[lvgl (5)] label usage

The official manual ：Label (lv_label) — LVGL documentationhttps://docs.lvgl.io/master/widgets/core/label.html

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label (lv_label)

Labels are the basic object types used to display text .

In the box model , Composition of labels ：

• LV_PART_MAIN Rectangular part ( Box area ). Fill values can be used to add space between text and background .   
• LV_PART_SCROLLBAR When the text to be displayed is larger than the size of the part , Scroll bar part of the display .   
• LV_PART_SELECTED When text is selected , Highlighted part .label Only use text_color and bg_color Style attribute

Create a label

lv_obj_t * label = lv_label_create(parent);

Set text

Set the text to display

Dynamically allocate buffers , Do not keep the passed text .

lv_label_set_text(label, "HELLOW LVGL");

It can also display text from the static character buffer . Text is not stored in dynamic memory , Instead, use the given buffer directly .

lv_label_set_text_static(label, "Text")

Format the display text

lv_label_set_text_fmt(label, "Value: %d", 15)

Line break

Use \n Line break , for example ：

lv_label_set_text(label, "line1\nline2\n\nline4");

Set text size

By default, the size of the label is set to  LV_SIZE_CONTENT It will automatically expand to the same size as the text .

If width or height is set , Text wider than the label width can be manipulated according to several long mode strategies .

lv_obj_set_width(label,50);    // Set width     
lv_obj_set_height(label,20);    // Set height 
lv_obj_set_size(label,20,50); 

In this way, the width or height of the text may appear label The situation of , You need to make some adjustments .

• LV_LABEL_LONG_WRAP： Wrap too long . If the height is LV_SIZE_CONTENT The height of the label will be expanded , Otherwise the text will be clipped . （ Default ） 
• LV_LABEL_LONG_DOT： Place the bottom right corner of the label at the end 3 Characters replaced with dots ( ...) 
• LV_LABEL_LONG_SCROLL： If the text is wider than the label , Then scroll back and forth horizontally . If it is higher , Please scroll vertically . Scroll in only one direction , Horizontal scrolling has a higher priority . 
• LV_LABEL_LONG_SCROLL_CIRCULAR： If the text is wider than the label , Then continuous horizontal scrolling . If it is higher , Please scroll vertically . Scroll in only one direction , Horizontal scrolling has a higher priority . 
• LV_LABEL_LONG_CLIP： Just cut the text outside the label

Be careful ：LV_LABEL_LONG_DOT yes Directly manipulate the text buffer to add / Delete point . If you use lv_label_set_text and lv_label_set_text_fmt They allocate a separate buffer , No problem . But if you use lv_label_set_text_static The buffer we pass to it must be writable .

Set interface

lv_label_set_long_mode(label, LV_LABEL_LONG_...)

Set the font style

Setting a custom font is the same

lv_obj_t * label = lv_label_create(lv_scr_act());    //  Create a label parts ( object ), Its parent object is the active screen object 
lv_obj_set_style_text_font(label, &lv_font_simsun_16_cjk, 0);    //  Use the built-in  cjk  Word stock 
lv_label_set_text(label, "text");

Recolor text

Change the label color

lv_obj_set_style_bg_color(label, lv_color_hex(0xf7b37b), 0);    
lv_obj_set_style_bg_opa(label, 100, 0);   // The opacity 

You can change the color by style

lv_style_set_text_color(&style_obj, lv_color_hex(0xf7b37b));    // Shared styles 
lv_obj_set_style_text_color(label, lv_color_hex(0xf7b37b), 0);    // Local style 

You can recolor some parts of the text

explain ：#0000ff Re-color#： Color value ：0x0000ff, Change the text ：Re-color

lv_label_set_recolor(label, true);
lv_label_set_text(label, "#0000ff Re-color# #ff00ff words# #ff0000 of a# label");

Text selection

If in lv_conf.h Open in LV_LABEL_TEXT_SELECTION ( Default on ), You can select part of the text . This is with us PC Selecting text with the mouse is similar , But this effect can only be in the text box (lv_textarea) To realize .Label You can only manually select the text of the specified range in advance

lv_label_get_text_selection_start(label, start_char_index);
lv_label_get_text_selection_start(label, end_char_index);

lv_label_set_text_sel_start(label, 1);
lv_label_set_text_sel_end(label, 6);

Built in icon

  Show icons directly

lv_label_set_text(my_label, LV_SYMBOL_OK);

Use with strings

lv_label_set_text(my_label, LV_SYMBOL_OK "Apply");

Many icons together

lv_label_set_text(my_label, LV_SYMBOL_OK LV_SYMBOL_WIFI LV_SYMBOL_PLAY);

event

Label Input events are not received by default , If we want to set the style or event of input type, it will not take effect , It needs to be opened LV_OBJ_FLAG_CLICKABLE

lv_obj_add_flag(label, LV_OBJ_FLAG_CLICKABLE);
lv_obj_add_event_cb(label, function, LV_EVENT_ALL, 0);