【问题标题】：Pygame ship movement only Up & Down (left right is working)Pygame 船舶仅上下移动（左右工作）
【发布时间】：2017-09-27 22:48:07
【问题描述】：

这部分是gamefunction.py文件

import sys

import pygame

def check_keydown_events(event,ship):
    """Respond to the keypressess."""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        ship.moving_left = True
    elif event.key == pygame.K_UP:
        ship.moving_up = True
    elif event.key == pygame.K_DOWN:
        ship.moving_down = True 


def check_keyup_events(event, ship):
    """Respond to the keyreleases."""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False
    elif event.key == pygame.K_UP:
        ship.moving_up = False
    elif event.key == pygame.K_DOWN:
        ship.moving_down = False

def check_events(ship):
    """Respond to keypresses and mouse events."""
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()

        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event,ship)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event, ship)

这被命名为 ship.py

import pygame

class Ship():

    def __init__(self,ai_settings,screen):
        """Initialize the ship and set its starting position."""
        self.screen = screen
        self.ai_settings = ai_settings
        #Load the ship image and get its rect.
        self.image = pygame.image.load('images/ship.png')
        self.rect = self.image.get_rect()
        self.screen_rect = screen.get_rect()

        #Start each new ship at the bottom center of the screen.
        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom
        
        #Store a decimal value for the ship's center.
        self.center = float(self.rect.centerx) 
        #Movement Flags
        self.moving_right = False
        self.moving_left = False
        self.moving_up = False
        self.moving_down = False


    def update(self):
        """Update the ship's position based on the movement flag."""
        #Update the ship's center value, not the rect
        if self.moving_right and self.rect.right<self.screen_rect.right:
            self.center += self.ai_settings.ship_speed_factor
        if self.moving_left and self.rect.left>0:
            self.center -= self.ai_settings.ship_speed_factor 
        #Up-dwon motion added ***Please check the logic for 1200x800 screen*** 
        if self.moving_up and self.rect.top<self.screen_rect.top:
            self.center += self.ai_settings.ship_speed_factor
        if self.moving_down and self.rect.bottom>800:
            self.center -= self.ai_settings.ship_speed_factor

        #Update rect object from self.center.
        self.rect.centerx = self.center

【问题讨论】：

您的问题是什么？你有错误吗？代码没有按您的预期运行吗？您需要在正文中定义问题并解释问题所在，您希望它做什么，并提供minimal reproducible example。确保您的代码格式正确，以便更容易阅读代码。
代码在上下移动时未按预期执行
当你问一个问题时，你必须确保它的格式正确以便它可读（不过我现在已经为你做了）。您还必须解释代码在做什么（正在发生什么）并解释您试图做什么。由于您没有提供minimal reproducible example，我们无法测试代码以找出问题所在。当您编写“代码未按预期执行”时，我们只能猜测问题所在。如果你改为写“这艘船的移动方向与我希望它移动的方向相反”我们就会知道要寻找什么。

标签： python python-2.7 pygame

【解决方案1】：

来源：Python Crash Course

在ship.py 只需几周时间：

在self.center = float(self.rect.centerx) 下，添加self.bottom = float(self.rect.bottom) 并更改：

if self.moving_up and self.rect.top<self.screen_rect.top:
    self.center += self.ai_settings.ship_speed_factor
if self.moving_down and self.rect.bottom>800:
    self.center -= self.ai_settings.ship_speed_factor

到：

if self.moving_up and self.rect.top<self.screen_rect.top:
    self.bottom -= self.ai_settings.ship_speed_factor
if self.moving_down and self.rect.bottom<800:
    self.bottom += self.ai_settings.ship_speed_factor

最后在self.rect.centerx = self.center 下，添加self.rect.bottom = self.bottom。

这应该使您能够在游戏中上下波动！

【讨论】：

【解决方案2】：

这是我在这些函数中发现的一个问题：

check_keydown_events
check_keyup_events
check_events

在每种情况下，您都在执行if-elif-elif-elif 语句。这意味着当if 语句为True 时，elif 语句将不会运行。

在您的情况下，如果按下左键或右键，您将永远无法向上或向下移动。

您应该更改此代码，以便仅将if-elif 与上/下和左/右移动分开使用。

这是一个（更正的）示例：

if event.key == pygame.K_RIGHT:
    ship.moving_right = True
elif event.key == pygame.K_LEFT:
    ship.moving_left = True
if event.key == pygame.K_UP:
    ship.moving_up = True
elif event.key == pygame.K_DOWN:
    ship.moving_down = True

如果您将每个 if-elif-elif-elif 语句更改为 if-elif-if-elif，您的问题将得到解决。

【讨论】：

【解决方案3】：

Ship.py

.....
self.bottom = float(self.rect.bottom)
self.moving_up = False
self.moving_down = False

def update(self):
    .....
    # check if the ship is moving up and stop the ship to move up if 
    # it's top edge position is less than 
    # screen's top (top right corner is 0,0) position
    if self.moving_up and self.rect.top > self.screen_rect.top:
        self.bottom -= self.ai_settings.ship_speed_factor

    # check if the ship is moving down and stop the ship when it's
    # bottom position is greater than the screen bottom edge position.
    if self.moving_down and self.rect.bottom < self.screen_rect.bottom:
        self.bottom += self.ai_settings.ship_speed_factor

    self.rect.bottom = self.bottom

game_function.py

def check_keydown_event(event, ship):
    """Respond to keypresses"""
    ....
    elif event.key == pygame.K_UP:
        ship.moving_up = True
    elif event.key == pygame.K_DOWN:
        ship.moving_down = True


def check_keyup_event(event, ship):
    ....
    elif event.key == pygame.K_UP:
        ship.moving_up = False
    elif event.key == pygame.K_DOWN:
        ship.moving_down = False

【讨论】：