Pygame through SSH does not register keystrokes (Raspberry Pi 3)

问题

So I got raspi 3 and simple 8x8 LED matrix. After some playing with it I decided to make a simple snake game (displaying on that matrix) with pygame's events, I have no prior experience with pygame. There is no screen/display connected besides the led matrix.

So the problem at first was "pygame.error: video system not initialized", though I think i got it fixed by setting an env variable: os.putenv('DISPLAY', ':0.0') Now that I got it working I run it...and nothing happens, like no keystrokes are registered. Just this "junk", I don't know how to call it The dot on LED matrix is not moving. If i alter the snake's x or y position somewhere in the loop it moves as intended.

My code:

#!/usr/bin/python2
import pygame
import max7219.led as led
from max7219.font import proportional, SINCLAIR_FONT, TINY_FONT, CP437_FONT
import numpy as nqp
import os

SIZE = (8, 8)

class Board:
    def __init__(self, size, snake):
        "Board object for snake game"
        self.matrix = np.zeros(size, dtype=np.int8)
        self.device = led.matrix()
        self.snake = snake
    def draw(self):
        #add snake
        self.matrix = np.zeros(SIZE, dtype=np.int8)
        self.matrix[self.snake.x][self.snake.y] = 1
        for x in range(8):
            for y in range(8):
                self.device.pixel(x, y, self.matrix[x][y], redraw=False)
        self.device.flush()
    def light(self, x, y):
        "light specified pixel"
        self.matrix[x][y] = 1
    def dim(self, x, y):
        "off specified pixel"
        self.matrix[x][y] = 0

class Snake:
    def __init__(self):
        "Object representing an ingame snake"
        self.length = 1
        self.x = 3
        self.y = 3

if __name__=="__main__":
    os.putenv('DISPLAY', ':0.0')
    pygame.init()
    snake = Snake()
    board = Board(SIZE, snake)
    done = False
    while not done:
        for event in pygame.event.get():
            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_UP:
                    snake.y -= 1
                elif event.key == pygame.K_DOWN:
                    snake.y += 1
                elif event.key == pygame.K_LEFT:
                    snake.x -= 1
                elif event.key == pygame.K_RIGHT:
                    snake.x += 1
        board.draw()

I'm using pygame because I don't know anything else (Well I can't use pygame either but I just don't know of any alternatives). If it can be done simpler I will be happy to do it. Thank You in advance!

回答1:

You should be able to use curses. Here's a simple example:

import curses


def main(screen):
    key = ''
    while key != 'q':
        key = screen.getkey()
        screen.addstr(0, 0, 'key: {:<10}'.format(key))


if __name__ == '__main__':
    curses.wrapper(main)

You'll see that your key presses are registered - they're just strings.

However, this runs in blocking mode. Assuming that your code needs to do other things, you can turn nodelay on:

def main(screen):
    screen.nodelay(True)
    key = ''
    while key != 'q':
        try:
            key = screen.getkey()
        except curses.error:
            pass  # no keypress was ready
        else:
            screen.addstr(0, 0, 'key: {:<10}'.format(key))

In your scenario you probably would put this inside your game loop that's drawing out to your 8x8 display, so it would look something like this:

 game = SnakeGame()
 while game.not_done:
     try:
         key = screen.getkey()
     except curses.error:
         key = None

     if key == 'KEY_UP':
         game.turn_up()
     elif key == 'KEY_DOWN':
         game.turn_down()
     elif key == 'KEY_LEFT':
         game.turn_left()
     elif key == 'KEY_RIGHT':
         game.turn_right()

     game.tick()

One thing to note - this approach will take 100% of your CPU, so if you don't have some other way to limit what your app is doing it can cause you some problems. You could extend this approach using threading/multiprocessing, if you find that to be something that you need.

来源：https://stackoverflow.com/questions/38907681/pygame-through-ssh-does-not-register-keystrokes-raspberry-pi-3