Python实战（1）——外星人入侵，实现空格长按发射子弹_pygame实现长按功能

#经过对Python从入门到实践的学习，完成了外星人入侵的代码复现

#于是考虑能否在这个基础上进行一些小小的改进

问题说明

        我发现在射击的部分还存在一定的缺憾，想要快速地射击外星人，依靠每次按下发射一颗子弹有些费手，于是考虑实现长按空格键进行射击，网上搜索了一下没有这么实现的代码，而利用pygame.key.set_repeat() 也无法准确实现，反而影响正常射击。

        于是考虑与移动相似的方法设定一个flag来判断目前的射击状态

目标实现

首先在ship.py中添加了一个flag：self.shooting, 用以判断射击状态。

        # Movement flags.
        self.moving_right = False
        self.moving_left = False
        self.shooting = False

接着对game_function.py进行修改。

##原代码##
def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """Respond to keypresses."""
    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_SPACE:
        fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit()
        
def check_keyup_events(event, ship):
    """Respond to key releases."""
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False

将flag加入其中：

def check_keydown_events(event, ai_settings, screen, ship, bullets):
    """Respond to keypresses."""
    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_SPACE:
        ship.shooting = True
        # fire_bullet(ai_settings, screen, ship, bullets)
    elif event.key == pygame.K_q:
        sys.exit()
        
def check_keyup_events(event, ship):
    """Respond to key releases."""
    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_SPACE:
        ship.shooting = False

if ship.shooting:
    gf.fire_bullet(ai_settings, screen, ship, bullets)
 

定义后就可以在主函数中进行调用了，即 可以实现连续射击

while True:
 
        clock.tick(250)
        gf.check_events(ai_settings, screen, stats, sb, play_button, ship,
            aliens, bullets)
        
        if stats.game_active:
            if ship.shooting:
                gf.fire_bullet(ai_settings, screen, ship, bullets)
            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--
 

但是这样在主代码中显得有些臃肿，于是再进行修改。将if shooting放入fire_bullet()中。

 
def fire_bullet(ai_settings, screen, ship, bullets):
    """Fire a bullet, if limit not reached yet."""
    # Create a new bullet, add to bullets group.
    if len(bullets) < ai_settings.bullets_allowed and ship.shooting:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)

 这样主代码变为：

       --snip--
 
        if stats.game_active:
            gf.fire_bullet(ai_settings, screen, ship, bullets)
            ship.update()
 
            --snip--

目前基本实现了预期目的，感觉还可以再精进一下.......