES
/**
* Create a fake text shadow
*/
void lv_example_label_2(void)
{
/*Create a style for the shadow*/
static lv_style_t style_shadow;
lv_style_init(&style_shadow);
lv_style_set_text_opa(&style_shadow, LV_OPA_30);
lv_style_set_text_color(&style_shadow, lv_color_black());
/*Create a label for the shadow first (it's in the background)*/
lv_obj_t * shadow_label = lv_label_create(lv_screen_active());
lv_obj_add_style(shadow_label, &style_shadow, 0);
/*Create the main label*/
lv_obj_t * main_label = lv_label_create(lv_screen_active());
lv_label_set_text(main_label, "A simple method to create\n"
"shadows on a text.\n"
"It even works with\n\n"
"newlines and spaces.");
/*Set the same text for the shadow label*/
lv_label_set_text(shadow_label, lv_label_get_text(main_label));
/*Position the main label*/
lv_obj_align(main_label, LV_ALIGN_CENTER, 0, 0);
/*Shift the second label down and to the right by 2 pixel*/
lv_obj_align_to(shadow_label, main_label, LV_ALIGN_TOP_LEFT, 2, 2);
}
#endif
Show LTR, RTL and Chinese texts
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_BUILD_EXAMPLES && LV_FONT_DEJAVU_16_PERSIAN_HEBREW && LV_FONT_SIMSUN_16_CJK && LV_USE_BIDI
/**
* Show mixed LTR, RTL and Chinese label
*/
void lv_example_label_3(void)
{
lv_obj_t * ltr_label = lv_label_create(lv_screen_active());
lv_label_set_text(ltr_label, "In modern terminology, a microcontroller is similar to a system on a chip (SoC).");
lv_obj_set_style_text_font(ltr_label, &lv_font_montserrat_16, 0);
lv_obj_set_width(ltr_label, 310);
lv_obj_align(ltr_label, LV_ALIGN_TOP_LEFT, 5, 5);
lv_obj_t * rtl_label = lv_label_create(lv_screen_active());
lv_label_set_text(rtl_label,
"מעבד, או בשמו המלא יחידת עיבוד מרכזית (באנגלית: CPU - Central Processing Unit).");
lv_obj_set_style_base_dir(rtl_label, LV_BASE_DIR_RTL, 0);
lv_obj_set_style_text_font(rtl_label, &lv_font_dejavu_16_persian_hebrew, 0);
lv_obj_set_width(rtl_label, 310);
lv_obj_align(rtl_label, LV_ALIGN_LEFT_MID, 5, 0);
lv_obj_t * cz_label = lv_label_create(lv_screen_active());
lv_label_set_text(cz_label,
"嵌入式系统（Embedded System），\n是一种嵌入机械或电气系统内部、具有专一功能和实时计算性能的计算机系统。");
lv_obj_set_style_text_font(cz_label, &lv_font_simsun_16_cjk, 0);
lv_obj_set_width(cz_label, 310);
lv_obj_align(cz_label, LV_ALIGN_BOTTOM_LEFT, 5, -5);
}
#endif
Draw label with gradient color
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_FONT_MONTSERRAT_24 && LV_USE_CANVAS && LV_BUILD_EXAMPLES && LV_DRAW_SW_COMPLEX
#define MASK_WIDTH 150
#define MASK_HEIGHT 60
static void generate_mask(lv_draw_buf_t * mask, int32_t w, int32_t h, const char * txt)
{
/*Create a "8 bit alpha" canvas and clear it*/
lv_obj_t * canvas = lv_canvas_create(lv_screen_active());
lv_canvas_set_draw_buf(canvas, mask);
lv_canvas_fill_bg(canvas, lv_color_black(), LV_OPA_TRANSP);
lv_layer_t layer;
lv_canvas_init_layer(canvas, &layer);
/*Draw a label to the canvas. The result "image" will be used as mask*/
lv_draw_label_dsc_t label_dsc;
lv_draw_label_dsc_init(&label_dsc);
label_dsc.color = lv_color_white();
label_dsc.align = LV_TEXT_ALIGN_CENTER;
label_dsc.text = txt;
label_dsc.font = &lv_font_montserrat_24;
lv_area_t a = {0, 0, w - 1, h - 1};
lv_draw_label(&layer, &label_dsc, &a);
lv_canvas_finish_layer(canvas, &layer);
lv_obj_delete(canvas);
}
/**
* Draw label with gradient color
*/
void lv_example_label_4(void)
{
/* Create the mask of a text by drawing it to a canvas*/
LV_DRAW_BUF_DEFINE_STATIC(mask, MASK_WIDTH, MASK_HEIGHT, LV_COLOR_FORMAT_L8);
LV_DRAW_BUF_INIT_STATIC(mask);
generate_mask(&mask, MASK_WIDTH, MASK_HEIGHT, "Text with gradient");
/* Create an object from where the text will be masked out.
* Now it's a rectangle with a gradient but it could be an image too*/
lv_obj_t * grad = lv_obj_create(lv_screen_active());
lv_obj_set_size(grad, MASK_WIDTH, MASK_HEIGHT);
lv_obj_center(grad);
lv_obj_set_style_bg_color(grad, lv_color_hex(0xff0000), 0);
lv_obj_set_style_bg_grad_color(grad, lv_color_hex(0x0000ff), 0);
lv_obj_set_style_bg_grad_dir(grad, LV_GRAD_DIR_HOR, 0);
lv_obj_set_style_bitmap_mask_src(grad, &mask, 0);
}
#endif
Customize circular scrolling animation
C code
View on GitHub#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_BUILD_EXAMPLES
/**
* Show customizing the circular scrolling animation of a label with `LV_LABEL_LONG_SCROLL_CIRCULAR`
* long mode.
*/
void lv_example_label_5(void)
{
static lv_anim_t animation_template;
static lv_style_t label_style;
lv_anim_init(&animation_template);
lv_anim_set_delay(&animation_template, 1000); /*Wait 1 second to start the first scroll*/
lv_anim_set_repeat_delay(&animation_template,
3000); /*Repeat the scroll 3 seconds after the label scrolls back to the initial position*/
/*Initialize the label style with the animation template*/
lv_style_init(&label_style);
lv_style_set_anim(&label_style, &animation_template);
lv_obj_t * label1 = lv_label_create(lv_screen_active());
lv_label_set_long_mode(label1, LV_LABEL_LONG_SCROLL_CIRCULAR); /*Circular scroll*/
lv_obj_set_width(label1, 150);
lv_label_set_text(label1, "It is a circularly scrolling text. ");
lv_obj_align(label1, LV_ALIGN_CENTER, 0, 40);
lv_obj_add_style(label1, &label_style, LV_STATE_DEFAULT); /*Add the style to the label*/
}
#endif