一、前言

上节我们主要了解了lvgl以及在Windows上搭建基于wsl2和vscode的lvgl模拟运行环境，其demo程序已经成功运行起来，接下来我们根据其框架将lvgl的一些常用控件demo和示例提取出来在模拟环境下都跑一跑，熟悉一下对应的接口和比较常用的label、button、slider三个控件。

二、常见控件示例demo模拟环境运行及接口熟悉

如果lv_port_pc_vscode相关内容无法修改，则很可能是目录和文件权限不对，使用了root用户进行下载处理，这时只需要修改权限即可：

sudo chown user lv_port_pc_vscode/ -R
sudo chgrp user lv_port_pc_vscode/ -R
//user就是你当前使用的用户，可以使用ls -alh查看文件夹权限

（重要）如何修改示例main函数测试各种示例

备份原有的main.c，然后修改main.c，将其原来lv_demo_widgets();修改为label相关的函数，主要是lvgl/examples/widgets/label/下的label的示例：

/**
 * @file main
 *
 */

/*********************
 *      INCLUDES
 *********************/
#define _DEFAULT_SOURCE /* needed for usleep() */
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include "lvgl/lvgl.h"
#include "lvgl/examples/lv_examples.h"
#include "lvgl/demos/lv_demos.h"

/*********************
 *      DEFINES
 *********************/

/**********************
 *      TYPEDEFS
 **********************/

/**********************
 *  STATIC PROTOTYPES
 **********************/
static lv_display_t * hal_init(int32_t w, int32_t h);

/**********************
 *  STATIC VARIABLES
 **********************/

/**********************
 *      MACROS
 **********************/

/**********************
 *   GLOBAL FUNCTIONS
 **********************/

/*********************
 *      DEFINES
 *********************/

/**********************
 *      TYPEDEFS
 **********************/

/**********************
 *      VARIABLES
 **********************/

/**********************
 *  STATIC PROTOTYPES
 **********************/

/**********************
 *   GLOBAL FUNCTIONS
 **********************/

int main(int argc, char **argv)
{
  (void)argc; /*Unused*/
  (void)argv; /*Unused*/

  /*初始化LVGL*/
  lv_init();

  /*初始化硬件抽象层 (显示屏, 输入设备, 滴答设备) */
  hal_init(480, 272);

  lv_example_label_1();
  //lv_example_label_2();
  //lv_example_label_3();
  //lv_example_label_4();
  //lv_example_label_5();

  while(1) {
    /* 定期调用 lv_task 回掉.
     * 它也可以在定时器中断或操作系统任务中完成 */
    lv_timer_handler();
    usleep(5 * 1000);
  }

  return 0;
}

/**********************
 *   STATIC FUNCTIONS
 **********************/

/**
 * 初始化 LVGL 图形的硬件抽象层 (HAL) 库
 */
static lv_display_t * hal_init(int32_t w, int32_t h)
{
    //创建默认group
  lv_group_set_default(lv_group_create());

    //创建显示窗口
  lv_display_t * disp = lv_sdl_window_create(w, h);

    //创建鼠标
  lv_indev_t * mouse = lv_sdl_mouse_create();
  lv_indev_set_group(mouse, lv_group_get_default());
  lv_indev_set_display(mouse, disp);
  lv_display_set_default(disp);

    //声明图像文件
  LV_IMAGE_DECLARE(mouse_cursor_icon);
  lv_obj_t * cursor_obj;
    //为光标创建图像对象
  cursor_obj = lv_image_create(lv_screen_active());
    //设置源图像
  lv_image_set_src(cursor_obj, &mouse_cursor_icon);
    //将图像对象连接到驱动程序
  lv_indev_set_cursor(mouse, cursor_obj);

    //创建鼠标滚轮并绑定
  lv_indev_t * mousewheel = lv_sdl_mousewheel_create();
  lv_indev_set_display(mousewheel, disp);
  lv_indev_set_group(mousewheel, lv_group_get_default());

    //创建键盘
  lv_indev_t * kb = lv_sdl_keyboard_create();
  lv_indev_set_display(kb, disp);
  lv_indev_set_group(kb, lv_group_get_default());

  return disp;
}

之后在之前的build目录下重新make后运行main程序即可：

cd lv_port_pc_vscode/build
make
../bin/main

1、label示例

1.1、label示例1（标签基础示例）

#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_BUILD_EXAMPLES

/**
 * 显示换行、重新着色、行对齐和文本滚动
 */
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);     /*长行换行*/
    lv_label_set_text(label1, "Recolor is not supported for v9 now.");
    lv_obj_set_width(label1, 150);  /*设置较小的宽度以使线条换行*/
    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);     /*循环滚动*/
    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

展示了：

• 静态的切换长内容的label，设置更小的行宽度以及显示位置、设置内容等基本的方法；
• 滚动显示内容的label。
  

1.2、label示例2（标签带阴影效果）

#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_BUILD_EXAMPLES

/**
 * 创建假文本阴影
 */
void lv_example_label_2(void)
{
    /*创建阴影样式*/
    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());

    /*首先为阴影创建一个标签（在背景中）*/
    lv_obj_t * shadow_label = lv_label_create(lv_screen_active());
    lv_obj_add_style(shadow_label, &style_shadow, 0);

    /*创建主标签*/
    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.");

    /*为阴影标签设置相同的文本*/
    lv_label_set_text(shadow_label, lv_label_get_text(main_label));

    /*定位主标签*/
    lv_obj_align(main_label, LV_ALIGN_CENTER, 0, 0);

    /*将第二个标签向右下方移动 2 个像素*/
    lv_obj_align_to(shadow_label, main_label, LV_ALIGN_TOP_LEFT, 2, 2);
}

#endif

展示：

• 带阴影的label，实际上是两个label，一个label为主，用于显示内容，一个label专门用来作为背景稍微偏移一下实现阴影效果，组合起来就是带有阴影样式的label
  

1.3、label示例3（标签字体设置）

#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

/**
 * 显示混合 LTR、RTL 和中文标签
 */
void lv_example_label_3(void)
{
    //LTR标签（左对齐）
    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);

    //RTL标签（右对齐）
    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);

    //中文标签
    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

这里有一些宏默认是0，需要跳转到lv_conf.h中去设置1，其中lv_obj_set_style_text_font这里我设置为了目前的lv_font_montserrat_16，但是项目默认使用的字体是lv_font_montserrat_14，所以要么把这里改为lv_font_montserrat_14，要么就在lv_conf.h中修改：

#define LV_FONT_DEFAULT &lv_font_montserrat_16

且

#define LV_FONT_MONTSERRAT_14 0
#define LV_FONT_MONTSERRAT_16 1

之后重新make后运行main程序：

所以这里label主要展示：

• 设置label文字内容以及设置文字不同字体
• 设置内容对齐方式
  

1.4、label示例4（目前未完成）

#include "../../lv_examples.h"
//TODO
#if LV_USE_LABEL && LV_USE_CANVAS && LV_BUILD_EXAMPLES && LV_DRAW_SW_COMPLEX && 0

#define MASK_WIDTH 100
#define MASK_HEIGHT 45

static void add_mask_event_cb(lv_event_t * e)
{
    static lv_draw_mask_map_param_t m;
    static int16_t mask_id;

    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t * obj = lv_event_get_target(e);
    lv_opa_t * mask_map = lv_event_get_user_data(e);
    if(code == LV_EVENT_COVER_CHECK) {
        lv_event_set_cover_res(e, LV_COVER_RES_MASKED);
    }
    else if(code == LV_EVENT_DRAW_MAIN_BEGIN) {
        lv_draw_mask_map_init(&m, &obj->coords, mask_map);
        mask_id = lv_draw_mask_add(&m, NULL);

    }
    else if(code == LV_EVENT_DRAW_MAIN_END) {
        lv_draw_mask_free_param(&m);
        lv_draw_mask_remove_id(mask_id);
    }
}

/**
 * Draw label with gradient color
 */
void lv_example_label_4(void)
{
    /* Create the mask of a text by drawing it to a canvas*/
    static lv_color_t mask_map[MASK_WIDTH * MASK_HEIGHT];

    /*Create a "8 bit alpha" canvas and clear it*/
    lv_obj_t * canvas = lv_canvas_create(lv_screen_active());
    lv_canvas_set_buffer(canvas, mask_map, MASK_WIDTH, MASK_HEIGHT, LV_COLOR_FORMAT_NATIVE);
    lv_canvas_fill_bg(canvas, lv_color_black(), LV_OPA_TRANSP);

    /*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 = "Text with gradient";
    lv_canvas_draw_text(canvas, 5, 5, MASK_WIDTH, &label_dsc);

    /*The mask is reads the canvas is not required anymore*/
    lv_obj_delete(canvas);

    /*Convert the mask to A8*/
    uint32_t i;
    uint8_t * mask8 = (uint8_t *) mask_map;
    lv_color_t * mask_c = mask_map;
    for(i = 0; i < MASK_WIDTH * MASK_HEIGHT; i++) {
        mask8[i] = lv_color_brightness(mask_c[i]);
    }

    /* 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_add_event_cb(grad, add_mask_event_cb, LV_EVENT_ALL, mask_map);
}

#endif

示例4显示TODO，明显还没有完成，应该会随着后续升级完成，强行去掉0这个宏的话编译也会报错，这里看应该是想实现绘制画布来做label的一些功能，后续升级版本后再看看，可以订阅官方的邮箱来了解其更新情况。

1.5、label示例5（标签内容滚动动画效果）

#include "../../lv_examples.h"
#if LV_USE_LABEL && LV_BUILD_EXAMPLES

/**
 * 显示使用“LV_LABEL_LONG_SCROLL_CIRCULAR”自定义标签的圆形滚动动画长模式
 */
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);           /*等待 1 秒开始第一个滚动*/
    lv_anim_set_repeat_delay(&animation_template,
                             3000);    /*标签滚动回初始位置后重复滚动 3 秒*/

    /*使用动画模板初始化标签样式*/
    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);      /*循环滚动*/
    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);           /*将样式添加到标签*/
}

#endif

展示：

• 延迟一秒后开始滚动，滚动三秒后回到初始状态
• 实现label滚动效果的延迟处理

这种应该场景应该不是很多，所以基本上前三种示例满足大部分场景了。

2、button示例

button目前有三个示例。

2.1、button示例1（基础按钮和切换按钮）

#include "../../lv_examples.h"
#if LV_USE_BUTTON && LV_BUILD_EXAMPLES

static void event_handler(lv_event_t * e)
{
    lv_event_code_t code = lv_event_get_code(e);

    if(code == LV_EVENT_CLICKED) {
        LV_LOG_USER("Clicked");
    }
    else if(code == LV_EVENT_VALUE_CHANGED) {
        LV_LOG_USER("Toggled");
    }
}

void lv_example_button_1(void)
{
    lv_obj_t * label;

    lv_obj_t * btn1 = lv_button_create(lv_screen_active());
    lv_obj_add_event_cb(btn1, event_handler, LV_EVENT_ALL, NULL);
    lv_obj_align(btn1, LV_ALIGN_CENTER, 0, -40);
    lv_obj_remove_flag(btn1, LV_OBJ_FLAG_PRESS_LOCK);

    label = lv_label_create(btn1);
    lv_label_set_text(label, "Button");
    lv_obj_center(label);

    lv_obj_t * btn2 = lv_button_create(lv_screen_active());
    lv_obj_add_event_cb(btn2, event_handler, LV_EVENT_ALL, NULL);
    lv_obj_align(btn2, LV_ALIGN_CENTER, 0, 40);
    lv_obj_add_flag(btn2, LV_OBJ_FLAG_CHECKABLE);
    lv_obj_set_height(btn2, LV_SIZE_CONTENT);

    label = lv_label_create(btn2);
    lv_label_set_text(label, "Toggle");
    lv_obj_center(label);

}
#endif

展示：

• 如何创建button或者Toggle
• button或者toggle上添加文本内容通过label来实现
• toggle除了button的点击事件完，还有对应的切换事件，根据切换状态会更改对应颜色
• 并且根据对应触发的事件可以在回调中做进一步处理
  

2.2、button示例2（按钮阴影和按钮点击后样式变化）

#include "../../lv_examples.h"
#if LV_USE_BUTTON && LV_BUILD_EXAMPLES

/**
 * 从头开始设计按钮
 */
void lv_example_button_2(void)
{
    /*初始化默认状态的样式*/
    static lv_style_t style;
    lv_style_init(&style);

    lv_style_set_radius(&style, 3);

    lv_style_set_bg_opa(&style, LV_OPA_100);
    lv_style_set_bg_color(&style, lv_palette_main(LV_PALETTE_BLUE));
    lv_style_set_bg_grad_color(&style, lv_palette_darken(LV_PALETTE_BLUE, 2));
    lv_style_set_bg_grad_dir(&style, LV_GRAD_DIR_VER);

    lv_style_set_border_opa(&style, LV_OPA_40);
    lv_style_set_border_width(&style, 2);
    lv_style_set_border_color(&style, lv_palette_main(LV_PALETTE_GREY));

    lv_style_set_shadow_width(&style, 8);
    lv_style_set_shadow_color(&style, lv_palette_main(LV_PALETTE_GREY));
    lv_style_set_shadow_offset_y(&style, 8);

    lv_style_set_outline_opa(&style, LV_OPA_COVER);
    lv_style_set_outline_color(&style, lv_palette_main(LV_PALETTE_BLUE));

    lv_style_set_text_color(&style, lv_color_white());
    lv_style_set_pad_all(&style, 10);

    /*初始化按下的样式*/
    static lv_style_t style_pr;
    lv_style_init(&style_pr);

    /*按下时添加大轮廓*/
    lv_style_set_outline_width(&style_pr, 30);
    lv_style_set_outline_opa(&style_pr, LV_OPA_TRANSP);

    lv_style_set_translate_y(&style_pr, 5);
    lv_style_set_shadow_offset_y(&style_pr, 3);
    lv_style_set_bg_color(&style_pr, lv_palette_darken(LV_PALETTE_BLUE, 2));
    lv_style_set_bg_grad_color(&style_pr, lv_palette_darken(LV_PALETTE_BLUE, 4));

    /*向轮廓添加过渡*/
    static lv_style_transition_dsc_t trans;
    static lv_style_prop_t props[] = {LV_STYLE_OUTLINE_WIDTH, LV_STYLE_OUTLINE_OPA, 0};
    lv_style_transition_dsc_init(&trans, props, lv_anim_path_linear, 300, 0, NULL);

    lv_style_set_transition(&style_pr, &trans);

    lv_obj_t * btn1 = lv_button_create(lv_screen_active());
    lv_obj_remove_style_all(btn1);                          /*删除来自主题的样式*/
    lv_obj_add_style(btn1, &style, 0);
    lv_obj_add_style(btn1, &style_pr, LV_STATE_PRESSED);
    lv_obj_set_size(btn1, LV_SIZE_CONTENT, LV_SIZE_CONTENT);
    lv_obj_center(btn1);

    lv_obj_t * label = lv_label_create(btn1);
    lv_label_set_text(label, "Button");
    lv_obj_center(label);
}
#endif

展示：

• button的初始化样式，比如阴影
• 设置button点击后的样式，使其更加酷炫
  

2.3、button示例3（按钮样式过渡动画效果）

#include "../../lv_examples.h"
#if LV_BUILD_EXAMPLES && LV_USE_BUTTON

/**
 * 在按钮上创建样式过渡，单击时就像口香糖一样
 */
void lv_example_button_3(void)
{
    /*要转换的属性*/
    static lv_style_prop_t props[] = {
        LV_STYLE_TRANSFORM_WIDTH, LV_STYLE_TRANSFORM_HEIGHT, LV_STYLE_TEXT_LETTER_SPACE, 0
    };

    /*返回默认状态时的转换描述符。
     *添加一些延迟以确保即使按下时间很短，按下过渡也可见*/
    static lv_style_transition_dsc_t transition_dsc_def;
    lv_style_transition_dsc_init(&transition_dsc_def, props, lv_anim_path_overshoot, 250, 100, NULL);

    /*进入按下状态时的转换描述符。
     *无延迟，立即进入按下状态*/
    static lv_style_transition_dsc_t transition_dsc_pr;
    lv_style_transition_dsc_init(&transition_dsc_pr, props, lv_anim_path_ease_in_out, 250, 0, NULL);

    /*仅将新的转换添加到默认状态*/
    static lv_style_t style_def;
    lv_style_init(&style_def);
    lv_style_set_transition(&style_def, &transition_dsc_def);

    /*向按压状态添加过渡和一些转换。*/
    static lv_style_t style_pr;
    lv_style_init(&style_pr);
    lv_style_set_transform_width(&style_pr, 10);
    lv_style_set_transform_height(&style_pr, -10);
    lv_style_set_text_letter_space(&style_pr, 10);
    lv_style_set_transition(&style_pr, &transition_dsc_pr);

    lv_obj_t * btn1 = lv_button_create(lv_screen_active());
    lv_obj_align(btn1, LV_ALIGN_CENTER, 0, -80);
    lv_obj_add_style(btn1, &style_pr, LV_STATE_PRESSED);
    lv_obj_add_style(btn1, &style_def, 0);

    lv_obj_t * label = lv_label_create(btn1);
    lv_label_set_text(label, "Gum");
}
#endif

展示：

• 在按钮上创建样式过渡，单击时就像口香糖一样
• 将多种样式融合起来，在点击过程中进行按钮样式过度，使其具备更加动态的显示效果，button点击起来更具备科技感和交互感
  

3、slider示例

3.1、slider示例1（基础滑块）

#include "../../lv_examples.h"
#if LV_USE_SLIDER && LV_BUILD_EXAMPLES

static void slider_event_cb(lv_event_t * e);
static lv_obj_t * slider_label;

/**
 * 带有显示当前值的标签的默认滑块
 */
void lv_example_slider_1(void)
{
    /*在显示屏中央创建一个滑块*/
    lv_obj_t * slider = lv_slider_create(lv_screen_active());
    lv_obj_center(slider);
    lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_VALUE_CHANGED, NULL);

    lv_obj_set_style_anim_duration(slider, 2000, 0);
    /*在滑块下方创建标签*/
    slider_label = lv_label_create(lv_screen_active());
    lv_label_set_text(slider_label, "0%");

    lv_obj_align_to(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
}

static void slider_event_cb(lv_event_t * e)
{
    lv_obj_t * slider = lv_event_get_target(e);
    char buf[8];
    lv_snprintf(buf, sizeof(buf), "%d%%", (int)lv_slider_get_value(slider));
    lv_label_set_text(slider_label, buf);
    lv_obj_align_to(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
}

#endif

展示：

• 带有显示当前值的标签的默认滑块
  

3.2、slider示例2（设置滑块样式）

#include "../../lv_examples.h"
#if LV_USE_SLIDER && LV_BUILD_EXAMPLES

/**
 * 展示如何设置滑块的样式
 */
void lv_example_slider_2(void)
{
    /*创建过渡*/
    static const lv_style_prop_t props[] = {LV_STYLE_BG_COLOR, 0};
    static lv_style_transition_dsc_t transition_dsc;
    lv_style_transition_dsc_init(&transition_dsc, props, lv_anim_path_linear, 300, 0, NULL);

    static lv_style_t style_main;
    static lv_style_t style_indicator;
    static lv_style_t style_knob;
    static lv_style_t style_pressed_color;
    lv_style_init(&style_main);
    lv_style_set_bg_opa(&style_main, LV_OPA_COVER);
    lv_style_set_bg_color(&style_main, lv_color_hex3(0xbbb));
    lv_style_set_radius(&style_main, LV_RADIUS_CIRCLE);
    lv_style_set_pad_ver(&style_main, -2); /*使指标变大*/

    lv_style_init(&style_indicator);
    lv_style_set_bg_opa(&style_indicator, LV_OPA_COVER);
    lv_style_set_bg_color(&style_indicator, lv_palette_main(LV_PALETTE_CYAN));
    lv_style_set_radius(&style_indicator, LV_RADIUS_CIRCLE);
    lv_style_set_transition(&style_indicator, &transition_dsc);

    lv_style_init(&style_knob);
    lv_style_set_bg_opa(&style_knob, LV_OPA_COVER);
    lv_style_set_bg_color(&style_knob, lv_palette_main(LV_PALETTE_CYAN));
    lv_style_set_border_color(&style_knob, lv_palette_darken(LV_PALETTE_CYAN, 3));
    lv_style_set_border_width(&style_knob, 2);
    lv_style_set_radius(&style_knob, LV_RADIUS_CIRCLE);
    lv_style_set_pad_all(&style_knob, 6); /*使旋钮变大*/
    lv_style_set_transition(&style_knob, &transition_dsc);

    lv_style_init(&style_pressed_color);
    lv_style_set_bg_color(&style_pressed_color, lv_palette_darken(LV_PALETTE_CYAN, 2));

    /*创建滑块并添加样式*/
    lv_obj_t * slider = lv_slider_create(lv_screen_active());
    lv_obj_remove_style_all(slider);        /*删除来自主题的样式*/

    lv_obj_add_style(slider, &style_main, LV_PART_MAIN);
    lv_obj_add_style(slider, &style_indicator, LV_PART_INDICATOR);
    lv_obj_add_style(slider, &style_pressed_color, LV_PART_INDICATOR | LV_STATE_PRESSED);
    lv_obj_add_style(slider, &style_knob, LV_PART_KNOB);
    lv_obj_add_style(slider, &style_pressed_color, LV_PART_KNOB | LV_STATE_PRESSED);

    lv_obj_center(slider);
}

#endif

• 展示如何设置滑块的样式。
  

3.3、slider示例3（滑块值样式设置及显示）

#include "../../lv_examples.h"
#if LV_USE_SLIDER && LV_BUILD_EXAMPLES

static void slider_event_cb(lv_event_t * e);

/**
 * 通过展开抽屉按下滑块时显示当前值
 *
 */
void lv_example_slider_3(void)
{
    /*在显示屏中央创建一个滑块*/
    lv_obj_t * slider;
    slider = lv_slider_create(lv_screen_active());
    lv_obj_center(slider);

    lv_slider_set_mode(slider, LV_SLIDER_MODE_RANGE);
    lv_slider_set_value(slider, 70, LV_ANIM_OFF);
    lv_slider_set_left_value(slider, 20, LV_ANIM_OFF);

    lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_ALL, NULL);
    lv_obj_refresh_ext_draw_size(slider);
}

static void slider_event_cb(lv_event_t * e)
{
    lv_event_code_t code = lv_event_get_code(e);
    lv_obj_t * obj = lv_event_get_target(e);

    /*为该值提供一些额外的空间*/
    if(code == LV_EVENT_REFR_EXT_DRAW_SIZE) {
        lv_event_set_ext_draw_size(e, 50);
    }
    else if(code == LV_EVENT_DRAW_MAIN_END) {
        if(!lv_obj_has_state(obj, LV_STATE_PRESSED)) return;

        lv_slider_t * slider = (lv_slider_t *) obj;
        const lv_area_t * indic_area = &slider->bar.indic_area;
        char buf[16];
        lv_snprintf(buf, sizeof(buf), "%d - %d", (int)lv_slider_get_left_value(obj), (int)lv_slider_get_value(obj));

        lv_point_t label_size;
        lv_text_get_size(&label_size, buf, LV_FONT_DEFAULT, 0, 0, LV_COORD_MAX, 0);
        lv_area_t label_area;
        label_area.x1 = 0;
        label_area.x2 = label_size.x - 1;
        label_area.y1 = 0;
        label_area.y2 = label_size.y - 1;

        lv_area_align(indic_area, &label_area, LV_ALIGN_OUT_TOP_MID, 0, -10);

        lv_draw_label_dsc_t label_draw_dsc;
        lv_draw_label_dsc_init(&label_draw_dsc);
        label_draw_dsc.color = lv_color_hex3(0x888);
        label_draw_dsc.text = buf;
        label_draw_dsc.text_local = true;
        lv_layer_t * layer = lv_event_get_layer(e);
        lv_draw_label(layer, &label_draw_dsc, &label_area);
    }
}

#endif

• 展开抽屉按下滑块时显示当前值
  

3.4、slider示例4（滑块方向相反）

#include "../../lv_examples.h"
#if LV_USE_SLIDER && LV_BUILD_EXAMPLES

static void slider_event_cb(lv_event_t * e);
static lv_obj_t * slider_label;

/**
 * 滑块方向相反
 */
void lv_example_slider_4(void)
{
    /*在显示屏中央创建一个滑块*/
    lv_obj_t * slider = lv_slider_create(lv_screen_active());
    lv_obj_center(slider);
    lv_obj_add_event_cb(slider, slider_event_cb, LV_EVENT_VALUE_CHANGED, NULL);
    /*反转滑块的方向*/
    lv_slider_set_range(slider, 100, 0);
    /*在滑块下方创建标签*/
    slider_label = lv_label_create(lv_screen_active());
    lv_label_set_text(slider_label, "0%");

    lv_obj_align_to(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
}

static void slider_event_cb(lv_event_t * e)
{
    lv_obj_t * slider = lv_event_get_target(e);
    char buf[8];
    lv_snprintf(buf, sizeof(buf), "%d%%", (int)lv_slider_get_value(slider));
    lv_label_set_text(slider_label, buf);
    lv_obj_align_to(slider_label, slider, LV_ALIGN_OUT_BOTTOM_MID, 0, 10);
}

#endif

• 滑块方向相反
  

三、最后

基本常用的几个基础控件就先总结到这里，接下来总结一下样式的相关使用。