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前面的知识和案例中我们也用了一下键盘，那时候是用了pygame.event.get()获取所有的事件，当event.type == KEYDOWN的时候，再判断event.key的种类。今天我们再介绍一个方法，pygame.key.get_pressed()来获得所有按下的键值，它会返回一个元组。这个元组的索引就是键值，对应的就是是否按下，比如说：

当我们按下右键时，得到的 get_pressed 元组列表如下（注意有一个1）：

(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)

pygame.K_RIGHT 是一个常量, 值是275.

key_pressed[pygame.K_RIGHT] 实质上就是key_pressed[275]==1代表右键被按下

当然key模块下还有很多函数：

key.get_focused —— 返回当前的pygame窗口是否激活

key.get_pressed —— 刚刚解释过了

key.get_mods —— 按下的组合键（Alt, Ctrl, Shift）

key.set_mods —— 你也可以模拟按下组合键的效果（KMOD_ALT, KMOD_CTRL, KMOD_SHIFT）

key.set_repeat —— 无参数调用设置pygame不产生重复按键事件，二参数(delay, interval)调用设置重复事件发生的时间

key.name —— 接受键值返回键名

使用键盘控制方向

根据坐标变化规律，通过这张图帮助理解键盘如何控制方向：

我们使用key.get_pressed()修改之前的程序：

background_image_filename = './img/Underwater.png'
sprite_image_filename = './img/fish-b.png'

import pygame
from pygame.locals import *
from sys import exit
from Vec2d import *
 
pygame.init()
 
screen = pygame.display.set_mode((640, 480), 0, 32)
 
background = pygame.image.load(background_image_filename).convert()
sprite = pygame.image.load(sprite_image_filename).convert_alpha()
 
clock = pygame.time.Clock()
sprite_pos = Vec2d(200, 150)
sprite_speed = 300.
 
while True:
 
    for event in pygame.event.get():
        if event.type == QUIT:
            exit()
 
    pressed_keys = pygame.key.get_pressed()

    key_direction = Vec2d(0, 0)
    if pressed_keys[K_LEFT]:
        print(pressed_keys)
        key_direction.x = -1
    elif pressed_keys[K_RIGHT]:
        key_direction.x = +1
    if pressed_keys[K_UP]:
        key_direction.y = -1
    elif pressed_keys[K_DOWN]:
        key_direction.y = +1

    key_direction.normalized()

    screen.blit(background, (0,0))
    screen.blit(sprite, sprite_pos)

    time_passed = clock.tick(30)
    time_passed_seconds = time_passed / 1000.0

    sprite_pos+= key_direction * sprite_speed * time_passed_seconds

    pygame.display.update()

如果你不知道Vec2d是什么，传送门-->pygame游戏编程入门-向量类的使用

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