1 #include "../lv_examples.h"
2 #if LV_BUILD_EXAMPLES && LV_USE_FLEX
3
scroll_event_cb(lv_event_t * e)4 static void scroll_event_cb(lv_event_t * e)
5 {
6 lv_obj_t * cont = lv_event_get_target(e);
7
8 lv_area_t cont_a;
9 lv_obj_get_coords(cont, &cont_a);
10 lv_coord_t cont_y_center = cont_a.y1 + lv_area_get_height(&cont_a) / 2;
11
12 lv_coord_t r = lv_obj_get_height(cont) * 7 / 10;
13 uint32_t i;
14 uint32_t child_cnt = lv_obj_get_child_cnt(cont);
15 for(i = 0; i < child_cnt; i++) {
16 lv_obj_t * child = lv_obj_get_child(cont, i);
17 lv_area_t child_a;
18 lv_obj_get_coords(child, &child_a);
19
20 lv_coord_t child_y_center = child_a.y1 + lv_area_get_height(&child_a) / 2;
21
22 lv_coord_t diff_y = child_y_center - cont_y_center;
23 diff_y = LV_ABS(diff_y);
24
25 /*Get the x of diff_y on a circle.*/
26 lv_coord_t x;
27 /*If diff_y is out of the circle use the last point of the circle (the radius)*/
28 if(diff_y >= r) {
29 x = r;
30 }
31 else {
32 /*Use Pythagoras theorem to get x from radius and y*/
33 uint32_t x_sqr = r * r - diff_y * diff_y;
34 lv_sqrt_res_t res;
35 lv_sqrt(x_sqr, &res, 0x8000); /*Use lvgl's built in sqrt root function*/
36 x = r - res.i;
37 }
38
39 /*Translate the item by the calculated X coordinate*/
40 lv_obj_set_style_translate_x(child, x, 0);
41
42 /*Use some opacity with larger translations*/
43 lv_opa_t opa = lv_map(x, 0, r, LV_OPA_TRANSP, LV_OPA_COVER);
44 lv_obj_set_style_opa(child, LV_OPA_COVER - opa, 0);
45 }
46 }
47
48 /**
49 * Translate the object as they scroll
50 */
lv_example_scroll_6(void)51 void lv_example_scroll_6(void)
52 {
53 lv_obj_t * cont = lv_obj_create(lv_scr_act());
54 lv_obj_set_size(cont, 200, 200);
55 lv_obj_center(cont);
56 lv_obj_set_flex_flow(cont, LV_FLEX_FLOW_COLUMN);
57 lv_obj_add_event_cb(cont, scroll_event_cb, LV_EVENT_SCROLL, NULL);
58 lv_obj_set_style_radius(cont, LV_RADIUS_CIRCLE, 0);
59 lv_obj_set_style_clip_corner(cont, true, 0);
60 lv_obj_set_scroll_dir(cont, LV_DIR_VER);
61 lv_obj_set_scroll_snap_y(cont, LV_SCROLL_SNAP_CENTER);
62 lv_obj_set_scrollbar_mode(cont, LV_SCROLLBAR_MODE_OFF);
63
64 uint32_t i;
65 for(i = 0; i < 20; i++) {
66 lv_obj_t * btn = lv_btn_create(cont);
67 lv_obj_set_width(btn, lv_pct(100));
68
69 lv_obj_t * label = lv_label_create(btn);
70 lv_label_set_text_fmt(label, "Button %"LV_PRIu32, i);
71 }
72
73 /*Update the buttons position manually for first*/
74 lv_event_send(cont, LV_EVENT_SCROLL, NULL);
75
76 /*Be sure the fist button is in the middle*/
77 lv_obj_scroll_to_view(lv_obj_get_child(cont, 0), LV_ANIM_OFF);
78 }
79
80 #endif
81
