处于非活动状态等我们创建Play按钮后玩家才能开始游戏。

由于Pygame没有内置创建按钮的方法为此新建一个Button类。

button.py

__init__(self,ai_settings,screen,msg):初始化按钮属性self.screen

screen.get_rect()#设置按钮尺寸及其他属性self.width,self.height

(0,255,0)#指定颜色为亮绿self.text_color

(255,255,255)#指定字体None为默认48字号self.font

pygame.font.SysFont(None,48)#创建按钮的rect对象并使其居中self.rect

pygame.Rect(0,0,self.width,self.height)self.rect.center

self.screen_rect.center#按钮的标签只需创建一次def

preg_msg(self,msg):将要显示的文本msg渲染成图像并使其在按钮上居中self.msg_image

self.font.render(msg,True,self.text_color,self.button_color)self.msg_image_rect

self.msg_image.get_rect()self.msg_image_rect.center

self.rect.centerdef

draw_button(self):#绘制一个用颜色填充的按钮再绘制文本self.screen.fill(self.button_color,self.rect)self.screen.blit(self.msg_image,self.msg_image_rect)在屏幕上绘制按钮

alien_invasion.py

run_game():--snip--pygame.display.set_caption(Alien

Button(ai_settings,screen,Play)--snip--#

True:--snip--gf.update_screen(ai_settings,screen,stats,ship,aliens,bullets,play_button)run_game()成功显示按钮后再考虑逐步添加按钮的功能

修改update_screen()使得游戏处于非活动状态下才显示Play按钮且按钮位于其他所有屏幕元素上面

game_functions.py

update_screen(ai_settings.screen,stats,ship,aliens,bullets,play_button):#更新屏幕上的图像并切换到新屏幕--snip--#如果游戏处于非活动状态就绘制Play按钮if

not

stats.game_active:play_button.draw_button()#

让最近绘制的屏幕可见pygame.display.flip()开始游戏

单击按钮时检测MOUSEKEYDOWN事件获取其位置使用pygame.mouse.get_pos()返回其坐标值以判断是否处于按钮的rect内如果是就将game_active设置为True并重置统计信息、删除现有外星人和子弹、创建一批新的外星人群、让飞船居中游戏就此开始。

为观感体验游戏开始后需要隐藏光标的出现。

同时给游戏新增开始游戏的快捷键P。

game_functions.py

check_events(ai_settings,screen,stats,play_button,ship,bullets):#

响应按键和鼠标事件for

pygame.MOUSEBUTTONDOWN:mouse_x,mouse_y

pygame.mouse.get_pos()check_play_button(ai_settings,screen,stats,play_button,ship,aliens,bullets,mouse_x,mouse_y)def

check_play_button(ai_settings,screen,stats,play_button,ship,aliens,bullets,mouse_x,mouse_y)::#在玩家单击Play按钮时开始游戏button_clicked

play_button.rect.collidepoint(mouse_x,mouse_y)if

play_button.rect.collidepoint(mouse_x,mouse_y):stats.game_active

True#重置游戏统计信息if

#隐藏光标pygame.mouse.set_visible(False)stats.reset_stats()stats.game_active

True#清空外星人列表和子弹列表aliens.empty()bullets.empty()#创建一群新的外星人并让飞船居中create_fleet(ai_settings,screen,ship,aliens)ship.center_ship()--snip--

def

ship_hit(ai_settings,stats,screen,ship,aliens,bullets):#

stats.ship_left

0:--snip--else:stats.game_active

False#游戏结束后重新显示光标pygame.mouse.set_visible(True)alien_invasion.py

True:gf.check_events(ai_settings,screen,stats,play_button,ship,bullets)提高等级

在消灭完整群外星人后适当提高游戏难度比如提高外星人的移动速度。

settings.py

设置背景色由RGB指定230230,230为浅灰色self.ship_speed_factor

3self.bullet_height

10#控制游戏节奏随着玩家等级提高的加快速度self.speedup_scale

1.5#初始化随游戏进行而变化的属性self.initialize_dynamic_settings()def

increase_speed(self):#提高速度设置self.ship_speed_factor

self.speedup_scaleself.bullet_speed_factor

self.speedup_scaleself.alien_speed_factor

self.speedup_scale#提高点数并设置为整数self.alien_points

game_functions.py

check_bullet_alien_collisions(ai_settings,screen,ship,aliens,bullets):#

pygame.sprite.groupcollide(bullets,

aliens,

删除现有的子弹加快游戏节奏并新建一群外星人bullets.empty()ai_settings.increase_speed()create_fleet(ai_settings,screen,ship,aliens)

--snip--

check_play_button(ai_settings,screen,stats,play_button,ship,aliens,bullets,mouse_x,mouse_y)::#在玩家单击Play按钮时开始游戏button_clicked

play_button.rect.collidepoint(mouse_x,mouse_y)if

play_button.rect.collidepoint(mouse_x,mouse_y):stats.game_active

True#重置游戏统计信息if

#重置游戏设置ai_settings.initialize_dynamic_settings()--snip--现在游戏更加具备了挑战性每当玩家将屏幕上的外星人消灭干净后游戏都将加快节奏。

根据游戏体验找到最佳的settings.speedup_scale值。

添加计分属性实时跟踪玩家的得分并显示最高得分、当前等级和余下的飞船数。

为在每次开始游戏时都重置得分我们在reset_stats()而不是__init__()中初始化score

而鉴于在任何情况下都不会重置最高分我们在__init__()中初始化high_score

game_stas.py

ai_settingsself.reset_stats()self.game_active

True#在任何情况下都不应重置最高分self.high_score0def

reset_stats(self):#初始化随游戏进行可能变化的统计信息self.ship_left

self.ai_settings.ship_limitself.score

0self.level1-为在屏幕上显示得分创建一个新类Scoreboard

scoreboard.py

__init__(self,ai_settings,screen,stats):#初始化显示得分涉及的属性self.screen

screen.get_rect()self.ai_settings

stats#显示得分信息时使用的字体设置self.text_color

(30,30,30)self.font

pygame.font.SysFont(None,48)#准备包含最高得分和当前得分的图像self.prep_score()self.prep_high_score()#显示等级self.prep_level()self.prep_ships()def

prep_score(self):#将得分转换为一副渲染的图像#将得分圆整到最近的10的整数倍rounded_score

int(round(self.stats.score,-1))#添加千位分隔符score_str

{:,}.format(rounded_score)self.score_image

self.font.render(score_str,True,self.text_color,self.ai_settings.bg_color)#将得分放在屏幕右上方self.score_rect

self.score_image.get_rect()#确保得分始终锚定在右边让其右边缘与屏幕右边缘相距20像素self.score_rect.right

20#使上边缘与屏幕上边缘相距20像素self.score_rect.top

20def

prep_high_score(self):#将最高得分转换为一副渲染的图像high_score

int(round(self.stats.high_score,-1))high_score_str

{:,}.format(high_score)self.high_score_image

self.font.render(high_score_str,True,self.text_color,self.ai_settings.bg_color)#将最高得分放在屏幕顶部中央self.high_score_rect

self.high_score_image.get_rect()self.high_score_rect.centerx

self.screen_rect.centerxself.high_score_rect.top

prep_level(self):#将等级转换为渲染的图像self.level_image

self.font.render(str(self.stats.level),True,self.text_color,self.ai_settings.bg_color)#将等级放在得分下方self.level_rect

self.level_image.get_rect()self.level_rect.right

self.score_rect.right#给得分和等级之间留出空间self.level_rect.top

10def

prep_ships(self):#显示还余下多少飞船self.ships

Group()for

range(self.stats,ships_left):#创建一搜新飞船ship

Ship(self.ai_settings,self.screen)#让整个飞船编组都位于屏幕左边且左边距都为10像素ship.rect.x

ship_number

ship.rect.width#y坐标设置为离屏幕上边缘10像素让所有飞船与得分图像对齐ship.rect.y

10#将每搜新飞船都添加到编组ships中self.ships.add(ship)def

show_score(self):#在屏幕上显示飞船和得分self.screen.blit(self.score_image,self.score_rect)self.screen.blit(self.high_score_image,self.high_score_rect)self.screen.blit(self.level_image,self.level_rect)#绘制飞船self.ships.draw(self.screen)为显示得分更新alien_invasion.py

True:gf.check_events(ai_settings,screen,stats,play_button,ship,aliens,bullets)--snip--

from

run_game():--snip--#创建存储游戏统计信息的实例并创建记分牌stats

Scoreboard(ai_settings,screen,stats)--snip--#游戏的主循环while

True:--snip--gf.update_screen(ai_settings,screen,stats,sb,ship,aliens,bullets,play_button)run_game()显示得分并在外星人被消灭时更新得分提高速度

settings.py

initialize_dynamic_settings(self):--snip--#指定击落一个外星人的得分self.alien_points

50def

increase_speed(self):#提高速度设置self.ship_speed_factor

self.speedup_scaleself.bullet_speed_factor

self.speedup_scaleself.alien_speed_factor

self.speedup_scale#提高点数并设置为整数self.alien_points

self.score_scale)#显示分数注意确认点数在不断增加后要删除该语句以防影响性能及分散玩家注意力print(self.alien_points)显示余下的飞船数

ship.py

__init__(self,ai_settings,screen):#

初始化飞船并设置其初始位置#导入Sprite让ship继承super(Ship,self).__init__()--snip--确保开始游戏时充分调用

game_functions.py

check_events(ai_settings,screen,stats,sb,play_button,ship,aliens,bullets):#

响应按键和鼠标事件for

pygame.MOUSEBUTTONDOWN:mouse_x,mouse_y

pygame.mouse.get_pos()check_play_button(ai_settings,screen,stats,sb,play_button,ship,aliens,bullets,mouse_x,mouse_y)def

check_play_button(ai_settings,screen,stats,sb,play_button,ship,aliens,bullets,mouse_x,mouse_y):#在玩家单击Play按钮时开始游戏button_clicked

play_button.rect.collidepoint(mouse_x,mouse_y)if

play_button.rect.collidepoint(mouse_x,mouse_y):stats.game_active

True#重置游戏统计信息if

#重置游戏设置ai_settings.initialize_dynamic_settings()#重置记分图像sb.prep_score()sb.prep_high_score()sb.prep_level()sb.prep_ships()#隐藏光标pygame.mouse.set_visible(False)stats.reset_stats()stats.game_active

True#清空外星人列表和子弹列表aliens.empty()bullets.empty()#创建一群新的外星人并让飞船居中create_fleet(ai_settings,screen,ship,aliens)ship.center_ship()--snip--def

check_bullet_alien_collisions(ai_settings,screen,stats,sb,ship,aliens,bullets):#

pygame.sprite.groupcollide(bullets,

aliens,

删除现有的子弹加快游戏节奏并新建一群外星人bullets.empty()ai_settings.increase_speed()#提高等级stats.level

1sb.prep_level()create_fleet(ai_settings,screen,ship,aliens)#子弹撞到外星人时返回一个字典collisions更新得分if

aliens

collisions.values():stats.score

ai_settings.alien_pointssb.prep_score()check_high_score(stats,sb)def

update_bullets(ai_settings,screen,stats,sb,ship,aliens,bullets):#

更新子弹的位置并删除已消失的子弹bullets.update()for

bullet

0:bullets.remove(bullet)check_bullet_alien_collisions(ai_settings,screen,stats,sb,ship,aliens,bullets)def

check_aliens_bottom(ai_settings,screen,stats,sb,ship,aliens,bullets):#

screen.get_rect()for

像飞船被外星人撞到一样处理ship_hit(ai_settings,screen,stats,sb,ship,aliens,bullets)breakdef

update_aliens(ai_settings,screen,stats,sb,ship,aliens,bullets):#

检查并更新外星人群中所有外星人的位置check_fleet_edges(ai_settings,aliens)aliens.update()check_aliens_bottom(ai_settings,stats,screen,ship,aliens,bullets)#

pygame.sprite.spritecollideany(ship,aliens):ship_hit(ai_settings,stats,screen,sb,ship,aliens,bullets)#检查是否有外星人抵达屏幕底端check_aliens_bottom(ai_settings,screen,stats,sb,ship,aliens,bullets)def

ship_hit(ai_settings,screen,stats,sb,ship,aliens,bullets):#

stats.ship_left

清空外星人列表和子弹列表--snip--else:stats.game_active

False#游戏结束后重新显示光标pygame.mouse.set_visible(True)def

check_high_score(stats,sb):#检查是否诞生了新的最高得分if

stats.score

stats.high_score:stats.high_score

stats.scoresb.prep_high_score()--snip--相应的修改主while循环中的代码传递实参sb

alien_invasion.py*

run_game():--snip--#创建存储游戏统计信息的实例并创建记分牌stats

Scoreboard(ai_settings,screen,stats)#游戏的主循环while

True:gf.check_events(ai_settings,screen,stats,sb,play_button,ship,aliens,bullets)if

stats.game_active:ship.update()gf.update_bullets(ai_settings,screen,stats,sb,ship,aliens,bullets)gf.update_aliens(ai_settings,screen,stats,sb,ship,aliens,bullets)--snip--gf.update_screen(ai_settings,screen,stats,sb,ship,aliens,bullets,play_button)run_game()--snip--