littlevgl按键屏幕切换流程例程

下面是一个使用 LittlevGL 库的按键屏幕切换流程的示例程序：

#include <lvgl/lvgl.h>

/* 定义屏幕 ID */
enum {
    SCREEN_1,
    SCREEN_2,
    SCREEN_3
};

/* 定义控件指针 */
static lv_obj_t *btn1;
static lv_obj_t *btn2;
static lv_obj_t *btn3;
static lv_obj_t *label1;
static lv_obj_t *label2;
static lv_obj_t *label3;

/* 按钮回调函数 */
static void btn_click_action(lv_obj_t *obj, lv_event_t event)
{
    if (event == LV_EVENT_CLICKED) {
        /* 根据按钮 ID 切换到相应屏幕 */
        if (obj == btn1) {
            lv_scr_load(SCREEN_1);
        } else if (obj == btn2) {
            lv_scr_load(SCREEN_2);
        } else if (obj == btn3) {
            lv_scr_load(SCREEN_3);
        }
    }
}

/* 创建屏幕和控件 */
void create_screen(void)
{
    /* 创建屏幕 1 */
    lv_obj_t *scr1 = lv_obj_create(NULL, NULL);
    lv_scr_load(scr1);

    /* 创建控件 */
    label1 = lv_label_create(scr1, NULL);
    lv_label_set_text(label1, "Screen 1");
    lv_obj_align(label1, NULL, LV_ALIGN_CENTER, 0, 0);

    /* 创建屏幕 2 */
    lv_obj_t *scr2 = lv_obj_create(NULL, NULL);

    /* 创建控件 */
    label2 = lv_label_create(scr2, NULL);
    lv_label_set_text(label2, "Screen 2");
    lv_obj_align(label2, NULL, LV_ALIGN_CENTER, 0, 0);

    /* 创建屏幕 3 */
    lv_obj_t *scr3 = lv_obj_create(NULL, NULL);

    /* 创建控件 */
    label3 = lv_label_create(scr3, NULL);
    lv_label_set_text(label3, "Screen 3");
    lv_obj_align(label3, NULL, LV_ALIGN_CENTER, 0, 0);

    /* 创建按钮 */
    btn1 = lv_btn_create(scr1, NULL);
    lv_obj_set_event_cb(btn1, btn_click_action);
    lv_obj_align(btn1, NULL, LV_ALIGN_IN_BOTTOM_MID, 0, -20);
    lv_obj_t *label_btn1 = lv_label_create(btn1, NULL);
    lv_label_set_text(label_btn1, "Go to Screen 2");

    btn2 = lv_btn_create(scr2, NULL);
    lv_obj_set_event_cb(btn2, btn_click_action);
    lv_obj_align(btn2, NULL, LV_ALIGN_IN_BOTTOM_MID, 0, -20);
    lv_obj_t *label_btn2 = lv_label_create(btn2, NULL);
    lv_label_set_text(label_btn2, "Go to Screen 3");

    btn3 = lv_btn_create(scr3, NULL);
    lv_obj_set_event_cb(btn3, btn_click_action);
    lv_obj_align(btn3, NULL, LV_ALIGN_IN_BOTTOM_MID, 0, -20);
    lv_obj_t *label_btn3 = lv_label_create(btn3, NULL);
    lv_label_set_text(label_btn3, "Go to Screen 1");
}

int main(void)
{
    lv_init();

    /* 创建屏幕和控件 */
    create_screen();

    while (1) {
        lv_task_handler();
    }

    return 0;
}

在这个例程中，我们创建了三个屏幕和三个按钮。每个按钮都关联到一个回调函数，当用户点击按钮时，通过调用 `lv_scr_load()` 函数来切换到相应的屏幕。在每个屏幕中，我们创建了一个标签控件来显示屏幕内容。