第4步-添加用户控件#

现在我们需要能够让用户四处走动。

首先，在程序的顶部添加一个常量，该常量控制角色每次更新的像素数：

04_USER_CONTRONT.PY-玩家移动速度恒定#
# Movement speed of player, in pixels per frame
PLAYER_MOVEMENT_SPEED = 5

接下来，在我们的 setup 方法，我们需要创建一个物理引擎，以移动我们的球员，并防止她跑过墙壁。这个 PhysicsEngineSimple 类有两个参数：移动的精灵和移动的精灵不能移动的精灵列表。

有关本教程中使用的物理引擎的更多信息，请参阅 arcade.PhysicsEngineSimple 。

注解

可以有多个物理引擎，每个移动的精灵一个。这些都是非常简单但容易的物理引擎。看见 PyMunk平台 一个更先进的物理引擎。

04_USER_CONTRONT.PY-创建物理引擎#
        # Create the 'physics engine'
        self.physics_engine = arcade.PhysicsEngineSimple(
            self.player_sprite, self.scene.get_sprite_list("Walls")
        )

每个精灵都有 center_x 和 center_y 属性。更改这些设置将更改精灵的位置。(还有用于移动精灵的顶部、底部、左侧、右侧和角度的属性。)

每个精灵都有 change_x 和 change_y 变量。这些可以用来保持精灵移动的速度。我们将根据用户点击的键来调整这些设置。如果用户按向右箭头键，我们想要一个正值 change_x 。如果该值为5，则每帧将移动5个像素。

在这种情况下，当用户按下一个键时，我们会改变精灵的x和y。物理引擎会查看这一点，并移动玩家，除非她会撞到墙上。

04_USER_CONTRONT.py-手柄按下键#
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    def on_key_press(self, key, modifiers):
        """Called whenever a key is pressed."""

        if key == arcade.key.UP or key == arcade.key.W:
            self.player_sprite.change_y = PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.DOWN or key == arcade.key.S:
            self.player_sprite.change_y = -PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.LEFT or key == arcade.key.A:
            self.player_sprite.change_x = -PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.RIGHT or key == arcade.key.D:
            self.player_sprite.change_x = PLAYER_MOVEMENT_SPEED

一松开钥匙，我们就会把速度调回到零。

04_USER_CONTRONT.PY-手柄向上键#
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    def on_key_release(self, key, modifiers):
        """Called when the user releases a key."""

        if key == arcade.key.UP or key == arcade.key.W:
            self.player_sprite.change_y = 0
        elif key == arcade.key.DOWN or key == arcade.key.S:
            self.player_sprite.change_y = 0
        elif key == arcade.key.LEFT or key == arcade.key.A:
            self.player_sprite.change_x = 0
        elif key == arcade.key.RIGHT or key == arcade.key.D:
            self.player_sprite.change_x = 0

注解

这种跟踪玩家按键的速度的方法很简单，但并不完美。如果玩家同时按下左键和右键，然后松开左键，我们预计玩家会向右移动。此方法不支持这一点。如果需要稍微复杂一点的方法，请参见 更好地通过键盘移动 。

我们的 on_update 方法每秒大约被调用60次。我们会要求物理引擎根据她来移动我们的玩家 change_x 和 change_y 。

04_USER_Contro.py-更新子画面#
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    def on_update(self, delta_time):
        """Movement and game logic"""

        # Move the player with the physics engine
        self.physics_engine.update()

源代码#

04_USER_Contro.py-用户控件#
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"""
Platformer Game
"""
import arcade

# Constants
SCREEN_WIDTH = 1000
SCREEN_HEIGHT = 650
SCREEN_TITLE = "Platformer"

# Constants used to scale our sprites from their original size
CHARACTER_SCALING = 1
TILE_SCALING = 0.5

# Movement speed of player, in pixels per frame
PLAYER_MOVEMENT_SPEED = 5


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

    def __init__(self):

        # Call the parent class and set up the window
        super().__init__(SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_TITLE)

        # Our Scene Object
        self.scene = None

        # Separate variable that holds the player sprite
        self.player_sprite = None

        # Our physics engine
        self.physics_engine = None

        arcade.set_background_color(arcade.csscolor.CORNFLOWER_BLUE)

    def setup(self):
        """Set up the game here. Call this function to restart the game."""

        # Initialize Scene
        self.scene = arcade.Scene()

        # Set up the player, specifically placing it at these coordinates.
        image_source = ":resources:images/animated_characters/female_adventurer/femaleAdventurer_idle.png"
        self.player_sprite = arcade.Sprite(image_source, CHARACTER_SCALING)
        self.player_sprite.center_x = 64
        self.player_sprite.center_y = 128
        self.scene.add_sprite("Player", self.player_sprite)

        # Create the ground
        # This shows using a loop to place multiple sprites horizontally
        for x in range(0, 1250, 64):
            wall = arcade.Sprite(":resources:images/tiles/grassMid.png", TILE_SCALING)
            wall.center_x = x
            wall.center_y = 32
            self.scene.add_sprite("Walls", wall)

        # Put some crates on the ground
        # This shows using a coordinate list to place sprites
        coordinate_list = [[512, 96], [256, 96], [768, 96]]

        for coordinate in coordinate_list:
            # Add a crate on the ground
            wall = arcade.Sprite(
                ":resources:images/tiles/boxCrate_double.png", TILE_SCALING
            )
            wall.position = coordinate
            self.scene.add_sprite("Walls", wall)

        # Create the 'physics engine'
        self.physics_engine = arcade.PhysicsEngineSimple(
            self.player_sprite, self.scene.get_sprite_list("Walls")
        )

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

        # Clear the screen to the background color
        self.clear()

        # Draw our Scene
        self.scene.draw()

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

        if key == arcade.key.UP or key == arcade.key.W:
            self.player_sprite.change_y = PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.DOWN or key == arcade.key.S:
            self.player_sprite.change_y = -PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.LEFT or key == arcade.key.A:
            self.player_sprite.change_x = -PLAYER_MOVEMENT_SPEED
        elif key == arcade.key.RIGHT or key == arcade.key.D:
            self.player_sprite.change_x = PLAYER_MOVEMENT_SPEED

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

        if key == arcade.key.UP or key == arcade.key.W:
            self.player_sprite.change_y = 0
        elif key == arcade.key.DOWN or key == arcade.key.S:
            self.player_sprite.change_y = 0
        elif key == arcade.key.LEFT or key == arcade.key.A:
            self.player_sprite.change_x = 0
        elif key == arcade.key.RIGHT or key == arcade.key.D:
            self.player_sprite.change_x = 0

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

        # Move the player with the physics engine
        self.physics_engine.update()


def main():
    """Main function"""
    window = MyGame()
    window.setup()
    arcade.run()


if __name__ == "__main__":
    main()