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使你的 Python 游戏玩家能够向前和向后跑

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使用 Pygame 模块来使你的 Python 平台开启侧滚效果，来让你的玩家自由奔跑。

这是仍在进行中的关于使用 Pygame 模块来在 Python 3 中在创建电脑游戏的第九部分。先前的文章是：

在这一系列关于使用 Pygame 模块来在 Python 3 中创建电脑游戏的先前文章中，你已经设计了你的关卡设计布局，但是你的关卡的一些部分可能已近超出你的屏幕的可视区域。在平台类游戏中，这个问题的普遍解决方案是，像术语“侧滚side-scroller”表明的一样，滚动。

滚动的关键是当玩家精灵接近屏的幕边缘时，使在玩家精灵周围的平台移动。这样给予一种错觉，屏幕是一个在游戏世界中穿梭追拍的摄像机。

这个滚动技巧需要两个在屏幕边缘的绝对区域，在绝对区域内的点处，在世界滚动期间，你的化身静止不动。

在侧滚动条中放置卷轴

如果你希望你的玩家能够后退，你需要一个触发点来向前和向后。这两个点仅仅是两个变量。设置它们各个距各个屏幕边缘大约 100 或 200 像素。在你的设置部分中创建变量。在下面的代码中，前两行用于上下文说明，所以仅需要添加这行后的代码：

player_list.add(player)
steps = 10
forwardX  = 600
backwardX = 230

在主循环中，查看你的玩家精灵是否在 forwardx 或 backwardx 滚动点处。如果是这样，向左或向右移动使用的平台，取决于世界是向前或向后移动。在下面的代码中，代码的最后三行仅供你参考：

        # scroll the world forward
        if player.rect.x >= forwardx:
                scroll = player.rect.x - forwardx
                player.rect.x = forwardx
                for p in plat_list:
                        p.rect.x -= scroll

        # scroll the world backward
        if player.rect.x <= backwardx:
                scroll = backwardx - player.rect.x
                player.rect.x = backwardx
                for p in plat_list:
                        p.rect.x += scroll

        ## scrolling code above
    world.blit(backdrop, backdropbox)
    player.gravity() # check gravity
    player.update()

启动你的游戏，并尝试它。

Scrolling the world in Pygame

滚动像预期的一样工作，但是你可能注意到一个发生的小问题，当你滚动你的玩家和非玩家精灵周围的世界时：敌人精灵不随同世界滚动。除非你要你的敌人精灵要无休止地追逐你的玩家，你需要修改敌人代码，以便当你的玩家快速撤退时，敌人被留在后面。

敌人卷轴

在你的主循环中，你必须对卷轴平台为你的敌人的位置的应用相同的规则。因为你的游戏世界将（很可能）有不止一个敌人在其中，该规则应该被应用于你的敌人列表，而不是一个单独的敌人精灵。这是分组类似元素到列表中的优点之一。

前两行用于上下文注释，所以只需添加这两行后面的代码到你的主循环中：

    # scroll the world forward
    if player.rect.x >= forwardx:
        scroll = player.rect.x - forwardx
        player.rect.x = forwardx
        for p in plat_list:
            p.rect.x -= scroll
        for e in enemy_list:
            e.rect.x -= scroll

来滚向另一个方向：

    # scroll the world backward
    if player.rect.x <= backwardx:
        scroll = backwardx - player.rect.x
        player.rect.x = backwardx
        for p in plat_list:
            p.rect.x += scroll
        for e in enemy_list:
            e.rect.x += scroll

再次启动游戏，看看发生什么。

这里是到目前为止你已经为这个 Python 平台所写所有的代码：

#!/usr/bin/env python3
# draw a world
# add a player and player control
# add player movement
# add enemy and basic collision
# add platform
# add gravity
# add jumping
# add scrolling
# GNU All-Permissive License
# Copying and distribution of this file, with or without modification,
# are permitted in any medium without royalty provided the copyright
# notice and this notice are preserved.  This file is offered as-is,
# without any warranty.
import pygame
import sys
import os
'''
Objects
'''
class Platform(pygame.sprite.Sprite):
# x location, y location, img width, img height, img file    
def __init__(self,xloc,yloc,imgw,imgh,img):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load(os.path.join('images',img)).convert()
self.image.convert_alpha()
self.rect = self.image.get_rect()
self.rect.y = yloc
self.rect.x = xloc
class Player(pygame.sprite.Sprite):
'''
Spawn a player
'''
def __init__(self):
pygame.sprite.Sprite.__init__(self)
self.movex = 0
self.movey = 0
self.frame = 0
self.health = 10
self.collide_delta = 0
self.jump_delta = 6
self.score = 1
self.images = []
for i in range(1,9):
img = pygame.image.load(os.path.join('images','hero' + str(i) + '.png')).convert()
img.convert_alpha()
img.set_colorkey(ALPHA)
self.images.append(img)
self.image = self.images[0]
self.rect  = self.image.get_rect()
def jump(self,platform_list):
self.jump_delta = 0
def gravity(self):
self.movey += 3.2 # how fast player falls
if self.rect.y > worldy and self.movey >= 0:
self.movey = 0
self.rect.y = worldy-ty
def control(self,x,y):
'''
control player movement
'''
self.movex += x
self.movey += y
def update(self):
'''
Update sprite position
'''
self.rect.x = self.rect.x + self.movex
self.rect.y = self.rect.y + self.movey
# moving left
if self.movex < 0:
self.frame += 1
if self.frame > ani*3:
self.frame = 0
self.image = self.images[self.frame//ani]
# moving right
if self.movex > 0:
self.frame += 1
if self.frame > ani*3:
self.frame = 0
self.image = self.images[(self.frame//ani)+4]
# collisions
enemy_hit_list = pygame.sprite.spritecollide(self, enemy_list, False)
for enemy in enemy_hit_list:
self.health -= 1
#print(self.health)
plat_hit_list = pygame.sprite.spritecollide(self, plat_list, False)
for p in plat_hit_list:
self.collide_delta = 0 # stop jumping
self.movey = 0
if self.rect.y > p.rect.y:
self.rect.y = p.rect.y+ty
else:
self.rect.y = p.rect.y-ty
ground_hit_list = pygame.sprite.spritecollide(self, ground_list, False)
for g in ground_hit_list:
self.movey = 0
self.rect.y = worldy-ty-ty
self.collide_delta = 0 # stop jumping
if self.rect.y > g.rect.y:
self.health -=1
print(self.health)
if self.collide_delta < 6 and self.jump_delta < 6:
self.jump_delta = 6*2
self.movey -= 33  # how high to jump
self.collide_delta += 6
self.jump_delta    += 6
class Enemy(pygame.sprite.Sprite):
'''
Spawn an enemy
'''
def __init__(self,x,y,img):
pygame.sprite.Sprite.__init__(self)
self.image = pygame.image.load(os.path.join('images',img))
self.movey = 0
#self.image.convert_alpha()
#self.image.set_colorkey(ALPHA)
self.rect = self.image.get_rect()
self.rect.x = x
self.rect.y = y
self.counter = 0
def move(self):
'''
enemy movement
'''
distance = 80
speed = 8
self.movey += 3.2
if self.counter >= 0 and self.counter <= distance:
self.rect.x += speed
elif self.counter >= distance and self.counter <= distance*2:
self.rect.x -= speed
else:
self.counter = 0
self.counter += 1
if not self.rect.y >= worldy-ty-ty:
self.rect.y += self.movey
plat_hit_list = pygame.sprite.spritecollide(self, plat_list, False)
for p in plat_hit_list:
self.movey = 0
if self.rect.y > p.rect.y:
self.rect.y = p.rect.y+ty
else:
self.rect.y = p.rect.y-ty
ground_hit_list = pygame.sprite.spritecollide(self, ground_list, False)
for g in ground_hit_list:
self.rect.y = worldy-ty-ty
class Level():
def bad(lvl,eloc):
if lvl == 1:
enemy = Enemy(eloc[0],eloc[1],'yeti.png') # spawn enemy
enemy_list = pygame.sprite.Group() # create enemy group
enemy_list.add(enemy)              # add enemy to group
if lvl == 2:
print("Level " + str(lvl) )
return enemy_list
def loot(lvl,lloc):
print(lvl)
def ground(lvl,gloc,tx,ty):
ground_list = pygame.sprite.Group()
i=0
if lvl == 1:
while i < len(gloc):
ground = Platform(gloc[i],worldy-ty,tx,ty,'ground.png')
ground_list.add(ground)
i=i+1
if lvl == 2:
print("Level " + str(lvl) )
return ground_list
def platform(lvl,tx,ty):
plat_list = pygame.sprite.Group()
ploc = []
i=0
if lvl == 1:
ploc.append((0,worldy-ty-128,3))
ploc.append((300,worldy-ty-256,3))
ploc.append((500,worldy-ty-128,4))
while i < len(ploc):
j=0
while j <= ploc[i][2]:
plat = Platform((ploc[i][0]+(j*tx)),ploc[i][1],tx,ty,'ground.png')
plat_list.add(plat)
j=j+1
print('run' + str(i) + str(ploc[i]))
i=i+1
if lvl == 2:
print("Level " + str(lvl) )
return plat_list
'''
Setup
'''
worldx = 960
worldy = 720
fps = 40 # frame rate
ani = 4  # animation cycles
clock = pygame.time.Clock()
pygame.init()
main = True
BLUE  = (25,25,200)
BLACK = (23,23,23 )
WHITE = (254,254,254)
ALPHA = (0,255,0)
world = pygame.display.set_mode([worldx,worldy])
backdrop = pygame.image.load(os.path.join('images','stage.png')).convert()
backdropbox = world.get_rect()
player = Player() # spawn player
player.rect.x = 0
player.rect.y = 0
player_list = pygame.sprite.Group()
player_list.add(player)
steps = 10
forwardx = 600
backwardx = 230
eloc = []
eloc = [200,20]
gloc = []
#gloc = [0,630,64,630,128,630,192,630,256,630,320,630,384,630]
tx = 64 #tile size
ty = 64 #tile size
i=0
while i <= (worldx/tx)+tx:
gloc.append(i*tx)
i=i+1
enemy_list = Level.bad( 1, eloc )
ground_list = Level.ground( 1,gloc,tx,ty )
plat_list = Level.platform( 1,tx,ty )
'''
Main loop
'''
while main == True:
for event in pygame.event.get():
if event.type == pygame.QUIT:
pygame.quit(); sys.exit()
main = False
if event.type == pygame.KEYDOWN:
if event.key == pygame.K_LEFT or event.key == ord('a'):
print("LEFT")
player.control(-steps,0)
if event.key == pygame.K_RIGHT or event.key == ord('d'):
print("RIGHT")
player.control(steps,0)
if event.key == pygame.K_UP or event.key == ord('w'):
print('jump')
if event.type == pygame.KEYUP:
if event.key == pygame.K_LEFT or event.key == ord('a'):
player.control(steps,0)
if event.key == pygame.K_RIGHT or event.key == ord('d'):
player.control(-steps,0)
if event.key == pygame.K_UP or event.key == ord('w'):
player.jump(plat_list)
if event.key == ord('q'):
pygame.quit()
sys.exit()
main = False
# scroll the world forward
if player.rect.x >= forwardx:
scroll = player.rect.x - forwardx
player.rect.x = forwardx
for p in plat_list:
p.rect.x -= scroll
for e in enemy_list:
e.rect.x -= scroll
# scroll the world backward
if player.rect.x <= backwardx:
scroll = backwardx - player.rect.x
player.rect.x = backwardx
for p in plat_list:
p.rect.x += scroll
for e in enemy_list:
e.rect.x += scroll
world.blit(backdrop, backdropbox)
player.gravity() # check gravity
player.update()
player_list.draw(world) #refresh player position
enemy_list.draw(world)  # refresh enemies
ground_list.draw(world)  # refresh enemies
plat_list.draw(world)   # refresh platforms
for e in enemy_list:
e.move()
pygame.display.flip()
clock.tick(fps)

via: https://opensource.com/article/19/12/python-platformer-game-run

作者：Seth Kenlon 选题：lujun9972 译者：robsean 校对：wxy

本文由 LCTT 原创编译，Linux中国 荣誉推出

使你的 Python 游戏玩家能够向前和向后跑

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/255891.html

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