Pygame：同时触发KEYDOWN和KEYUP导致没有净移动

Question

I've made it so when a user clicks WASD it makes smooth_x or smooth_y to 5 to constantly add to their x or y coordinates to simulate motion.

However I have a problem where if the user is holding down A then they click D at the same time, it causes smooth_x to be 0, causing the user to stay in place.

EG User Clicks D (smooth_x = 5) User Clicks A (smooth_x = -5) User is holding D then holds A then lets go of D resulting in smooth_x being = 0 causing the user to stop moving which I don't want. In this scenario smooth_x should be = -5

while gameloop == True:
num_scraps = 0
fps.tick(60) #Sets FPS to 60
for event in pygame.event.get(): #Checks each event
    if event.type == pygame.QUIT: #If one of the events are quit (when the user clicks the X in the top right corner) the window closes
        pygame.quit()
    if event.type == pygame.KEYUP:
        print(event)
        #If the user stop pressing one of the arrow keys it sets all the smooth values to 0 so it stops increasing the x or y coordinate
        if event.key == pygame.K_w:
            smoothy = 0
        if event.key == pygame.K_s:
            smoothy = 0 
        if event.key == pygame.K_a:
            smoothx = 0
        if event.key ==pygame.K_d:
            smoothx = 0

    if event.type == pygame.KEYDOWN: #Checks for a keypress
        print(event)
        if  event.key == pygame.K_w:
            smoothy -= 5 #reduces the y by 5 so player moves up
        if  event.key == pygame.K_s:
            smoothy += 5 #increases the y by 5 so player moves down
        if  event.key == pygame.K_a:
            smoothx -= 5 #reduces the x by 5 so player moves left
        if  event.key == pygame.K_d:
            smoothx += 5 #increases the x by 5 so player moves right

Answer 1

Use add/substract in KEYUP like you do in KEYDOWN but with the opposite sign.

    if event.type == pygame.KEYUP:
        print(event)
        if event.key == pygame.K_w:
            smoothy += 5
        if event.key == pygame.K_s:
            smoothy -= 5 
        if event.key == pygame.K_a:
            smoothx += 5
        if event.key ==pygame.K_d:
            smoothx -= 5

    if event.type == pygame.KEYDOWN: #Checks for a keypress
        print(event)
        if  event.key == pygame.K_w:
            smoothy -= 5 #reduces the y by 5 so player moves up
        if  event.key == pygame.K_s:
            smoothy += 5 #increases the y by 5 so player moves down
        if  event.key == pygame.K_a:
            smoothx -= 5 #reduces the x by 5 so player moves left
        if  event.key == pygame.K_d:
            smoothx += 5 #increases the x by 5 so player moves right

Answer 2

I usually handle the movement in this way: I set the x- and y-velocity to the desired value if a key was pressed and update the position in the main loop. To stop the left-right movement, I also check if the character is moving to the left or to the right smoothx > 0 before I set the value back to 0. Then the character won't stop if you press both the left and right key at the same time.

if event.type == pygame.KEYDOWN:
    if  event.key == pygame.K_w:
        smoothy = -5
    elif  event.key == pygame.K_s:
        smoothy = 5
    elif  event.key == pygame.K_a:
        smoothx = -5
    elif  event.key == pygame.K_d:
        smoothx = 5
elif event.type == pygame.KEYUP:
    if event.key == pygame.K_w and smoothy < 0:
        smoothy = 0
    elif event.key == pygame.K_s and smoothy > 0:
        smoothy = 0
    elif event.key == pygame.K_a and smoothx < 0:
        smoothx = 0
    elif event.key ==pygame.K_d and smoothx > 0:
        smoothx = 0

For the up-down movement it doesn't matter so much, because it's very hard to press both up and down at the same time, but of course you can check that as well to be sure.