Pygame中绘制动态矢量箭头的技巧与常见陷阱

import pygame
import math
import ctypes # 用于错误弹窗

try:
    pygame.init()

    # 屏幕设置
    length = 1380
    width = 720
    display = pygame.display.set_mode((length, width))
    pygame.display.set_caption("Pygame 动态矢量箭头绘制")

    # 颜色定义
    white = (255, 255, 255)
    black = (0, 0, 0)
    green = (0, 153, 51)
    yellow = (255, 204, 0)

    # 球的初始位置
    ball_x, ball_y = 80, 620
    ball_radius = 10

    # 箭头参数
    ARROW_LENGTH = 15  # 箭头翼的长度
    ARROW_DEGREES = 25 # 箭头翼与主线段的半夹角（度）

    def draw_arrow(surface, color, start_pos, end_pos, line_width=3):
        """
        在Pygame表面上绘制一个带箭头的线段。
        :param surface: Pygame显示表面。
        :param color: 箭头的颜色。
        :param start_pos: 线段的起始坐标 (x1, y1)。
        :param end_pos: 线段的结束坐标 (x2, y2)，箭头尖端。
        :param line_width: 线段的宽度。
        """
        # 绘制主线段
        pygame.draw.line(surface, color, start_pos, end_pos, line_width)

        # 计算矢量分量
        dx = end_pos[0] - start_pos[0]
        dy = end_pos[1] - start_pos[1]

        # 如果矢量长度过短，不绘制箭头，避免几何问题
        if math.sqrt(dx**2 + dy**2) < ARROW_LENGTH + 5: # 加上一点裕量
            return

        # 计算矢量角度 (使用 atan2 确保所有象限正确)
        angle = math.atan2(dy, dx)
        arrow_radians = math.radians(ARROW_DEGREES)

        # 计算箭头两个翼的顶点坐标
        # 第一个翼点
        p1_x = end_pos[0] - ARROW_LENGTH * math.cos(angle - arrow_radians)
        p1_y = end_pos[1] - ARROW_LENGTH * math.sin(angle - arrow_radians)
        # 第二个翼点
        p2_x = end_pos[0] - ARROW_LENGTH * math.cos(angle + arrow_radians)
        p2_y = end_pos[1] - ARROW_LENGTH * math.sin(angle + arrow_radians)

        # 绘制箭头三角形
        pygame.draw.polygon(surface, color, [end_pos, (p1_x, p1_y), (p2_x, p2_y)])

    # 判断鼠标是否在球上
    def is_mouse_over_ball(mouse_pos, ball_center, ball_radius):
        distance = math.sqrt((mouse_pos[0] - ball_center[0])**2 + (mouse_pos[1] - ball_center[1])**2)
        return distance <= ball_radius

    running = True
    is_dragging_ball = False

    while running:
        display.fill(black) # 每次循环清空屏幕

        # 绘制球
        pygame.draw.circle(display, green, (ball_x, ball_y), ball_radius)

        mouse_pos = pygame.mouse.get_pos()

        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                running = False

            if event.type == pygame.MOUSEBUTTONDOWN:
                if is_mouse_over_ball(mouse_pos, (ball_x, ball_y), ball_radius):
                    is_dragging_ball = True
            elif event.type == pygame.MOUSEBUTTONUP:
                is_dragging_ball = False

        if is_dragging_ball:
            # 当拖动时，绘制从球心到鼠标位置的矢量箭头
            draw_arrow(display, yellow, (ball_x, ball_y), mouse_pos, 3)

        # 刷新屏幕内容
        pygame.display.update() 

    pygame.quit()

except Exception as e:
    ctypes.windll.user32.MessageBoxW(0, str(e), "ErrorBox", 16)