Button（按钮） (lv_btn)

Overview

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Buttons have no new features compared to the Base object. They are usuful for semantic purposes and have slightly different default settings.

Buttons, by default, differ from Base object in the following ways:

• Not scrollable

• Added to the default group

• Default height and width set to LV_SIZE_CONTENT

与 基础对象 相比，按钮没有新功能。 它们可用于语义目的，并且默认设置略有不同。

默认情况下，按钮在以下方面与基础对象不同：

• 不可滚动

• 添加到默认组

• 默认高度和宽度设置为 LV_SIZE_CONTENT

Parts and Styles（零件和样式）

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• LV_PART_MAIN The background of the button. Uses the typical background style properties.

• LV_PART_MAIN 按钮的背景。使用典型的背景样式属性。

Usage（用法）

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There are no new features compared to Base object.

与 基础对象 相比，没有新功能。

Events（事件）

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• LV_EVENT_VALUE_CHANGED when the LV_OBJ_FLAG_CHECKABLE flag is enabled and the object is clicked. The event happens on transition to/from the checked state.

Learn more about Events.

• 如果打开了 LV_OBJ_FLAG_CHECKABLE ，当对象被点击时有选中切换(Toggle)状态的效果，并且可以在 LV_EVENT_VALUE_CHANGED 事件类型中处理事件。

详细了解 事件。

Keys（按键）

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Note that the state of LV_KEY_ENTER is translated to LV_EVENT_PRESSED/PRESSING/RELEASED etc.

See the events of the Base object too.

Learn more about Keys.

请注意，LV_KEY_ENTER 的状态被转换为 LV_EVENT_PRESSED/PRESSING/RELEASED 等。

参见 基础对象 的事件。

了解有关 Keys 的更多信息。

Example

Simple Buttons

C code  

 GitHub

#include "../../lv_examples.h"
#if LV_USE_BTN && 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_btn_1(void)
{
    lv_obj_t * label;

    lv_obj_t * btn1 = lv_btn_create(lv_scr_act());
    lv_obj_add_event_cb(btn1, event_handler, LV_EVENT_ALL, NULL);
    lv_obj_align(btn1, LV_ALIGN_CENTER, 0, -40);

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

    lv_obj_t * btn2 = lv_btn_create(lv_scr_act());
    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

MicroPython code  

 GitHub Simulator

def event_handler(evt):
    code = evt.get_code()

    if code == lv.EVENT.CLICKED:
            print("Clicked event seen")
    elif code == lv.EVENT.VALUE_CHANGED:
        print("Value changed seen")
        
# create a simple button
btn1 = lv.btn(lv.scr_act())

# attach the callback
btn1.add_event_cb(event_handler,lv.EVENT.ALL, None)

btn1.align(lv.ALIGN.CENTER,0,-40)
label=lv.label(btn1)
label.set_text("Button")

# create a toggle button
btn2 = lv.btn(lv.scr_act())

# attach the callback
#btn2.add_event_cb(event_handler,lv.EVENT.VALUE_CHANGED,None)
btn2.add_event_cb(event_handler,lv.EVENT.ALL, None)

btn2.align(lv.ALIGN.CENTER,0,40)
btn2.add_flag(lv.obj.FLAG.CHECKABLE)
btn2.set_height(lv.SIZE.CONTENT)

label=lv.label(btn2)
label.set_text("Toggle")
label.center()

---

Styling buttons

C code  

 GitHub

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

/**
 * Style a button from scratch
 */
void lv_example_btn_2(void)
{
    /*Init the style for the default state*/
    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_ofs_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);

    /*Init the pressed style*/
    static lv_style_t style_pr;
    lv_style_init(&style_pr);

    /*Add a large outline when pressed*/
    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_ofs_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));

    /*Add a transition to the outline*/
    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_btn_create(lv_scr_act());
    lv_obj_remove_style_all(btn1);                          /*Remove the style coming from the theme*/
    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

MicroPython code  

 GitHub Simulator

#
# Style a button from scratch
#

# Init the style for the default state
style = lv.style_t()
style.init()

style.set_radius(3)

style.set_bg_opa(lv.OPA.COVER)
style.set_bg_color(lv.palette_main(lv.PALETTE.BLUE))
style.set_bg_grad_color(lv.palette_darken(lv.PALETTE.BLUE, 2))
style.set_bg_grad_dir(lv.GRAD_DIR.VER)

style.set_border_opa(lv.OPA._40)
style.set_border_width(2)
style.set_border_color(lv.palette_main(lv.PALETTE.GREY))

style.set_shadow_width(8)
style.set_shadow_color(lv.palette_main(lv.PALETTE.GREY))
style.set_shadow_ofs_y(8)

style.set_outline_opa(lv.OPA.COVER)
style.set_outline_color(lv.palette_main(lv.PALETTE.BLUE))

style.set_text_color(lv.color_white())
style.set_pad_all(10)

# Init the pressed style
style_pr = lv.style_t()
style_pr.init()

# Add a large outline when pressed
style_pr.set_outline_width(30)
style_pr.set_outline_opa(lv.OPA.TRANSP)

style_pr.set_translate_y(5)
style_pr.set_shadow_ofs_y(3)
style_pr.set_bg_color(lv.palette_darken(lv.PALETTE.BLUE, 2))
style_pr.set_bg_grad_color(lv.palette_darken(lv.PALETTE.BLUE, 4))

# Add a transition to the outline
trans = lv.style_transition_dsc_t()
props = [lv.STYLE.OUTLINE_WIDTH, lv.STYLE.OUTLINE_OPA, 0]
trans.init(props, lv.anim_t.path_linear, 300, 0, None)

style_pr.set_transition(trans)

btn1 = lv.btn(lv.scr_act())
btn1.remove_style_all()                          # Remove the style coming from the theme
btn1.add_style(style, 0)
btn1.add_style(style_pr, lv.STATE.PRESSED)
btn1.set_size(lv.SIZE.CONTENT, lv.SIZE.CONTENT)
btn1.center()

label = lv.label(btn1)
label.set_text("Button")
label.center()

---

Gummy button

C code  

 GitHub

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

/**
 * Create a style transition on a button to act like a gum when clicked
 */
void lv_example_btn_3(void)
{
    /*Properties to transition*/
    static lv_style_prop_t props[] = {
            LV_STYLE_TRANSFORM_WIDTH, LV_STYLE_TRANSFORM_HEIGHT, LV_STYLE_TEXT_LETTER_SPACE, 0
    };

    /*Transition descriptor when going back to the default state.
     *Add some delay to be sure the press transition is visible even if the press was very short*/
    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);

    /*Transition descriptor when going to pressed state.
     *No delay, go to presses state immediately*/
    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);

    /*Add only the new transition to he default state*/
    static lv_style_t style_def;
    lv_style_init(&style_def);
    lv_style_set_transition(&style_def, &transition_dsc_def);

    /*Add the transition and some transformation to the presses state.*/
    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_btn_create(lv_scr_act());
    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

MicroPython code  

 GitHub Simulator

#
# Create a style transition on a button to act like a gum when clicked
#

# Properties to transition
props = [lv.STYLE.TRANSFORM_WIDTH, lv.STYLE.TRANSFORM_HEIGHT, lv.STYLE.TEXT_LETTER_SPACE, 0]

# Transition descriptor when going back to the default state.
# Add some delay to be sure the press transition is visible even if the press was very short*/
transition_dsc_def = lv.style_transition_dsc_t()
transition_dsc_def.init(props, lv.anim_t.path_overshoot, 250, 100, None)

# Transition descriptor when going to pressed state.
# No delay, go to pressed state immediately
transition_dsc_pr = lv.style_transition_dsc_t()
transition_dsc_pr.init(props, lv.anim_t.path_ease_in_out, 250, 0, None)

# Add only the new transition to the default state
style_def = lv.style_t()
style_def.init()
style_def.set_transition(transition_dsc_def)

# Add the transition and some transformation to the presses state.
style_pr = lv.style_t()
style_pr.init()
style_pr.set_transform_width(10)
style_pr.set_transform_height(-10)
style_pr.set_text_letter_space(10)
style_pr.set_transition(transition_dsc_pr)

btn1 = lv.btn(lv.scr_act())
btn1.align(lv.ALIGN.CENTER, 0, -80)
btn1.add_style(style_pr, lv.STATE.PRESSED)
btn1.add_style(style_def, 0)

label = lv.label(btn1)
label.set_text("Gum")

---

API

Functions

lv_obj_t *lv_btn_create(lv_obj_t *parent)

Create a button object

参数

parent -- pointer to an object, it will be the parent of the new button

返回

pointer to the created button

Variables

const lv_obj_class_t lv_btn_class

struct lv_btn_t

Public Members

lv_obj_t obj