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ndg/examples/scroll/lv_example_scroll_6.py

69 lines
2.0 KiB
Python

def scroll_event_cb(e):
cont = e.get_target()
cont_a = lv.area_t()
cont.get_coords(cont_a)
cont_y_center = cont_a.y1 + cont_a.get_height() // 2
r = cont.get_height() * 7 // 10
child_cnt = cont.get_child_cnt()
for i in range(child_cnt):
child = cont.get_child(i)
child_a = lv.area_t()
child.get_coords(child_a)
child_y_center = child_a.y1 + child_a.get_height() // 2
diff_y = child_y_center - cont_y_center
diff_y = abs(diff_y)
# Get the x of diff_y on a circle.
# If diff_y is out of the circle use the last point of the circle (the radius)
if diff_y >= r:
x = r
else:
# Use Pythagoras theorem to get x from radius and y
x_sqr = r * r - diff_y * diff_y
res = lv.sqrt_res_t()
lv.sqrt(x_sqr, res, 0x8000) # Use lvgl's built in sqrt root function
x = r - res.i
# Translate the item by the calculated X coordinate
child.set_style_translate_x(x, 0)
# Use some opacity with larger translations
opa = lv.map(x, 0, r, lv.OPA.TRANSP, lv.OPA.COVER)
child.set_style_opa(lv.OPA.COVER - opa, 0)
#
# Translate the object as they scroll
#
cont = lv.obj(lv.scr_act())
cont.set_size(200, 200)
cont.center()
cont.set_flex_flow(lv.FLEX_FLOW.COLUMN)
cont.add_event_cb(scroll_event_cb, lv.EVENT.SCROLL, None)
cont.set_style_radius(lv.RADIUS.CIRCLE, 0)
cont.set_style_clip_corner(True, 0)
cont.set_scroll_dir(lv.DIR.VER)
cont.set_scroll_snap_y(lv.SCROLL_SNAP.CENTER)
cont.set_scrollbar_mode(lv.SCROLLBAR_MODE.OFF)
for i in range(20):
btn = lv.btn(cont)
btn.set_width(lv.pct(100))
label = lv.label(btn)
label.set_text("Button " + str(i))
# Update the buttons position manually for first*
lv.event_send(cont, lv.EVENT.SCROLL, None)
# Be sure the fist button is in the middle
#lv.obj.scroll_to_view(cont.get_child(0), lv.ANIM.OFF)
cont.get_child(0).scroll_to_view(lv.ANIM.OFF)