I am trying to make a janggi(chess variant) game using flet. As I have to use the board in multiple places, I made a class called janggiBoard which inherits from ft.Stack. I wanted to use drag and drop for the pieces, so I followed the Solitaire tutorial on the flet docs. The problem occured when I tried to do the “move_on_top” part. In the Solitaire code, there is page.update() in the move_on_top function. So I naturally followed it by adding a piece.board.update(). However, when I do this, It causes an AssertionError as below.
Future exception was never retrieved
future: <Future finished exception=AssertionError('Control must be added to the page first.')>
Traceback (most recent call last):
File "C:UsersandypAppDataLocalProgramsPythonPython312Libconcurrentfuturesthread.py", line 58, in run
result = self.fn(*self.args, **self.kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:UsersandypAppDataLocalProgramsPythonPython312Libsite-packagesflet_corepage.py", line 950, in wrapper
handler(*args)
File "c:limbaksajanggi-v2janggiBoard.py", line 25, in start_drag
e.control.update()
File "C:UsersandypAppDataLocalProgramsPythonPython312Libsite-packagesflet_corecontrol.py", line 314, in update
assert self.__page, "Control must be added to the page first."
^^^^^^^^^^^
AssertionError: Control must be added to the page first.
import flet as ft
from janggiplayer import AI
import flet.canvas as cv
import janggibase
from db import db
def move_on_top(piece,controls):
controls.remove(piece)
controls.append(piece)
piece.board.update()
def start_drag(e:ft.DragStartEvent):
move_on_top(e.control,e.control.board.controls)
e.control.board.move_start_top=e.control.top
e.control.board.move_start_left=e.control.left
if e.control.piece.color == e.control.board.board.turn and (
not e.control.board.ai or e.control.piece.color != e.control.board.aiturn
):
for slot in e.control.board.slots:
if e.control.piece.isValidMove(e.control.board.slots.index(slot)):
slot.content = ft.Image(f"img/able.png")
e.control.board.controls.remove(slot)
e.control.board.controls.append(slot)
e.control.update()
slot.update()
def bounce_back(board,piece):
piece.top=board.move_start_top
piece.left=board.move_start_left
piece.update()
def drag(e: ft.DragUpdateEvent):
e.control.top = max(0, e.control.top + e.delta_y)
e.control.left = max(0, e.control.left + e.delta_x)
e.control.update()
def drop(e:ft.DragEndEvent):
for slot in e.control.board.slots:
slot.content=None
slot.update()
for slot in e.control.board.slots:
if (
abs(e.control.top - slot.top) < 20
and abs(e.control.left - slot.left) < 20
):
place(e.control, slot)
break
else:
bounce_back(e.control.board,e.control)
e.control.update()
def place(piece,slot):
piece.top=slot.top
piece.left=slot.left
piece.update()
class janggiPiece(ft.GestureDetector):
def __init__(self, piece: janggibase.Piece, board: "janggiBoard"):
super().__init__()
self.piece=piece
self.board=board
self.mouse_cursor=ft.MouseCursor.MOVE
self.drag_interval=5
self.on_pan_start=start_drag
self.on_pan_update=drag
self.on_pan_end=drop
self.left = 60 * (piece.location // 10)
self.top = 60 * (9 - piece.location % 10)
self.content=ft.Container(
width=60,
height=60,
border_radius=ft.border_radius.all(5),
content=ft.Image(f"img/{str(piece).upper()}{piece.color}.png"),
)
class Slot(ft.Container):
def __init__(self, top, left):
super().__init__()
self.width = 60
self.height = 60
self.left = left
self.top = top
class janggiBoard(ft.Stack):
def __init__(self, board: janggibase.Board, ai=False, aiturn=None):
super().__init__()
self.board = board
self.slots = []
self.controls = []
self.width = 540
self.height = 600
self.piecelist = []
self.move_start_top=None
self.move_start_left=None
self.ai = AI(self.board, aiturn) if ai else None
self.aiturn = aiturn
def did_mount(self):
cp = cv.Canvas(
[
cv.Path(
[
cv.Path.MoveTo(30, 30),
cv.Path.LineTo(30, 570),
cv.Path.MoveTo(90, 30),
cv.Path.LineTo(90, 570),
cv.Path.MoveTo(150, 30),
cv.Path.LineTo(150, 570),
cv.Path.MoveTo(210, 30),
cv.Path.LineTo(210, 570),
cv.Path.MoveTo(270, 30),
cv.Path.LineTo(270, 570),
cv.Path.MoveTo(330, 30),
cv.Path.LineTo(330, 570),
cv.Path.MoveTo(390, 30),
cv.Path.LineTo(390, 570),
cv.Path.MoveTo(450, 30),
cv.Path.LineTo(450, 570),
cv.Path.MoveTo(510, 30),
cv.Path.LineTo(510, 570),
cv.Path.MoveTo(30, 30),
cv.Path.LineTo(510, 30),
cv.Path.MoveTo(30, 90),
cv.Path.LineTo(510, 90),
cv.Path.MoveTo(30, 150),
cv.Path.LineTo(510, 150),
cv.Path.MoveTo(30, 210),
cv.Path.LineTo(510, 210),
cv.Path.MoveTo(30, 270),
cv.Path.LineTo(510, 270),
cv.Path.MoveTo(30, 330),
cv.Path.LineTo(510, 330),
cv.Path.MoveTo(30, 390),
cv.Path.LineTo(510, 390),
cv.Path.MoveTo(30, 450),
cv.Path.LineTo(510, 450),
cv.Path.MoveTo(30, 510),
cv.Path.LineTo(510, 510),
cv.Path.MoveTo(30, 570),
cv.Path.LineTo(510, 570),
cv.Path.MoveTo(210, 30),
cv.Path.LineTo(330, 150),
cv.Path.MoveTo(330, 30),
cv.Path.LineTo(210, 150),
cv.Path.MoveTo(210, 450),
cv.Path.LineTo(330, 570),
cv.Path.MoveTo(330, 450),
cv.Path.LineTo(210, 570),
],
paint=ft.Paint(
color="white",
stroke_width=2,
style=ft.PaintingStyle.STROKE,
),
),
],
width=float("inf"),
expand=True,
)
self.controls.append(cp)
for i in range(90):
self.slots.append(Slot(60 * (9 - i % 10), 60 * (i // 10)))
self.controls.extend(self.slots)
for color in range(2):
for piece in self.board.pieces[color]:
self.piecelist.append(janggiPiece(piece, self))
self.controls.extend(self.piecelist)
self.update()
return super().did_mount()
if __name__ == "__main__":
def main(page):
page.add(janggiBoard(janggibase.Board(15)))
ft.app(target=main)
This is the code for the Board. The full code is on my github.
After I commented the piece.board.update(), everythng else works as expected. I could move pieces to different slots. However, the piece wasn’t on top of other pieces becasue the board wasn’t updated. Is there a way to update the board without causing the error?