mirror of
https://github.com/lvgl/lvgl.git
synced 2026-05-11 05:37:37 +08:00
Mutahhar Mustafa Khan
90 lines
3.2 KiB
C
90 lines
3.2 KiB
C
#include "../lv_examples.h"
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#if LV_BUILD_EXAMPLES && LV_USE_FLEX
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static void scroll_event_cb(lv_event_t * e)
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{
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lv_obj_t * cont = lv_event_get_target_obj(e);
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lv_area_t cont_a;
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lv_obj_get_coords(cont, &cont_a);
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int32_t cont_y_center = cont_a.y1 + lv_area_get_height(&cont_a) / 2;
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int32_t r = lv_obj_get_height(cont) * 7 / 10;
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int32_t i;
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int32_t child_cnt = (int32_t)lv_obj_get_child_count(cont);
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for(i = 0; i < child_cnt; i++) {
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lv_obj_t * child = lv_obj_get_child(cont, i);
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lv_area_t child_a;
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lv_obj_get_coords(child, &child_a);
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int32_t child_y_center = child_a.y1 + lv_area_get_height(&child_a) / 2;
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int32_t diff_y = child_y_center - cont_y_center;
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diff_y = LV_ABS(diff_y);
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/*Get the x of diff_y on a circle.*/
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int32_t x;
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/*If diff_y is out of the circle use the last point of the circle (the radius)*/
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if(diff_y >= r) {
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x = r;
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}
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else {
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/*Use Pythagoras theorem to get x from radius and y*/
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uint32_t x_sqr = r * r - diff_y * diff_y;
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lv_sqrt_res_t res;
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lv_sqrt(x_sqr, &res, 0x8000); /*Use lvgl's built in sqrt root function*/
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x = r - res.i;
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}
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/*Translate the item by the calculated X coordinate*/
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lv_obj_set_style_translate_x(child, x, 0);
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/*Use some opacity with larger translations*/
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lv_opa_t opa = (lv_opa_t)lv_map(x, 0, r, LV_OPA_TRANSP, LV_OPA_COVER);
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lv_obj_set_style_opa(child, LV_OPA_COVER - opa, 0);
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}
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}
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/**
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* @title Circular scroll translate effect
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* @brief Bow a column of buttons along a circle while they scroll past center.
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*
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* A 200x200 container is given `LV_RADIUS_CIRCLE`, `clip_corner`,
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* `LV_FLEX_FLOW_COLUMN`, `LV_SCROLL_SNAP_CENTER` on Y, and
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* `LV_SCROLLBAR_MODE_OFF`. Twenty full-width buttons are scrolled vertically.
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* An `LV_EVENT_SCROLL` callback computes each child's vertical offset from
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* the container center, maps it onto a circle with radius 7/10 of the height
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* via `lv_sqrt`, writes the result to `translate_x`, and fades children with
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* larger offsets toward `LV_OPA_TRANSP`.
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*/
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void lv_example_scroll_6(void)
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{
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lv_obj_t * cont = lv_obj_create(lv_screen_active());
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lv_obj_set_size(cont, 200, 200);
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lv_obj_center(cont);
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lv_obj_set_flex_flow(cont, LV_FLEX_FLOW_COLUMN);
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lv_obj_add_event_cb(cont, scroll_event_cb, LV_EVENT_SCROLL, NULL);
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lv_obj_set_style_radius(cont, LV_RADIUS_CIRCLE, 0);
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lv_obj_set_style_clip_corner(cont, true, 0);
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lv_obj_set_scroll_dir(cont, LV_DIR_VER);
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lv_obj_set_scroll_snap_y(cont, LV_SCROLL_SNAP_CENTER);
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lv_obj_set_scrollbar_mode(cont, LV_SCROLLBAR_MODE_OFF);
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uint32_t i;
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for(i = 0; i < 20; i++) {
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lv_obj_t * btn = lv_button_create(cont);
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lv_obj_set_width(btn, lv_pct(100));
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lv_obj_t * label = lv_label_create(btn);
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lv_label_set_text_fmt(label, "Button %" LV_PRIu32, i);
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}
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/*Update the buttons position manually for first*/
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lv_obj_send_event(cont, LV_EVENT_SCROLL, NULL);
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/*Be sure the fist button is in the middle*/
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lv_obj_scroll_to_view(lv_obj_get_child(cont, 0), LV_ANIM_OFF);
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}
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#endif
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