本文将解决Pygame游戏开发中，由于主循环的持续运行，导致特定事件（如碰撞检测）触发后，其相关代码被重复执行的问题。通过引入状态变量，我们可以确保事件只在特定条件下执行一次，从而避免不必要的重复操作，实现更精确的游戏逻辑。这对于需要在碰撞发生时只执行一次的逻辑（例如，给予玩家一次性的奖励或触发一次性的动画效果）至关重要。
问题分析
在Pygame游戏的主循环中，事件检测和游戏逻辑会不断执行。当某个条件满足时（例如，角色与道具发生碰撞），相应的代码块会被执行。然而，由于循环的持续运行，即使条件只满足一瞬间，该代码块也会在多个连续的帧中被执行，导致重复触发。
以下面的代码片段为例，每当 current_time 是 10 的倍数且不为 0 时，会生成一个能量立方体，并检测其与恐龙的碰撞。 如果发生碰撞，则会打印能量立方体的值。问题在于，碰撞检测在循环中持续进行，导致能量立方体的值被多次打印。
if current_time % 10 == 0 and current_time != 0:
energycube_rect_2 = energycube_enlarged.get_rect(topleft = (120,350))
screen.blit(energycube_enlarged,energycube_rect_2)
energycuberandom = random.randint(0,5)
energycubelist = [1,1,2,2,3,4]
energycubevalue = energycubelist[energycuberandom]
energycollide = pygame.Rect.colliderect(dinosaur_rect_2, energycube_rect_2)
if energycollide:
energycubevalue = energycubelist[energycuberandom]
if energycubevalue == 1:
print('1')
elif energycubevalue == 2:
print('2')
elif energycubevalue == 3:
print('3')
elif energycubevalue == 4:
print('4')
else:
print('error')解决方案：使用状态变量
为了解决这个问题，我们可以引入一个布尔类型的状态变量，用于记录碰撞是否已经发生。只有当碰撞发生，并且之前没有发生过碰撞时，才执行相应的代码。
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初始化状态变量： 在主循环之前，定义一个变量 collision_detected 并将其初始化为 False。
collision_detected = False
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在碰撞检测代码中加入状态判断： 在碰撞检测的代码块中，首先检查 collision_detected 的值。如果为 False，则表示之前没有发生过碰撞，可以执行相应的代码，并将 collision_detected 设置为 True。如果 collision_detected 已经为 True，则跳过代码块。
if current_time % 10 == 0 and current_time != 0: energycube_rect_2 = energycube_enlarged.get_rect(topleft = (120,350)) screen.blit(energycube_enlarged,energycube_rect_2) energycuberandom = random.randint(0,5) energycubelist = [1,1,2,2,3,4] energycubevalue = energycubelist[energycuberandom] energycollide = pygame.Rect.colliderect(dinosaur_rect_2, energycube_rect_2) if energycollide: if not collision_detected: collision_detected = True energycubevalue = energycubelist[energycuberandom] if energycubevalue == 1: print('1') elif energycubevalue == 2: print('2') elif energycubevalue == 3: print('3') elif energycubevalue == 4: print('4') else: print('error') -
重置状态变量： 当碰撞不再发生时，需要将 collision_detected 重置为 False，以便下次碰撞可以再次触发代码。 可以在没有碰撞发生时，将 collision_detected 设置为 False。
if energycollide: if not collision_detected: collision_detected = True energycubevalue = energycubelist[energycuberandom] if energycubevalue == 1: print('1') elif energycubevalue == 2: print('2') elif energycubevalue == 3: print('3') elif energycubevalue == 4: print('4') else: print('error') else: collision_detected = False
完整代码示例
将上述步骤整合到你的Pygame代码中，可以得到以下示例：
import pygame
import random
from sys import exit
import time
pygame.init()
screen = pygame.display.set_mode((800, 700))
pygame.display.set_caption("Don't Get Sliced!")
clock = pygame.time.Clock()
test_font = pygame.font.Font('Pixeltype.ttf')
game_active = False
start_time = 0
#play again screen
dinosaur_image = pygame.image.load('Dinosaur/dinosaur.png')
dinosaur_image_enlarged = pygame.transform.scale(dinosaur_image, (245,301))
dinosaur_image_rect = dinosaur_image_enlarged.get_rect(center = (400,350))
text_1 = test_font.render("Don't Get Sliced!", False, 'Black')
text_1_surf = pygame.transform.scale_by(text_1, (9,9))
text_1_rect = text_1_surf.get_rect(center = (400,100))
text_2 = test_font.render('Press Any Key To Start', False, 'Black')
text_2_surf = pygame.transform.scale_by(text_2, (6,6))
text_2_rect = text_2_surf.get_rect(center = (400,600))
score_present = 0
butcher_knife_rect_speed_inc = 2
knife_rect_speed_inc = 2
# score = test_font.render('Score: ', False, 'Black')
# score_surf = pygame.transform.scale_by(score, (5,5))
# score_rect = score_surf.get_rect(center = (400,50))
background = pygame.image.load('metalbackground2.png')
background_surf = pygame.transform.scale(background, (1200,800))
side_wall_1 = pygame.image.load('metalwall2.png')
side_wall_1_surf = pygame.transform.scale(side_wall_1, (120,700))
side_wall_2 = pygame.image.load('metalwall2.png')
side_wall_2_flipped = pygame.transform.flip(side_wall_2, True, False)
side_wall_2_surf = pygame.transform.scale(side_wall_2_flipped, (120,700))
butcher_knife = pygame.image.load('Weapons/butcherknife.png')
butcher_knife_surf = pygame.transform.scale(butcher_knife, (228,80))
butcher_knife_rect = butcher_knife_surf.get_rect(topleft=(40,170))
butcher_knife_y_pos = 570
knife = pygame.image.load('Weapons/knife.png').convert_alpha()
knife_boy = pygame.transform.scale(knife, (220,40)).convert_alpha()
knife_surf = pygame.transform.flip(knife_boy, True, False)
knife_rect = knife_surf.get_rect(topleft=(520,600))
knife_y_pos = 570
dinosaur = pygame.image.load('Dinosaur/dinosaur.png')
dinosaur_enlarged = pygame.transform.scale(dinosaur, (87.5,107.5))
dinosaur_rotation = 270
dinosaur_flipped = False
dinosaur_rotated = pygame.transform.rotate(dinosaur_enlarged, dinosaur_rotation)
dinosaur_rect = dinosaur_rotated.get_rect(topleft=(500,-400))
dinosaur_x = 120
dinosaur_y = 300
dinosaur_direction = 1
dinosaur_position = "left"
#energy cube
energycube = pygame.image.load('energycube/energycube.png')
energycube_enlarged = pygame.transform.scale(energycube,(64,64))
energycube_rect = energycube_enlarged.get_rect(topleft = (120,350))
energy_y = 500
collision_detected = False
while True:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit()
exit()
if game_active:
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_SPACE:
if dinosaur_position == "left":
dinosaur_x = 570
dinosaur_position = "right"
else:
dinosaur_x = 120
dinosaur_position = "left"
dinosaur_rotation = 270
dinosaur_flipped = not dinosaur_flipped
else:
if event.type == pygame.KEYDOWN:
game_active = True
butcher_knife_rect.top = 170
knife_rect.top = 600
start_time = int(pygame.time.get_ticks() / 1500)
if game_active:
screen.blit(background, (-400,-50))
screen.blit(side_wall_1_surf, (0,0))
screen.blit(side_wall_2_surf, (680,0))
butcher_knife_rect.y -= butcher_knife_rect_speed_inc
butcher_knife_rect_speed_inc +=0.0005
if butcher_knife_rect.y <= 0:
butcher_knife_rect.y = 700
screen.blit(butcher_knife_surf, butcher_knife_rect)
knife_rect.y -= knife_rect_speed_inc
knife_rect_speed_inc +=0.0005
if knife_rect.y <= 0:
knife_rect.y = 700
screen.blit(knife_surf, knife_rect)
dinosaur_rect = pygame.transform.rotate(dinosaur_enlarged, dinosaur_rotation)
dinosaur_image_flipped = pygame.transform.flip(dinosaur_rect, dinosaur_flipped, False)
dinosaur_rect_2 = dinosaur_image_flipped.get_rect(topleft = (dinosaur_x, dinosaur_y))
screen.blit(dinosaur_image_flipped, dinosaur_rect_2)
current_time = int(pygame.time.get_ticks() / 1500) - start_time
score_surf = test_font.render(f'{current_time}', False, (255,255,255))
score_enlarged = pygame.transform.scale_by(score_surf, (5,5))
score_rect = score_enlarged.get_rect(center = (400,50))
screen.blit(score_enlarged,score_rect)
if current_time % 10 == 0 and current_time != 0:
energycube_rect_2 = energycube_enlarged.get_rect(topleft = (120,350))
screen.blit(energycube_enlarged,energycube_rect_2)
energycuberandom = random.randint(0,5)
energycubelist = [1,1,2,2,3,4]
energycubevalue = energycubelist[energycuberandom]
energycollide = pygame.Rect.colliderect(dinosaur_rect_2, energycube_rect_2)
if energycollide:
if not collision_detected:
collision_detected = True
energycubevalue = energycubelist[energycuberandom]
if energycubevalue == 1:
print('1')
elif energycubevalue == 2:
print('2')
elif energycubevalue == 3:
print('3')
elif energycubevalue == 4:
print('4')
else:
print('error')
else:
collision_detected = False
#screen.blit(score_surf, score_rect)
current_time = int(pygame.time.get_ticks() / 1500) - start_time
score_surf = test_font.render(f'{current_time}', False, (255,255,255))
score_enlarged = pygame.transform.scale_by(score_surf, (5,5))
score_rect = score_enlarged.get_rect(center = (400,50))
screen.blit(score_enlarged,score_rect)
#energy cube in loop
#collision
collidewithknife = pygame.Rect.colliderect(dinosaur_rect_2, butcher_knife_rect) or pygame.Rect.colliderect(dinosaur_rect_2, knife_rect)
if collidewithknife:
score_present = current_time
game_active = False
else:
screen.blit(background,(-400,-50))
screen.blit(dinosaur_image_enlarged,dinosaur_image_rect)
screen.blit(text_1_surf, text_1_rect)
screen.blit(text_2_surf, text_2_rect)
score_present_surf = test_font.render(f"Score: {score_present}", False, "Black")
score_present_s = pygame.transform.scale_by(score_present_surf, (5,5))
score_present_rect = score_present_s.get_rect(center = (400,150))
screen.blit(score_present_s, score_present_rect)
butcher_knife_rect_speed_inc = 2
knife_rect_speed_inc = 2
energy_y = 500
#mouse_pos = pygame.mouse.get_pos()
#print(mouse_pos)
pygame.display.update()
clock.tick(60) # limits FPS to总结
通过使用状态变量，我们可以有效地控制Pygame游戏主循环中代码的执行次数，确保事件只在特定条件下触发一次。这种方法可以应用于各种需要精确控制的游戏逻辑，例如一次性奖励、动画效果、音效播放等。 在实际开发中，可以根据具体需求调整状态变量的重置时机，以实现更灵活的控制。
