太空射击第13课： 爆炸效果

这是我们“Shmup”项目的第10部分。如果您尚未通读前面的部分，请从第 1 部分开始。在本课中，我们将在玩家射击流星时进行一些动画爆炸。

视频

您可以在此处观看本课程的视频：

自动开火

首先，让我们对玩家的射击方式进行一些小的改变。现在，我们必须为每次射击按空格键。这导致玩家快速敲击键盘空格键。相反，只要按住空格键，我们就可以让飞船自动射击。

为此，我们将向玩家添加两个新属性：

self.shoot_delay = 250
self.last_shot = pygame.time.get_ticks()

shoot_delay将测量飞船在发射另一颗子弹之前应该等待多长时间（以毫秒为单位）。last_shot跟踪最后一颗子弹的发射时间，以便确定经过足够的时间再次开火。

现在，我们将在玩家更新中将 fire 键添加到键盘检查中：

def update(self):
    self.speedx = 0
    keystate = pygame.key.get_pressed()
    if keystate[pygame.K_LEFT]:
        self.speedx = -8
    if keystate[pygame.K_RIGHT]:
        self.speedx = 8
    if keystate[pygame.K_SPACE]:
        self.shoot()

我们将把所有的射击逻辑放在一个新的方法中：

def shoot(self):
    now = pygame.time.get_ticks()
    if now - self.last_shot > self.shoot_delay:
        self.last_shot = now
        bullet = Bullet(self.rect.centerx, self.rect.top)
        all_sprites.add(bullet)
        bullets.add(bullet)

现在，当空格键被按住时，游戏将检查自创建最后一颗子弹以来已经过去了多少时间。如果已经过shoot_delay毫秒，则发射另一颗子弹并更新last_shot。最后，我们可以从游戏循环中删除以下行：

elif event.type == pygame.KEYDOWN:
    if event.key == pygame.K_SPACE:
        player.shoot()

动画爆炸

对于我们的下一个补充，我们希望通过使流星爆炸而不仅仅是消失，使流星的破坏更具视觉吸引力。为了实现这一点，我们需要一组用于爆炸图形的动画帧，并且我们需要在被摧毁的流星的位置创建一个精灵，该精灵将在动画帧序列中循环。以下是我们将要使用的动画序列：

单击此处下载这些图像的压缩包。

首先，我们需要将这些图形加载到游戏中，并将它们存储在列表中。与玩家精灵一样，我们将需要调整图像大小，当我们这样做时，我们将创建两个不同大小的爆炸：一个大爆炸，当流星被摧毁时;和一个小的，当流星击中玩家的盾牌时。因此，我们将有一个字典explosion_anim ，其中包含两个列表lg和sm .由于这些文件的名称相同，数字从00-08，我们可以使用循环将它们全部加载，调整大小并将它们附加到列表中：

explosion_anim = {
    }
explosion_anim['lg'] = []
explosion_anim['sm'] = []
for i in range(9):
    filename = 'regularExplosion0{}.png'.format(i)
    img = pygame.image.load(path.join(img_dir, filename)).convert()
    img.set_colorkey(BLACK)
    img_lg = pygame.transform.scale(img, (75, 75))
    explosion_anim['lg'].append(img_lg)
    img_sm = pygame.transform.scale(img, (32, 32))
    explosion_anim['sm'].append(img_sm)

爆炸精灵

接下来，我们将定义一个新的精灵，当它出现在屏幕上时，它将是实际的爆炸。此精灵的图像将在我们的动画帧列表中从一个图像快速更改为下一个图像。当它到达最后一帧时，该精灵将被删除。当我们生成精灵时，我们会告诉它在哪里生成（流星的位置），以及使用哪个大小。类似于我们执行上面的自动射击功能，我们也有一个frame_rate属性，它将使我们能够控制动画运行的速度 - 如果我们每次更新（$\frac{1}{60}$秒）更改图像，那么整个爆炸只会持续大约$\frac{1}{10}$秒。下面是Explosion精灵的代码：

class Explosion(pygame.sprite.Sprite):
    def __init__(self, center, size):
        pygame.sprite.Sprite.__init__(self)
        self.size = size
        self.image = explosion_anim[self.size][0]
        self.rect = self.image.get_rect()
        self.rect.center = center
        self.frame = 0
        self.last_update = pygame.time.get_ticks()
        self.frame_rate = 50

    def update(self):
        now = pygame.time.get_ticks()
        if now - self.last_update > self.frame_rate:
            self.last_update = now
            self.frame += 1
            if self.frame == len(explosion_anim[self.size]):
                self.kill()
            else:
                center = self.rect.center
                self.image = explosion_anim[self.size][self.frame]
                self.rect = self.image.get_rect()
                self.rect.center = center

现在，每当敌人被摧毁时，我们需要生成其中一个：

# check to see if a bullet hit a mob
hits = pygame.sprite.groupcollide(mobs, bullets, True, True)
for hit in hits:
    score += 50 - hit.radius
    random.choice(expl_sounds).play()
    expl = Explosion(hit.rect.center, 'lg')
    all_sprites.add(expl)
    newmob()

当玩家被击中时：

# check to see if a mob hit the player
hits = pygame.sprite.spritecollide(player, mobs, True, pygame.sprite.collide_circle)
for hit in hits:
    player.shield -= hit.radius * 2
    expl = Explosion(hit.rect.center, 'sm')
    all_sprites.add(expl)
    newmob()
    if player.shield <= 0:
        running = False

现在我们可以看到最终结果：

在下一部分中，我们将通过为玩家添加生命来使游戏持续更长时间。

此部分的完整代码

# KidsCanCode - Game Development with Pygame video series
# Shmup game - part 10
# Video link: https://www.youtube.com/watch?v=AdG_ITCFHDI
# Explosions
# Frozen Jam by tgfcoder <https://twitter.com/tgfcoder> licensed under CC-BY-3
# Art from Kenney.nl
import pygame
import random
from os import path

img_dir = path.join(path.dirname(__file__), 'img')
snd_dir = path.join(path.dirname(__file__), 'snd')

WIDTH = 480
HEIGHT = 600
FPS = 60

# define colors
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 0, 255)
YELLOW = (255, 255, 0)

# initialize pygame and create window
pygame.init()
pygame.mixer.init()
screen = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Shmup!")
clock = pygame.time.Clock()

font_name = pygame.font.match_font('arial')
def draw_text(surf, text, size, x, y):
    font = pygame.font.Font(font_name, size)
    text_surface = font.render(text, True, WHITE)
    text_rect = text_surface.get_rect()
    text_rect.midtop = (x, y)
    surf.blit(text_surface, text_rect)

def newmob():
    m = Mob()
    all_sprites.add(m)
    mobs.add(m)

def draw_shield_bar(surf, x, y, pct):
    if pct < 0:
        pct = 0
    BAR_LENGTH = 100
    BAR_HEIGHT = 10
    fill = (pct / 100) * BAR_LENGTH
    outline_rect = pygame.Rect(x, y, BAR_LENGTH, BAR_HEIGHT)
    fill_rect = pygame.Rect(x, y, fill, BAR_HEIGHT)
    pygame.draw.rect(surf, GREEN, fill_rect)
    pygame.draw.rect(surf, WHITE, outline_rect, 2)

class Player(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image = pygame.transform.scale(player_img, (50, 38))
        self.image.set_colorkey(BLACK)
        self.rect = self.image.get_rect()
        self.radius = 20
        # pygame.draw.circle(self.image, RED, self.rect.center, self.radius)
        self.rect.centerx = WIDTH / 2
        self.rect.bottom = HEIGHT - 10
        self.speedx = 0
        self.shield = 100
        self.shoot_delay = 250
        self.last_shot = pygame.time.get_ticks()

    def update(self):
        self.speedx = 0
        keystate = pygame.key.get_pressed()
        if keystate[pygame.K_LEFT]:
            self.speedx = -8
        if keystate[pygame.K_RIGHT]:
            self.speedx = 8
        if keystate[pygame.K_SPACE]:
            self.shoot()
        self.rect.x += self.speedx
        if self.rect.right > WIDTH:
            self.rect.right = WIDTH
        if self.rect.left < 0:
            self.rect.left = 0

    def shoot(self):
        now = pygame.time.get_ticks()
        if now - self.last_shot > self.shoot_delay:
            self.last_shot = now
            bullet = Bullet(self.rect.centerx, self.rect.top)
            all_sprites.add(bullet)
            bullets.add(bullet)
            shoot_sound.play()

class Mob(pygame.sprite.Sprite):
    def __init__(self):
        pygame.sprite.Sprite.__init__(self)
        self.image_orig = random.choice(meteor_images)
        self.image_orig.set_colorkey(BLACK)
        self.image = self.image_orig.copy()
        self.rect = self.image.get_rect()
        self.radius = int(self.rect.width * .85 / 2)
        # pygame.draw.circle(self.image, RED, self.rect.center, self.radius)
        self.rect.x = random.randrange(WIDTH - self.rect.width)
        self.rect.bottom = random.randrange(-80, -20)
        self.speedy = random.randrange(1, 8)
        self.speedx = random.randrange(-3, 3)
        self.rot = 0
        self.rot_speed = random.randrange(-8, 8)
        self.last_update = pygame.time.get_ticks()

    def rotate(self):
        now = pygame.time.get_ticks()
        if now - self.last_update > 50:
            self.last_update = now
            self.rot = (self.rot + self.rot_speed) % 360
            new_image = pygame.transform.rotate(self.image_orig, self.rot)
            old_center = self.rect.center
            self.image = new_image
            self.rect = self.image.get_rect()
            self.rect.center = old_center

    def update(self):
        self.rotate()
        self.rect.x += self.speedx
        self.rect.y += self.speedy
        if self.rect.top > HEIGHT + 10 or self.rect.left < -100 or self.rect.right > WIDTH + 100:
            self.rect.x = random.randrange(WIDTH - self.rect.width)
            self.rect.y = random.randrange(-100, -40)
            self.speedy = random.randrange(1, 8)

class Bullet(pygame.sprite.Sprite):
    def __init__(self, x, y):
        pygame.sprite.Sprite.__init__(self)
        self.image = bullet_img
        self.image.set_colorkey(BLACK)
        self.rect = self.image.get_rect()
        self.rect.bottom = y
        self.rect.centerx = x
        self.speedy = -10

    def update(self):
        self.rect.y += self.speedy
        # kill if it moves off the top of the screen
        if self.rect.bottom < 0:
            self.kill()

class Explosion(pygame.sprite.Sprite):
    def __init__(self, center, size):
        pygame.sprite.Sprite.__init__(self)
        self.size = size
        self.image = explosion_anim[self.size][0]
        self.rect = self.image.get_rect()
        self.rect.center = center
        self.frame = 0
        self.last_update = pygame.time.get_ticks()
        self.frame_rate = 50

    def update(self):
        now = pygame.time.get_ticks()
        if now - self.last_update > self.frame_rate:
            self.last_update = now
            self.frame += 1
            if self.frame == len(explosion_anim[self.size]):
                self.kill()
            else:
                center = self.rect.center
                self.image = explosion_anim[self.size][self.frame]
                self.rect = self.image.get_rect()
                self.rect.center = center

# Load all game graphics
background = pygame.image.load(path.join(img_dir, "starfield.png")).convert()
background_rect = background.get_rect()
player_img = pygame.image.load(path.join(img_dir, "playerShip1_orange.png")).convert()
bullet_img = pygame.image.load(path.join(img_dir, "laserRed16.png")).convert()
meteor_images = []
meteor_list = ['meteorBrown_big1.png', 'meteorBrown_med1.png', 'meteorBrown_med1.png',
               'meteorBrown_med3.png', 'meteorBrown_small1.png', 'meteorBrown_small2.png',
               'meteorBrown_tiny1.png']
for img in meteor_list:
    meteor_images.append(pygame.image.load(path.join(img_dir, img)).convert())
explosion_anim = {}
explosion_anim['lg'] = []
explosion_anim['sm'] = []
for i in range(9):
    filename = 'regularExplosion0{}.png'.format(i)
    img = pygame.image.load(path.join(img_dir, filename)).convert()
    img.set_colorkey(BLACK)
    img_lg = pygame.transform.scale(img, (75, 75))
    explosion_anim['lg'].append(img_lg)
    img_sm = pygame.transform.scale(img, (32, 32))
    explosion_anim['sm'].append(img_sm)
# Load all game sounds
shoot_sound = pygame.mixer.Sound(path.join(snd_dir, 'pew.wav'))
expl_sounds = []
for snd in ['expl3.wav', 'expl6.wav']:
    expl_sounds.append(pygame.mixer.Sound(path.join(snd_dir, snd)))
pygame.mixer.music.load(path.join(snd_dir, 'tgfcoder-FrozenJam-SeamlessLoop.ogg'))
pygame.mixer.music.set_volume(0.4)

all_sprites = pygame.sprite.Group()
mobs = pygame.sprite.Group()
bullets = pygame.sprite.Group()
player = Player()
all_sprites.add(player)
for i in range(8):
    newmob()

score = 0
pygame.mixer.music.play(loops=-1)
# Game loop
running = True
while running:
    # keep loop running at the right speed
    clock.tick(FPS)
    # Process input (events)
    for event in pygame.event.get():
        # check for closing window
        if event.type == pygame.QUIT:
            running = False

    # Update
    all_sprites.update()

    # check to see if a bullet hit a mob
    hits = pygame.sprite.groupcollide(mobs, bullets, True, True)
    for hit in hits:
        score += 50 - hit.radius
        random.choice(expl_sounds).play()
        expl = Explosion(hit.rect.center, 'lg')
        all_sprites.add(expl)
        newmob()

    # check to see if a mob hit the player
    hits = pygame.sprite.spritecollide(player, mobs, True, pygame.sprite.collide_circle)
    for hit in hits:
        player.shield -= hit.radius * 2
        expl = Explosion(hit.rect.center, 'sm')
        all_sprites.add(expl)
        newmob()
        if player.shield <= 0:
            running = False

    # Draw / render
    screen.fill(BLACK)
    screen.blit(background, background_rect)
    all_sprites.draw(screen)
    draw_text(screen, str(score), 18, WIDTH / 2, 10)
    draw_shield_bar(screen, 5, 5, player.shield)
    # *after* drawing everything, flip the display
    pygame.display.flip()

pygame.quit()

第11部分：玩家生活