Pygame - Smoother Movement

问题:

I have added an Object/Image on the main_screen, the object is called cancer_cell. What I'm trying to do here is that I want the object move smoothly. I have to repeatedle press on the arrow keys to keep it moving. How do I make it move while arrow keys are pressed ?

here's the code:

exitgame = False
cellpos_x = 0
cellpos_y = cancer_cell.get_rect().height*2
while not exitgame:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            exitgame = True
            quitgame()
        if event.type == pygame.KEYDOWN:
            if event.key == pygame.K_LEFT:
                cellpos_x -= 10
            if event.key == pygame.K_RIGHT:
                cellpos_x += 10


    gameplay_bg = pygame.image.load("/Users/wolf/Desktop/python/img/gameplay_bg.png").convert()
    main_screen.fill(white)
    main_screen.blit(gameplay_bg, [0,0])
    main_screen.blit(cancer_cell, [cellpos_x, cellpos_y])
    pygame.display.flip()
    clock.tick(20)

someone told me to try the solution at How to use pygame.KEYDOWN: but that didn't work either. Or maybe i did it wrong:

if event.type == pygame.KEYDOWN:
    key_pressed = pygame.key.get_pressed()
    if key_pressed[pygame.K_LEFT]:
        cellpos_x -= 10
    if key_pressed[pygame.K_RIGHT]:
        cellpos_x += 10

回答1:

PROBLEM SOLVED

I have solved the problem by just unindenting this part from the FOR loop while not exitgame:

    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            exitgame = True
            quitgame()

    key_pressed = pygame.key.get_pressed()
    if key_pressed[pygame.K_LEFT]:
        cellpos_x -= 10
    if key_pressed[pygame.K_RIGHT]:
        cellpos_x += 10

回答2:

I see you've solved the indentation issue, here's another version of your example:

import pygame

class Player(object):
    def __init__(self, img_path):
        self.image = pygame.image.load(img_path)
        self.x = 0
        self.y = self.image.get_rect().height*2

    def handle_keys(self):
        key = pygame.key.get_pressed()
        dist = 1
        if key[pygame.K_RIGHT]:
            self.x += dist
        elif key[pygame.K_LEFT]:
            self.x -= dist

    def draw(self, surface):
        surface.blit(self.image, (self.x, self.y))


pygame.init()
clock = pygame.time.Clock()
size = width, height = 1024, 768
speed = [2, 2]
white = 1, 1, 1
main_screen = pygame.display.set_mode(size)
gameplay_bg = pygame.image.load("background.jpg")
cancer_cell = Player("player.jpg")
running = False

while not running:
    event = pygame.event.poll()

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

    main_screen.fill(white)
    main_screen.blit(gameplay_bg, [0, 0])

    cancer_cell.handle_keys()
    cancer_cell.draw(main_screen)

    pygame.display.flip()

    clock.tick(50)
    pygame.display.set_caption("fps: " + str(clock.get_fps()))

You need to adjust the paths of the images ("background.jpg", "player.jpg"), with this version you're not loading over and over your sprite in the game event loop and the Player movement will be smooth.