python和pygame图像移动

Question

Ok so my code is below, right now I'm new to pygame and trying to figure out how to move images on the screen. From what I've seen of pygame the following code should move the image up(the only possible movement right now). However when I push up the image doesn't move. Python is recognizing that I'm pushing up because it prints in the system tray, however there is just no movement, can someone help?

import pygame, sys
from pygame.locals import *

FPS = 30


WIN_WIDTH = 800
WIN_HEIGHT = 600
HALF_WIDTH = int(WIN_WIDTH / 2)
HALF_HEIGHT = int(WIN_HEIGHT / 2)

COLOR = (255, 0, 255)
IMAGE = pygame.image.load('squirrel.png')
STARTSIZE = 25

LEFT = 'left'

def main():
    pygame.init()
    FPS_CLOCK = pygame.time.Clock()
    movement = 1

    moveUp = False

    DISPLAY_SURFACE = pygame.display.set_mode((WIN_WIDTH, WIN_HEIGHT))

    while True:
        DISPLAY_SURFACE.fill(COLOR)

        playerObj = {'surface': pygame.transform.scale(IMAGE, (STARTSIZE, STARTSIZE)),
                     'facing': LEFT,
                     'size': STARTSIZE,
                     'x': HALF_WIDTH,
                     'y': HALF_HEIGHT}

        playerObj['rect'] = pygame.Rect( (playerObj['x'], playerObj['y'], playerObj['size'], playerObj['size']) )
        DISPLAY_SURFACE.blit(playerObj['surface'], playerObj['rect'])


        for event in pygame.event.get():

            if event.type == KEYDOWN:
                if event.key == K_UP:
                    moveUp = True

            if event.type == KEYUP:
                if event.key == K_UP:
                    moveUp = False

            elif event.type == QUIT:
                pygame.quit()
                sys.exit()

        if moveUp:
            playerObj['y'] += movement
            print("moving up")

        else:
            print('stopped')

        pygame.display.update()
        FPS_CLOCK.tick(FPS)

if __name__ == '__main__':
    main()

Answer 1

You're creating a new playerObj each time it iterates through the while loop so you're not going to see it move (as it is setting it's 'y' value to HALF_HEIGHT each time). Move the playerObj definition out of the while loop.

Answer 2

You must create the playerObj before you enter the while-loop, and then only draw it to the DISPLAY_SURFACE each time. Also, increasing the key y of your dictionary won't help, you must modify the rect instead. A minimally invasive solution would be:

import pygame, sys
from pygame.locals import *

FPS = 30


WIN_WIDTH = 800
WIN_HEIGHT = 600
HALF_WIDTH = int(WIN_WIDTH / 2)
HALF_HEIGHT = int(WIN_HEIGHT / 2)

COLOR = (255, 0, 255)
IMAGE = pygame.image.load('squirrel.png')
STARTSIZE = 25

LEFT = 'left'

def main():
    pygame.init()
    FPS_CLOCK = pygame.time.Clock()
    movement = 1

    moveUp = False

    DISPLAY_SURFACE = pygame.display.set_mode((WIN_WIDTH, WIN_HEIGHT))

    playerObj = {'surface': pygame.transform.scale(IMAGE, (STARTSIZE, STARTSIZE)),
                     'facing': LEFT,
                     'size': STARTSIZE,
                     'x': HALF_WIDTH,
                     'y': HALF_HEIGHT}

    playerObj['rect'] = pygame.Rect( (playerObj['x'], playerObj['y'], playerObj['size'], playerObj['size']) )

    while True:
        DISPLAY_SURFACE.fill(COLOR)
        DISPLAY_SURFACE.blit(playerObj['surface'], playerObj['rect'])
        for event in pygame.event.get():

            if event.type == KEYDOWN:
                if event.key == K_UP:
                    moveUp = True

            if event.type == KEYUP:
                if event.key == K_UP:
                    moveUp = False

            elif event.type == QUIT:
                pygame.quit()
                sys.exit()

        if moveUp:
            playerObj['rect'].y -= movement
            print("moving up")

        else:
            print('stopped')

        pygame.display.update()
        FPS_CLOCK.tick(FPS)

if __name__ == '__main__':
    main()

It works, I tried it myself. But you sould refactor your code, no need to carry along the initial x,y, etc. values in your dictionary.

EDIT With movement in all four directions this would be:

import pygame, sys
from pygame.locals import *

FPS = 30


WIN_WIDTH = 800
WIN_HEIGHT = 600
HALF_WIDTH = int(WIN_WIDTH / 2)
HALF_HEIGHT = int(WIN_HEIGHT / 2)

COLOR = (255, 0, 255)
IMAGE = pygame.image.load('squirrel.png')
STARTSIZE = 25

LEFT = 'left'

def move_rect(rect, key, distance):
    if key == K_UP: 
        rect.y-=distance
    elif key == K_DOWN: 
        rect.y+=distance
    elif key == K_LEFT: 
        rect.x-=distance
    elif key == K_RIGHT: 
        rect.x+=distance

def main():
    pygame.init()
    FPS_CLOCK = pygame.time.Clock()
    movement = 1

    key2mvmt = {K_UP:False, K_DOWN:False, K_LEFT:False, K_RIGHT:False}

    DISPLAY_SURFACE = pygame.display.set_mode((WIN_WIDTH, WIN_HEIGHT))

    playerObj = {'surface': pygame.transform.scale(IMAGE, (STARTSIZE, STARTSIZE)),
                     'facing': LEFT,
                     'size': STARTSIZE,
                     'x': HALF_WIDTH,
                     'y': HALF_HEIGHT}

    playerObj['rect'] = pygame.Rect( (playerObj['x'], playerObj['y'], playerObj['size'], playerObj['size']) )

    while True:
        DISPLAY_SURFACE.fill(COLOR)
        DISPLAY_SURFACE.blit(playerObj['surface'], playerObj['rect'])
        for event in pygame.event.get():

            if event.type == KEYDOWN:
                if key2mvmt.has_key(event.key):
                    key2mvmt[event.key]= True

            if event.type == KEYUP:
                if key2mvmt.has_key(event.key):
                    key2mvmt[event.key]= False

            elif event.type == QUIT:
                pygame.quit()
                sys.exit()

        for k in key2mvmt.keys():
            if key2mvmt[k]:
                move_rect(playerObj['rect'], k, movement)

        else:
            print('stopped')

        pygame.display.update()
        FPS_CLOCK.tick(FPS)

if __name__ == '__main__':
    main()