无法在 Pygame 中跨屏幕移动图像

Question

I'm a beginner in Python, and I am trying to come up with a function to draw a square which moves horizontally and vertically across the screen with the help of Pygame. The square should move as we click the arrows in the keyboard.

My issue: although the square is shown in screen, it doesn't move at all, yet Python isn't showing any kind of error.

Would anyone know what's missing? Thanks in advance!

Here's what I've written so far:

import pygame

altura_tela = 600
largura_tela = 800
tela = pygame.display.set_mode((largura_tela, altura_tela))

vermelho = (255, 0, 0)

altura_quadrado = 100
largura_quadrado = 100

def desenhaQuadrado(quadrado):
    pygame.draw.rect(tela, vermelho, (350,250,largura_quadrado, altura_quadrado))

def posicaoquadrado(quadradoPos):
    tela.blit(quadrado, (quadradoPos[0],quadradoPos[1]))

def moveQuadrado(teclas, quadradoPos):
    if teclas[0] and quadradoPos[1] > 0:
        quadradoPos[1] -= 20
    elif teclas[2] and quadradoPos[1] < 420:
        quadradoPos[1] += 20
    if teclas[1] and quadradoPos[0] > 0:
        quadradoPos[0] -= 20
    elif teclas[3]and quadradoPos[0] < 570:
        quadradoPos[0] += 20
    return quadradoPos

def main():
    pygame.init()
    teclas = [False, False, False, False]
    quadradoPos = [350,250]

    pygame.display.set_caption('Movimentação do Quadrado')

    terminou = False
    while not terminou:

        for event in pygame.event.get():

            if event.type == pygame.QUIT:
                terminou = True

            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_UP:
                    teclas[0] = True
                elif event.key == pygame.K_DOWN:
                    teclas[1] = True
                elif event.key == pygame.K_LEFT:
                    teclas[2] = True
                elif event.key == pygame.K_RIGHT:
                    teclas[3] = True

            if event.type == pygame.KEYUP:
                if event.key == pygame.K_UP:
                    teclas[0] = False
                elif event.key == pygame.K_DOWN:
                    teclas[1] = False
                elif event.key == pygame.K_LEFT:
                    teclas[2] = False
                elif event.key == pygame.K_RIGHT:
                    teclas[3] = False

            quadradoPos = moveQuadrado(teclas, quadradoPos)
            desenhaQuadrado(quadradoPos)

            pygame.display.update()


    pygame.display.quit()

    pygame.quit()

if __name__ == '__main__':
    main()

Answer 1

In your function:

def desenhaQuadrado(quadrado):
    pygame.draw.rect(tela, vermelho, (350,250,largura_quadrado, altura_quadrado))

You are passing an argument quadrado but you never use it. Also your coordinates never update 350, 250 . So this function basically draws same rect over and over again.

I modified your code:

import pygame

clock = pygame.time.Clock()

altura_tela = 600
largura_tela = 800
tela = pygame.display.set_mode((largura_tela, altura_tela))

FPS = 30

vermelho = (255, 0, 0)

altura_quadrado = 100
largura_quadrado = 100


def redraw(quadradoPos):
    tela.fill(pygame.Color("white"))
    pygame.draw.rect(tela, vermelho, (quadradoPos[0], quadradoPos[1], largura_quadrado, altura_quadrado))
    pygame.display.update()


def main():
    pygame.init()
    quadradoPos = [300,250]
    pygame.display.set_caption('Movimentação do Quadrado')

    terminou = False
    while not terminou:

        clock.tick(FPS)

        for event in pygame.event.get():

            if event.type == pygame.QUIT:
                terminou = True

            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_UP and quadradoPos[1] > 0:
                    quadradoPos[1] -= 50
                elif event.key == pygame.K_DOWN and quadradoPos[1] <= altura_tela - altura_quadrado:
                    quadradoPos[1] += 50
                elif event.key == pygame.K_LEFT and quadradoPos[0] >= 0:
                    quadradoPos[0] -= 50
                elif event.key == pygame.K_RIGHT and quadradoPos[0] <= largura_tela - largura_quadrado:
                    quadradoPos[0] += 50

            redraw(quadradoPos)

    pygame.quit()

if __name__ == '__main__':
    main()

NOTE:

-do not forget tela.fill(pygame.Color("white")) , otherwise you will get "traces" of all rects that are drawn on the screen.

-I added clock in order to control the frame rate.

-You cannot blit rect on the screen like you did in posicaoquadrado(quadradoPos) it will cause the TypeError . You can blit Surface only.

Hope this answers your question.

Answer 2

There are some static values inside the desenhaQuadrado function

def desenhaQuadrado(quadrado):
    pygame.draw.rect(tela, vermelho, (350,250,largura_quadrado, altura_quadrado))

Change it to the code bellow and it will move.

def desenhaQuadrado(quadrado):
    pygame.draw.rect(tela, vermelho, (quadrado[0],quadrado[1],largura_quadrado, altura_quadrado))

Although you will have some others problems to solve as you will see. I created a script that is basicly what you want, check it in case you want some help https://github.com/eng-robsonsampaio/pygame_move_square.git

import pygame
from pygame.locals import *

UP = 0
DOWN = 1
LEFT = 2
RIGHT = 3
GAME_ON = True
SPEED = 20

screen = pygame.display.set_mode((400, 400))
clock = pygame.time.Clock()

square = pygame.Surface((50,50))
square.fill((255,0,0))
POS = [(200,200)]

def move_square(direction):
    if UP == direction:
        POS.append((POS[0][0], POS[0][1] - 20))
    elif direction == DOWN:
        POS.append((POS[0][0], POS[0][1] + 20))
    elif direction == LEFT:
        POS.append((POS[0][0] - 20, POS[0][1]))
    else:
        POS.append((POS[0][0] + 20, POS[0][1]))
    POS.pop(0)


while GAME_ON:

    for event in pygame.event.get():
        if event.type == QUIT:
            GAME_ON = False
        if event.type == KEYDOWN:
            if event.key==K_UP:
                print("UP")
                move_square(UP)                
            elif event.key==K_LEFT:
                print("LEFT")
                move_square(LEFT)               
            elif event.key==K_DOWN:
                print("DOWN")
                move_square(DOWN)                
            elif event.key==K_RIGHT:
                print("RIGHT")
                move_square(RIGHT)

    screen.fill((0,0,0))
    screen.blit(square, POS[0])
    pygame.display.update()

pygame.quit()

I also have a snake game tutorial in medium: https://medium.com/@robsonsampaio90/snake-game-in-python-with-pygame-291f5206a35e

You might find some help in this links.