更好地通过键盘移动#

用键盘移动精灵的屏幕截图

如果玩家按下左键，精灵应该向左移动。如果球员同时左击和右击，球员应该停下来。如果玩家松开左键，保持右键不动，玩家就应该向右移动。

处理击键的较简单方法将无法正确处理此问题。此代码跟踪哪个键是按下的还是向上的，并正确处理它。

请参见高亮显示的部分。

sprite_move_keyboard_better.py#
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"""
Better Move Sprite With Keyboard

Simple program to show moving a sprite with the keyboard.
This is slightly better than sprite_move_keyboard.py example
in how it works, but also slightly more complex.

Artwork from https://kenney.nl

If Python and Arcade are installed, this example can be run from the command line with:
python -m arcade.examples.sprite_move_keyboard_better
"""

import arcade

SPRITE_SCALING = 0.5

SCREEN_WIDTH = 800
SCREEN_HEIGHT = 600
SCREEN_TITLE = "Better Move Sprite with Keyboard Example"

MOVEMENT_SPEED = 5


class Player(arcade.Sprite):

    def update(self):
        """ Move the player """
        # Move player.
        # Remove these lines if physics engine is moving player.
        self.center_x += self.change_x
        self.center_y += self.change_y

        # Check for out-of-bounds
        if self.left < 0:
            self.left = 0
        elif self.right > SCREEN_WIDTH - 1:
            self.right = SCREEN_WIDTH - 1

        if self.bottom < 0:
            self.bottom = 0
        elif self.top > SCREEN_HEIGHT - 1:
            self.top = SCREEN_HEIGHT - 1


class MyGame(arcade.Window):
    """
    Main application class.
    """

    def __init__(self, width, height, title):
        """
        Initializer
        """

        # Call the parent class initializer
        super().__init__(width, height, title)

        # Variables that will hold sprite lists
        self.player_list = None

        # Set up the player info
        self.player_sprite = None

        # Track the current state of what key is pressed
        self.left_pressed = False
        self.right_pressed = False
        self.up_pressed = False
        self.down_pressed = False

        # Set the background color
        arcade.set_background_color(arcade.color.AMAZON)

    def setup(self):
        """ Set up the game and initialize the variables. """

        # Sprite lists
        self.player_list = arcade.SpriteList()

        # Set up the player
        self.player_sprite = Player(":resources:images/animated_characters/female_person/femalePerson_idle.png",
                                    SPRITE_SCALING)
        self.player_sprite.center_x = 50
        self.player_sprite.center_y = 50
        self.player_list.append(self.player_sprite)

    def on_draw(self):
        """ Render the screen. """

        # Clear the screen
        self.clear()

        # Draw all the sprites.
        self.player_list.draw()

    def update_player_speed(self):

        # Calculate speed based on the keys pressed
        self.player_sprite.change_x = 0
        self.player_sprite.change_y = 0

        if self.up_pressed and not self.down_pressed:
            self.player_sprite.change_y = MOVEMENT_SPEED
        elif self.down_pressed and not self.up_pressed:
            self.player_sprite.change_y = -MOVEMENT_SPEED
        if self.left_pressed and not self.right_pressed:
            self.player_sprite.change_x = -MOVEMENT_SPEED
        elif self.right_pressed and not self.left_pressed:
            self.player_sprite.change_x = MOVEMENT_SPEED

    def on_update(self, delta_time):
        """ Movement and game logic """

        # Call update to move the sprite
        # If using a physics engine, call update player to rely on physics engine
        # for movement, and call physics engine here.
        self.player_list.update()

    def on_key_press(self, key, modifiers):
        """Called whenever a key is pressed. """

        if key == arcade.key.UP:
            self.up_pressed = True
            self.update_player_speed()
        elif key == arcade.key.DOWN:
            self.down_pressed = True
            self.update_player_speed()
        elif key == arcade.key.LEFT:
            self.left_pressed = True
            self.update_player_speed()
        elif key == arcade.key.RIGHT:
            self.right_pressed = True
            self.update_player_speed()

    def on_key_release(self, key, modifiers):
        """Called when the user releases a key. """

        if key == arcade.key.UP:
            self.up_pressed = False
            self.update_player_speed()
        elif key == arcade.key.DOWN:
            self.down_pressed = False
            self.update_player_speed()
        elif key == arcade.key.LEFT:
            self.left_pressed = False
            self.update_player_speed()
        elif key == arcade.key.RIGHT:
            self.right_pressed = False
            self.update_player_speed()


def main():
    """ Main function """
    window = MyGame(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)
    window.setup()
    arcade.run()


if __name__ == "__main__":
    main()