《Python编程：从入门到实践》外星人入侵项目课后练习13-6_外星人入侵项目答案

13-6 :屏幕底端有一个可以左右移动的玩家，屏幕顶端有一个球，水平位置随机，使这个球按固定速度下落，如果角色抓到球或者球碰到屏幕底端，就让球消失，并在顶端重新创建一个球，跟踪玩家没接到球的次数，达到三次结束游戏。

我这里只是将球换为礼物盒的形式，实现的功能未发生变化。
用到的模块如下：

卡通人物图片：

礼物盒图片：

两张图片均放在image文件夹中即可。
首先是一些基本设置，屏幕的长宽、背景颜色、礼物盒下落速度、人物左右移动速度等。

settings.py

class Settings():
    def __init__(self):
        self.screen_width = 1900
        self.screen_height = 1000
        self.bg_color = (255,255,255)  # 设置背景色，浅灰色
        self.drop_speed = 1
        self.moving_speed = 2
        self.moving_right = False
        self.moving_left = False
        self.state = 3
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人物的一些基本设置，如何获得人物、初始化任务位置、左右移动更新位置、显示人物。

person.py

import pygame

class Person():
    def __init__(self,scratch_settings,screen):
        self.scratch_settings = scratch_settings
        self.screen = screen
        self.screen_rect = screen.get_rect()

        self.image = pygame.image.load('C:/Users/Xin/PycharmProjects/alien_invasion/image/person_scratch.bmp')
        self.rect = self.image.get_rect()

        self.rect.centerx = self.screen_rect.centerx
        self.rect.bottom = self.screen_rect.bottom

        self.x = float(self.rect.centerx)

    def update(self,scratch_settings):
        if scratch_settings.moving_right:
            self.x +=  scratch_settings.moving_speed
        if scratch_settings.moving_left:
            self.x -= scratch_settings.moving_speed

        self.rect.centerx = self.x

    def biltme(self):
        self.screen.blit(self.image, self.rect)
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礼物盒的一些基本设置，如何获得礼物盒图片、初始化礼物盒位置、位置更新、显示礼物盒。

gifts.py

import pygame
from random import randint

class Gift():
    def __init__(self, scratch_settings, screen, ):
        self.scratch_settings = scratch_settings
        self.screen = screen
        self.screen_rect = screen.get_rect()

        self.image = pygame.image.load('C:/Users/Xin/PycharmProjects/alien_invasion/image/gift.bmp')
        self.rect = self.image.get_rect()


        self.rect.centerx = randint(int(self.rect.width / 2), scratch_settings.screen_width - int (self.rect.width / 2))
        self.rect.y = 0

        self.y = float(self.rect.y)


    def update(self,scratch_settings):
        self.y += scratch_settings.drop_speed
        self.rect.y = self.y

    def biltme(self):
        self.screen.blit(self.image, self.rect)
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用一个State类记录游戏中未接到礼物的次数.
state.py

class State():
    def __init__(self,scratch_settings):
        self.scratch_settings = scratch_settings
        
        #每次重新运行都需要重置
        self.reset_game()
        #表示游戏是否可以继续执行
        self.game_state = True
    def reset_game(self):
        self.opportunity = self.scratch_settings.state
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用到的主要函数，响应键盘和鼠标的操作，人物是左移还是右移，更新人物的位置，检查礼物盒的位置，是否触碰到卡通人物或者触碰到屏幕底端，游戏是否可以继续执行，显示人物和礼物盒的位置。

game_function.py

import pygame
import sys
from random import randint

def check_events(scratch_settings):
    #响应鼠标和键盘的操作
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYDOWN:
            check_keydown_events(event,scratch_settings)
        elif event.type == pygame.KEYUP:
            check_keyup_events(event,scratch_settings)

def check_keydown_events(event,scratch_settings):
    #人物是左移还是右移还是退出游戏
    if event.key == pygame.K_RIGHT:
        scratch_settings.moving_right = True
    elif event.key == pygame.K_LEFT:
        scratch_settings.moving_left = True
    elif event.key == pygame.K_q:
        sys.exit()

def check_keyup_events(event,scratch_settings):
    if event.key == pygame.K_RIGHT:
        scratch_settings.moving_right = False
    elif event.key == pygame.K_LEFT:
        scratch_settings.moving_left = False

def new_position_of_gift(gift,scratch_settings):
    #礼物盒被捕捉或者触碰到底端之后，出现在屏幕顶端，位置不定
    gift.rect.centerx = randint(int(gift.rect.width / 2), scratch_settings.screen_width - int(gift.rect.width / 2))
    gift.y = 0

def check_gift_scratch_or_edge(gift,person,scratch_settings,gift_state):
    #判断是否被接到
    if gift.rect.right >= person.rect.left and gift.rect.left <= person.rect.right and gift.rect.bottom == person.rect.top:
        new_position_of_gift(gift, scratch_settings)
    #判断是否碰触到屏幕底端
    elif  gift.rect.bottom == gift.screen_rect.bottom:
        #游戏是否可以继续，未接到的次数是否小于3
        if gift_state.opportunity > 1:
            new_position_of_gift(gift, scratch_settings)
            gift_state.opportunity -= 1
        else:
            gift_state.game_state = False


def update_gift(gift,person,scratch_settings,gift_state):
    #更新礼物盒的位置
    check_gift_scratch_or_edge(gift,person,scratch_settings,gift_state)
    gift.update(scratch_settings)

def update_screen(scratch_settings,screen,gift,person):
    screen.fill(scratch_settings.bg_color)  # 将背景色填满整个屏幕
    gift.biltme()
    person.biltme()
    # 让最近绘制的屏幕可见
    pygame.display.flip()
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主文件部分。
start_scratch.py

import pygame
from scratch.settings import Settings
from scratch.gifts import Gift
import scratch.game_function as gf
from scratch.person import Person
from scratch.state import State

def run():
    scratch_settings = Settings()
    screen = pygame.display.set_mode((scratch_settings.screen_width,scratch_settings.screen_height))
    gift = Gift(scratch_settings,screen)
    scratch_person = Person(scratch_settings,screen)
    gift_state = State(scratch_settings)

    while True:
        #不管游戏是否运行，都需要响应鼠标和键盘的操作以及显示屏幕
        gf.check_events(scratch_settings)
        #当游戏运行时
        if gift_state.game_state:
            gf.update_gift(gift,scratch_person,scratch_settings,gift_state)
            scratch_person.update(scratch_settings)
        gf.update_screen(scratch_settings,screen,gift,scratch_person)

run()

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